Crew Return Vehicle
Encyclopedia
The Crew Return Vehicle (CRV), sometimes referred to as the Assured Crew Return Vehicle (ACRV), is the proposed lifeboat
Lifeboat (shipboard)
A lifeboat is a small, rigid or inflatable watercraft carried for emergency evacuation in the event of a disaster aboard ship. In the military, a lifeboat may be referred to as a whaleboat, dinghy, or gig. The ship's tenders of cruise ships often double as lifeboats. Recreational sailors sometimes...

 or escape module for the International Space Station
International Space Station
The International Space Station is a habitable, artificial satellite in low Earth orbit. The ISS follows the Salyut, Almaz, Cosmos, Skylab, and Mir space stations, as the 11th space station launched, not including the Genesis I and II prototypes...

 (ISS). A number of different vehicles and designs have been considered over the past two decades – with several flying as developmental test prototypes – but no one single design has been built as the dedicated CRV. In April 2010, President Obama directed NASA
NASA
The National Aeronautics and Space Administration is the agency of the United States government that is responsible for the nation's civilian space program and for aeronautics and aerospace research...

 to develop a CRV based on the Orion
Orion (spacecraft)
Orion is a spacecraft designed by Lockheed Martin for NASA, the space agency of the United States. Orion development began in 2005 as part of the Constellation program, where Orion would fulfill the function of a Crew Exploration Vehicle....

 technology.

In the original space station design, emergencies were intended to be dealt with by having a "safe area" on the station that the crew could evacuate to, pending a rescue from a U.S. 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...

. However, the 1986 Space Shuttle Challenger disaster
Space Shuttle Challenger disaster
The Space Shuttle Challenger disaster occurred on January 28, 1986, when Space Shuttle Challenger broke apart 73 seconds into its flight, leading to the deaths of its seven crew members. The spacecraft disintegrated over the Atlantic Ocean, off the coast of central Florida at 11:38 am EST...

 and the subsequent grounding of the shuttle fleet caused station planners to rethink this concept. Planners foresaw the need for a CRV to address three specific scenarios:
  • Crew return if a space shuttle or Soyuz
    Soyuz spacecraft
    Soyuz , Union) is a series of spacecraft initially designed for the Soviet space programme by the Korolyov Design Bureau in the 1960s, and still in service today...

     capsule was unavailable;
  • An escape vehicle from a major time-critical space station emergency;
  • Full or partial crew return in case of a medical emergency.

Medical considerations

The ISS is equipped with a Health Maintenance Facility (HMF) to handle a certain level of medical situations, which are broken into three main classifications:
  • Class I: non-life-threatening illnesses and injuries (headache, lacerations).
  • Class II: moderate to severe, possibly life-threatening (appendicitis, kidney stones).
  • Class III: severe, incapacitating, life-threatening (major trauma, toxic exposure).

However, the HMF is not designed to have general surgical capability, so a means of evacuating a crew member in case of a medical situation that is beyond the HMF's capabilities is essential.

A number of studies have attempted to assess the medical risks for long-term space station habitation, but the results are inconclusive, as epidemiological data is lacking. It is, however, understood that longer periods in space increase the risk of serious problems. The closest estimates show an illness/injury rate of 1:3 per year, with 1% estimated to require emergency evacuation by means of a CRV. For an eight-person ISS crew, this results in an expected need for a CRV flight once every four to 12 years. These estimates have been partially corroborated by experiences on board the Soviet Union's Mir
Mir
Mir was a space station operated in low Earth orbit from 1986 to 2001, at first by the Soviet Union and then by Russia. Assembled in orbit from 1986 to 1996, Mir was the first modular space station and had a greater mass than that of any previous spacecraft, holding the record for the...

 space station. In the 1980s, the Soviets had at least three incidents where cosmonauts had to be returned under urgent medical conditions.

