Non-rocket spacelaunch
Encyclopedia
Non-rocket space launch (NRS) is a launch into space
where some or all needed speed and altitude is provided by non-rocket means, rather than simply using conventional chemical rocket
s from the ground. A number of alternatives to rockets have been proposed. In some systems, such as rocket sled launch
and air launch
, a rocket is involved to reach orbit, but it ignites after helpful initial altitude or velocity is obtained in another manner.
Transportation to orbit
is one factor in the expense of space endeavors; if it can be made more efficient the total cost of space flight can be reduced. Present-day launch costs are very high – $10,000 to $25,000 per kilogram from Earth to low Earth orbit
. Since theoretical minimum intrinsic energy costs are orders of magnitude less, major cost reduction is conceivable. To settle outer space
, e.g. space exploration
and space colonization
, much cheaper launch methods are required. Another benefit may be increased safety and reliability of launches, which, in addition to lower cost, would avail for space disposal of radioactive waste. Once having overcome the Earth gravity barrier, vehicles may instead use other, non-rocket-based methods of propulsion, e.g. ion thruster
s, which have a higher propellant efficiency (specific impulse
) and potential maximum velocity than conventional rockets, but are not suitable for spacelaunch.
(a) References in this column apply to entire row unless specifically replaced
(b) All monetary values in un-inflated dollars based on reference publication date except as noted
(c) CY2008 estimate from description in 1993 reference system
(d) Requires first stage to ~5 km/s
(e) Subject to very rapid increase via bootstrapping
(f) Requires Boeing proposed DF-9 vehicle first stage to ~4 km/s
(g) Based on Gen-1 reference design, 2010 version
(h) Jules Verne
's novel, From the Earth to the Moon
. Newton's cannonball
in the 1728 book A Treatise of the System of the World was considered a thought experiment.
. To avoid an immediate need for a vehicle launched at orbital velocity to raise its perigee
, a tower would have to extend above the edge of space (above the 100 km Kármán line
), but far lesser tower height could reduce atmospheric drag losses during ascent. Satellites can orbit temporarily in elliptical orbits dipping as low as 135 km or less, yet orbital decay
causing reentry
would be rapid unless altitude was later raised to hundreds of kilometers. If the tower went all the way to geosynchronous orbit
at approximately 36,000 km, objects released at such height could then drift away with minimal power and would be in a circular orbit, though a tower to that extreme height is not doable with current materials on Earth. The concept of a structure reaching to geosynchronous orbit was first conceived by Konstantin Tsiolkovsky
, who proposed a compression structure, or "Tsiolkovsky tower."
A parallel-sided structure made of conventional brick and stone cannot reach past 2000 meters as bricks at the bottom would be crushed under the weight. Other materials could allow the tower to reach a greater height, if a tapered structure, but cost increases exponentially with construction height. Buckling
may be a failure mode before exceeding a material's nominal compressive yield strength
(though designs such as with a truss
may help compensate), but, aside from that and aside from design against weather, the theoretical scale height of a structure is the allowable load of its material divided by the product of density and local gravitational acceleration, where needed material cross-section increases by a factor of e (2.718...) over each scale height.
For common plain carbon steel under a typical allowable stress limit, its scale height is ≈ 1.635 kilometers. A 4.9 kilometer high tower (3x its scale height) of such would accordingly mass at least 20 times the weight supported at its top (as e3 ≈ 20). In contrast, an example of a more expensive high-performance aerospace material, Amoco T300/ERL1906 carbon composite, has a scale height of 54 kilometers at a safety factor of 2, though construction challenges including wind loading would apply. Earth's atmosphere has approximately 50% of its mass under 6 kilometers elevation, 90% below 16 kilometers, and 99% below 30 kilometers of altitude.
Natural mountains reach up to 9 km altitude. The current tallest man-made structure is 0.8 kilometers. A tower or other high-altitude facility could form one component of a launch system, such as being the base station of a space elevator, or a support pillar for the distal part of a mass driver or the "gun barrel
" of a space gun.
Alternatives other than compressive structures, such as tethers hanging down from high-altitude balloons or superconductor-based magnetic levitation, may take advantage of how the characteristic length of Kevlar and some other macro-scale material performance in tension (instead of compression) is up to hundreds of kilometers; compressive buckling becomes no longer applicable; and setup may be simpler. Inflatable, kinetic, and electronic structures may also be options.
Orbital tethers can be tidally locked (skyhooks) or rotating (rotovators). They can be designed (in theory) to pick up the payload when the payload is stationary or when the payload is hypersonic (has a high but not orbital velocity).
Endo-atmospheric tethers can be used to transfer kinetics (energy and momentum) between large conventional aircraft (subsonic or low supersonic) or other motive force and smaller aerodynamic vehicles, propelling them to hypersonic velocities without exotic propulsion systems.
is a tidally locked
tether, i.e., it rotates once each time it orbits around a planet or moon.
An example use of a skyhook is that a payload, launched from the ground, can be attached to the base of the skyhook, which is then carried to orbit. This means that a single stage to skyhook approach can be employed, and a high-specific impulse
drive or propellantless electromagnetic tether can be used to make up the momentum debt of the payload- or payload flow can be balanced from the moon.
A space elevator a.k.a. beanstalk or "synchronous skyhook" is a stationary skyhook. It focuses on tensile structures (tethers) reaching from the ground to geosynchronous orbit.
The most common proposal is a tether
, usually in the form of a cable
or ribbon
, spanning from the surface near the equator to a point beyond geosynchronous orbit
. Neglecting perturbations, it would be possible to design such a tether to barely touch the ground while remaining in orbit. All proposals however have additional ballast placed at the two ends to provide stability. As the planet rotates, the inertia at the upper end of the tether counteracts gravity, and keeps the cable taut. Vehicles can then climb the tether and reach orbit without the use of rocket propulsion. Such a structure could hypothetically permit delivery of cargo
and people to orbit at a fraction of the cost of launching payloads by rocket.
Current technology is not capable of manufacturing materials that are sufficiently strong and light enough to build an Earth-based space elevator as the total mass of conventional materials needed to construct such a structure would be far too great. Recent proposals for a space elevator are notable in their plans to use carbon nanotube
-based materials as the tensile element in the tether design, since the theoretical strength of carbon nanotubes appears great enough to make this practical, if strength on the macro scale can be obtained comparable to the figures for individual nanotubes.
Another difficulty includes shielding the passengers from the Van Allen belts which would require extremely heavy and comprehensive shielding to prevent significant health issues such as cancer
and may prevent manned launch for quite some time irrespective of the other issues.
Current technology may be able to support elevators in other locations in the solar system however, and other designs for space elevators exist that use current materials.
A partial space elevator can also be less than the full length from orbit to the surface Subsystems for an orbiting space elevator have been demonstrated with the X-43 http://www.nasa.gov/missions/research/x43-main.html and TIPS http://projects.nrl.navy.mil/tips/ flights.
A hypersonic skyhook is a relatively short tether that reaches from just above the edge of space to its design length.
Without the two end ballasts, a space elevator would still be in geosynchronous orbit, and thus stationary relative to the ground. If that tether were to be shorter and still reach the surface, the center of gravity would need to drop also. This would cause the lower tip to have a velocity in the orbital direction. The shorter the tether is, the faster becomes the lower tip velocity. With higher tip velocity, lower material properties are needed to make a practical design but the less benefit is obtained from this method. Eventually, any such design becomes a balance between the expense of providing the velocity to the payload at pick-up and the expense of launching the mass of the tether and power plant as dictated by available materials. Also, the lower tip is raised out of the atmosphere to avoid heating problems.
A reference design was published using materials similar to Spectra 2000 and relying on one Titan IV launch to orbit a fully functional hypersonic skyhook. To keep the tether weight within the launch capacity, a payload pick-up velocity of 5 km/s was assumed. Though the reference design was limited to an Initial Operating Condition of 1,500 kg payload size, at a maximum rate of about one payload each 17 days, the prime limitation to higher capacity was power plant size. One launch of additional power plant would almost double the available power and capacity.
The problem is getting the payload to the altitude (100 km) and velocity (5 km/s) required for pick-up.
A SpaceShaft is a proposed atmospherically levitating
structure that would serve as an elevator
system to near-space
altitude
s. It will support multiple platforms distributed at several elevation
s that would provide habitation facilities
for long term human operations throughout the mid-atmosphere and near-space altitudes. A SpaceShaft is also a candidate of the technologies cataloged for non-rocket spacelaunch.
