Tier One - AbsoluteAstronomy.com

Scaled Composites

Scaled Composites is an aerospace company founded by Burt Rutan and currently owned by Northrop Grumman that is located at the Mojave Spaceport, Mojave, California, United States...

' program of suborbital human spaceflight

Human spaceflight

Human spaceflight is spaceflight with humans on the spacecraft. When a spacecraft is manned, it can be piloted directly, as opposed to machine or robotic space probes and remotely-controlled satellites....

using the reusable spacecraft

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...

SpaceShipOne and its launcher White Knight. The craft was designed by Burt Rutan

Burt Rutan

Elbert Leander "Burt" Rutan is an American aerospace engineer noted for his originality in designing light, strong, unusual-looking, energy-efficient aircraft...

, and the project is funded 20 million US Dollars by Paul Allen

Paul Allen

Paul Gardner Allen is an American business magnate, investor, and philanthropist. Allen co-founded Microsoft with Bill Gates...

. In 2004 it made the first privately funded human spaceflight

SpaceShipOne flight 15P

-Flight profile:All times are in PDT, which is seven hours behind UTC. This was the local civil time at the spaceport on the day of the flight. All measurements are first stated in the U.S...

and won the 10 million US Dollars Ansari X Prize

Ansari X Prize

The Ansari X Prize was a space competition in which the X Prize Foundation offered a US$10,000,000 prize for the first non-government organization to launch a reusable manned spacecraft into space twice within two weeks...

for the first non-governmental reusable manned spacecraft.

The objective of the project is to develop technology for low-cost routine access to space. Tier One is not itself intended to carry paying passengers, but it is envisioned that there will be commercial spinoffs, initially in 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...

. The company Mojave Aerospace Ventures

Mojave Aerospace Ventures

Mojave Aerospace Ventures is a company founded by Paul Allen and Burt Rutan to handle the commercial spinoffs from the Tier One project. It owns the intellectual property arising from Tier One, and it is in turn owned by Paul Allen and Burt Rutan...

was formed to manage commercial exploitation of the technology. A deal with Virgin Galactic

Virgin Galactic

Virgin Galactic is a company within Richard Branson's Virgin Group which plans to provide sub-orbital spaceflights to the paying public, along with suborbital space science missions and orbital launches of small satellites...

could see routine space tourism, using a spacecraft based on Tier One technology, starting as soon as 2011.

Design

The design concept is to 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 three-person piloted spacecraft which climbs to slightly above 100 km (62.1 mi) altitude using a hybrid rocket

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....

motor and then glides to the ground and lands horizontally. Scaled Composites lists the following components of the program:

launch aircraft (White Knight)
three-seater human-rated spacecraft (SpaceShipOne)
hybrid rocket
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....

propulsion system
mobile propulsion test facility
flight simulator
Flight simulator
A flight simulator is a device that artificially re-creates aircraft flight and various aspects of the flight environment. This includes the equations that govern how aircraft fly, how they react to applications of their controls and other aircraft systems, and how they react to the external...
inertial-nav flight director
mobile mission control center
spacecraft systems
pilot training program
flight test program

Spacecraft

Tier One's spacecraft, Scaled Composites model 316, known as SpaceShipOne, is a 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...

designed to:

carry three humans (one of them a pilot) in a sea-level pressurized cabin
be propelled by 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...

from an altitude of 15 km (9.3 mi) to in excess of 100 km (62.1 mi)
reenter atmosphere and shed kinetic energy in an aerodynamically stable configuration
glide transonically and subsonically
land horizontally on a standard runway
Runway
According to ICAO a runway is a "defined rectangular area on a land aerodrome prepared for the landing and take-off of aircraft." Runways may be a man-made surface or a natural surface .- Orientation and dimensions :Runways are named by a number between 01 and 36, which is generally one tenth...

The fuselage is cigar-shaped, with an overall diameter of about 1.52 m (5 ft). The main structure is of a graphite

Graphite

The mineral graphite is one of the allotropes of carbon. It was named by Abraham Gottlob Werner in 1789 from the Ancient Greek γράφω , "to draw/write", for its use in pencils, where it is commonly called lead . Unlike diamond , graphite is an electrical conductor, a semimetal...

/epoxy

Epoxy

Epoxy, also known as polyepoxide, is a thermosetting polymer formed from reaction of an epoxide "resin" with polyamine "hardener". Epoxy has a wide range of applications, including fiber-reinforced plastic materials and general purpose adhesives....

composite material

Composite material

Composite materials, often shortened to composites or called composition materials, are engineered or naturally occurring materials made from two or more constituent materials with significantly different physical or chemical properties which remain separate and distinct at the macroscopic or...

. From front to back, it contains the crew cabin, oxidizer tank, fuel casing, and rocket nozzle. The craft has short, wide wings, with a span of 5 m (16.4 ft) and a chord

Chord (aircraft)

In aeronautics, chord refers to the imaginary straight line joining the trailing edge and the center of curvature of the leading edge of the cross-section of an airfoil...

of 3 m (9.8 ft). There are large vertical tailbooms mounted on the end of each wing, with horizontal stabilisers protruding from the tailbooms. It has gear for horizontal landings.

The overall mass of the fully fueled craft is 3600 kg (7,936.6 lb), of which 2700 kg (5,952.5 lb) is taken by the fully loaded rocket motor. Empty mass of the spacecraft is 1200 kg (2,645.5 lb), including the 300 kg (661.4 lb) empty motor casing.