Because of its potential use as a medical evacuation method, the CRV design was required to address a number of issues that are not factors for a standard manned space vehicle. Foremost of these are the g-loadings
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...

 as influenced by reentry profiles and deceleration/landing methods upon patients with hemorrhagic shock issues. Patient security issues are more critical for injured astronauts than for uninjured personnel. Additionally, depending on the nature of the injury, it may be unlikely that the patient could be placed in an environmentally contained space suit or minicapsule, therefore the CRV needs to have the capability to provide a "shirt sleeve" environment. The ability to address air purity issues is included in this requirement, as air purity is especially critical in medical as well as toxic exposure situations.

Early NASA concepts

NASA
NASA
The National Aeronautics and Space Administration is the agency of the United States government that is responsible for the nation's civilian space program and for aeronautics and aerospace research...

 planners developed a number of early concepts for a space station lifeboat:

Capsule systems

  • The Station Crew Return Alternative Module (SCRAM) was a capsule which could hold up to six astronauts. Reentry heat protection was provided by the use of a heat shield designed for the NASA Viking Mars probe. Costing US$600 million, the primary drawback to this design was high g-loadings on landing, which were not ideal in case of a medically necessitated evacuation.
  • As a follow-on to the Viking-based concept, NASA considered a 1986 proposal by General Electric
    General Electric
    General Electric Company , or GE, is an American multinational conglomerate corporation incorporated in Schenectady, New York and headquartered in Fairfield, Connecticut, United States...

     and NIS Space Ltd. for a commercially developed derivative of the U.S. Air Force Discoverer recovery capsule called MOSES. These capsules were being planned for unmanned microgravity experiments, and initially were planned for up to four occupants, but the idea of scaling the capsule up to accommodate eight crew members was considered for a time before also being dropped. However, g-loads of up to 8-gs make this vehicle unsuitable for critical medical situations.
  • In 1989, NASA engineers patented a capsule-type ACRV concept.

HL-20 PLS

The HL-20 Crew Rescue Vehicle
HL-20 Personnel Launch System
The HL-20 Personnel Launch System was a circa 1990 NASA spaceplane concept for manned orbital missions studied by NASA's Langley Research Center in Hampton, Virginia. HL-20 was envisaged as a lifting body re-entry vehicle based on the Soviet BOR-4 spaceplane design featuring low operational costs,...

 was based on the Personnel Launch System (PLS) concept being developed by NASA as an outgrowth of earlier lifting body
Lifting body
A lifting body is a fixed-wing aircraft configuration in which the body itself produces lift. In contrast to a flying wing, which is a wing with minimal or no conventional fuselage, a lifting body can be thought of as a fuselage with little or no conventional wing...

 research. In October 1989, Rockwell International
Rockwell International
Rockwell International was a major American manufacturing conglomerate in the latter half of the 20th century, involved in aircraft, the space industry, both defense-oriented and commercial electronics, automotive and truck components, printing presses, valves and meters, and industrial automation....

 (Space Systems Division) began a year-long contracted effort managed by Langley Research Center
Langley Research Center
Langley Research Center is the oldest of NASA's field centers, located in Hampton, Virginia, United States. It directly borders Poquoson, Virginia and Langley Air Force Base...

 to perform an in-depth study of PLS design and operations with the HL-20 concept as a baseline for the study. In October 1991, the Lockheed Advanced Development Company (better known as the Skunk Works
Skunk works
Skunk Works is an official alias for Lockheed Martin’s Advanced Development Programs , formerly called Lockheed Advanced Development Projects. Skunk Works is responsible for a number of famous aircraft designs, including the U-2, the SR-71 Blackbird, the F-117 Nighthawk, and the F-22 Raptor...

) began a study to determine the feasibility of developing a prototype and operational system. A cooperative agreement between NASA, North Carolina State University
North Carolina State University
North Carolina State University at Raleigh is a public, coeducational, extensive research university located in Raleigh, North Carolina, United States. Commonly known as NC State, the university is part of the University of North Carolina system and is a land, sea, and space grant institution...

 and North Carolina A&T University led to the construction of a full-scale model of the HL-20 PLS for further human factors research on this concept. Of all the options, a lifting body presents the most ideal medical environment in terms of controlled environment as well as low g-loading during reentry and landing. However, the price tag for the HL-20 project was US$2 billion, and Congress cut the program from NASA's budget in 1990.

