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The Constellation Program (abbreviated CxP) is a human spaceflight program within NASA, the space agency of the United States. The stated goals of the program were to gain significant experience in operating away from Earth's environment, develop technologies needed for opening the space frontier, and conduct fundamental science.
Constellation began in response to the goals laid out in the Vision for Space Exploration under NASA Administrator Sean O'Keefe. It had already begun development, under several proposals  After Sean O'Keefe's retirement, his replacement Michael D. Griffin ordered a complete review, termed the Exploration Systems Architecture Study, which reshaped how NASA would pursue the goals laid out in the Vision for Space Exploration. With the NASA Authorization Act of 2005 formalizing the findings of the Exploration Systems Architecture Study, work began on this revised Constellation Program to send astronauts first to the International Space Station, then to the Moon, and afterward to Mars and other destinations beyond.
On February 1, 2010, President Barack Obama announced a proposal to cancel the program, effective with the U.S. 2011 fiscal year budget, but later announced changes to the proposal in a major space policy speech at Kennedy Space Center on April 15, 2010. Obama signed the NASA Authorization Act of 2010 on October 11 which brought the program to an end despite promises to fully fund space flight during his campaign for election to President of the United States in 2008, but Constellation contracts remain in place until Congress acts to overturn the previous mandate. The program has been replaced by the U.S. National Space Policy of the Barack Obama administration. NASA announced that it had selected the design of the Space Launch System in September 2011.
Constellation included the development of spacecraft and booster vehicles to replace the Space Shuttle. NASA had already begun designing two boosters, the Ares I and Ares V. Ares I would have had the sole function of launching mission crews into orbit, while Ares V would have been used to launch other hardware for use on missions requiring a heavier lift capacity than the Ares I booster. In addition to these two boosters, NASA designed a set of other spacecraft for use during Constellation. These included the Orion crew capsule, the Earth Departure Stage and the Altair lunar lander.
Orion was originally designed as the crew compartment for the Constellation program and Earth orbit missions. Lockheed Martin was selected as the prime contractor to build Orion on August 31, 2006, and Boeing was selected to build the primary heat shield for the Orion crew exploration vehicle on September 15, 2006. NASA planned to develop different Orion capsules tailored for specific missions. The Block I Orion was to be used for International Space Station crew rotation and resupply and other Earth orbit missions, while the Block II and III variants were designed for deep-space exploration.
Orion consists of three main parts: a Crew Module (CM) similar to the Apollo Command Module but capable of holding four to six crew members; a cylindrical Service Module (SM) containing the primary propulsion systems and consumable supplies; and the Launch Abort System (LAS) which provides capability for the astronauts and Crew Module to escape from the launch vehicle should problems arise during launch ascent. The Orion Crew Module is designed to be reusable for up to ten flights, allowing NASA to construct a fleet of Orion crew modules.
Altair (formerly known as the Lunar Surface Access Module, LSAM) would have been the main transport vehicle for lunar-bound astronauts. The Altair design was much larger than the Apollo Lunar Module (LM), with almost five times the volume, occupying a total of 1,120 cubic feet (32 m3) compared with the Apollo lander's 235 cubic feet (6.7 m3). It was to stand 32 feet (9.8 m) tall and span 49 feet (15 m) wide from landing gear tip to tip.
Like its Apollo LM predecessor, Altair consisted of two parts: an ascent stage which houses the four-person crew; and a descent stage which has the landing legs, the majority of the crew's consumables (oxygen and water), and scientific equipment. Unlike the Apollo LM, Altair would have touched down in the lunar polar regions favored by NASA for future lunar base construction. Altair, like the LM, is not reusable; the ascent stage would be discarded after use.
The Altair descent stage was to be powered by four RL-10 rocket engines that are used for the Centaur upper stage used on the Atlas V rocket. Unlike the current RL-10 engines in use, the newer RL-10s would be able to throttle down to as low as 10% rated thrust (the current specifications allow for 20%), thus allowing the use of Altair for both the lunar orbit insertion (LOI) and landing stages of the lunar mission. The ascent stage was to be powered by a single engine, likely a hypergolic engine similar or identical to the main engine of the Orion CSM, using the descent stage as a launchpad and as a platform for future base construction. There was a small possibility that the original plan of using LOX/CH4 – fueled engines on board the Block II (lunar) Orion CSM and Altair ascent stage could come to pass.