Originally the nozzle protruded from the back, but this turned out to be aerodynamically disadvantageous. In June 2004, between flights 14P

SpaceShipOne flight 14P

Flight 14P of SpaceShipOne was its third powered flight, which occurred on May 13, 2004. The pilot was Mike Melvill.SpaceShipOne was released from White Knight at an altitude of 46,000 feet and a speed of 120 knots . After ten seconds the rocket was lit, for a 55 second burn.At burn-out the...

and 15P

SpaceShipOne flight 15P

-Flight profile:All times are in PDT, which is seven hours behind UTC. This was the local civil time at the spaceport on the day of the flight. All measurements are first stated in the U.S...

, a fairing was added, smoothly extending the fuselage shape to meet the flared end of the nozzle. On flight 15P the new fairing overheated, due to being black on the inside and facing a hot, black nozzle. The fairing softened, and the lower part crumpled inwards during boost. Following that flight the interior of the fairing was painted white, and some small stiffening ribs were added.

The craft has a single unsteerable and unthrottleable hybrid rocket

Hybrid rocket

motor, a cold gas reaction control system

Reaction control system

A reaction control system is a subsystem of a spacecraft whose purpose is attitude control and steering by the use of thrusters. An RCS system is capable of providing small amounts of thrust in any desired direction or combination of directions. An RCS is also capable of providing torque to allow...

, and aerodynamic control surfaces. All can be controlled manually. See the separate section below concerning the rocket engine.

The reaction control system is the only way to control spacecraft attitude outside the atmosphere. It consists of three sets of thrusters: there are thrusters at each wingtip to control roll, at the top and bottom of the nose to control pitch, and at the sides of the fuselage to control yaw. All thrusters have redundant backups, so there are twelve thrusters in all.

The aerodynamic control surfaces are designed to operate in two distinct flight regimes, subsonic and supersonic. The supersonic flight regime is of primary interest during the boost phase of a flight, and the subsonic mode when gliding. There are separate upper and lower rudders, and elevon

Elevon

Elevons are aircraft control surfaces that combine the functions of the elevator and the aileron , hence the name. They are frequently used on tailless aircraft such as flying wings. An elevon that is not part of the main wing, but instead is a separate tail surface, is a stabilator...

s. These are controlled using aviation

Aviation

Aviation is the design, development, production, operation, and use of aircraft, especially heavier-than-air aircraft. Aviation is derived from avis, the Latin word for bird.-History:...

-style stick and pedals. In supersonic mode the trim tabs are controlled electrically, whereas the subsonic mode uses mechanical cable-and-rod linkage.

The wings can be pneumatically tilted forwards into an aerodynamically stable high-drag

Drag (physics)

In fluid dynamics, drag refers to forces which act on a solid object in the direction of the relative fluid flow velocity...

"feathered" shape. This removes most of the need to actively control attitude during the early part of reentry: Scaled Composites refer to this as "care-free reentry". One of the early test flights actually performed re-entry inverted, demonstrating the flexibility and inherent stability of Burt Rutan

Burt Rutan

Elbert Leander "Burt" Rutan is an American aerospace engineer noted for his originality in designing light, strong, unusual-looking, energy-efficient aircraft...

's "shuttlecock" design.

This feathered reentry mode is inherently far safer than the behaviour at similar speeds of the only comparable craft previously built, the Space Shuttle

Space Shuttle

The Space Shuttle was a manned orbital rocket and spacecraft system operated by NASA on 135 missions from 1981 to 2011. The system combined rocket launch, orbital spacecraft, and re-entry spaceplane with modular add-ons...

. The Shuttle undergoes enormous aerodynamic stresses and must be precisely steered in order to remain in a stable glide. (Although this is an interesting comparison of behaviour, it is not an entirely fair comparison of design concepts: the Shuttle starts reentry at much higher speed than SpaceShipOne, and so has some very different requirements.)

An early design called for a permanently shuttlecock

Shuttlecock

A shuttlecock, sometimes called a bird or birdie, is a high-drag projectile used in the sport of badminton. It has an open conical shape: the cone is formed from sixteen or so overlapping feathers, usually goose or duck and from the left wing only, embedded into a rounded cork base...

-like shape, with a ring of feather

Feather

Feathers are one of the epidermal growths that form the distinctive outer covering, or plumage, on birds and some non-avian theropod dinosaurs. They are considered the most complex integumentary structures found in vertebrates, and indeed a premier example of a complex evolutionary novelty. They...

-like stabilising fins. This would have made the spacecraft incapable of landing independently, requiring mid-air retrieval

Mid-air retrieval

Mid-air retrieval is a technique used in atmospheric reentry when the reentering vehicle is incapable of a satisfactory unassisted landing. The vehicle is slowed by means of parachutes, and then a specially-equipped aircraft matches the vehicle's trajectory and catches it in mid-air.This is a risky...

. This was deemed too risky, and the hybrid final design manages to incorporate the feathering capability into a craft that can land in a conventional manner. The tiltable rear sections of the wings and the tailbooms are collectively referred to as "the feather".

The landing gear consists of two widely separated main wheels and a nose skid. These are deployed using springs, assisted by gravity. Once deployed, they cannot be retracted inflight.

The spacecraft is incapable of independent takeoff from the ground. It requires a launch aircraft to carry it to launch altitude for an air launch

Air launch

.

The parts of the craft that experience the greatest heating, such as the leading edges of the wings, have about 6.5 kg (14.3 lb) of ablative thermal protection material applied. The main ingredient of this material was accidentally leaked to Air and Space. If it flew with no thermal protection, the spacecraft would survive reentry but would be damaged.