European Space Agency concepts

As a part of their wide ranging studies of potential manned spaceflight programs, the European Space Agency
European Space Agency
The European Space Agency , established in 1975, is an intergovernmental organisation dedicated to the exploration of space, currently with 18 member states...

 (ESA) began a six-month, first-phase ACRV study in October 1992. Prime contractors for the study were Aérospatiale
Aérospatiale
Aérospatiale was a French aerospace manufacturer that built both civilian and military aircraft, rockets and satellites. It was originally known as Société Nationale Industrielle Aérospatiale...

, Alenia Spazio and Deutsche Aerospace.

The ESA studied several concepts for a CRV:
  • Apollo-type capsule: This would have been a scaled-up version of the 1960s Apollo
    Apollo spacecraft
    The Apollo spacecraft was composed of five combined parts designed to accomplish the American Apollo program's goal of landing astronauts on the Moon by the end of the 1960s and returning them safely to Earth...

     capsule capable of carrying eight astronauts. A tower that sat on top of the capsule would contain a docking tunnel as well as the capsule's rocket engines, again similar to the Apollo configuration. The tower would be jettisoned just before reentry. Landing would be via deceleration parachutes and air bags.
  • Also during Phase 1 studies, the ESA looked at a conical capsule known as the "Viking". Like the Apollo-style concept, it would have reentered base-first, but it had a more aerodynamic shape. The rocket engines for the "Viking" module were derivatives of the Ariane Transfer Vehicle. The design work continued until the end of Phase 1 in March 1995.
  • A Blunt Biconic concept was studied in 1993–1994. This design was expected to be more maneuverable, but would have been heavier and more expensive.


The ESA's US$1.7 billion ACRV program was cancelled in 1995, although French protests resulted in a two-year contract to perform further studies, which led to a scaled-down Atmospheric Reentry Demonstrator
Atmospheric Reentry Demonstrator
The Advanced Reentry Demonstrator was a suborbital reentry test flown on the third Ariane 5 flight. The ARD was launched on October 21, 1998, and was released shortly after separation of the launcher's cryogenic main stage 12 minutes after lift-off from the Guiana Space Centre, Europe's spaceport...

 capsule, which was flown in 1997. The ESA instead elected to join NASA's X-38 CRV program in May 1996, after that program finished its Phase A study.

Lifeboat Alpha

The idea of using a Russian-built craft as a CRV dates back to March 1993, when President Bill Clinton
Bill Clinton
William Jefferson "Bill" Clinton is an American politician who served as the 42nd President of the United States from 1993 to 2001. Inaugurated at age 46, he was the third-youngest president. He took office at the end of the Cold War, and was the first president of the baby boomer generation...

 directed NASA to redesign Space Station Freedom
Space Station Freedom
Space Station Freedom was a NASA project to construct a permanently manned Earth-orbiting space station in the 1980s. Although approved by then-president Ronald Reagan and announced in the 1984 State of the Union Address, Freedom was never constructed or completed as originally designed, and after...

 and consider including Russian elements. The design was revised that summer, resulting in Space Station Alpha (later the International Space Station
International Space Station
The International Space Station is a habitable, artificial satellite in low Earth orbit. The ISS follows the Salyut, Almaz, Cosmos, Skylab, and Mir space stations, as the 11th space station launched, not including the Genesis I and II prototypes...

). One of the Russian elements considered as a part of the redesign was the use of Soyuz "lifeboats." It was estimated that using the Soyuz capsules for CRV purposes would save NASA US$500 million over the cost expected for Freedom.

However, in 1995, a joint venture between Energia
Energia
Energia was a Soviet rocket that was designed by NPO Energia to serve as a heavy-lift expendable launch system as well as a booster for the Buran spacecraft. Control system main developer enterprise was the NPO "Electropribor"...