A SpaceShaft is comparable to a maritime oil spar platform
. Although a SpaceShaft is also described as a structure
, it is not a space tower because it does not stand on foundations in contact with the surface of the planet as to support compressive forces caused by weight
, (note; pure weight becomes significant at the elevation where buoyancy becomes null). On the contrary, it is a very dynamic system since it would be constantly moving upwards. A SpaceShaft is not an orbital insertion system, as is assumed to intrinsically be the case with the Brad Edwards' proposed Centrifugally Extended Carbon-Nanotube Tether Space Elevator
. However, from a platform at the top of a SpaceShaft either spaceplane
s or spacecraft
s with built-in propulsion
systems could be launched.
Because of the orbital insertion
incapability of the SpaceShaft, some people do not regard a SpaceShaft as a true space elevator, but this is a questionable criticism.
The SpaceShaft was originally proposed at the 2nd Eurospaceward Conference on December 2008 in Luxembourg as part of a possible transportation method for the CNT
tether spools that the popular ISEC space elevator system will need for its deployment from space. The system has never been adopted by the proponents of the ISEC model. However, the group has become a common face among the European groups that advocate the use of space elevators.
Bolus tethers give in almost all ways have the same benefits as skyhooks. However, due to the retrograde velocity, the lower tip can achieve a specified Mach number with a shorter tether. This, despite the rotational forces, produces lower stresses in the tether so that lower strength to weight ratio materials can be used for the same results.
A rotovator is a bolus such that the retrograde velocity of the tip fully cancels the orbital velocity. To a stationary payload, it appears as though the tether tip decelerates as it drops straight down from the sky, and then accelerates back upward. The payload must grapple the tip of the tether during that short duration when the tip has come to a stop.
Hans Moravec
's description of this was "a satellite that rotates like a wheel." With current materials a rotovator to reach Earth's surface is impractical however; but is possible on other interplanetary bodies such as Mars and the Moon.
Similar to skyhook, a spinning bolus space tether
can be a much shorter tether than its stationary equivalent and this allows it to pick up its payload at hypersonic speeds. The Hypersonic Airplane, Space Tether, Orbital Launch (HASTOL) is one design for this.
An endo-atmospheric tether uses the long cable within the atmosphere to provide some or all of the velocity needed to reach orbit. The tether is used to transfer kinetics (energy and momentum) from a massive, slow end (typically a large subsonic or low supersonic aircraft) to a hypersonic end through aerodynamics or centripetal action. The Kinetics Interchange TEther (KITE) Launcher is one proposed endo-atmospheric tether.
A space fountain is a proposed form of space elevator
that does not require the structure to be in geosynchronous orbit
, and does not rely on tensile strength
for support. In contrast to the original space elevator design (a tether
ed satellite
), a space fountain is a tremendously tall tower
extending up from the ground
. Since such a tall tower could not support its own weight
using traditional materials, massive pellets
are projected upward from the bottom of the tower and redirected back down once they reach the top, so that the force
of redirection holds the top of the tower aloft.
An Orbital Ring is a concept for a space elevator that consists of a ring in low earth orbit
that rotates at slightly above orbital speed, and has fixed tethers hanging down to the ground.
The first design of an orbital ring offered by A. Yunitsky in 1982.
In the 1982 Paul Birch
JBIS design of an orbital ring system, a rotating cable is placed in a low Earth orbit, rotating at slightly faster than orbital speed. Not in orbit, but riding on this ring, supported electromagnetically on superconducting magnets, are Ring Stations that stay in one place above some designated point on Earth. Hanging down from these Ring Stations are short space elevators made from cables with high tensile strength to mass ratio. Paul Birch found that since the Ring Station can be used to accelerate the orbital ring eastwards as well as hold the tether, it is possible to deliberately cause the orbital ring to precess
around Earth instead of staying fixed in inertial space
while the Earth rotates beneath it. By making the precession rate large enough, the Orbital Ring can be made to precess once per day at the rate of rotation of the Earth. The ring is now "geostationary" without having to be either at the normal geostationary altitude or even in the equatorial plane.
A launch loop or Lofstrom loop is a design for a belt
-based maglev orbital launch system that would be around 2000 km long and maintained at an altitude of up to 80 km (50 mi). Vehicles
weighing 5 metric tons would be electromagnetically accelerated on top of the cable which forms an acceleration track, from which they would be projected into Earth orbit
or even beyond. The structure would constantly need around 200 MW of power to keep it in place.
The system is designed to be suitable for launching humans for space tourism
, space exploration
and space colonization
with a maximum of 3g acceleration.
) tubular columns inflated with a low density gas mix, and with dynamic stabilization systems including gyroscopes and "pressure balancing". Suggested benefits in contrast to other space elevator designs include avoiding working with the great lengths of structure involved in some other designs, construction from the ground instead of orbit, and functional access to the entire range of altitudes within the design's practical reach. The design presented is "at 5 km altitude and extending to 20 km above sea level", and the authors suggest that "The approach may be further scaled to provide direct access to altitudes above 200 km".
A mass driver is basically a very long and mainly horizontally aligned launch track
for spacelaunch, targeted upwards at the end.
It would use a linear motor
to accelerate payloads up to high speeds
. Sequential firing of a row of electromagnet
s accelerates the payload along a path. After leaving the path, the payload continues to move due to inertia
.
is a pair of conductive rails with a projectile between them.
A space gun is a method of launching an object into outer space
using a large gun
, or cannon
.
However, even with a "gun barrel
" through both the Earth's crust and troposphere
, the g-forces required to generate escape velocity
would still be more than what a human tolerates. Therefore, the space gun would be restricted to freight and ruggedized satellites. Also, the projectile needs either an internal or external means to stabilize on orbit.
A blast wave accelerator is similar to a space gun but it differs in that rings of explosive along the length of the barrel are detonated in sequence to keep the accelerations high. Also, rather than just relying on the pressure behind the projectile, the blast wave accelerator specifically times the explosions to squeeze on a tail cone on the projectile, as one might shoot a pumpkin seed by squeezing the tapered end.
and/or scramjet
combustion processes to accelerate the projectile
to extremely high speeds.
It is a long tube filled with a mixture of combustible gasses with a frangible diaphragm at either end to contain the gasses. The projectile, which is shaped like a ram jet core, is fired by another means (e.g., a light gas gun
) supersonically through the first diaphragm into the end of the tube. It then burns the gasses as fuel, accelerating down the tube under jet propulsion. Other physics come into play at higher velocities.
s are accelerated along a rigid tube or track that typically has circular or spiral turns, or combinations of these geometries in two or three dimensions. A projectile is accelerated in the curved tube by propelling the entire tube in a small-amplitude circular motion of constant or increasing frequency without changing the orientation of the tube, i.e., the entire tube gyrates but does not spin.
This gyration continually displaces the tube with a component along the direction of the centripetal force acting on the projectile, so that work is continually done on the projectile as it advances through the machine. The centripetal force experienced by the projectile is the accelerating force, and is proportional to the projectile mass.
This technique was used on the X-15, SpaceshipOne and other launches.
The main disadvantages are that the mothership tends to be quite large, and separation within the airflow at supersonic speeds has never been demonstrated, thus the boost given is relatively modest.
A spaceplane is an aircraft
designed to pass the edge of space. It combines some features of an aircraft with some of a spacecraft
. Typically, it takes the form of a spacecraft equipped with aerodynamic surfaces
, one or more rocket engines, and sometimes additional airbreathing propulsion
as well.
Early spaceplanes were used to explore hypersonic flight (e.g. X-15).
Some air-breathing engine-based designs (c.f. X-30) such as aircraft based on scramjet
s or pulse detonation engine
s could potentially achieve orbital velocity or go some useful way to doing so; however, these designs still must perform a final rocket burn at their apogee to circularize their trajectory to avoid returning to the atmosphere.
Other, reusable turbojet-like designs like Skylon which uses precooled jet engines up to Mach 5.5 before employing rockets to enter orbit appears to have a mass budget that permits a larger payload than pure rockets while achieving it in a single stage.
is a form of Beam-powered propulsion
where the energy source is a remote laser
system which can be ground-based, airborne, orbital, or a combination of these. While climbing out of the atmosphere, the surrounding air can provide the reaction mass. This form of propulsion differs from a conventional chemical rocket
where both energy and reaction mass come from the solid or liquid propellants carried on board the vehicle.
The concept of laser propelled vehicles was introduced by Arthur Kantrowitz
in 1972.
However, balloons have relatively low payload (although see the Sky Cat
project for an example of a heavy-lift balloon intended for use in the lower atmosphere), and this decreases even more with increasing altitude.
The lifting gas is usually helium, which is expensive in large quantities. This makes balloons an expensive launch assist technique. Hydrogen could be used as it has the advantage of being cheaper and lighter than helium, but the disadvantage of also being highly flammable.
s it is possible to construct a space port in the stratosphere
such as a sky anchor
. Rockets can start from it or a mass driver can accelerate payloads into the orbit. This has the advantage that most (about 90%) of the atmosphere is below the space port and that rockets start much closer to space. As a rough estimate, a rocket that reaches an altitude of 20 km when launched from the ground will reach 100 km if launched at an altitude of 20 km from a balloon.
do not start at zero airflow velocity) by electromagnetic or other sled launch
assist, in turn air-launching a second-stage rocket delivering a satellite to orbit.
