Project Constellation
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Project Constellation is a NASA program to create a new generation of spacecraft for human spaceflight, consisting primarily of the Ares I and Ares V launch vehicles, the Orion crew capsule, the Earth Departure Stage and the Altair lunar lander.[1] These spacecraft will be capable of performing a variety of missions, from Space Station resupply to lunar landings.
Most of the Constellation hardware is based on systems originally developed for the Space Shuttle, although Orion's two-part crew and service module system is heavily influenced by the earlier Apollo Spacecraft, and it uses engines derived from the Saturn V and Delta IV rockets. Proposed Constellation missions may employ both Earth Orbit Rendezvous and Lunar Orbit Rendezvous techniques.
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[edit] Constellation Program
NASA has formed the Constellation Program to achieve the objectives of maintaining American presence in low Earth orbit, returning to the Moon for purposes of establishing an outpost and laying the foundation to explore Mars and beyond in the first half of the 21st century.[2] The Constellation Program's heritage rests on the successes and lessons learned from NASA’s previous human spaceflight programs: Mercury, Gemini, Apollo, Skylab, Space Shuttle and the International Space Station (ISS).
[edit] Spacecraft
Orion will consist of two main parts, a Crew Module (CM) similar to the Apollo Command Module capable of holding four to six crew members, and a cylindrical Service Module (SM) containing the primary propulsion systems and consumable supplies. The Orion CM will be reusable for up to 10 flights, allowing NASA to construct a fleet of Orion CMs.
Current plans call for the phased introduction of Orion variants tailored for specific missions. The Block I Orion will be employed for ISS crew rotation and resupply and other Earth orbit missions, while the Block II and III variants will be designed for deep-space exploration.
[edit] Launch vehicles
As currently envisioned, the Orion spacecraft will be launched into a low earth orbit using the proposed Ares I rocket (the "Stick"). Formerly referred to as the Crew Launch Vehicle (CLV), the Ares I consists 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. The Orion spacecraft would be lifted into orbit atop this "stack", while a larger launch vehicle (the proposed Ares V) would be used to launch the heavier Earth Departure Stage and Altair.
In January 2007, NASA announced that a different launch vehicle design, the Ares IV, was actively under consideration for the program. If chosen, the Ares IV might replace both the Ares I and the Ares V launch vehicles for some Constellation launches at later dates, or all of them altogether.
[edit] Altair
Altair (formerly known as the Lunar Surface Access Module, LSAM) will be the main transport vehicle for lunar-bound astronauts. Like its Apollo Lunar Module (LM) predecessor, Altair consists 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 is to touch down in the lunar polar regions favored by NASA for future lunar base construction.[3] Altair, like its Apollo predecessor, is not reusable and is discarded after use.
The Altair descent stage will be powered by four RL-10 rocket engines that are currently 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 will 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 remains a small possibilty that the original plan of using LOX/CH4 - fueled engines onboard the Block II (lunar) Orion CSM and Altair ascent stage will come to pass; however, this appears very unlikely.
[edit] Earth Departure Stage
The Earth Departure Stage (EDS) is the main propulsion system that will send the entire Orion/Altair stack from low Earth orbit to the Moon. It will be launched on an Ares V rocket; Orion spacecraft will launch separately, rendezvous and dock with the EDS/Altair combination, which will then be configured for the journey to the Moon. This method, known as Earth orbit rendezvous, was considered by NASA for the Apollo program in the early stages of planning, but was dropped in favor of the lunar orbit rendezvous approach.
[edit] Mission profiles
- See also: List of Constellation missions
Like that of the Apollo Program, Project Constellation 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 lunar lander and Earth Departure Stage, on flights to the polar regions of the Moon. As of 2008, 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 phases.
[edit] Low-Earth Orbit
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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 spacecraft) and completion of major testing, including spacecraft integrity testing in a vacuum chamber, the components of the Orion/Ares I stack is assembled in the Vehicle Assembly Building in a manner similar to that of the stacking and assembly of both the Space Shuttle and Saturn IB/Saturn V rockets.
Once assembly is completed and a launch date is set, the Crawler-Transporter picks up and transports both the assembled Orion/Ares I stack, its launch tower, and the new Mobile Launcher Platform they are sitting on out to Launch Pad 39B, which is currently slated to be the primary launch platform for all Orion/Ares I launches. 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 then fills 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 all systems are cleared by controllers at both the Cape and Mission Control in Houston, the Ares I is then launched, with staging occurring in a little over two minutes and orbital insertion only 4.5 minutes later. A second, circularization burn, using the onboard J-2X engine on the Ares I second stage, places the Orion spacecraft on a proper course to the International Space Station.