, Rockwell International
Rockwell International
Rockwell International was a major American manufacturing conglomerate in the latter half of the 20th century, involved in aircraft, the space industry, both defense-oriented and commercial electronics, automotive and truck components, printing presses, valves and meters, and industrial automation....

 and Khrunichev
Khrunichev
Khrunichev State Research and Production Space Center is a Moscow-based producer of spacecraft and space-launch systems, including the Proton and Rokot rockets. The company's history dates back to 1916, when an automobile factory was established outside Moscow...

 proposed the Lifeboat Alpha design, derived from the Zarya
Zarya spacecraft
The Zarya spacecraft was a secret Soviet project of the late 1980s aiming to design and build a large, manned, vertical takeoff, vertical landing space capsule,a much larger replacement for the Soyuz spacecraft....

 reentry vehicle. The reentry motor was a solid propellant, and maneuvering thrusters utilized cold gas, so that it would have had a five-year on-station life cycle. The design was rejected, though, in June 1996 in favor of the NASA CRV/X-38 program.

X-38

Besides referring to a generalized role within the ISS program, the name Crew Return Vehicle also refers to a specific design program initiated by NASA and joined by the ESA. The concept was to produce a spaceplane that was dedicated to the CRV role only. As such, it was to have three specific missions: medical return, crew return in case of the ISS becoming uninhabitable, and crew return if the ISS cannot be resupplied.

CRV overview and concept development

As a follow-on to the HL-20 program, the NASA intent was to apply Administrator Dan Goldin's concept of "better, faster, cheaper" to the program. The CRV design concept incorporated three main elements: the lifting-body reentry vehicle, the international berthing/docking module, and the Deorbit Propulsion Stage. The vehicle was to be designed to accommodate up to seven crew members in a shirt-sleeve environment. Because of the need to be able to operate with incapacitated crew members, flight and landing operations were to be performed autonomously. The CRV design had no space maneuvering propulsion system.

NASA and ESA agreed that the CRV would be designed to be launched on top of an expendable launch vehicle (ELV) such as the Ariane 5
Ariane 5
Ariane 5 is, as a part of Ariane rocket family, an expendable launch system used to deliver payloads into geostationary transfer orbit or low Earth orbit . Ariane 5 rockets are manufactured under the authority of the European Space Agency and the Centre National d'Etudes Spatiales...

. The program envisioned the construction of four CRV vehicles and two berthing/docking modules. The vehicles and berthing/docking modules were to be delivered to the ISS by the Space Shuttle, and each would remained docked for three years.

Depending on which mission was being operated, maximum mission duration was intended to be up to nine hours. If the mission was related to emergency medical return, the mission duration could be reduced to three hours, given optimum sequencing between ISS departure and the deorbit/reentry burn. Under normal operations, the undocking process would take up to 30 minutes, but in an emergency the CRV could separate from the ISS in as little as three minutes.

The CRV was to have a length of 29.8 ft (9.1 m) and a cabin volume of 416.4 ft³ (11.8 m³). Maximum landing weight was to be 22,046 lb (10,000 kg). The autonomous landing system was intended to place the vehicle on the ground within 3,000 ft (0.9 km) of its intended target.

The Deorbit Propulsion Stage was designed by Aerojet GenCorp
Aerojet
Aerojet is an American rocket and missile propulsion manufacturer based primarily in Rancho Cordova, California with divisions in Redmond, Washington, Orange, Gainesville and Camden, Arkansas. Aerojet is owned by GenCorp. They are the only US propulsion company that provides both solid rocket...

 under contract to the Marshall Space Flight Center
Marshall Space Flight Center
The George C. Marshall Space Flight Center is the U.S. government's civilian rocketry and spacecraft propulsion research center. The largest center of NASA, MSFC's first mission was developing the Saturn launch vehicles for the Apollo moon program...

. The module was to be attached to the aft of the spacecraft at six points, and is 15.5 ft (4.72 m) long and 6 ft (1.83 m) wide. Fully fueled, the module would weigh about 6,000 lb (2721.5 kg). The module was designed with eight 100 lbf (0.4448221615 kN)-thrust rocket engines fueled by hydrazine
Hydrazine
Hydrazine is an inorganic compound with the formula N2H4. It is a colourless flammable liquid with an ammonia-like odor. Hydrazine is highly toxic and dangerously unstable unless handled in solution. Approximately 260,000 tons are manufactured annually...

, which would burn for ten minutes to deorbit the CRV. Eight reaction control thrusters would then control the ship's attitude during deorbit. Once the burn was completed, the module was to be jettisoned, and would burn most of its mass up as it reentered the atmosphere.