All forms of projectile launchers are at least partially hybrid systems if launching to low earth orbit
, due to the requirement for orbit circularization, at a minimum entailing several percent of total delta-v
to raise perigee
(e.g. a tiny rocket burn), or in some concepts much more from a rocket thruster to ease ground accelerator development.
Some technologies can have exponential scaling if used in isolation, making the effect of combinations be of counter-intuitive magnitude. For instance, 270 m/s is under 4% of the velocity of low earth orbit
, but a NASA study estimated that Maglifter sled launch
at that velocity could increase the payload of a conventional ELV
rocket
by 80% when also having the track go up a 3000-meter mountain.
Forms of ground launch limited to a given maximum acceleration (such as due to human g-force
tolerances if intended to carry passengers) have the corresponding minimum launcher length scale not linearly but with velocity squared. Tethers can have even more non-linear, exponential scaling. The tether-to-payload mass ratio of a space tether
would be around 1:1 at a tip velocity 60% of its characteristic velocity but becomes more than 1000:1 at a tip velocity 240% of its characteristic velocity. For instance, for anticipated practicality and a moderate mass ratio with current materials, the HASTOL concept would have the first half (4 km/s) of velocity to orbit be provided by other means than the tether itself.
Combining multiple technologies would in itself be an increase to complexity and development challenges, but reducing the performance requirements of a given subsystem may allow reduction in its individual complexity or cost. For instance, the number of parts in a liquid-fueled rocket engine may be two orders of magnitude less if pressure-fed rather than pump-fed if its delta-v
requirements are limited enough to make the weight penalty of such be a practical option, or a high-velocity ground launcher may be able to use a relatively moderate performance and inexpensive solid fuel or hybrid
small motor on its projectile. Assist by non-rocket methods may compensate against the weight penalty of making an orbital rocket reusable
. Though suborbital, the first private manned spaceship, SpaceShipOne had reduced rocket performance requirements due to being a combined system with its air launch
.
Space launch
Space launch is the earliest part of a flight that reaches space. Space launch involves liftoff, when a rocket or other space launch vehicle leaves the ground at the start of a flight...
where some or all needed speed and altitude is provided by non-rocket means, rather than simply using conventional chemical rocket
Rocket
A rocket is a missile, spacecraft, aircraft or other vehicle which obtains thrust from a rocket engine. In all rockets, the exhaust is formed entirely from propellants carried within the rocket before use. Rocket engines work by action and reaction...
s from the ground. A number of alternatives to rockets have been proposed. In some systems, such as rocket sled launch
Rocket sled launch
A rocket sled launch is a method of launching space vehicles. A rail or maglev track and a rocket or jet booster is used to accelerate a sled holding a vehicle up an eastward facing mountain slope...
and air launch
Air launch
Air launching is the practice of dropping a parasite aircraft, rocket, or missile from a mothership. The parasite aircraft or missile is usually tucked under the wing of the larger mothership and then "dropped" from underneath the wing while in flight...
, a rocket is involved to reach orbit, but it ignites after helpful initial altitude or velocity is obtained in another manner.
Transportation to orbit
Orbit
In physics, an orbit is the gravitationally curved path of an object around a point in space, for example the orbit of a planet around the center of a star system, such as the Solar System...
is one factor in the expense of space endeavors; if it can be made more efficient the total cost of space flight can be reduced. Present-day launch costs are very high – $10,000 to $25,000 per kilogram from Earth to low Earth orbit
Low Earth orbit
A low Earth orbit is generally defined as an orbit within the locus extending from the Earth’s surface up to an altitude of 2,000 km...
. Since theoretical minimum intrinsic energy costs are orders of magnitude less, major cost reduction is conceivable. To settle outer space
Outer space
Outer space is the void that exists between celestial bodies, including the Earth. It is not completely empty, but consists of a hard vacuum containing a low density of particles: predominantly a plasma of hydrogen and helium, as well as electromagnetic radiation, magnetic fields, and neutrinos....
, e.g. space exploration
Space exploration
Space exploration is the use of space technology to explore outer space. Physical exploration of space is conducted both by human spaceflights and by robotic spacecraft....
and space colonization
Space colonization
Space colonization is the concept of permanent human habitation outside of Earth. Although hypothetical at the present time, there are many proposals and speculations about the first space colony...
, much cheaper launch methods are required. Another benefit may be increased safety and reliability of launches, which, in addition to lower cost, would avail for space disposal of radioactive waste. Once having overcome the Earth gravity barrier, vehicles may instead use other, non-rocket-based methods of propulsion, e.g. ion thruster
Ion thruster
An ion thruster is a form of electric propulsion used for spacecraft propulsion that creates thrust by accelerating ions. Ion thrusters are categorized by how they accelerate the ions, using either electrostatic or electromagnetic force. Electrostatic ion thrusters use the Coulomb force and...
s, which have a higher propellant efficiency (specific impulse
Specific impulse
Specific impulse is a way to describe the efficiency of rocket and jet engines. It represents the derivative of the impulse with respect to amount of propellant used, i.e., the thrust divided by the amount of propellant used per unit time. If the "amount" of propellant is given in terms of mass ,...
) and potential maximum velocity than conventional rockets, but are not suitable for spacelaunch.
Comparison
| Method(a) | Publication year |
Estimated build-cost US$B(b) |
Payload Size kg |
Estimated cost to LEO Low Earth orbit A low Earth orbit is generally defined as an orbit within the locus extending from the Earth’s surface up to an altitude of 2,000 km... US$/kg(b) |
Capacity metric tons per year |
Technology readiness level Technology Readiness Level Technology Readiness Level is a measure used by some United States government agencies and many of the world's major companies to assess the maturity of evolving technologies prior to incorporating that technology into a system or subsystem... |
|---|---|---|---|---|---|---|
| Conventional rocket Launch vehicle In spaceflight, a launch vehicle or carrier rocket is a rocket used to carry a payload from the Earth's surface into outer space. A launch system includes the launch vehicle, the launch pad and other infrastructure.... |
700-130,000 Comparison of orbital launch systems This page exposes the full list of orbital launch systems. For the short simple list of launchers families, see Comparison of orbital launchers families.... |
4,000-20,000 Comparison of orbital launch systems This page exposes the full list of orbital launch systems. For the short simple list of launchers families, see Comparison of orbital launchers families.... |
≈ 200 | 9 | ||
| Space elevator Space elevator A space elevator, also known as a geostationary orbital tether or a beanstalk, is a proposed non-rocket spacelaunch structure... |
2004 | |||||
| Hypersonic Skyhook | 1993 | 1<1(c) | 1,500(d) | 30(e) | 2 | |
| Rotovator | 1977 | 2 | ||||
| HASTOL | 2000 | 15,000(f) | 2 | |||
| Orbital ring Orbital ring An Orbital Ring is a concept for a space elevator that consists of a ring in low earth orbit that rotates at above orbital speed, that has fixed tethers hanging down to the ground.The structure is intended to be used for space launch.... |
1980 | 15 | <0.05 | 2 | ||
| Launch loop Launch loop A launch loop or Lofstrom loop is a proposed system for launching objects into space orbit using a moving cable-like system attached to the earth at two ends and suspended above the atmosphere in the middle... (small) |
1985 | 10 | 5,000 | 300 | 40,000 | 2+ |
| Launch loop Launch loop A launch loop or Lofstrom loop is a proposed system for launching objects into space orbit using a moving cable-like system attached to the earth at two ends and suspended above the atmosphere in the middle... (large) |
1985 | 30 | 5,000 | 3 | 6,000,000 | 2+ |
| KITE Launcher | 2005 | 2 | ||||
| StarTram StarTram StarTram is a proposal for a maglev space launch system. The initial Generation 1 facility would be cargo only, launching from a mountain peak at 3 km to 7 km altitude with an evacuated tube staying at local surface level, raising ≈150,000 tons to orbit annually... |
2001 | 20(g) | 35,000 | 43 | 150,000 | |
| Rocket sled launch Rocket sled launch A rocket sled launch is a method of launching space vehicles. A rail or maglev track and a rocket or jet booster is used to accelerate a sled holding a vehicle up an eastward facing mountain slope... , e.g. turbo fan skyramp |
4 | |||||
| Ram accelerator Ram accelerator A ram accelerator has the same function as a gun; i.e., it is a device for accelerating projectiles; however, it is entirely different in that jet-engine-like propulsion cycles utilizing ramjet and/or scramjet combustion processes are used to accelerate a projectile to extremely high speeds... |
2004 | 500<500 | 6 | |||
| Space gun Space gun A space gun is a method of launching an object into outer space using a large gun, or cannon. It provides a method of non-rocket spacelaunch.In the HARP Project a U.S... |
1865(h) | 0.5 | 450 | 500 | 6 | |
| Slingatron | 100 | 2 | ||||
| Spaceplane Spaceplane A spaceplane is a vehicle that operates as an aircraft in Earth's atmosphere, as well as a spacecraft when it is in space. It combines features of an aircraft and a spacecraft, which can be thought of as an aircraft that can endure and maneuver in the vacuum of space or likewise a spacecraft that... |
1992 | 10-15 | 12,000 | 3,000 | 7 | |
| Laser propulsion Laser propulsion Laser propulsion is a form of beam-powered propulsion where the energy source is a remote laser system and separate from the reaction mass... |
2 | 100 | 550 | 3000 | 4up to 4 | |
(a) References in this column apply to entire row unless specifically replaced
(b) All monetary values in un-inflated dollars based on reference publication date except as noted
(c) CY2008 estimate from description in 1993 reference system
(d) Requires first stage to ~5 km/s
(e) Subject to very rapid increase via bootstrapping
(f) Requires Boeing proposed DF-9 vehicle first stage to ~4 km/s
(g) Based on Gen-1 reference design, 2010 version
(h) Jules Verne
Jules Verne
Jules Gabriel Verne was a French author who pioneered the science fiction genre. He is best known for his novels Twenty Thousand Leagues Under the Sea , A Journey to the Center of the Earth , and Around the World in Eighty Days...