The Earth Departure Stage (EDS) was the main propulsion system that would have sent the Ares V Orion/Altair upper stage from low Earth orbit to the Moon. It was to have been the second liquid stage of the Ares V rocket. The Orion spacecraft would have launched separately on Ares I, and rendezvous and dock with the Ares V EDS/Altair combination, which would have then been configured for the journey to the Moon (known as Earth orbit rendezvous).
NASA would have used the vehicles of the Constellation Program to replace the Space Shuttle. But unlike the X-33 and other programs meant to replace the Shuttle, Constellation reused concepts already learned from the Apollo and Space Shuttle programs.
For instance, the shape of the Orion command ship closely resembled the aerodynamic shape of the Apollo Command/Service Module. However, in other respects – such as with the cockpit displays and heatshield – Orion employs new technology. The design of the launch vehicle taking Orion into orbit, the Ares I, was closely based on Apollo designs. It was based on a J-2X engine, a redesigned version of the J-2 engine used in the Saturn family of boosters.
In working on the J-2X, NASA engineers visited museums, searched for Apollo-era documentation and consulted with engineers who worked on the Apollo program. "The mechanics of landing on the moon and getting off the moon to a large extent have been solved," said Constellation program manager Jeff Hanley. "That is the legacy that Apollo gave us."
Like Apollo, Constellation would have flown a lunar orbit rendezvous mission profile, but unlike Apollo, Constellation would have also employed an Earth orbit rendezvous. The lander, known as Altair, would have been launched separately on the Ares V rocket, a rocket based on both Space Shuttle and Apollo technologies. Orion would have been launched separately and would have linked up with Altair in low earth orbit. Also unlike Apollo, Orion would have remained unmanned in lunar orbit while the entire crew landed on the lunar surface (specifically at the lunar polar regions, unlike the equatorial regions explored by Apollo). At the end of the mission, the Altair spacecraft would have launched into lunar orbit to link up with the Orion spacecraft in lunar orbit rendezvous.
Unlike the Saturn V and Space Shuttle, where the crew and cargo were launched together on the same rocket, NASA planned to use two separate launch vehicles for the Constellation Program – the Ares I for crew and the Ares V for cargo. This would have allowed the two launch vehicles to be optimized for their respective missions, especially for a much heavier cargo load per mission. The Constellation Program thus combined the Lunar Orbit Rendezvous method which was used by Apollo with the Earth Orbit Rendezvous method.
The Orion spacecraft would have been launched into a low Earth orbit using the Ares I rocket (the "Stick"), developed by Alliant Techsystems, Rocketdyne, and Boeing. Formerly referred to as the Crew Launch Vehicle (CLV), the Ares I consisted of a single Solid Rocket Booster (SRB) derived from the boosters used in the Space Shuttle system, connected at its upper end by an interstage support assembly to a new liquid-fueled second stage powered by an uprated Apollo-era J-2X rocket engine. NASA selected the Ares designs for their anticipated overall safety, reliability and cost-efficiency.
NASA began developing the Ares I low Earth orbit launch vehicle (analogous to Apollo's Saturn IB), returning to a development philosophy used for the original Saturn I, test-launching one stage at a time, which George Mueller abandoned in favor of "all-up" testing for the Saturn V. As of May 2010, the program got as far as launching the first Ares I-X first-stage flight on October 28, 2009 and testing the Orion launch abort system.
Ares V would have had a maximum payload capacity of about 188 metric tons (414,000 lb) to low earth orbit (LEO), compared to the Space Shuttle's capacity of 24.4 metric tons, and the Saturn V's 118 metric tons. The Ares V would have carried about 71 metric tons (157,000 lb) to the Moon, versus the Saturn V's 45 metric tons moon payload.