The cabin of the CRV was designed to be a "windowless cockpit", as windows and windshields add considerable weight to the design and pose additional flight risks to the spacecraft. Instead, the CRV was to have a "virtual cockpit window" system that used synthetic vision tools to provide an all-weather, day/night, real-time, 3-D visual display to the occupants.

X-38 Advanced Technology Demonstrator

In order to develop the design and technologies for the operational CRV at a fraction of the cost of other space vehicles, NASA launched a program to develop a series of low-cost, rapid-prototype vehicles that were designated the X-38 Advanced Technology Demonstrators. As described in EAS Bulletin 101, the X-38 program "is a multiple application technology demonstration and risk mitigation programme, finding its first application as the pathfinder for the operational Crew Return Vehicle (CRV) for the International Space Station (ISS)."

NASA acted as its own prime contractor for the X-38 program, with the Johnson Space Center taking the project lead. All aspects of construction and development were managed in-house, although specific tasks were contracted out. For the production CRV, NASA intended to select an outside prime contractor to build the craft.

Four test vehicles were planned, but only two were built, both atmospheric test vehicles. The airframes, which were largely built of composite materials, were constructed under contract 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 first flew its maiden flight
Maiden flight
The maiden flight of an aircraft is the first occasion on which an aircraft leaves the ground of its own accord. This is similar to a ship's maiden voyage....

 on March 12, 1998. The X-38 utilized a unique parafoil
Parafoil
A parafoil is a nonrigid airfoil with an aerodynamic cell structure which is inflated by the wind. Ram-air inflation forces the parafoil into a classic wing cross-section. Parafoils are most commonly constructed out of ripstop nylon....

 landing system designed by Pioneer Aerospace. The ram-air inflated parafoil used in the flight test program was the largest in the world, with a surface area of 7,500 ft² (700 m²). The parafoil was actively controlled by an onboard guidance system that was based on GPS navigation.

Controversy

NASA's plans for the development program did not include an operational test of the actual CRV, which would have involved it being launched to the ISS, remaining docked there for up to three months, and then conducting an "empty" return to Earth. Instead, NASA had planned to "human rate" the spacecraft based on the results of the X-38's orbital testing. Three independent review groups, as well as the NASA Office of Inspector General
NASA Office of Inspector General
The NASA Office of Inspector General is the inspector general office in the National Aeronautics and Space Administration, the space agency of the United States...

, expressed concerns about the wisdom and safety of this plan.

The rapid-prototyping method of development, as opposed to the approach of sequential design, development, test and engineering evaluation also raised some concerns about program risk.

Funding issues

In 1999, NASA projected the cost of the X-38 program at US$96 million (Space Flight Advanced Projects funds) and the actual CRV program at US$1.1 billion (ISS Program funds). A year later, the X-38 costs had risen to US$124.3 million, with the increased cost being paid for by ISS funds. Part of the increased cost was the result of the need to operationally test the CRV with at least one, and possibly more, shuttle launches.

The ESA chose not to fund the CRV program directly, but instead decided to allow ESA-participating governments to fund the program individually, starting in 1999. Belgium, France, Germany, The Netherlands, Italy, Spain, Sweden, and Switzerland all indicated that they would make substantial contributions.

U.S. funding for the NASA/ESA CRV was never a settled issue. In the Fiscal Year (FY) 2002 funding bill, Congress recommended a funding amount of US$275 million, but made it clear that this was conditional:
[T]he Committee does not anticipate providing additional funds for this purpose unless it is made clear that the Administration and the international partners are committed to the International Space Station as a research facility. For this reason, the language included in the bill would rescind the $275,000,000 unless the Administration requests at least $200,000,000 for the crew return vehicle in the fiscal year 2003 NASA budget request.
Furthermore, funding of the CRV program was tied to Administration justification of the mission of the ISS:
By March 1, 2002, the President shall submit to the Committees on Appropriations of the House and Senate a comprehensive plan that meets the following terms and conditions: First, a clear and unambiguous statement on the role of research in the International Space Station program. Second, a detailed outline of the efforts being pursued to provide habitation facilities for a full-time crew of no less than six persons.... Third, the anticipated costs of the crew return vehicle program by fiscal year.... Fourth, the relative priority of the crew return vehicle development program in the context of the International Space Station. The Committee does not intend to provide any additional funds or approve the release of any of the $275,000,000 provided in this bill, until all conditions are fully satisfied.