After a two-day chasedown, the Orion spacecraft meets up with the International Space Station, and then, after getting the go ahead from Houston, docks with the ISS. The six-man crew, the largest number that can fly on an Orion spacecraft, then enters the station and performs 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," seals off the hatches between it and the ISS, and then undocks 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 single Aerojet AJ-10 engine. After the deorbit 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 25) 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 by three main parachutes and airbags filled with nitrogen (N2), which does not combust when exposed to heat, allowing the spacecraft to splashdown.[4] 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 10 times under normal operating conditions.
[edit] Lunar flights
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- See also: Lunar sortie and Lunar outpost (NASA)
.jpg/180px-Orion_lunar_orbit_(Sept_2006).jpg)
Unlike the Apollo flights, when both the Apollo Command/Service Module and the Apollo Lunar Module were launched together on the Saturn V rocket, the first phase of a lunar mission will occur with the launch of the Shuttle-derived Ares V. Like the Ares I, the Ares V will be assembled at the VAB, but upon approaching the launch date, the Ares V would then be transported to Launch Pad 39A, the same launch pad used by NASA to launch the Apollo 11 spacecraft on its history-making mission. Upon giving the clearance to launch, the five RS-68 engines will ignite and upon verification by the on-board computer, the twin five-segment SRBs will ignite. At the same time, the EDS swing arms and Ares V core stage collect "chocks" will retract, and the booster will then lift off from the pad.
After clearing the tower, the Ares V will perform a roll maneuver and travel due east from the launch pad so that the orbital inclination is the same as the latitude of Cape Canaveral, 28.5 degrees. This launch profile has the twin five-segment SRBs jettison at 2 minutes into the flight and the main engines shutting down approximately 8½ minutes later, followed by the jettisoning of the core stage and launch shroud. The spent core stage and its RS-68 engine cluster will then burn up in the atmosphere over the Indian Ocean west of Australia. The EDS, powered by its single J-2X motor, will steer the Altair/EDS combination into a stable 360 km (approx. 225 mi) high circular orbit.
Approximately 90 minutes after the Ares V launch, the Orion/Ares I stack, on Pad 39B and transported approximately a day after the Ares V stack, will lift off from the adjacent launch pad at the same orbital inclination, allowing the manned Orion CSM to dock with the Altair/EDS combination already in low-Earth orbit. After the systems are configured for lunar flight, the EDS will fire for the five-minute translunar injection (TLI) burn, which will accelerate the spacecraft stack from 28,000 km/h (17,500 mph) to 40,200 km/h (25,000 mph). Unlike the Apollo/Saturn TLI burn, the Orion/Altair/EDS TLI burn will be done in the same "eyeballs out" fashion (with the astronauts being "pulled" from their seats) similar to that envisioned with the Manned Venus Flyby missions planned during the Apollo Applications Program in the late 1960s. After the TLI burn, the EDS is jettisoned, and either enters into an orbit around the Sun or steers into a slightly different trajectory to crash into the lunar surface (similar to that employed by the S-IVB stages from Apollos 13 to 17). During the remaining Orion/Altair combination's trans-lunar coast, which will last 3 days, the four-man crew will monitor the Orion's systems, inspect their Altair spacecraft and its support equipment, and, if necessary, change their trajectory to allow the Altair to land in a near-polar landing site suitable for a future lunar base.
Three days after TLI, the Orion/Altair combination, approaching the lunar far side, will orient the Altair's engines in the proper direction for the lunar orbit insertion (LOI) burn to begin. Once in orbit, the crew will refine the trajectory and configure the Orion CSM for unmanned flight, then all crew members will transfer to the Altair, undocking from the Orion CSM after receiving clearance from Houston. Ground controllers will next perform an inspection of the Altair using a remote, near-time (a signal takes approximately 3 seconds total to go to and from the Earth and Moon due to the distance) TV camera; formerly this was performed by the Apollo Command Module Pilot (CMP). Once the subsequent separation maneuver is completed, the unmanned Orion CSM is placed in a 95 to 110 km (approx. 60 to 70 mi) high circular orbit to wait for the Altair's return.