The Ares V design incorporated six RS-68 engines with assistance from a pair of 5.5-segment SRBs. Five Space Shuttle Main Engines (SSME) were originally planned for the Ares V, but the RS-68 engines are more powerful and less complex and therefore less expensive than the SSMEs. The Ares V would have flown for the first eight minutes of powered flight, then the Earth Departure Stage would have placed itself and the Altair spacecraft into low Earth orbit while awaiting the arrival of the Orion.
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A number of alternatives to Constellation have been suggested in response to critiques of the program. Debates persist regarding whether the present program should continue, be discontinued, or rectified in some way.
On January 14, 2004 President George W. Bush requested NASA develop a proposal for continuing manned space exploration after the completion of the International Space Station and the planned retirement of the Space Shuttle program in 2010. This proposal was to be a way to "establish an extended human presence on the Moon" to "vastly reduce the costs of further space exploration." Inclusive to this would be the "harvesting and processing of lunar soil into rocket fuel or breathable air." According to Bush, experience gained could help "develop and test new approaches and technologies and systems" to begin a "sustainable course of long-term exploration."
When President Bush established his new space exploration policy to return humans to the moon, NASA estimated the policy would cost $230 billion (in 2004 dollars) through 2025. This figure includes the Commercial Crew and Cargo program, which is separate from the Constellation program. NASA has estimated that the Constellation program would cost over $97 billion (in 2008 dollars) through 2020, half of which would be for Ares I and Orion. However, unsolved technical and design challenges made it impossible for NASA to provide a credible estimate. To provide some perspective, in 1972 NASA estimated the life-cycle costs (development, procurement, and twelve years of operation) of the Space Shuttle program at $16.1 billion (in 1972 dollars). The actual life-cycle costs for twelve years of operation came to $25 billion (in 1972 dollars), a 55% over-run.
President Obama's stance has been that Constellation is "over budget, behind schedule, and lacking in innovation." A review had concluded that it would cost on the order of $150 billion for Constellation to reach its objective if hewing to the original schedule.
In 2009, concerned by price increases on the program, U.S. President Obama ordered a review of the project which indicated that both returning to the Moon and manned flights to Mars were out of NASA's current budget. The Augustine panel proposed various options that included two primary destination points (the Moon, and Deep Space), three different types of Super Heavy Launch vehicles, and utilizing Commercially based crew to LEO transport systems, as well as a robust research and development program that would include work on propellant depots.
After reviewing the report, following congressional testimony, the Obama administration decided to exclude Constellation from the 2011 United States federal budget. On February 1, 2010, the President's proposed budget was released, which included no funding for the project.
President Obama's response to critics is that the lifetime for the International Space Station would be extended by an additional five years and an additional US$6 billion would be paid to private companies for shuttling astronauts to and from it after the Space Shuttle program ends while NASA develops new technology for future space exploration missions. According to Obama, his vision embodies a "bold new approach to human space flight that embraces commercial industry, forges international partnerships, and invests in the building blocks of a more capable approach to space exploration."
President Obama hosted a Space Conference on April 15, 2010, in Florida. This came at a time when the Obama administration was taking a considerable amount of criticism for leaving the Constellation Program out of the 2011 budget. At the conference Obama and top officials as well as leaders in space discussed the future of U.S. efforts in human space flight and unveiled a plan for NASA that follows the Augustine Panel's "Flexible Path to Mars" option, modifying Obama's prior proposal in two important respects:
Neil Armstrong, commander of Apollo 11 and the first man on the Moon, has expressed strong support for the Constellation program, unlike his former Apollo crewmate Buzz Aldrin, who has expressed strong support for the Obama administration's new plan.
Testifying before the United States Congress in 2010, Neil Armstrong opposed an administrative scrap of Constellation, stating "substantial turmoil" has arisen "by the President's proposal ... because a few planners with little or no space operation experience attempted an end run on the normal planning process." Armstrong argued that "a return to the Moon would be a most productive path to expanding the human presence in the Solar System."
Armstrong testified, "The lunar vicinity is an exceptional location to learn about traveling to difficult distant places.... The long communication delays to destinations beyond the Moon may mandate new techniques and procedures for spacecraft operations ... in the case of severe emergencies."