Cancellation

On April 29, 2002, NASA announced that it was cancelling the CRV and X-38 programs, due to budget pressures associated with other elements of the ISS. The agency had been faced with a US$4 billion shortfall, and so radically redesigned the scope of the ISS, calling the new version U.S. Core Complete. This scaled-down station did not include the X-38-based CRV. Although the FY 2002 House budget had proposed US$275 million for the CRV, this was not included in the final budget bill. House-Senate conferees, however, saw the need to keep the CRV options open, believing that NASA's redesign and consequent deletion of the CRV premature, and so directed NASA to spend up to US$40 million to keep the X-38 program alive.

The cancellation created its own controversy, with Congressman Ralph Hall
Ralph Hall
Ralph Moody Hall is a United States Representative from . First elected in 1980, Hall is the chairman of the Science Committee and a senior member of the Energy and Commerce Committee...

 (D-TX) taking NASA to task in an open letter. Hall offered the following criticisms of NASA's CRV cancellation:
  • "No quantitative analysis of the costs and benefits of X-38/CRV alternatives was conducted prior to the decision to terminate the program."
  • "2010 is estimated to be the "earliest" availability date for a Crew Transfer Vehicle (CTV) to support crew return functions on the International Space Station."
  • "No estimates of the cost to develop and operate a CTV are provided."
  • "NASA has no plans to purchase Soyuz crew return vehicles from Russia. The letter does not address the limits on Russian cooperation imposed by the Iran Nonproliferation Act, nor does it describe how a crew return capability will be provided for either a 3-person or larger crew-size Station once the Russian obligation to provide Soyuz vehicles ends in 2006."
  • "NASA now estimates the cost of a CRV fleet at $3 billion, which constitutes a massive increase from the $1.3–1.4 billion estimate consistently provided to Congress prior to the Administrator's termination announcement. NASA's new position is that a CRV would not be available until 2008, which appears to be due to OMB's decision last year to defer work on the program rather than any technical or management problems. Mr. O'Keefe's June 2002 announcement of the cancellation of the X-38/CRV program did not raise cost growth or schedule as factors in that decision. It seems clear to me that the new cost and schedule estimates for the CRV are not based on a thorough technical analysis, but rather on a desire to portray CTV development in a more favorable light."

Orbital Space Plane

As a part of NASA's Integrated Space Transportation Plan (ISTP) which restructured the Space Launch Initiative (SLI), focus moved in 2002 to developing the Orbital Space Plane (OSP) (early on referred to as the Crew Transfer Vehicle, or CTV), which would serve as both crew transport and as the CRV. In the restructuring, program priorities were changed, as NASA declared: "NASA's needs for transporting US crew to and from the Space Station is a driving space transportation requirement and must be addressed as an agency priority. It is NASA's responsibility to ensure that a capability for emergency return of the ISS crew is available. The design and development of an evolvable and flexible vehicle architecture that will initially provide crew return capability and then evolve into a crew transport vehicle is now the near-term focus of SLI."

A Crew Transfer Vehicle/Crew Rescue Vehicle Study, conducted by the SLI program in 2002, concluded that a multi-purpose Orbital Space Plane that can perform both the crew transfer and crew return functions for the Space Station is viable and could provide the greatest long-term benefit for NASA's investment. One of the key missions for the OSP, as defined by NASA in 2002, was to provide "rescue capability for no fewer than four Space Station crew members as soon as practical, but no later than 2010." As a part of the flight evaluation program that was to explore and validate technologies to be used in the OSP, NASA initiated the X-37
Boeing X-37
The Boeing X-37 is an American unmanned vertical-takeoff, horizontal-landing spaceplane. The X-37 is operated by the United States Air Force for orbital spaceflight missions intended to demonstrate reusable space technologies...

 program, selecting Boeing Integrated Defense Systems
Boeing Integrated Defense Systems
Boeing Defense, Space & Security formerly known as Boeing Integrated Defense Systems is a unit of The Boeing Company responsible for defense and aerospace products and services. Boeing Integrated Defense Systems was formed in 2002 by combining the former "Military Aircraft and Missile Systems"...

 as the prime contractor.