There is an acknowledged "known deficiency" with the spacecraft's aerodynamic design that makes it susceptible to roll

Flight dynamics

Flight dynamics is the science of air vehicle orientation and control in three dimensions. The three critical flight dynamics parameters are the angles of rotation in three dimensions about the vehicle's center of mass, known as pitch, roll and yaw .Aerospace engineers develop control systems for...

excursions. This has been seen on SpaceShipOne flight 15P

SpaceShipOne flight 15P

-Flight profile:All times are in PDT, which is seven hours behind UTC. This was the local civil time at the spaceport on the day of the flight. All measurements are first stated in the U.S...

where wind shear caused a large roll immediately after ignition, and SpaceShipOne flight 16P

SpaceShipOne flight 16P

Flight 16P of SpaceShipOne was a spaceflight in the Tier One program that took place on September 29, 2004. It was the first competitive flight in the Ansari X PRIZE competition to demonstrate a non-governmental reusable manned spacecraft, and is hence also referred to as the X1 flight...

where circumstances not yet fully understood caused multiple rapid rolls. This flaw is not considered dangerous, but in both of these flights led to the achievement of a much lower altitude than expected. The details of the flaw are not public.

Navigation

The core of the spacecraft avionics

Avionics

Avionics are electronic systems used on aircraft, artificial satellites and spacecraft.Avionic systems include communications, navigation, the display and management of multiple systems and the hundreds of systems that are fitted to aircraft to meet individual roles...

is the System Navigation Unit (SNU). Together with the Flight Director Display (FDD), it comprises the Flight Navigation Unit. The unit was developed jointly by Fundamental Technology Systems and Scaled Composites

Scaled Composites

Scaled Composites is an aerospace company founded by Burt Rutan and currently owned by Northrop Grumman that is located at the Mojave Spaceport, Mojave, California, United States...

.

The SNU is a GPS-based inertial navigation system, which processes spacecraft sensor data and subsystem health data. It downlinks telemetry data by radio

Radio

Radio is the transmission of signals through free space by modulation of electromagnetic waves with frequencies below those of visible light. Electromagnetic radiation travels by means of oscillating electromagnetic fields that pass through the air and the vacuum of space...

to mission control.

The FDD display data from the SNU on a colour LCD. It has several distinct display modes for different phases of flight, including the boost phase, coast, reentry, and gliding. The FDD is particularly important to the pilot during the boost and coast phase in order to "turn the corner" and null rates caused by asymmetric thrust. A mix of commercial and bespoke software is used in the FDD.

Cabin

The spacecraft cabin, designed to hold three humans, is shaped as a short cylinder, diameter 1.52 m (5 ft), with a pointed forward end. The pilot sits towards the front, and two passengers can be seated behind.

The cabin is pressurized, maintaining a sea level

Sea level

Mean sea level is a measure of the average height of the ocean's surface ; used as a standard in reckoning land elevation...

breathable atmosphere. Oxygen

Oxygen

Oxygen is the element with atomic number 8 and represented by the symbol O. Its name derives from the Greek roots ὀξύς and -γενής , because at the time of naming, it was mistakenly thought that all acids required oxygen in their composition...

is introduced to the cabin from a bottle, and carbon dioxide

Carbon dioxide

Carbon dioxide is a naturally occurring chemical compound composed of two oxygen atoms covalently bonded to a single carbon atom...

and water vapor are removed by absorbers. The occupants do not wear spacesuits or breathing masks, because the cabin has been designed to maintain pressure in the face of faults: all windows and seals are doubled.

The cabin has sixteen round double-pane windows, positioned to provide a view of the horizon at all stages of flight. The windows are small compared to the gaps between them, but there are sufficiently many for human occupants to patch together a moderately good view.

The nose section can be removed, and there is also a hatch below the rear windows on the left side. Crew ingress and egress is possible by either route.

Launch aircraft

Tier One's launch aircraft, Scaled Composites model 318, known as White Knight, is designed to take off and land horizontally and attain an altitude of about 15 km (9.3 mi), all while carrying the Tier One spacecraft in a parasite aircraft

Parasite aircraft

A parasite aircraft is a component of a composite aircraft which is carried, and air launched by, a mother ship aircraft.The first use for parasite aircraft was in 1916, when the British used a Bristol Scout, flying from a Felixstowe Porte Baby, a giant flying boat of its time. This eventually...

configuration. Its propulsion is by twin turbojets: afterburning J-85-GE-5 engines, rated at 15.6 kN (15,600 N) of thrust each.

It has the same cabin, avionics

Avionics

, and trim system as SpaceShipOne. This means it can flight-qualify almost all components of SpaceShipOne. It also has a high thrust-to-weight ratio and large speed brakes. These features combined allow it to be used as a high-fidelity moving platform flight simulator

Flight simulator

A flight simulator is a device that artificially re-creates aircraft flight and various aspects of the flight environment. This includes the equations that govern how aircraft fly, how they react to applications of their controls and other aircraft systems, and how they react to the external...

for SpaceShipOne. White Knight is also equipped with a trim system which (when activated) causes it to have the same glide profile as SpaceShipOne; this allows the pilots to practice for landing SpaceShipOne. The same pilots fly White Knight as fly SpaceShipOne.

The aircraft's distinctive shape features long, thin wings, in a flattened "W" shape, with a wingspan of 25 m (82 ft), dual tailplanes, and four wheels (front and rear at each side). The rear wheels retract, but the front ones, which are steerable, are permanently deployed, with small fairings, referred to as "spats", in front. Another way to look at the overall shape is as two conventional planes, with very thin fuselages, side-by-side and joined together at their wingtips, with the cockpit and engines mounted at the point of joining.