Armstrong clarified this point with an example: "For Mission Control on Earth to play an important and timely role in flight operations," with Moon travelers "communication delays with Earth are less than two seconds." By contrast, "Mission Control cannot provide a Mars crew their normal helpful advice if ... the time delay of radar, communications and telemetry back to Earth is 19 minutes.... Flight experience at lunar distance can provide valuable insights into practical solutions for handling such challenges."
Armstrong stated that he finds the arguments of opponents to Constellation's return to the Moon "mystifying." "Afterall, they say, we have already been there." But, he continued, "there is much to be learned on Luna – learning to survive in the lunar environment, investigating many science opportunities, determining the practicality of extracting Helium 3 from the lunar regolith, prospecting for Palladium group metals, meeting challenges not yet identified." To date the Moon "leaves more than 14 million square miles yet to be explored" (or about 36 million square kilometres).
In response to a request for what he believes U.S. spaceflight priorities ought to be, Armstrong responded:
Armstrong cited Constellation as among those federal programs that "motivate the citizenry ... inspiring them."
The National Space Society (NSS) regards a return to the Moon as a high space program priority, to begin development of the knowledge and identification of the industries unique to the Moon. "Such industries can provide economic leverage and support for NASA activities, saving the government millions."[Tumlinson 1] The NSS believes that the Moon may be a repository of the history and possible future of our planet, and that the six Apollo landings only scratched the surface.
According to NASA, the answer to the question, "Why should we return to the Moon?," would be to:
In the words of former NASA Administrator, Michael D. Griffin, "The goal isn't just scientific exploration.... It's also about extending the range of human habitat out from Earth into the solar system as we go forward in time.... In the long run a single-planet species will not survive.... If we humans want to survive for hundreds of thousands or millions of years, we must ultimately populate other planets ... colonize the solar system and one day go beyond."
Senator Richard Shelby has stated "It is unfortunate that this administration is choosing to abandon our nation's only chance at remaining the leader in human space flight. It is ironic that Constellation, a program born out of the recommendations of the Columbia Accident Investigation Board, would be eliminated in lieu of rockets repeatedly deemed unsafe for astronauts by NASA's own Aerospace Safety Advisory Panel." Shelby argues further, "If this budget is enacted, NASA will no longer be an agency of innovation and hard science; it will be the agency of pipe dreams and fairy tales."
"As I see it, the commission didn't find anything wrong with the current program, didn't find anything safer, more reliable, cheaper or faster," former NASA Administrator Michael D. Griffin has testified to Congress. "The roots are healthy. So why throw away four years and $8 billion pulling the flowers? Let's apply some plant nutrient and watch them grow.... Exactly why does the policy which we established in law – twice – need to be changed?" According to Griffin, NASA spending has declined approximately 20% since 1993.
Further hearings regarding the program's proposed cancellation continue within the United States Congress. Particularly, the United States House Science Subcommittee on Space and Aeronautics and the United States Senate Commerce Subcommittee on Science and Space must now review and offer individual recommendations...
Hearings held to date regarding the Constellation's proposed cancellation within the House Subcommittee include NASA Aerospace Safety Advisory Panel Chairperson and retired US Navy Vice Admiral Joseph W. Dyer concluding that the proposed cancellation, without alternative "demonstrated capability or proven superiority is unwise and probably not cost-effective." Regarding any risk associated with Ares I, Admiral Dyer notes, "If the goal is to minimize the gap between the Shuttle and the follow-on, the Ares I offers the safest, quickest opportunity and probably the most cost-effective one. If the nation is willing to accept a wider gap, more risk, and a higher cost, then other opportunities avail themselves." Ranking member of the United States House Committee on Science and Technology, Representative Ralph Hall continues, it is "naïve to assume that a do-over will somehow deliver a safer, cheaper system faster than the current path we’re on."
Proposed manned Commercial Crew Development Vehicle alternatives to Ares I for servicing the Space Station are the Boeing/Bigelow Aerospace unofficially-named "Orion-Lite" capsule launched on a future-man-rated Delta IV Heavy, the manned version of the SpaceX Dragon spacecraft, and Sierra Nevada Dreamchaser. None of these spacecraft are designed to leave low earth orbit as required for lunar missions and the majority of the Constellation program, they are purely alternative methods for space station access.