's novel, From the Earth to the Moon
From the Earth to the Moon
From the Earth to the Moon is a humorous science fantasy novel by Jules Verne and is one of the earliest entries in that genre. It tells the story of the president of a post-American Civil War gun club in Baltimore, his rival, a Philadelphia maker of armor, and a Frenchman, who build an enormous...
. Newton's cannonball
Newton's cannonball
Newton's cannonball was a thought experiment Isaac Newton used to hypothesize that the force of gravity was universal, and it was the key force for planetary motion...
in the 1728 book A Treatise of the System of the World was considered a thought experiment.
Static structures
In this usage, the term "static" is intended to convey the understanding that the structural portion of the system has no internal moving parts.Compressive structures
Compressive structures for non-rocket spacelaunch are proposals to use long, very strong structures like guyed antenna towers or artificial mountains up which payloads can be raised.Space tower
A space tower is a tower that would reach outer spaceOuter space
Outer space is the void that exists between celestial bodies, including the Earth. It is not completely empty, but consists of a hard vacuum containing a low density of particles: predominantly a plasma of hydrogen and helium, as well as electromagnetic radiation, magnetic fields, and neutrinos....
. To avoid an immediate need for a vehicle launched at orbital velocity to raise its perigee
Perigee
Perigee is the point at which an object makes its closest approach to the Earth.. Often the term is used in a broader sense to define the point in an orbit where the orbiting body is closest to the body it orbits. The opposite is the apogee, the farthest or highest point.The Greek prefix "peri"...
, a tower would have to extend above the edge of space (above the 100 km Kármán line
Karman line
The Kármán line lies at an altitude of above the Earth's sea level, and is commonly used to define the boundary between the Earth's atmosphere and outer space...
), but far lesser tower height could reduce atmospheric drag losses during ascent. Satellites can orbit temporarily in elliptical orbits dipping as low as 135 km or less, yet orbital decay
Orbital decay
Orbital decay is the process of prolonged reduction in the altitude of a satellite's orbit.This can be due to drag produced by an atmosphere due to frequent collisions between the satellite and surrounding air molecules. The drag experienced by the object is larger in the case of increased solar...
causing reentry
Reentry
Reentry can have several meanings:* Atmospheric reentry, the movement of human-made or natural objects as they enter the atmosphere of a planet from outer space** Ballistic reentry** Skip reentry...
would be rapid unless altitude was later raised to hundreds of kilometers. If the tower went all the way to geosynchronous orbit
Geosynchronous orbit
A geosynchronous orbit is an orbit around the Earth with an orbital period that matches the Earth's sidereal rotation period...
at approximately 36,000 km, objects released at such height could then drift away with minimal power and would be in a circular orbit, though a tower to that extreme height is not doable with current materials on Earth. The concept of a structure reaching to geosynchronous orbit was first conceived by Konstantin Tsiolkovsky
Konstantin Tsiolkovsky
Konstantin Eduardovich Tsiolkovsky was an Imperial Russian and Soviet rocket scientist and pioneer of the astronautic theory. Along with his followers the German Hermann Oberth and the American Robert H. Goddard, he is considered to be one of the founding fathers of rocketry and astronautics...
, who proposed a compression structure, or "Tsiolkovsky tower."
A parallel-sided structure made of conventional brick and stone cannot reach past 2000 meters as bricks at the bottom would be crushed under the weight. Other materials could allow the tower to reach a greater height, if a tapered structure, but cost increases exponentially with construction height. Buckling
Buckling
In science, buckling is a mathematical instability, leading to a failure mode.Theoretically, buckling is caused by a bifurcation in the solution to the equations of static equilibrium...
may be a failure mode before exceeding a material's nominal compressive yield strength
Compressive strength
Compressive strength is the capacity of a material or structure to withstand axially directed pushing forces. When the limit of compressive strength is reached, materials are crushed. Concrete can be made to have high compressive strength, e.g...
(though designs such as with a truss
Truss
In architecture and structural engineering, a truss is a structure comprising one or more triangular units constructed with straight members whose ends are connected at joints referred to as nodes. External forces and reactions to those forces are considered to act only at the nodes and result in...
may help compensate), but, aside from that and aside from design against weather, the theoretical scale height of a structure is the allowable load of its material divided by the product of density and local gravitational acceleration, where needed material cross-section increases by a factor of e (2.718...) over each scale height.
For common plain carbon steel under a typical allowable stress limit, its scale height is ≈ 1.635 kilometers. A 4.9 kilometer high tower (3x its scale height) of such would accordingly mass at least 20 times the weight supported at its top (as e3 ≈ 20). In contrast, an example of a more expensive high-performance aerospace material, Amoco T300/ERL1906 carbon composite, has a scale height of 54 kilometers at a safety factor of 2, though construction challenges including wind loading would apply. Earth's atmosphere has approximately 50% of its mass under 6 kilometers elevation, 90% below 16 kilometers, and 99% below 30 kilometers of altitude.
Natural mountains reach up to 9 km altitude. The current tallest man-made structure is 0.8 kilometers. A tower or other high-altitude facility could form one component of a launch system, such as being the base station of a space elevator, or a support pillar for the distal part of a mass driver or the "gun barrel
Gun barrel
A gun barrel is the tube, usually metal, through which a controlled explosion or rapid expansion of gases are released in order to propel a projectile out of the end at a high velocity....
" of a space gun.
Alternatives other than compressive structures, such as tethers hanging down from high-altitude balloons or superconductor-based magnetic levitation, may take advantage of how the characteristic length of Kevlar and some other macro-scale material performance in tension (instead of compression) is up to hundreds of kilometers; compressive buckling becomes no longer applicable; and setup may be simpler. Inflatable, kinetic, and electronic structures may also be options.
Tensile structures
Tensile structures for non-rocket spacelaunch are proposals to use long, very strong cables (known as tethers) to drag a payload into, or fling it toward, space. Tethers can also be used for changing orbit once in space.Orbital tethers can be tidally locked (skyhooks) or rotating (rotovators). They can be designed (in theory) to pick up the payload when the payload is stationary or when the payload is hypersonic (has a high but not orbital velocity).
Endo-atmospheric tethers can be used to transfer kinetics (energy and momentum) between large conventional aircraft (subsonic or low supersonic) or other motive force and smaller aerodynamic vehicles, propelling them to hypersonic velocities without exotic propulsion systems.
Skyhooks
A skyhookSkyhook (structure)
Skyhooks are a theoretical class of cable based techniques intended to lift payloads to high altitudes and speeds. The name skyhook is a reference to an imaginary hook that hangs from the sky....
is a tidally locked
Tidal locking
Tidal locking occurs when the gravitational gradient makes one side of an astronomical body always face another; for example, the same side of the Earth's Moon always faces the Earth. A tidally locked body takes just as long to rotate around its own axis as it does to revolve around its partner...
tether, i.e., it rotates once each time it orbits around a planet or moon.