Although White Knight was developed for certain roles in the Tier One program, it is a very capable aircraft in its own right. Scaled Composites describe it as a "high-altitude research aircraft".

Hybrid rocket motor

Tier One uses a hybrid rocket

Hybrid rocket

motor supplied by SpaceDev

SpaceDev

SpaceDev, a part of the "Space Systems Business" of Sierra Nevada Corporation, is prominent for its spaceflight and microsatellite work. It designed and built the hybrid rocket motors for Paul Allen's Tier One suborbital SpaceShipOne space program operated by Scaled Composites...

, with solid hydroxyl-terminated polybutadiene

Hydroxyl-terminated polybutadiene

Hydroxyl-terminated polybutadiene is a polymer of butadiene terminated at each end with a hydroxyl functional group. It reacts with diisocyanate to form polyurethane, a stable and easily stored synthetic material....

(HTPB, or rubber

Rubber

Natural rubber, also called India rubber or caoutchouc, is an elastomer that was originally derived from latex, a milky colloid produced by some plants. The plants would be ‘tapped’, that is, an incision made into the bark of the tree and the sticky, milk colored latex sap collected and refined...

) fuel

Fuel

Fuel is any material that stores energy that can later be extracted to perform mechanical work in a controlled manner. Most fuels used by humans undergo combustion, a redox reaction in which a combustible substance releases energy after it ignites and reacts with the oxygen in the air...

and liquid nitrous oxide

Nitrous oxide

Nitrous oxide, commonly known as laughing gas or sweet air, is a chemical compound with the formula . It is an oxide of nitrogen. At room temperature, it is a colorless non-flammable gas, with a slightly sweet odor and taste. It is used in surgery and dentistry for its anesthetic and analgesic...

oxidiser. It generates 88 kN (88,000 N) of thrust, and can burn for about 87 s.

The physical layout of the engine is novel. The oxidiser tank is a primary structural component, and is the only part of the engine that is structurally connected to the spacecraft: the tank is in fact an integral part of the spacecraft fuselage. The tank is a short cylinder

Cylinder (geometry)

A cylinder is one of the most basic curvilinear geometric shapes, the surface formed by the points at a fixed distance from a given line segment, the axis of the cylinder. The solid enclosed by this surface and by two planes perpendicular to the axis is also called a cylinder...

of diameter approximately 1.52 m (5 ft), with domed ends, and is the forwardmost part of the engine. The fuel casing is a narrow cylinder cantilever

Cantilever

A cantilever is a beam anchored at only one end. The beam carries the load to the support where it is resisted by moment and shear stress. Cantilever construction allows for overhanging structures without external bracing. Cantilevers can also be constructed with trusses or slabs.This is in...

ed to the tank, pointing backwards. The cantilevered design means that a variety of motor sizes can be accommodated without changing the interface or other components. The nozzle

Nozzle

A nozzle is a device designed to control the direction or characteristics of a fluid flow as it exits an enclosed chamber or pipe via an orifice....

is a simple extension of the fuel casing; the casing and nozzle are actually a single component, referred to as the CTN (case, throat, and nozzle). Burt Rutan

Burt Rutan

Elbert Leander "Burt" Rutan is an American aerospace engineer noted for his originality in designing light, strong, unusual-looking, energy-efficient aircraft...

has applied for a patent

Patent

A patent is a form of intellectual property. It consists of a set of exclusive rights granted by a sovereign state to an inventor or their assignee for a limited period of time in exchange for the public disclosure of an invention....

on this engine configuration.

There is considerable use of composite material

Composite material

s in the engine design. The oxidiser tank consists of a composite liner with graphite

Graphite

/epoxy

Epoxy

over-wrap and titanium

Titanium

Titanium is a chemical element with the symbol Ti and atomic number 22. It has a low density and is a strong, lustrous, corrosion-resistant transition metal with a silver color....

interface flanges. The CTN uses a high-temperature composite insulator with a graphite/epoxy structure. Incorporating the solid fuel (and hence the main part of the engine) and the ablative

Ablation

Ablation is removal of material from the surface of an object by vaporization, chipping, or other erosive processes. This occurs in spaceflight during ascent and atmospheric reentry, glaciology, medicine, and passive fire protection.-Spaceflight:...

nozzle into this single bonded component minimizes the possible leak paths.

The oxidiser tank and CTN are bolted together at the main valve bulkhead, which is integrated into the tank. There are O-ring

O-ring

An O-ring, also known as a packing, or a toric joint, is a mechanical gasket in the shape of a torus; it is a loop of elastomer with a disc-shaped cross-section, designed to be seated in a groove and compressed during assembly between two or more parts, creating a seal at the interface.The O-ring...

s at the interface to prevent leakage; this is the main potential leak path in the engine. The ignition system, main control valve, and injector are mounted on the valve bulkhead, inside the tank. Slosh baffles are also mounted on this bulkhead. Because the oxidiser is stored under pressure, no pump is required.

The tank liner and the fuel casing are built in-house by Scaled Composites

Scaled Composites

Scaled Composites is an aerospace company founded by Burt Rutan and currently owned by Northrop Grumman that is located at the Mojave Spaceport, Mojave, California, United States...

. The tank over-wrap is supplied by Thiokol

Thiokol

Thiokol is a U.S. corporation concerned initially with rubber and related chemicals, and later with rocket and missile propulsion systems...

. The ablative nozzle is supplied by AAE Aerospace. The oxidiser fill, vent, and dump system is supplied by Environmental Aeroscience Corporation. The remaining components — the ignition system, main control valve, injector, tank bulkheads, electronic controls, and solid fuel casting — are supplied by SpaceDev

SpaceDev

.