The Delta IV is a rocket family, designed to launch payloads into orbit for the US Air Force Evolved Expendable Launch Vehicle (EELV) program as well as for commercial satellite launches. The most powerful variant of the family, Delta IV Heavy, is capable of delivering 25 tonnes of payload to LEO, matching the capability of the Ares I.
The Aerospace Corporation was asked by NASA three times, in 2005, 2008 and 2009, to assess technical feasibility and cost of human-rating an EELV. Two latter assessments addressed the possibility of replacing the Ares I with Delta IV Heavy. The reports indicate that the Delta IV Heavy meets ISS and lunar target performance requirements. Unlike other modifications of Delta IV, the Heavy variant does not use solid rocket boosters.
The first launch of a Delta IV rocket occurred in 2002. The first launch of the Heavy variant was performed in 2004.
The Falcon 9 launch vehicle along with the manned version of the Dragon capsule, developed by SpaceX, have been contemplated as a possible commercial alternative. NASA has already awarded SpaceX a contract to deliver unmanned cargo to the ISS under the Commercial Orbital Transportation Services (COTS) program.
CST-100 is a planned manned vehicle, developed by Boeing and Bigelow Aerospace, that would deliver astronauts to ISS as well as Bigelow Space Station. It could be launched on an Atlas V, Delta IV, or Falcon 9 rocket.
The Dream Chaser is a planned manned suborbital and orbital spacecraft being developed by SpaceDev, a wholly owned subsidiary of Sierra Nevada Corporation. It is a spaceplane based on previous NASA & Soviet spaceplane work.
Like that of the Apollo Program, Constellation program will involve its main vehicle, the Orion spacecraft, flying missions in low earth orbit (LEO) with an emphasis of servicing the International Space Station, and in conjunction with the Altair and Earth Departure Stage, on flights to the polar regions of the Moon. As of 2008[update], there are no well-defined plans for a manned flight to Mars, as flights to the Red Planet will most likely not occur before 2030, but a mission to a Near-Earth asteroid is in the initial planning phase.
After being brought together at the Kennedy Space Center from various parts of the country (Utah and Louisiana for the Ares I booster, and various Lockheed Martin facilities in the southern U.S. for the Orion) and completion of major testing, including spacecraft integrity testing in a vacuum chamber, the components of the Orion/Ares I stack would be assembled in the Vehicle Assembly Building in a manner similar to the stacking and assembly of both the Shuttle and the Saturn IB and Saturn V rockets.
Once assembly is completed and a launch date set, the Crawler-Transporter will pick up and transport the completed Orion-Ares I stack, along with the launch support tower and the Mobile Launcher Platform, out to Launch Pad 39B, which is currently undergoing conversion from use in Shuttle missions to be used for Ares I operations. Once the Crawler-Transporter reaches the pad, the Ares I and its platform is left in place and the Crawler-Transporter is taken to a safe, yet reasonable distance in order to facilitate pickup of the platform for an equipment rollback to the VAB.
After final checks, the ground crew will fill up the second stage with liquid hydrogen (LH2) and liquid oxygen (LOX), with the crew, suited up in new all-purpose spacesuits, entering the spacecraft only three hours before liftoff. Once locked in, and after all systems are cleared by controllers at both the Cape and Mission Control in Houston, the Ares I is then launched, clearing the launch tower and (after a roll program and pitch over), heads out on the proper trajectory.
At T+120 seconds into the flight the solid-fueled first stage is jettisoned for recovery, and the onboard J-2X engine is ignited. 30 seconds later both the launch abort system and the fairings covering the Orion crew and service modules would also be jettisoned. At T+330 seconds after liftoff, the J-2X engine cuts off, and the Orion spacecraft would enter an initial entry orbit, which, 45 minutes later, is circularized by a second burn of the onboard J-2X engine, after which the Orion spacecraft separates (allowing the second stage to burn up in the atmosphere) and extends a pair of paddle-shaped solar panels.