An example use of a skyhook is that a payload, launched from the ground, can be attached to the base of the skyhook, which is then carried to orbit. This means that a single stage to skyhook approach can be employed, and a high-specific impulse
Specific impulse
Specific impulse is a way to describe the efficiency of rocket and jet engines. It represents the derivative of the impulse with respect to amount of propellant used, i.e., the thrust divided by the amount of propellant used per unit time. If the "amount" of propellant is given in terms of mass ,...
drive or propellantless electromagnetic tether can be used to make up the momentum debt of the payload- or payload flow can be balanced from the moon.
Space elevator
The most common proposal is a tether
Tether
A tether is a cord, fixture, or signal that anchors something movable to a reference point which may be fixed or moving. There are a number of applications for tethers: balloons, kites, tethered wind-energy conversion systems, anchors, tethered water-flow energy conversion systems, towing, animal...
, usually in the form of a cable
Cable
A cable is two or more wires running side by side and bonded, twisted or braided together to form a single assembly. In mechanics cables, otherwise known as wire ropes, are used for lifting, hauling and towing or conveying force through tension. In electrical engineering cables are used to carry...
or ribbon
Ribbon
A ribbon or riband is a thin band of material, typically cloth but also plastic or sometimes metal, used primarily for binding and tying. Cloth ribbons, most commonly silk, are often used in connection with clothing, but are also applied for innumerable useful, ornamental and symbolic purposes...
, spanning from the surface near the equator to a point beyond geosynchronous orbit
Geosynchronous orbit
A geosynchronous orbit is an orbit around the Earth with an orbital period that matches the Earth's sidereal rotation period...
. Neglecting perturbations, it would be possible to design such a tether to barely touch the ground while remaining in orbit. All proposals however have additional ballast placed at the two ends to provide stability. As the planet rotates, the inertia at the upper end of the tether counteracts gravity, and keeps the cable taut. Vehicles can then climb the tether and reach orbit without the use of rocket propulsion. Such a structure could hypothetically permit delivery of cargo
Cargo
Cargo is goods or produce transported, generally for commercial gain, by ship, aircraft, train, van or truck. In modern times, containers are used in most intermodal long-haul cargo transport.-Marine:...
and people to orbit at a fraction of the cost of launching payloads by rocket.
Current technology is not capable of manufacturing materials that are sufficiently strong and light enough to build an Earth-based space elevator as the total mass of conventional materials needed to construct such a structure would be far too great. Recent proposals for a space elevator are notable in their plans to use carbon nanotube
Carbon nanotube
Carbon nanotubes are allotropes of carbon with a cylindrical nanostructure. Nanotubes have been constructed with length-to-diameter ratio of up to 132,000,000:1, significantly larger than for any other material...
-based materials as the tensile element in the tether design, since the theoretical strength of carbon nanotubes appears great enough to make this practical, if strength on the macro scale can be obtained comparable to the figures for individual nanotubes.
Another difficulty includes shielding the passengers from the Van Allen belts which would require extremely heavy and comprehensive shielding to prevent significant health issues such as cancer
Cancer
Cancer , known medically as a malignant neoplasm, is a large group of different diseases, all involving unregulated cell growth. In cancer, cells divide and grow uncontrollably, forming malignant tumors, and invade nearby parts of the body. The cancer may also spread to more distant parts of the...
and may prevent manned launch for quite some time irrespective of the other issues.
Current technology may be able to support elevators in other locations in the solar system however, and other designs for space elevators exist that use current materials.
A partial space elevator can also be less than the full length from orbit to the surface Subsystems for an orbiting space elevator have been demonstrated with the X-43 http://www.nasa.gov/missions/research/x43-main.html and TIPS http://projects.nrl.navy.mil/tips/ flights.
Hypersonic skyhook
Without the two end ballasts, a space elevator would still be in geosynchronous orbit, and thus stationary relative to the ground. If that tether were to be shorter and still reach the surface, the center of gravity would need to drop also. This would cause the lower tip to have a velocity in the orbital direction. The shorter the tether is, the faster becomes the lower tip velocity. With higher tip velocity, lower material properties are needed to make a practical design but the less benefit is obtained from this method. Eventually, any such design becomes a balance between the expense of providing the velocity to the payload at pick-up and the expense of launching the mass of the tether and power plant as dictated by available materials. Also, the lower tip is raised out of the atmosphere to avoid heating problems.
A reference design was published using materials similar to Spectra 2000 and relying on one Titan IV launch to orbit a fully functional hypersonic skyhook. To keep the tether weight within the launch capacity, a payload pick-up velocity of 5 km/s was assumed. Though the reference design was limited to an Initial Operating Condition of 1,500 kg payload size, at a maximum rate of about one payload each 17 days, the prime limitation to higher capacity was power plant size. One launch of additional power plant would almost double the available power and capacity.
The problem is getting the payload to the altitude (100 km) and velocity (5 km/s) required for pick-up.
SpaceShaft
A SpaceShaft is a proposed atmospherically levitating
Levitation
Levitation is the process by which an object is suspended by a physical force against gravity, in a stable position without solid physical contact...
structure that would serve as an elevator
Elevator
An elevator is a type of vertical transport equipment that efficiently moves people or goods between floors of a building, vessel or other structures...
system to near-space
Near space
Near space is the region of Earth's atmosphere that lies between 65,000 and 325,000–350,000 feet above sea level, encompassing the stratosphere, mesosphere, and thermosphere. A more understandable definition would be above where a commercial airliner flies but below the realm of an orbiting...
altitude
Altitude
Altitude or height is defined based on the context in which it is used . As a general definition, altitude is a distance measurement, usually in the vertical or "up" direction, between a reference datum and a point or object. The reference datum also often varies according to the context...
s. It will support multiple platforms distributed at several elevation
Elevation
The elevation of a geographic location is its height above a fixed reference point, most commonly a reference geoid, a mathematical model of the Earth's sea level as an equipotential gravitational surface ....
s that would provide habitation facilities
Habitation Module
thumb|right|250px|ISS Habitation moduleThe Habitation Module for the International Space Station was intended to be the Station's main living quarters designed with galley, toilet, shower, sleep stations and medical facilities. About the size of a bus, the module was canceled after its pressurized...
for long term human operations throughout the mid-atmosphere and near-space altitudes. A SpaceShaft is also a candidate of the technologies cataloged for non-rocket spacelaunch.
A SpaceShaft is comparable to a maritime oil spar platform
SPAR (platform)
A spar, named for logs used as buoys in shipping and moored in place vertically, is a type of floating oil platform typically used in very deep waters. Spar production platforms have been developed as an alternative to conventional platforms...
. Although a SpaceShaft is also described as a structure
Architectural structure
An architectural structure is a free-standing, immobile outdoor constructed element. The structure may be temporary or permanent.Structures include buildings and nonbuilding structures . Examples of building structures include houses, town halls, libraries, and skyscrapers...
, it is not a space tower because it does not stand on foundations in contact with the surface of the planet as to support compressive forces caused by weight
Weight
In science and engineering, the weight of an object is the force on the object due to gravity. Its magnitude , often denoted by an italic letter W, is the product of the mass m of the object and the magnitude of the local gravitational acceleration g; thus:...
, (note; pure weight becomes significant at the elevation where buoyancy becomes null). On the contrary, it is a very dynamic system since it would be constantly moving upwards. A SpaceShaft is not an orbital insertion system, as is assumed to intrinsically be the case with the Brad Edwards' proposed Centrifugally Extended Carbon-Nanotube Tether Space Elevator
Space elevator
A space elevator, also known as a geostationary orbital tether or a beanstalk, is a proposed non-rocket spacelaunch structure...
. However, from a platform at the top of a SpaceShaft either spaceplane
Spaceplane
A spaceplane is a vehicle that operates as an aircraft in Earth's atmosphere, as well as a spacecraft when it is in space. It combines features of an aircraft and a spacecraft, which can be thought of as an aircraft that can endure and maneuver in the vacuum of space or likewise a spacecraft that...
s or spacecraft
Spacecraft
A spacecraft or spaceship is a craft or machine designed for spaceflight. Spacecraft are used for a variety of purposes, including communications, earth observation, meteorology, navigation, planetary exploration and transportation of humans and cargo....
s with built-in propulsion
Spacecraft propulsion
Spacecraft propulsion is any method used to accelerate spacecraft and artificial satellites. There are many different methods. Each method has drawbacks and advantages, and spacecraft propulsion is an active area of research. However, most spacecraft today are propelled by forcing a gas from the...
systems could be launched.
Because of the orbital insertion
Orbit insertion
Orbit insertion is the spaceflight operation of adjusting a spacecraft’s momentum to allow for entry into a stable orbit around a planet, moon, or other celestial body...
incapability of the SpaceShaft, some people do not regard a SpaceShaft as a true space elevator, but this is a questionable criticism.