The CTN must be replaced between firings. This is the only part of the craft, other than the fuel and oxidiser themselves, that must be replaced.

The solid fuel is cast with four holes. This has the disadvantage that it is possible for chunks of fuel between the holes to become detached during a burn and obstruct the flow of oxidiser and exhaust. Such situations tend to rapidly self-correct.

The oxidiser tank is filled and vented through its forward bulkhead

Bulkhead (partition)

A bulkhead is an upright wall within the hull of a ship or within the fuselage of an airplane. Other kinds of partition elements within a ship are decks and deckheads.-Etymology:...

, on the opposite side of the tank from the fuel and the rest of the engine. This improves safety. It is filled to a pressure of 4.8 MPa (696.2 psi) at room temperature

Room temperature

-Comfort levels:The American Society of Heating, Refrigerating and Air-Conditioning Engineers has listings for suggested temperatures and air flow rates in different types of buildings and different environmental circumstances. For example, a single office in a building has an occupancy ratio per...

.

The nozzle has an expansion ratio of 25:1, which is optimised for the upper part of the atmosphere. A different nozzle, with an expansion ratio of 10:1, is used for test firing on the ground. The nozzles are black on the outside, but for aerodynamic testing, red dummy nozzles are used instead.

The rocket is not throttleable. Once lit, the burn can be aborted, but the power output cannot otherwise be controlled. The thrust in fact varies, for two reasons. Firstly, as the pressure in the oxidiser tank decreases, the flow rate reduces, reducing thrust. Secondly, in the late stages of a burn the oxidiser tank contains a mixture of liquid and gaseous oxidiser, and the power output of the engine varies greatly depending on whether it's using liquid or gaseous oxidiser at a particular moment. (The liquid, being far denser, allows a greater burn rate.)

Both the fuel and oxidiser can be stored without special precautions, and they do not burn when brought together without a significant source of heat. This makes the rocket far safer than conventional liquid or solid rockets. It is also relatively non-polluting: the combustion products are water vapor, carbon dioxide, hydrogen, nitrogen, and some carbon monoxide.

The engine was upgraded in September 2004, between flights 15P

SpaceShipOne flight 15P

-Flight profile:All times are in PDT, which is seven hours behind UTC. This was the local civil time at the spaceport on the day of the flight. All measurements are first stated in the U.S...

and 16P

SpaceShipOne flight 16P

. The upgrade increased the oxidiser tank size, to provide greater thrust in the early part of the burn, allow a longer burn, and delay the onset of the variable thrust phase at the end of the burn. Prior to the upgrade the engine generated 76 kN (76,000 N) of thrust and could burn for 76 s. After the upgrade it was capable of 88 kN (88,000 N) thrust and an 87 s burn.

Flight profile

SpaceShipOne takes off from the ground, attached to White Knight in a parasite

Parasite aircraft

configuration, and under White Knight's power. The combination of SpaceShipOne and White Knight can take off, land, and fly under jet power to high altitude. A captive carry flight is one where the two craft land together without launching SpaceShipOne; this is one of the main abort modes available.

For launch, the combined craft flies to an altitude of around 14 km (8.7 mi), which takes about an hour. SpaceShipOne is then drop-released, and briefly glides unpowered. Rocket ignition may take place immediately, or may be delayed. If the rocket is never lit then SpaceShipOne can glide down to the ground. This is another major abort mode, in addition to being flown deliberately in glide tests.

The rocket engine is ignited while the spacecraft is gliding. Once under power, it is raised into a 65° climb, which is further steepened in the higher part of the trajectory. The maximum possible acceleration is about 4 g

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...

.

By the end of the burn the craft is flying upwards at some multiple of the speed of sound, up to about 900 m/s and Mach

Mach number

Mach number is the speed of an object moving through air, or any other fluid substance, divided by the speed of sound as it is in that substance for its particular physical conditions, including those of temperature and pressure...

3.5, and it continues to coast upwards unpowered (i.e. ballistically

Ballistics

Ballistics is the science of mechanics that deals with the flight, behavior, and effects of projectiles, especially bullets, gravity bombs, rockets, or the like; the science or art of designing and accelerating projectiles so as to achieve a desired performance.A ballistic body is a body which is...

). If the burn was long enough then it will exceed an altitude of 100 km (62.1 mi), at which height the atmosphere presents no appreciable resistance, and the craft experiences free fall

Weightlessness

Weightlessness is the condition that exists for an object or person when they experience little or no acceleration except the acceleration that defines their inertial trajectory, or the trajectory of pure free-fall...

for a few minutes.

While at apogee the wings are reconfigured into high-drag mode. As the craft falls back it achieves high speeds comparable to those achieved on the way up; when it subsequently reenters the atmosphere it decelerates violently, up to about 5 g. At some altitude between 10 km (6.2 mi) and 20 km (12.4 mi) it reconfigures into low-drag glider mode, and glides down to a landing in about 20 minutes.

White Knight takes longer to descend, and typically lands a few minutes after SpaceShipOne.

