Project Constellation

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Conceptual drawing of the Earth Departure Stage, docked to the Crew Exploration Vehicle, firing its engine to leave Earth's orbit.

Project Constellation is NASA's latest road map for space exploration and, especially, space colonization.

It consists of a family of new spacecraft, launchers and associated hardware that allow for 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 the key hardware, the Crew Exploration Vehicle (CEV), is heavily based on the earlier Apollo-like capsule design.

The new transportations system, which uses both an Earth Orbit Rendezvous and a Lunar Orbit Rendezvous technique, can be broken down into three parts: The CEV Crew & Service Modules, the Lunar Surface Access Module, and the Earth Departure Stage. The rockets to be used for launching of the different components consists of the unmanned Ares V (for launch of cargo and the Earth Departure Stage), and the manned Ares I for launch of the CEV.

Contents

1 CEV Crew & Service Modules
2 Lunar Surface Access Module
3 Earth Departure Stage
4 Mission Profiles

4.1 Near-Earth Orbit & ISS Service Flights
4.2 Lunar Flights

5 See also

CEV Crew & Service Modules

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The CEV Crew & Service Modules (CSM) consists of two main parts--a conical crew module shaped similarly to the Apollo Command Module and capable of holding three to six crew members, and a cylindrical service module which will hold the spacecraft's onboard supplies. The CSM will be built on the designs of the Apollo CSM, but with the technologies introduced on the Space Shuttle in the past 20+ years of operation. Such technologies will include, but are not limited to, the "glass cockpit" technologies, improved waste management (the use of a miniaturized camping-style toilet instead of the much-hated plastic bags for fecal disposal, and a unisex "relief tube" for urine elimination), and an oxygen-nitrogen atmosphere at sea level or slightly reduced pressure instead of a pure oxygen atmosphere, the latter being extremely flammable as was the case in the Apollo 1 fire. The main feature that will be introduced in the new crew module will be a new recovery system that will employ the use of a combination of parachutes and airbags for capsule recovery. This will allow NASA to retrieve the CEV crew module on land, much like the Russian retrieval of the Soyuz descent module, and eliminate the need for an expensive naval recovery fleet employed on previous pre-Shuttle manned missions. A docking hatch and transfer tunnel, based on the Russian docking assembly for the Shuttle/Mir, and later Shuttle/ISS missions, eliminates the Apollo-era "probe and drogue" (male/female) system, and can allow, in extreme emergencies, for an in-space rescue without the need for an EVA transfer (as the two spacecraft would have the same docking adapter that was first demonstrated on the Apollo-Soyuz Test Project).

Another feature will be the partial reusability of the CEV crew module. Each crew module will be able to be reused for up to 10 flights, thus allowing NASA to construct a fleet of CEVs like that of the current Shuttle fleet. Part of this reusability will come from the landings made on solid ground, as the heatshield is discarded to expose the landing airbags, and that seawater, as evident on the pre-Shuttle splashdowns and recovery operations of the Solid Rocket Boosters is corrosive and difficult to remove (despite that the Mercury 4 Liberty Bell 7 capsule, which sunk into the Atlantic Ocean near The Bahamas in 1961, remained mostly undamaged due to the capsule being made primarily of titanium). In addition, the new capsule will have steering rockets fueled primarily from either pressurized gaseous nitrogen (N2), pressurized liquid nitrogen (LN2), hydrogen peroxide (H2O2), or a mixture of liquid oxygen and ethanol (C2H6O). This would allow NASA to steer completely away from hypergolic chemical used in the reaction control systems (RCS) used in every spacecraft since Gemini. Hydrogen peroxide, used in Project Mercury, is primarily water based, while pressurized nitrogen has been used on unmanned spacecraft. The combination of LOX and ethanol has been proposed as part of an upgrade for the Space Shuttle program prior to the breakup of Columbia in 2003.

The CEV service module is identical in shape (but not in size) to its Apollo predecessor, but unlike the Apollo SM, the new CEV SM, which will be shorter in height, will feature a pair of deployable Soyuz-like solar panels, eliminating the need to carry fuel cells. Instead, the LOX and liquid hydrogen (LH2) tanks will be utilized for the new main engine of the CEV SM, which will utilize an upgraded RL-10 rocket engine. Originally, NASA wanted to use a variant of the RL-10 or a derivative of the Apollo SM service propulsion system (SPS), in essence the present day orbital maneuvering system (OMS) used on the Shuttle, that burned LOX and liquid methane (LCH4).