However, the OSP received heavy congressional criticism for being too limited in mission ("...the primary shortcoming of the OSP is that, as currently envisioned, it leads nowhere besides the space station") and for costing as much as US$3 to $5 billion.

Then, in 2004, NASA's focus changed yet again, from the OSP to the Crew Exploration Vehicle
Orion (spacecraft)
Orion is a spacecraft designed by Lockheed Martin for NASA, the space agency of the United States. Orion development began in 2005 as part of the Constellation program, where Orion would fulfill the function of a Crew Exploration Vehicle....

 (CEV), and the X-37 project was transferred to DARPA, where some aspects of technology development were continued, but only as an atmospheric test vehicle.

Apollo-derivative capsule

With the cancellation of the OSP, the Apollo
Apollo spacecraft
The Apollo spacecraft was composed of five combined parts designed to accomplish the American Apollo program's goal of landing astronauts on the Moon by the end of the 1960s and returning them safely to Earth...

 capsule was once again looked at for use as a CRV, this time by NASA in March 2003. In the initial study of the concept, "the Team concluded unanimously that an Apollo-derived Crew Return Vehicle (CRV) concept, with a 4 to 6 person crew, appears to have the potential of meeting most of the OSP CRV Level 1 requirements. An Apollo derived Crew Transport Vehicle (CTV) would also appear to be able to meet most of the OSP CTV Level 1 requirements with the addition of a service module. The team also surmised that there would be an option to consider the Apollo CSM concept for a common CRV/CTV system. It was further concluded that using the Apollo Command Module (CM) and Service Module (SM) as an ISS CRV and CTV has sufficient merit to warrant a serious detailed study of the performance, cost, and schedule for this approach, in comparison with other OSP approaches, to the same Level 1 requirements."

The study identified a number of issues with development of this option: "On the one hand, the Apollo system is well understood, and proved to be a highly successful, rugged system with a very capable launch abort system. Documentation would be very helpful in leading the designers. On the other hand, nearly every system would have to be redesigned, even if it were to be replicated. None of the existing hardware (such as CMs in Museums) was thought to be usable, because of age, obsolescence, lack of traceability, and water immersion. There would be no need for fuel cells or cryogenics, and modern guidance and communications would be lighter and less expensive. Although the flight hardware would be less expensive, and its impact on the Expendable Launch Vehicles would be minimal (it's just another axisymmetrical payload), the landing sites for the CRV may drive the Life Cycle costs high. By adding a Service Module (smaller than the one required to go to the moon), orbital cross-range of 3000 to 5000 ft/s (1,524 m/s), might be gained, and the number of landing sites radically reduced. If land landings can be added to the system safely, another major reduction in life cycle costs would result, because the team believed that the system could be made re-usable."

Due to the capsule's somewhat aerodynamic design, g-loadings are in the moderate range, (2.5 to 3.5g). From a medical perspective, though, the Apollo-type capsule presents several disadvantages. The Apollo capsule would have an internal atmospheric operating pressure of only 5 PSI, as opposed to the station's 14.5 PSI. In addition, a water landing
Water landing
A water landing is, in the broadest sense, any landing on a body of water. All waterfowl, those seabirds capable of flight, and some human-built vehicles are capable of landing in water as a matter of course....

 on short notice presents some significant delays in capsule recovery.