Mission control

In addition to an office-based mission control, Tier One has a mobile mission control center. This is relatively small, built into a large road-going truck. It bears the Scaled Composites logo, but no other overt indication of its link to Tier One. The vehicle performs a combination of support functions:

telemetry
Telemetry
Telemetry is a technology that allows measurements to be made at a distance, usually via radio wave transmission and reception of the information. The word is derived from Greek roots: tele = remote, and metron = measure...

monitoring and recording
telecommunications
auxiliary environment control for White Knight and SpaceShipOne

This control center is used to support both rocket motor ground tests and all flight tests of White Knight and SpaceShipOne. Its primary function is to monitor and record test data, and to this end it is equipped with computers and radio communication gear. SpaceShipOne's avionics

Avionics

displays are duplicated in mission control. Telemetry data is received on a Data Reduction System (DRS), which automatically directs radio antennas

Antenna (radio)

An antenna is an electrical device which converts electric currents into radio waves, and vice versa. It is usually used with a radio transmitter or radio receiver...

to point at the craft being monitored. The telemetry system has a range of about 280 km (174 mi).

The control center is equipped to communicate with Scaled Composites' offices, as well as the aircraft and spacecraft.

The control center maintains a temperature-controlled atmosphere for its staff, and can be hooked up to provide temperature control for the White Knight and SpaceShipOne cabins. The physical structure of mission control also provides easier access to the White Knight cabin.

Nitrous oxide delivery

Unlike the solid fuel, the nitrous oxide

Nitrous oxide

oxidiser is handled as a bulk commodity and pumped into the spacecraft's oxidiser tank in the field. Tier One therefore has a mobile delivery system for nitrous oxide, which they call MONODS (mobile nitrous oxide delivery system).

MONODS is built on an open trailer, which can be carried by road in conventional manner. It consists principally of a 6.5 m³ (229.5 cu ft) tank, a temperature control unit, and a generator to power the temperature control unit. The nitrous oxide is stored at room temperature, at a pressure of 4.8 MPa (696.2 psi).

MONODS is refilled from a commercial supplier, which uses 50 m³ (1,765.7 cu ft) tankers and delivers the nitrous oxide at about -17 °C and 2 MPa (290.1 psi). MONODS heats the nitrous oxide to room temperature, increasing its pressure.

Propulsion testing

Tier One has a mobile thrust test stand, known as the Test Stand Trailer (TST). The advantage of making it mobile is that all the mounting and instrumentation work can be done in the hangar, so that at the test site all that needs to be done is to fill the oxidiser tank (from MONODS) and conduct the firing.

The test stand replicates the essential structural components of the spacecraft. It has an oxidiser tank and associated fittings identical to the one used in flight. This means that the motor test also automatically performs appropriate vibration

Oscillation

Oscillation is the repetitive variation, typically in time, of some measure about a central value or between two or more different states. Familiar examples include a swinging pendulum and AC power. The term vibration is sometimes used more narrowly to mean a mechanical oscillation but sometimes...

, stress

Stress (physics)

In continuum mechanics, stress is a measure of the internal forces acting within a deformable body. Quantitatively, it is a measure of the average force per unit area of a surface within the body on which internal forces act. These internal forces are a reaction to external forces applied on the body...

, and heat

Heat

In physics and thermodynamics, heat is energy transferred from one body, region, or thermodynamic system to another due to thermal contact or thermal radiation when the systems are at different temperatures. It is often described as one of the fundamental processes of energy transfer between...

tests of the spacecraft structure. The crew cabin, however, is not replicated.

For ground-based thrust tests, a rocket nozzle

Nozzle

A nozzle is a device designed to control the direction or characteristics of a fluid flow as it exits an enclosed chamber or pipe via an orifice....

with an expansion ratio of 10:1 is used, differing from the 25:1 nozzle used at altitude during actual flight.

The test stand is instrumented to record not only thrust but also side force and temperature and strain experienced by components. Data is recorded on a computer in a bunker at the test site. The data acquisition computer is remotely controlled from mission control.

Flight simulator

The SpaceShipOne flight simulator

Flight simulator

consists of a simulator program and a cockpit.

The flight simulator program aims to accurately simulate SpaceShipOne's behaviour under any circumstances and in all phases of flight. Rather than having a model of SpaceShipOne's overall flight behaviour, it uses computational fluid dynamics

Computational fluid dynamics

Computational fluid dynamics, usually abbreviated as CFD, is a branch of fluid mechanics that uses numerical methods and algorithms to solve and analyze problems that involve fluid flows. Computers are used to perform the calculations required to simulate the interaction of liquids and gases with...

to model the air around the craft. It calculates the aerodynamic and other forces operating on the craft, taking into account the positions of its control surfaces. This simulation is based on the computer modelling that was used during the design process and refined using data from flight tests. This yields a highly accurate image of craft behaviour, even in unanticipated modes of flight. (This is one of the first modern aircraft to be designed without wind tunnel

Wind tunnel

A wind tunnel is a research tool used in aerodynamic research to study the effects of air moving past solid objects.-Theory of operation:Wind tunnels were first proposed as a means of studying vehicles in free flight...

testing.)

The cockpit replica is on a static base, and so cannot accurately reproduce the equilibrioceptive and accelerative aspects of flight. However, White Knight is equipped to operate as a high-fidelity moving-base simulator; see White Knight's section above. The simulator cockpit is an accurate copy of the SpaceShipOne cabin, including its avionics

Avionics

. It is the system of pilot plus avionics, not just the pilot, that is being simulated to. The flight simulator program drives the sensor inputs that are used by the avionics, and also drives twelve display computers which use commercial graphics software to generate high-resolution images of the outside view for the pilot. These views appear on eleven monitors and one projector screen. Stick force feedback is not simulated in real time.

Ground-based flight simulation is not only used for pilot training. It is also used to train ground crew, develop procedures, and test the avionics software

Avionics software

Avionics software is embedded software with legally mandated safety and reliability concerns used in avionics. The main difference between avionic software and conventional embedded software is that the development process is required by law and is optimized for safety.It is claimed that the...

and hardware.