The SpaceShaft was originally proposed at the 2nd Eurospaceward Conference on December 2008 in Luxembourg as part of a possible transportation method for the CNT
Carbon nanotube
Carbon nanotubes are allotropes of carbon with a cylindrical nanostructure. Nanotubes have been constructed with length-to-diameter ratio of up to 132,000,000:1, significantly larger than for any other material...
tether spools that the popular ISEC space elevator system will need for its deployment from space. The system has never been adopted by the proponents of the ISEC model. However, the group has become a common face among the European groups that advocate the use of space elevators.
Bolus
A bolus is a tether that rotates more than once each time it orbits around a planet or moon. Bolus typically rotate in the same sense as they orbit such that the lower tip has a retrograde motion relative to the center of gravity.Bolus tethers give in almost all ways have the same benefits as skyhooks. However, due to the retrograde velocity, the lower tip can achieve a specified Mach number with a shorter tether. This, despite the rotational forces, produces lower stresses in the tether so that lower strength to weight ratio materials can be used for the same results.
Rotovators
A rotovator is a bolus such that the retrograde velocity of the tip fully cancels the orbital velocity. To a stationary payload, it appears as though the tether tip decelerates as it drops straight down from the sky, and then accelerates back upward. The payload must grapple the tip of the tether during that short duration when the tip has come to a stop.
Hans Moravec
Hans Moravec
Hans Moravec is an adjunct faculty member at the Robotics Institute of Carnegie Mellon University. He is known for his work on robotics, artificial intelligence, and writings on the impact of technology. Moravec also is a futurist with many of his publications and predictions focusing on...
's description of this was "a satellite that rotates like a wheel." With current materials a rotovator to reach Earth's surface is impractical however; but is possible on other interplanetary bodies such as Mars and the Moon.
Hypersonic bolus (HASTOL)
Similar to skyhook, a spinning bolus space tether
Space tether
Space tethers are cables, usually long and very strong, which can be used for propulsion, stabilization, or maintaining the formation of space systems by determining the trajectory of spacecraft and payloads...
can be a much shorter tether than its stationary equivalent and this allows it to pick up its payload at hypersonic speeds. The Hypersonic Airplane, Space Tether, Orbital Launch (HASTOL) is one design for this.
Endo-atmospheric tethers
Space fountain
Space elevator
A space elevator, also known as a geostationary orbital tether or a beanstalk, is a proposed non-rocket spacelaunch structure...
that does not require the structure to be in geosynchronous orbit
Geosynchronous orbit
A geosynchronous orbit is an orbit around the Earth with an orbital period that matches the Earth's sidereal rotation period...
, and does not rely on tensile strength
Tensile strength
Ultimate tensile strength , often shortened to tensile strength or ultimate strength, is the maximum stress that a material can withstand while being stretched or pulled before necking, which is when the specimen's cross-section starts to significantly contract...
for support. In contrast to the original space elevator design (a tether
Tether
A tether is a cord, fixture, or signal that anchors something movable to a reference point which may be fixed or moving. There are a number of applications for tethers: balloons, kites, tethered wind-energy conversion systems, anchors, tethered water-flow energy conversion systems, towing, animal...
ed satellite
Satellite
In the context of spaceflight, a satellite is an object which has been placed into orbit by human endeavour. Such objects are sometimes called artificial satellites to distinguish them from natural satellites such as the Moon....
), a space fountain is a tremendously tall tower
Tower
A tower is a tall structure, usually taller than it is wide, often by a significant margin. Towers are distinguished from masts by their lack of guy-wires....
extending up from the ground
Earth
Earth is the third planet from the Sun, and the densest and fifth-largest of the eight planets in the Solar System. It is also the largest of the Solar System's four terrestrial planets...
. Since such a tall tower could not support its own weight
Weight
In science and engineering, the weight of an object is the force on the object due to gravity. Its magnitude , often denoted by an italic letter W, is the product of the mass m of the object and the magnitude of the local gravitational acceleration g; thus:...
using traditional materials, massive pellets
Pelletizing
Pelletizing is the process of compressing or molding a material into the shape of a pellet. A wide range of different materials are pelletized including chemicals, iron ore, animal compound feed, and more.- Pelletizing of iron ore :...
are projected upward from the bottom of the tower and redirected back down once they reach the top, so that the force
Force
In physics, a force is any influence that causes an object to undergo a change in speed, a change in direction, or a change in shape. In other words, a force is that which can cause an object with mass to change its velocity , i.e., to accelerate, or which can cause a flexible object to deform...
of redirection holds the top of the tower aloft.
Orbital ring
Low Earth orbit
A low Earth orbit is generally defined as an orbit within the locus extending from the Earth’s surface up to an altitude of 2,000 km...
that rotates at slightly above orbital speed, and has fixed tethers hanging down to the ground.
The first design of an orbital ring offered by A. Yunitsky in 1982.
In the 1982 Paul Birch
Paul Birch (writer)
Paul Birch is a British author, engineer and scientist, who has worked in radioastronomy and satellite communications, and now writes full time.He is a former Fellow of the British Interplanetary Society....
JBIS design of an orbital ring system, a rotating cable is placed in a low Earth orbit, rotating at slightly faster than orbital speed. Not in orbit, but riding on this ring, supported electromagnetically on superconducting magnets, are Ring Stations that stay in one place above some designated point on Earth. Hanging down from these Ring Stations are short space elevators made from cables with high tensile strength to mass ratio. Paul Birch found that since the Ring Station can be used to accelerate the orbital ring eastwards as well as hold the tether, it is possible to deliberately cause the orbital ring to precess
Precession
Precession is a change in the orientation of the rotation axis of a rotating body. It can be defined as a change in direction of the rotation axis in which the second Euler angle is constant...
around Earth instead of staying fixed in inertial space
Inertial space
In physics, the expression inertial space refers to the background reference that is provided by the phenomenon of inertia.Inertia is opposition to change of velocity, that is: change of velocity with respect to the background, the background that all physical objects are embedded in....
while the Earth rotates beneath it. By making the precession rate large enough, the Orbital Ring can be made to precess once per day at the rate of rotation of the Earth. The ring is now "geostationary" without having to be either at the normal geostationary altitude or even in the equatorial plane.
Launch loop
Belt (mechanical)
A belt is a loop of flexible material used to link two or more rotating shafts mechanically. Belts may be used as a source of motion, to transmit power efficiently, or to track relative movement. Belts are looped over pulleys. In a two pulley system, the belt can either drive the pulleys in the...
-based maglev orbital launch system that would be around 2000 km long and maintained at an altitude of up to 80 km (50 mi). Vehicles
Spacecraft
A spacecraft or spaceship is a craft or machine designed for spaceflight. Spacecraft are used for a variety of purposes, including communications, earth observation, meteorology, navigation, planetary exploration and transportation of humans and cargo....
weighing 5 metric tons would be electromagnetically accelerated on top of the cable which forms an acceleration track, from which they would be projected into Earth orbit
Orbit
In physics, an orbit is the gravitationally curved path of an object around a point in space, for example the orbit of a planet around the center of a star system, such as the Solar System...
or even beyond. The structure would constantly need around 200 MW of power to keep it in place.
The system is designed to be suitable for launching humans for space tourism
Space tourism
Space Tourism is space travel for recreational, leisure or business purposes. A number of startup companies have sprung up in recent years, hoping to create a space tourism industry...
, space exploration
Space exploration
Space exploration is the use of space technology to explore outer space. Physical exploration of space is conducted both by human spaceflights and by robotic spacecraft....
and space colonization
Space colonization
Space colonization is the concept of permanent human habitation outside of Earth. Although hypothetical at the present time, there are many proposals and speculations about the first space colony...
with a maximum of 3g acceleration.
Pneumatic freestanding tower
One proposed design is a freestanding tower composed of high strength material (e.g. kevlarKevlar
Kevlar is the registered trademark for a para-aramid synthetic fiber, related to other aramids such as Nomex and Technora. Developed at DuPont in 1965, this high strength material was first commercially used in the early 1970s as a replacement for steel in racing tires...
) tubular columns inflated with a low density gas mix, and with dynamic stabilization systems including gyroscopes and "pressure balancing". Suggested benefits in contrast to other space elevator designs include avoiding working with the great lengths of structure involved in some other designs, construction from the ground instead of orbit, and functional access to the entire range of altitudes within the design's practical reach. The design presented is "at 5 km altitude and extending to 20 km above sea level", and the authors suggest that "The approach may be further scaled to provide direct access to altitudes above 200 km".
Projectile launchers
With any of these projectile launchers, the launcher gives a high velocity at, or near, ground level. In order to achieve orbit, the projectile must be given enough extra velocity to punch through the atmosphere. Also, the projectile needs either an internal or external means to perform orbital insertion. The designs below fall into three categories, electrically driven, chemically driven, and mechanically driven.Mass driver
Launch track
The launch track is the section of a launched roller coaster in which the train is accelerated to its full speed in a matter of seconds. A launch track is always straight and is usually banked upwards slightly, so that a train would roll backwards to the station in the event of a loss of power.A...
for spacelaunch, targeted upwards at the end.