After a two-day chase, the Orion spacecraft would meet with the International Space Station. After getting the go ahead from Houston, Orion would dock with the ISS. The six-man crew, the largest number that can fly on an Orion spacecraft, would then enter the station in order to perform numerous tasks and activities for the duration of their flight, usually lasting six months, but can be shortened to four or lengthened to eight, depending upon NASA's goals for that particular ISS Expedition. Once completed, the crew then reenters the Orion, which has been kept attached to the station as an emergency "lifeboat," seal off the hatches between it and the ISS, and then undock from the station.
Once the Orion reaches a safe distance from the ISS, the spacecraft will turn around so the main engine faces forward and fire its onboard Aerojet AJ-10 engine. After the de-orbit burn has been completed, the service module is then jettisoned, allowing it to burn up in the atmosphere while the crew module re-enters in the same manner as all NASA spacecraft prior to the Shuttle, using the ablative heat shield to both deflect heat from the spacecraft and to slow it down from a speed of 28,000 km/h (17,500 mph or Mach 5) to 480 km/h (300 mph or Mach 0.5). After reentry is completed, the forward assembly is jettisoned, and two drogue parachutes will be released, followed at 20,000 feet (6,100 m) by three main parachutes and airbags filled with nitrogen (N2), which does not combust when exposed to heat, allowing the spacecraft to splashdown. The Orion CM is then returned to Kennedy Space Center for refurbishment for a later flight. Unlike the Apollo CM, which was used only for one flight, an Orion CM can be used up to ten times under normal operating conditions.
Unlike the Apollo flights, where both the Apollo Command/Service Module and the Apollo Lunar Module were launched together on the Saturn V rocket, the manned Orion craft would be launched separately from the unmanned EDS and lunar lander. The Ares V/EDS/Altair stack would be assembled at the Vehicle Assembly Building and then transported to Pad A of Kennedy Space Center Launch Complex 39. Approximately a day later, the Ares I/Orion stack would be transported to the adjacent Pad 39B. The Ares V/EDS/Altair vehicle would be launched first, into a 360 kilometers (220 mi) high circular orbit. Approximately 90 minutes later, the Ares I/Orion would launch with the crew into a nearly identical orbit.
The Orion would then rendezvous and dock with the Altair/EDS combination already in low-Earth orbit. After the necessary preparations for lunar flight, the EDS would fire for 390 seconds to make the translunar injection (TLI) maneuver, accelerating the spacecraft to 40,200 kilometers per hour (25,000 mph). Unlike Apollo, the Constellation TLI burn would be done in an "eyeballs-out" fashion (with the astronauts facing the EDS and thus being pulled from their seats by the acceleration). After the TLI burn, the EDS would be jettisoned and sent either into an orbit around the Sun or to crash into the lunar surface.
During the three-day trans-lunar coast, the four-man crew monitor the Orion's systems, inspect their Altair spacecraft and its support equipment, and correct their flight path as necessary to allow the Altair to land at a near-polar landing site suitable for a future lunar base. Approaching the lunar far side, the Orion/Altair combination orients the Altair's engines forward and make the lunar orbit insertion (LOI) burn.
Once in lunar orbit, the crew refines the trajectory and configures the Orion CSM for unmanned flight, allowing all four crew members to transfer to the Altair and land on the Moon, while the Orion waits for its return. Upon receiving clearance from Mission Control, the Altair undocks from the Orion and performs an inspection maneuver, allowing ground controllers to inspect the spacecraft via live TV mounted on Orion for any visible problems that would prevent landing (on Apollo this was done by the Command Module Pilot). After receiving approval from ground controllers, the two craft separate to a safe distance and the Altair's descent engines fire again for powered descent to a pre-determined landing spot previously scouted out by unmanned spacecraft.
Upon landing, the crew dons their extravehicular activity (EVA) spacesuits and commence the first of five to seven lunar EVAs, collecting samples and deploying experiments. After completing their Lunar Sortie operations, the crew enters the Altair and fires the ascent stage engine to lift off from the surface, using the descent stage as a launchpad (and as a platform for future base construction). Upon entering orbit, the Altair rendezvous and docks with the waiting Orion spacecraft, and the crew then transfers, along with samples collected on the moon, back to the Orion. After jettisoning the Altair and sending it to crash into the lunar far side, the crew performs the Trans Earth Injection (TEI) burn for the return trip to Earth.