History and status

According to Scaled Composites, the concept for the program originated in April 1996, preliminary development began in 1999, and full development began in April 2001. It was initially kept secret, even after White Knight first flew on August 1, 2002. The program was announced to the public on April 18, 2003, when the program was ready to flight-test SpaceShipOne. Its first flight test, SpaceShipOne flight 01C, took place on May 20, 2003.

After months of glide tests, the first powered flight, SpaceShipOne flight 11P

SpaceShipOne flight 11P

Flight 11P of SpaceShipOne was its eighth independent flight, its first powered flight, and the first privately-funded manned flight to reach supersonic speeds. It occurred on December 17, 2003....

, was made on December 17, 2003. Further powered tests followed, reaching increasing altitudes, culminating on June 21, 2004 with the first privately funded human spaceflight, SpaceShipOne flight 15P

SpaceShipOne flight 15P

-Flight profile:All times are in PDT, which is seven hours behind UTC. This was the local civil time at the spaceport on the day of the flight. All measurements are first stated in the U.S...

. Ansari X Prize

Ansari X Prize

competitive flights followed. SpaceShipOne flight 16P

SpaceShipOne flight 16P

on September 29, 2004 and SpaceShipOne flight 17P

SpaceShipOne flight 17P

Flight 17P of SpaceShipOne was a spaceflight in the Tier One program that took place on October 4, 2004. It was the second competitive flight in the Ansari X Prize competition to demonstrate a non-governmental reusable manned spacecraft, and is hence also referred to as the X2 flight...

on October 4, 2004 were successful competitive flights, winning the X Prize.

The program will continue making test flights, to develop the technology further, in support of the development of successor spacecraft such as the Virgin SpaceShip. The program has ruled out carrying scientific payloads, despite several requests.

General characteristics

Crew: one pilot
Length: 5 m (16.4 ft)
Wingspan: 5 m (16.4 ft)
Height:
Core diameter: 1.52 m (5 ft)
Wing area: 15 m² (17.9 sq yd)
Empty: 1200 kg (2,645.5 lb)
Loaded: 3600 kg (7,936.6 lb)
Maximum takeoff:
Powerplant:

1x N2O/HTPB SpaceDev Hybrid Solid rocket engine

73.5 kN (73,500 N) thrust.

Isp
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 ,...

: 250 s (2.45 kN·s/kg)

burn time: 87 seconds

Performance

Maximum speed: Mach 3.09 3518 km/h (2,186 mph)
Range: 65 km (40.4 mi)
Service ceiling: 112000 m (367,454.1 ft)
Rate of climb: 25,000 m/min (82 021 ft/min)
Wing loading: 240 kg/m² at release, 80 kg/m² at burnout
Thrust-to-Weight: 20 N/kg at ignition

Funding

The costs of development, construction, and operation of Tier One, although not publicly released, are estimated to be in the range of 20 million to 30 million US dollars, roughly two to three times the value of the Ansari X Prize

Ansari X Prize

award. The sole sponsor, initially secret, was revealed to be Paul Allen

Paul Allen

Paul Gardner Allen is an American business magnate, investor, and philanthropist. Allen co-founded Microsoft with Bill Gates...

, a co-founder of Microsoft

Microsoft

Microsoft Corporation is an American public multinational corporation headquartered in Redmond, Washington, USA that develops, manufactures, licenses, and supports a wide range of products and services predominantly related to computing through its various product divisions...

and the fifth richest person in the world. The revelation, on December 17, 2003, the same day as the program's first powered flight test, followed speculation that Allen was involved.

Some commentators have drawn comparisons between the relative inexpense of the Tier One program and the high cost of the Space Shuttle

Space Shuttle

program, though the technological difficulties of the two programs are completely different. SpaceShipOne, because it flies suborbitally, does not need to reach the high speeds of the Space Shuttle (Mach

Mach number

3 vs. Mach 25), nor the same altitude (100 km (62.1 mi) suborbital vs. 400 km (248.5 mi) orbit). SpaceShipOne also does not carry the same crew (3 members vs. 7) or payload (negligible vs. 25 tons), and makes much shorter flights (a few minutes vs. several days). The SpaceShipOne program is a technical achievement more on a par with the X-15

North American X-15

The North American X-15 rocket-powered aircraft/spaceplane was part of the X-series of experimental aircraft, initiated with the Bell X-1, that were made for the USAAF/USAF, NACA/NASA, and the USN. The X-15 set speed and altitude records in the early 1960s, reaching the edge of outer space and...

than the Shuttle.

Inflation adjusted comparisons of the SpaceShipOne program with that of the X-15 budget, indicate that the Tier One program cost 1/100th that of the X-15 program, although the three X-15 aircraft made almost 200 test flights in their entire test program, typically exploring hypersonic flight between mach 4-7. Only a few dozen X-15 flights specificially sought to reach peak altitudes rather than achieve top speeds, though only two flights ever reached altitudes near those achieved by SpaceShipOne. On the other hand, the Tier One project also paid for construction of the White Knight mothership within its budget, while NASA had nearly free use of a pre-existing USAF B-52 bomber modified to perform drop tests of experimental aircraft of many kinds (currently in use for PegasusXL launches).

Publicity

Tier One was initially developed secretly, as is Scaled Composites' policy with new programs. On April 18, 2003 the program was publicly announced, and SpaceShipOne and White Knight were demonstrated to the media at a rollout attended by between 550 and 600 people. Media interest was so intense that what had been intended as a Family and Friends Day on April 24, 2003 was turned into a second media day.