After the crew receives approval from Houston, the four RL-10 engines on the Altair's descent stage will fire again, and like that of Apollo LM, the crew will land their Altair in a pre-determined landing spot that was scouted out before by unmanned spacecraft. Upon landing, the crew will don their moonwalking spacesuits and commence the first of five to seven lunar EVAs collecting samples and deploying experiments.
After completing their lunar deployment operations, the crew will enter the Altair's ascent stage and lift off from the Moon's surface, powered by a single ascent engine, likely a hypergolic engine similar to that used on the Orion CSM, using the descent stage as a launchpad (and as a platform for future base construction), then dock with the Orion CSM in lunar orbit. Once the crew transfers the samples and photographs over to the Orion CSM, the Altair will be jettisoned to crash into the lunar far side, and the Orion CSM will then ignite its single engine (Trans Earth Injection – TEI) for the return trip to Earth. Upon reaching Earth, the service module is jettisoned and a special reentry trajectory is established; the reentry trajectory is designed to both slow the vehicle from its speed of 40,200 km/h (25,000 mph) to 480 km/h (300 mph) and allow for a West Coast landing. The Orion CM will then splashdown in the same manner as an ISS-bound flight. Like that of the ISS-bound missions, the Orion CM will be flown back to KSC for refurbishment and reuse on another flight, while the lunar samples are flown to JSC for analysis at the Lunar Receiving Laboratory.
[edit] Other flights
As the Orion spacecraft is the "nucleus" of Project Constellation, its design would most likely be used for a possible flight to a near-Earth asteroid. At the same time, NASA has also been looking into using the Ares V to launch an 8-meter successor to the famed Hubble Space Telescope to the Sun-Earth Lagrange Point (SEL2), where the telescope, not being interfered by the Earth, can carry out uninterrupted searches for Earth-like planets around Sun-like or red dwarf stars.
The ultimate mission, a manned mission to Mars, would most likely occur after 2030. Such a mission would most likely follow a "split-sprint" profile in which a return vehicle, with an Orion-derived spacecraft capable of high-speed reentry, would take a slow route to the Red Planet, touching down in a predetermined spot on the Red Planet, while another ship, carrying a six-person crew and their equipment, would then follow on a faster trajectory that would see all six astronauts land on the planet six months after launch, with a total stay time of 2 years, during which a reactor utilizing the Sabatier reaction with the available materials found on the planet will keep the six astronauts alive (by making breathing oxygen from the available carbon dioxide found in the planet's atmosphere) and produce fuel for the return trip home.
After leaving Mars, the crew will most likely make a flyby of Venus during the return trip, with the Orion-derived landing capsule separating from the return vehicle and making a high-speed reentry for a Pacific Ocean splashdown, ending a mission lasting a total of 3 years and culminating in a goal that, if not deferred by the domestic and international issues of the 1960s and 1970s, would have occurred in 1985 as an off-shoot of the Apollo Applications Program.
[edit] Alternatives
The choice to accept the ESAS-recommended Ares launchers is not without controversy, and two major alternative launch architectures have been suggested to fill the Ares role:
- The DIRECT launch vehicle concept, which uses existing shuttle components, such as the solid rocket boosters and the external tank, with minimal development of new hardware.
- The original VSE architecture supported the use of manrated versions of the current EELV launchers to lift a modified CEV, as well as the components required for lunar exploration into Low Earth Orbit.
[edit] See also
- Exploration Systems Architecture Study
- NASA's Vision for Space Exploration
- Crew Space Transportation System (CSTS), European-Russian counterpart of the CEV and the Vision of Space Exploration
[edit] References
- ^ William H. Gerstenmaier (2007). Transitioning to a Next Generation Human Space Flight System (English). United States Senate Committee on Commerce, Science and Transportation. Retrieved on September 29, 2007.
- ^ Rejcek, Peter (December 6, 2007). To the moon (web). Inflatable habitat will first be tested in the harsh Antarctic environment. The Antarctic Sun. Retrieved on 2008-01-13.
- ^ NASA outlines plans for moon and Mars. Orlando Sentinel.
- ^ Orion landings to be splashdowns - KSC buildings to be demolished. NASA SpaceFlight.com (2007-08-05). Retrieved on 2007-08-05.
[edit] External links
- Official Constellation NASA Web Site
- Official Orion NASA Web Site
- Official Ares Web Site
- A Visual History of Project Constellation
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