After a two-and-a-half day coast, the crew jettisons the Service Module (allowing it to burn up in the atmosphere) and the CM reenters the Earth's atmosphere using a special reentry trajectory designed to slow the vehicle from its speed of 40,200 kilometers per hour (25,000 mph) to 480 kilometers per hour (300 mph) and allow a Pacific Ocean splashdown. The Crew Module is then flown back to KSC for refurbishment, while lunar samples are routed to the Johnson Space Center's (JSC) Lunar Receiving Laboratory for analysis.
The Orion Asteroid Mission is a proposed NASA mission to a near-Earth asteroid (NEA) which would use the standard Orion spacecraft, and a landing module based on Altair. Such a mission could assess the potential value of water, iron, nickel, platinum and other resources on the asteroid; test possible ways to extract them; and possibly examine or develop techniques which could be used to protect the Earth from asteroid impacts. This would be the first manned mission beyond both the Earth and the Moon, and would represent a step toward a manned mission to Mars, envisioned for after 2030.
The mission would start in a similar fashion to a Constellation lunar landing mission, with an Ares V launching the landing module into Low Earth orbit, followed by the launch of an Orion spacecraft, with a two or three person crew (as opposed to a four person crew for lunar missions) on an Ares I rocket. Once the Orion spacecraft docks with the landing module and the Earth Departure Stage (EDS), the EDS would then fire again and propel the Orion spacecraft to a nearby near-Earth asteroid where the crew would then land and explore its surface.
Once their task is completed, the Orion spacecraft will then depart from the asteroid and, upon reaching the vicinity of Earth, would jettison both the service module and the landing module in a manner similar to that of Apollo 13 (i.e. separating the service module before the landing module) before entering the atmosphere for a Pacific Ocean splashdown.
The Orion Mars mission plan for NASA's Constellation program is a manned mission with the intent to land humans on Mars in the 2030s. Originally the ultimate goal of NASA's Apollo Applications Program (AAP) in the 1960s, the Orion Mars Mission would utilize the hardware, primarily the Orion spacecraft (or a variation based on the Orion), and the Ares V cargo-launch vehicle, along with methods of carrying out the mission, which would be developed on board the International Space Station and the planned Lunar Outpost which is to be set up on the surface of the Moon after 2020.
Although no specific mission has yet been defined, it will most likely follow the Mars Direct concept developed by Robert Zubrin. Zubrin's concept utilizes an "Earth Return Vehicle", which would be sent out to Mars on a low-consumption trajectory which would arrive at Mars during the planet's conjunction period, when the planet is behind the Sun as seen from Earth. Once the Earth Return Vehicle lands it is planned to use an onboard Sabatier reactor in order to create liquid oxygen and methane fuel for the return trip; a second spacecraft, carrying the crew, would follow after. Arriving at Mars, the crew will land near the Earth Return Vehicle and will explore the planet for a period of nearly one Earth year. At the same time the astronaut crew explores the planet, another Earth Return Vehicle is sent to Mars, allowing NASA an "insurance policy" in the event the first Earth Return Vehicle is unable to perform its task.
Once the crew finishes its surface exploration of the planet, they will then enter the first Earth Return Vehicle and then lift off from the planet's surface. After docking with an orbiting return rocket, the crew then fires the rocket and returns to Earth, making a high-speed reentry in order to land approximately four months after leaving Mars.
Originally envisioned, along with the Apollo Lunar Base, the Voyager Mars Program, and the Manned Venus Flyby, the AAP "Man-on-Mars" program was canceled, along with the rest of the AAP program, and replaced by the Skylab "dry workshop" space station and the Space Shuttle. The Orion Mars Mission, if eventually launched, would occur in the 2030s. Had the AAP Mars mission not been canceled, the first manned landing on Mars was scheduled to have occurred around 1985.
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