Scaled Composites again courted publicity by announcing in advance the final test flight, SpaceShipOne flight 15P

SpaceShipOne flight 15P

-Flight profile:All times are in PDT, which is seven hours behind UTC. This was the local civil time at the spaceport on the day of the flight. All measurements are first stated in the U.S...

, intended to be the program's first spaceflight. About 11,000 people went to Mojave Spaceport

Mojave Spaceport

thumb|right|235px|A retired [[Boeing 767-200]] that flew for [[Ansett Australia]] being cut open for scrap at Mojave AirportThe Mojave Air and Space Port , also known as the Civilian Aerospace Test Center, is located in Mojave, California, at an elevation of...

to watch the flight, which was also televised

Television

Television is a telecommunication medium for transmitting and receiving moving images that can be monochrome or colored, with accompanying sound...

. The flight was run as an airshow

Airshow

An air show is an event at which aviators display their flying skills and the capabilities of their aircraft to spectators in aerobatics. Air shows without aerobatic displays, having only aircraft displayed parked on the ground, are called "static air shows"....

, with both the principal craft and the chase plane

Chase plane

A chase plane is an aircraft that "chases" another aircraft, a spacecraft or a rocket during flight. Safety can be one function of a chase plane; others are to photo or video the target vehicle, or to collect engineering data from it...

s making takeoffs and landings in front of the crowd, and celebratory flybys when the test succeeded. The flight was not only a technical success but also an unqualified popular success, triggering intense public interest in spaceflight.

Scaled Composites unsurprisingly remains very media-friendly with respect to Tier One, and more public spectacles are to be expected.

Future

The program name "Tier One" raises the question of what Tier Two will be.

In The Space Review
The Space Review
The Space Review is a free online publication, published weekly with in-depth articles, essays, commentary and reviews on space exploration and development. It was founded in February 2003 by Jeff Foust, the current editor, publisher and regular writer....

on June 21, 2004 (the day of Tier One's first spaceflight), Rutan was quoted as stating "The spaceship is model number 316 and the White Knight is model number 318. I will be making a presentation very quick of a model number 346.". Whether this refers to a prototype orbital craft, a suborbital tour bus, or some other concept remains to be seen.

In 2004 Rutan suggested that a ten-passenger suborbital spacecraft would make a profitable tour bus. On September 27, 2004, entrepreneur

Entrepreneur

An entrepreneur is an owner or manager of a business enterprise who makes money through risk and initiative.The term was originally a loanword from French and was first defined by the Irish-French economist Richard Cantillon. Entrepreneur in English is a term applied to a person who is willing to...

Sir Richard Branson announced a deal with Mojave Aerospace Ventures

Mojave Aerospace Ventures

to carry paying passengers on suborbital tourist flights, using a scaled-up version of SpaceShipOne, possibly beginning service in 2008. That same year, Burt Rutan also said "we're heading for orbit sooner than you think".

During an interview in the documentary Black Sky: The Race for Space, Rutan stated that Tier One will cover suborbital flights, Tier Two will cover orbital flights, and Tier Three will cover flights beyond Earth's orbit (including flights to the moon and other planets). In the same documentary he displayed designs for an orbital craft based on SpaceShipOne, which had a rocket roughly twice SpaceShipOne's length mounted to the ship's rear.

Commercial aspects

The stated objective of the Tier One program is to demonstrate suborbital human spaceflight operations at low cost. Before Burt Rutan began considering this project, there were three major barriers to the goal of affordable suborbital spaceflight:

the dangers and costs of liquid propulsion fuels (they explode);
the uncontrollable nature of solid fuel rocket motors (you can't turn them off);
the difficulties in getting back without burning up in the atmosphere.

Rutan's design appears to provide a cost-effective solution to all three issues.

Tier One itself is not intended to carry paying passengers, and US Government permits would be required if it did intend to do so. It is a technology testbed, and it is expressly intended that the technology developed in the program will later be used in commercial spaceflights. To that end, Paul Allen and Burt Rutan created a company, Mojave Aerospace Ventures

Mojave Aerospace Ventures

, which owns the project's intellectual property

Intellectual property

Intellectual property is a term referring to a number of distinct types of creations of the mind for which a set of exclusive rights are recognized—and the corresponding fields of law...

and will manage all commercial exploitation of it.

Scaled Composites initially expressed a hope that by about 2013 it would be possible for members of the public to experience a suborbital flight for about the price of a luxury cruise. On September 25, 2004 a deal was struck with Virgin Galactic

Virgin Galactic

to develop the Virgin SpaceShip based on a scaled-up version of SpaceShipOne. These spacecraft will be built by The Spaceship Company

The Spaceship Company

The Spaceship Company is a spacecraft manufacturing company formed by Burt Rutan and Richard Branson in mid-2005, jointly owned by Virgin Group and Scaled Composites, which will own the technology created by Scaled for Virgin Galactic's Virgin SpaceShip program...

External links

Tier One home page at Scaled Composites' website
The Space Review article "Prelude to history?" featuring Rutan quote about Model 346
The Space Review article "The future starts here"
Aerospace America article "SpaceShipOne: Riding a White Knight to Space", with several technical details
SPACE.com article "SpaceShipOne Rocket Engine Gets an Upgrade"
The Register article "Virgin to offer space flights"
BBC News article "'No experiments' for SpaceShipOne"
Why SpaceShipOne Never Did, Never Will, And None Of Its Direct Descendants Ever Will, Orbit The Earth (by Karen Pease)

The source of this article is wikipedia, the free encyclopedia. The text of this article is licensed under the GFDL.