It would use a linear motor
Linear motor
A linear motor is an electric motor that has had its stator and rotor "unrolled" so that instead of producing a torque it produces a linear force along its length...
to accelerate payloads up to high speeds
Velocity
In physics, velocity is speed in a given direction. Speed describes only how fast an object is moving, whereas velocity gives both the speed and direction of the object's motion. To have a constant velocity, an object must have a constant speed and motion in a constant direction. Constant ...
. Sequential firing of a row of electromagnet
Electromagnet
An electromagnet is a type of magnet in which the magnetic field is produced by the flow of electric current. The magnetic field disappears when the current is turned off...
s accelerates the payload along a path. After leaving the path, the payload continues to move due to inertia
Inertia
Inertia is the resistance of any physical object to a change in its state of motion or rest, or the tendency of an object to resist any change in its motion. It is proportional to an object's mass. The principle of inertia is one of the fundamental principles of classical physics which are used to...
.
Rail gun
A rail gunRailgun
A railgun is an entirely electrical gun that accelerates a conductive projectile along a pair of metal rails using the same principles as the homopolar motor. Railguns use two sliding or rolling contacts that permit a large electric current to pass through the projectile. This current interacts...
is a pair of conductive rails with a projectile between them.
StarTram
StarTram Generation 2 is a proposal for an evacuated tube at 22 km for launching vehicles into space, held up by a large current in superconducting cables that repels another set of cables on the ground with an opposing current flow. Other versions of the concept would fire vehicles from a tube exiting on a mountain peak.Space gun
A space gun is a method of launching an object into outer space
Outer space
Outer space is the void that exists between celestial bodies, including the Earth. It is not completely empty, but consists of a hard vacuum containing a low density of particles: predominantly a plasma of hydrogen and helium, as well as electromagnetic radiation, magnetic fields, and neutrinos....
using a large gun
Gun
A gun is a muzzle or breech-loaded projectile-firing weapon. There are various definitions depending on the nation and branch of service. A "gun" may be distinguished from other firearms in being a crew-served weapon such as a howitzer or mortar, as opposed to a small arm like a rifle or pistol,...
, or cannon
Cannon
A cannon is any piece of artillery that uses gunpowder or other usually explosive-based propellents to launch a projectile. Cannon vary in caliber, range, mobility, rate of fire, angle of fire, and firepower; different forms of cannon combine and balance these attributes in varying degrees,...
.
However, even with a "gun barrel
Gun barrel
A gun barrel is the tube, usually metal, through which a controlled explosion or rapid expansion of gases are released in order to propel a projectile out of the end at a high velocity....
" through both the Earth's crust and troposphere
Troposphere
The troposphere is the lowest portion of Earth's atmosphere. It contains approximately 80% of the atmosphere's mass and 99% of its water vapor and aerosols....
, the g-forces required to generate escape velocity
Escape velocity
In physics, escape velocity is the speed at which the kinetic energy plus the gravitational potential energy of an object is zero gravitational potential energy is negative since gravity is an attractive force and the potential is defined to be zero at infinity...
would still be more than what a human tolerates. Therefore, the space gun would be restricted to freight and ruggedized satellites. Also, the projectile needs either an internal or external means to stabilize on orbit.
Blast wave accelerator
Ram accelerator
A ram accelerator also uses chemical energy like the space gun but it is entirely different in that it relies on a jet-engine-like propulsion cycle utilizing ramjetRamjet
A ramjet, sometimes referred to as a stovepipe jet, or an athodyd, is a form of airbreathing jet engine using the engine's forward motion to compress incoming air, without a rotary compressor. Ramjets cannot produce thrust at zero airspeed and thus cannot move an aircraft from a standstill...
and/or scramjet
Scramjet
A scramjet is a variant of a ramjet airbreathing jet engine in which combustion takes place in supersonic airflow...
combustion processes to accelerate the projectile
Projectile
A projectile is any object projected into space by the exertion of a force. Although a thrown baseball is technically a projectile too, the term more commonly refers to a weapon....
to extremely high speeds.
It is a long tube filled with a mixture of combustible gasses with a frangible diaphragm at either end to contain the gasses. The projectile, which is shaped like a ram jet core, is fired by another means (e.g., a light gas gun
Light gas gun
The light-gas gun is an apparatus for physics experiments, a highly specialized gun designed to generate very high velocities. It is usually used to study high speed impact phenomena , such as the formation of impact craters by meteorites or the erosion of materials by micrometeoroids...
) supersonically through the first diaphragm into the end of the tube. It then burns the gasses as fuel, accelerating down the tube under jet propulsion. Other physics come into play at higher velocities.
Slingatron
In a slingatron, projectileProjectile
A projectile is any object projected into space by the exertion of a force. Although a thrown baseball is technically a projectile too, the term more commonly refers to a weapon....
s are accelerated along a rigid tube or track that typically has circular or spiral turns, or combinations of these geometries in two or three dimensions. A projectile is accelerated in the curved tube by propelling the entire tube in a small-amplitude circular motion of constant or increasing frequency without changing the orientation of the tube, i.e., the entire tube gyrates but does not spin.
This gyration continually displaces the tube with a component along the direction of the centripetal force acting on the projectile, so that work is continually done on the projectile as it advances through the machine. The centripetal force experienced by the projectile is the accelerating force, and is proportional to the projectile mass.
Air launch
In air launch a carrier aircraft carries the space vehicle to high altitude and speed, before release.This technique was used on the X-15, SpaceshipOne and other launches.
The main disadvantages are that the mothership tends to be quite large, and separation within the airflow at supersonic speeds has never been demonstrated, thus the boost given is relatively modest.
Spaceplanes
Aircraft
An aircraft is a vehicle that is able to fly by gaining support from the air, or, in general, the atmosphere of a planet. An aircraft counters the force of gravity by using either static lift or by using the dynamic lift of an airfoil, or in a few cases the downward thrust from jet engines.Although...
designed to pass the edge of space. It combines some features of an aircraft with some of a spacecraft
Spacecraft
A spacecraft or spaceship is a craft or machine designed for spaceflight. Spacecraft are used for a variety of purposes, including communications, earth observation, meteorology, navigation, planetary exploration and transportation of humans and cargo....
. Typically, it takes the form of a spacecraft equipped with aerodynamic surfaces
Wing
A wing is an appendage with a surface that produces lift for flight or propulsion through the atmosphere, or through another gaseous or liquid fluid...
, one or more rocket engines, and sometimes additional airbreathing propulsion
Jet engine
A jet engine is a reaction engine that discharges a fast moving jet to generate thrust by jet propulsion and in accordance with Newton's laws of motion. This broad definition of jet engines includes turbojets, turbofans, rockets, ramjets, pulse jets...
as well.
Early spaceplanes were used to explore hypersonic flight (e.g. X-15).
Some air-breathing engine-based designs (c.f. X-30) such as aircraft based on scramjet
Scramjet
A scramjet is a variant of a ramjet airbreathing jet engine in which combustion takes place in supersonic airflow...
s or pulse detonation engine
Pulse detonation engine
A pulse detonation engine, or "PDE", is a type of propulsion system that uses detonation waves to combust the fuel and oxidizer mixture. The engine is pulsed because the mixture must be renewed in the combustion chamber between each detonation wave initiated by an ignition source. Theoretically, a...
s could potentially achieve orbital velocity or go some useful way to doing so; however, these designs still must perform a final rocket burn at their apogee to circularize their trajectory to avoid returning to the atmosphere.
Other, reusable turbojet-like designs like Skylon which uses precooled jet engines up to Mach 5.5 before employing rockets to enter orbit appears to have a mass budget that permits a larger payload than pure rockets while achieving it in a single stage.
Laser propulsion
Laser propulsionLaser propulsion
Laser propulsion is a form of beam-powered propulsion where the energy source is a remote laser system and separate from the reaction mass...
is a form of Beam-powered propulsion
Beam-powered propulsion
Beam-powered propulsion is a class of aircraft or spacecraft propulsion mechanisms that use energy beamed to the spacecraft from a remote power plant to provide energy...
where the energy source is a remote laser
Laser
A laser is a device that emits light through a process of optical amplification based on the stimulated emission of photons. The term "laser" originated as an acronym for Light Amplification by Stimulated Emission of Radiation...
system which can be ground-based, airborne, orbital, or a combination of these. While climbing out of the atmosphere, the surrounding air can provide the reaction mass. This form of propulsion differs from a conventional chemical rocket
Rocket
A rocket is a missile, spacecraft, aircraft or other vehicle which obtains thrust from a rocket engine. In all rockets, the exhaust is formed entirely from propellants carried within the rocket before use. Rocket engines work by action and reaction...
where both energy and reaction mass come from the solid or liquid propellants carried on board the vehicle.