Soyuz TMA

With the cancellation of the X-38 and CRV programs in 2001, it was clear that the interim use of Soyuz capsules would be a longer term necessity. To make them more compatible with the needs of the ISS, Energia
S.P. Korolev Rocket and Space Corporation Energia
OAO S.P. Korolev Rocket and Space Corporation Energia , also known as RKK Energiya, is a Russian manufacturer of spacecraft and space station components...

 was contracted to modify the standard Soyuz TM capsule to the TMA configuration. The main modifications involve the interior layout, with new, improved seats to accommodate larger American astronaut anthropometric standards. A series of test drops of the improved capsule were made in 1998 and 1999 from an Ilyushin Il-76
Ilyushin Il-76
The Ilyushin Il-76 is a multi-purpose four-engined strategic airlifter designed by Ilyushin design bureau. It was first planned as a commercial freighter in 1967. Intended as a replacement for the Antonov An-12, the Il-76 was designed for delivering heavy machinery to remote, poorly-serviced areas...

 cargo plane to validate the landing capabilities of the TMA.

A Soyuz-TMA
Soyuz-TMA
The Soyuz-TMA is a recent revision of the Soyuz spacecraft, superseded in 2010 by the Soyuz TMA-M..It is used by the Russian Federal Space Agency for human spaceflight...

 capsule is always attached to the ISS in "standby" mode, in case of emergencies. Operated in this configuration, the TMA has a lifespan of about 200 days before it has to be rotated out, due to the degradation of the hydrogen peroxide used for its reaction control system. Because of this limitation, the vehicle is planned for a typical six-month changeout cycle. The first flight of the TMA to the ISS occurred on October 29, 2002 with the flight of the Soyuz TMA-1.

Because the TMA is limited to three occupants, the ISS was also likewise restricted to that number of occupants, which drastically reduces the amount of research that can be done on board the ISS to 20 person-hours per week, far lower than what was anticipated when the station was designed. With Expedition 20
Expedition 20
Expedition 20 was the twentieth long-duration flight to the International Space Station. The expedition marked the first time a six-member crew inhabited the station...

 in May 2009, the crew size of the ISS was increased from 3 to 6 persons with the simultaneously docked two Soyuz spacecrafts.

Soyuz TMA-M (originally TMAT) entered service in October 2010. This upgraded version will extend its lifespan in orbit to one year. That along with expanded production rate will enable the ISS to increase the crew size.

Commercial Crew Development

In 2008, NASA began administering a program (CCDev) to fund development of commercial crew transportation technologies. The program funded bids to develop specific technologies with awards when milestones were achieved. The first round of recipients in early 2010 included Boeing
Boeing
The Boeing Company is an American multinational aerospace and defense corporation, founded in 1916 by William E. Boeing in Seattle, Washington. Boeing has expanded over the years, merging with McDonnell Douglas in 1997. Boeing Corporate headquarters has been in Chicago, Illinois since 2001...

 for its CST-100 capsule and Sierra Nevada Corporation
Sierra Nevada Corporation
Sierra Nevada Corporation is an electronic systems provider and systems integrator specializing in microsatellites, energy, telemedicine, nanotechnology, and commercial orbital transportation services. The company contracts with the US military, NASA and private spaceflight companies. The company...

 for its Dream Chaser spaceplane. Further proposals submitted at the end of 2010 for a second round of funding included Orbital Sciences Corporation
Orbital Sciences Corporation
Orbital Sciences Corporation is an American company which specializes in the manufacturing and launch of satellites. Its Launch Systems Group is heavily involved with missile defense launch systems...

 for its Prometheus
Prometheus (spacecraft)
Prometheus was a proposed manned vertical-takeoff, horizontal-landing spaceplane concept put forward by Orbital Sciences Corporation in late 2010 as part of the second phase of NASA's Commercial Crew Development program.-Design:...

 spaceplane and SpaceX
SpaceX
Space Exploration Technologies Corporation, or more popularly and informally known as SpaceX, is an American space transport company that operates out of Hawthorne, California...

 for developing a launch abort system for its Dragon spacecraft.

Orion

, President Barack Obama
Barack Obama
Barack Hussein Obama II is the 44th and current President of the United States. He is the first African American to hold the office. Obama previously served as a United States Senator from Illinois, from January 2005 until he resigned following his victory in the 2008 presidential election.Born in...

 directed NASA Administrator Charles Bolden
Charles F. Bolden, Jr.
Charles Frank "Charlie" Bolden, Jr. is the current Administrator of NASA, a retired United States Marine Corps major general, and former NASA astronaut....

to immediately begin developing a rescue vehicle using the Orion technology

External links

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