The concept of laser propelled vehicles was introduced by Arthur Kantrowitz
Arthur Kantrowitz
Arthur Robert Kantrowitz was an American scientist, engineer, and educator.Kantrowitz grew up in The Bronx, and graduated from DeWitt Clinton High School. He earned his B.S., M.A. and, in 1947, his Ph.D. degrees in physics from Columbia University...
in 1972.
Balloon
Balloons can raise the initial altitude of rockets.However, balloons have relatively low payload (although see the Sky Cat
SkyCat
SkyCat is a class of proposed heavy-lift and ultra-heavy-lift hybrid aircraft which derive more than half of their lift by helium buoyancy and the balance via aerodynamic lift produced by aerodynamic shaping. Such vehicles are not "payload specific"...
project for an example of a heavy-lift balloon intended for use in the lower atmosphere), and this decreases even more with increasing altitude.
The lifting gas is usually helium, which is expensive in large quantities. This makes balloons an expensive launch assist technique. Hydrogen could be used as it has the advantage of being cheaper and lighter than helium, but the disadvantage of also being highly flammable.
Buoyant space port
By using big balloonBalloon
A balloon is an inflatable flexible bag filled with a gas, such as helium, hydrogen, nitrous oxide, oxygen, or air. Modern balloons can be made from materials such as rubber, latex, polychloroprene, or a nylon fabric, while some early balloons were made of dried animal bladders, such as the pig...
s it is possible to construct a space port in the stratosphere
Stratosphere
The stratosphere is the second major layer of Earth's atmosphere, just above the troposphere, and below the mesosphere. It is stratified in temperature, with warmer layers higher up and cooler layers farther down. This is in contrast to the troposphere near the Earth's surface, which is cooler...
such as a sky anchor
Sky anchor
A sky anchor is a system of two balloons in tandem, with a "zero-pressure" lifting gas balloon tethered to a superpressure balloon "anchor". The gas balloon is filled with a lifting gas and provides the buoyancy, while the superpressure balloon is filled with air, and pressurized to provide the...
. Rockets can start from it or a mass driver can accelerate payloads into the orbit. This has the advantage that most (about 90%) of the atmosphere is below the space port and that rockets start much closer to space. As a rough estimate, a rocket that reaches an altitude of 20 km when launched from the ground will reach 100 km if launched at an altitude of 20 km from a balloon.
Hybrid launch systems
Separate technologies may be combined. NASA in 2010 suggested that a future scramjet aircraft might be accelerated to 300 m/s (a solution to how ramjet enginesRamjet
A ramjet, sometimes referred to as a stovepipe jet, or an athodyd, is a form of airbreathing jet engine using the engine's forward motion to compress incoming air, without a rotary compressor. Ramjets cannot produce thrust at zero airspeed and thus cannot move an aircraft from a standstill...
do not start at zero airflow velocity) by electromagnetic or other sled launch
Rocket sled launch
A rocket sled launch is a method of launching space vehicles. A rail or maglev track and a rocket or jet booster is used to accelerate a sled holding a vehicle up an eastward facing mountain slope...
assist, in turn air-launching a second-stage rocket delivering a satellite to orbit.
All forms of projectile launchers are at least partially hybrid systems if launching to low earth orbit
Low Earth orbit
A low Earth orbit is generally defined as an orbit within the locus extending from the Earth’s surface up to an altitude of 2,000 km...
, due to the requirement for orbit circularization, at a minimum entailing several percent of total delta-v
Delta-v
In astrodynamics a Δv or delta-v is a scalar which takes units of speed. It is a measure of the amount of "effort" that is needed to change from one trajectory to another by making an orbital maneuver....
to raise perigee
Perigee
Perigee is the point at which an object makes its closest approach to the Earth.. Often the term is used in a broader sense to define the point in an orbit where the orbiting body is closest to the body it orbits. The opposite is the apogee, the farthest or highest point.The Greek prefix "peri"...
(e.g. a tiny rocket burn), or in some concepts much more from a rocket thruster to ease ground accelerator development.
Some technologies can have exponential scaling if used in isolation, making the effect of combinations be of counter-intuitive magnitude. For instance, 270 m/s is under 4% of the velocity of low earth orbit
Low Earth orbit
A low Earth orbit is generally defined as an orbit within the locus extending from the Earth’s surface up to an altitude of 2,000 km...
, but a NASA study estimated that Maglifter sled launch
Rocket sled launch
A rocket sled launch is a method of launching space vehicles. A rail or maglev track and a rocket or jet booster is used to accelerate a sled holding a vehicle up an eastward facing mountain slope...
at that velocity could increase the payload of a conventional ELV
Expendable launch system
An expendable launch system is a launch system that uses an expendable launch vehicle to carry a payload into space. The vehicles used in expendable launch systems are designed to be used only once , and their components are not recovered for re-use after launch...
rocket
Rocket
A rocket is a missile, spacecraft, aircraft or other vehicle which obtains thrust from a rocket engine. In all rockets, the exhaust is formed entirely from propellants carried within the rocket before use. Rocket engines work by action and reaction...
by 80% when also having the track go up a 3000-meter mountain.
Forms of ground launch limited to a given maximum acceleration (such as due to human g-force
G-force
The g-force associated with an object is its acceleration relative to free-fall. This acceleration experienced by an object is due to the vector sum of non-gravitational forces acting on an object free to move. The accelerations that are not produced by gravity are termed proper accelerations, and...
tolerances if intended to carry passengers) have the corresponding minimum launcher length scale not linearly but with velocity squared. Tethers can have even more non-linear, exponential scaling. The tether-to-payload mass ratio of a space tether
Space tether
Space tethers are cables, usually long and very strong, which can be used for propulsion, stabilization, or maintaining the formation of space systems by determining the trajectory of spacecraft and payloads...
would be around 1:1 at a tip velocity 60% of its characteristic velocity but becomes more than 1000:1 at a tip velocity 240% of its characteristic velocity. For instance, for anticipated practicality and a moderate mass ratio with current materials, the HASTOL concept would have the first half (4 km/s) of velocity to orbit be provided by other means than the tether itself.
Combining multiple technologies would in itself be an increase to complexity and development challenges, but reducing the performance requirements of a given subsystem may allow reduction in its individual complexity or cost. For instance, the number of parts in a liquid-fueled rocket engine may be two orders of magnitude less if pressure-fed rather than pump-fed if its delta-v
Delta-v
In astrodynamics a Δv or delta-v is a scalar which takes units of speed. It is a measure of the amount of "effort" that is needed to change from one trajectory to another by making an orbital maneuver....
requirements are limited enough to make the weight penalty of such be a practical option, or a high-velocity ground launcher may be able to use a relatively moderate performance and inexpensive solid fuel or hybrid
Hybrid rocket
A hybrid rocket is a rocket with a rocket motor which uses propellants in two different states of matter - one solid and the other either gas or liquid. The Hybrid rocket concept can be traced back at least 75 years....
small motor on its projectile. Assist by non-rocket methods may compensate against the weight penalty of making an orbital rocket reusable
Reusable launch system
A reusable launch system is a launch system which is capable of launching a launch vehicle into space more than once. This contrasts with expendable launch systems, where each launch vehicle is launched once and then discarded.No true orbital reusable launch system is currently in use. The...
. Though suborbital, the first private manned spaceship, SpaceShipOne had reduced rocket performance requirements due to being a combined system with its air launch
Air launch
Air launching is the practice of dropping a parasite aircraft, rocket, or missile from a mothership. The parasite aircraft or missile is usually tucked under the wing of the larger mothership and then "dropped" from underneath the wing while in flight...
.
See also
- Hopper (spacecraft)Hopper (spacecraft)Hopper was a proposed European Space Agency orbital and reusable launch vehicle. The shuttle prototype spaceplane was one of several proposals for a European reusable launch vehicle planned to cheaply ferry satellites into orbit by 2015...
- Orbital airshipOrbital airshipThe orbital airship, also called the space blimp, is a proposed space transportation system that carries payloads to and from low Earth orbit...
- Air launch to orbitAir launch to orbitAir launch to orbit is the method of launching rocket launch vehicles at altitude from a horizontal-takeoff turbojet aircraft, either subsonic or supersonic...
- Comparison of orbital launch systemsComparison of orbital launch systemsThis page exposes the full list of orbital launch systems. For the short simple list of launchers families, see Comparison of orbital launchers families....
External links
- Canonical List of Space Transportation and Engineering Methods
- Earth-to-Orbit Transportation Bibliography, an extensive publication about novel methods of Earth-to-orbit transportation