The use of LOX/LCH4 would allow NASA to develop the technologies that would be needed to convert, "in situ" any methane found on Mars, the lunar polar regions, and on any methane-rich body in the Solar System, especially Titan, Pluto and most trans-Neptunian objects in the Kuiper Belt. The use of LOX/LH2 would allow NASA to use the CEV SM to change course during the trans-lunar coast, and eventually allow the crew to return to Earth (the LSAM would brake the stack into lunar orbit). The RCS on the CEV SM, identical in "quadrant" arrangement to that on the Apollo SM, would use the same non-hypergolic fuels as to be used on the CEV crew capsule's RCS.

Concept of the Ares I rocket leaving Earth's atmosphere.

The CEV will be launched into a low earth orbit using the new Ares I rocket (formerly referred to as the Crew Launch Vehicle (CLV)). Based on the Shuttle's SRBs and Space Shuttle External Tank (ET), the Ares I will consist of a solid-fueled first stage, built using a modified SRB with five segments instead of four and with a new interstage assembly, and a liquid-fueled second stage fueled with LOX and LH2 and powered by an uprated Apollo-era J-2X rocket engine. Originally, the Ares I would have used a slightly modified 4-segment SRB and a second stage using a single throw-away version of the Space Shuttle Main Engine, but the expense of designing and constructing an air-startable version of this engine (the current SSME is a ground-started engine) forced NASA to redesign the booster to incorporate the newer J-2X engine. During the first two minutes of launch, the spacecraft will have the benefit of a launch-escape system (LES) similar in design to that used on the Soyuz spacecraft. Originally, the LES was to be bolted directly over the docking hatch assembly, but a recent NASA diagram shows the LES mounted onto a "boost protective cover" identical to that used on the Apollo CSM, and would protect the spacecraft thermal protection system during first stage (SRB operations) and would be discarded along with the LES after second-stage ignition.

NASA also has plans to build two unmanned variants of the CEV. One version will be identical in design and construction to the manned CEV, but with the pressurized crew module stripped of all crew-required equipment, and replaced with storage lockers that would bring up fresh supplies from Earth. This version, which can be recovered, will allow astronauts to return old experiments, or results from on-going experiments on a regular basis; a feature not possible on the current unmanned Progress spacecraft used by Russia. Another variant, which has the crew module completely replaced with an enlarged CEV SM and docking system, will allow NASA to boost the ISS into a higher orbit than that currently possible with the Progress vehicle, which has limited fuel supplies for reboosts. This will allow NASA to reduce the need for reboost flights from three times per year to only once or twice per year, depending upon the 11-year solar activity period.

Lunar Surface Access Module

The Lunar Surface Access Module (LSAM) is the main transport vehicle for lunar-bound astronauts and has its heritage from the Apollo Lunar Module (LM). Like its Apollo predecessor, the LSAM consists of two parts, a sideways cylindrical ascent stage which houses the four-person crew, and an octagonal descent stage which has the landing legs, the majority of the crew's consumables (oxygen and water), and scientific equipment. The LSAM, like the LM, descends from lunar orbit on the descent stage, and uses the bottom half as a launchpad when the ascent stage departs from the Moon. Unlike the Apollo LM, the LSAM will play a major role in braking the CEV stack into lunar orbit, which can be an Apollo-like (0 to 30-degree) equatorial, or an ISS-style (55 to 60-degree) inclinational orbit, allowing the LSAM to touch down in the lunar polar regions favored by NASA for future lunar base construction. [link]. This "lunar orbit insertion" (LOI) technique is similar to the former Soviet Union's lunar mission profile in which the Soyuz orbiter and lunar lander, attached to the "Block E" stage of the N-1 rocket, would enter lunar orbit, allowing a spacesuited cosmonaut to make a transfer spacewalk to the lander, which only then the Soyuz and lunar lander would separate and then proceed with the lunar landing.

This use of the LSAM for braking the stack into lunar orbit will be accomplished by the use of four of the same RL-10 rocket engines already planned for use on the CEV. Unlike the current RL-10 engines used on the Centaur upper stages used on the Atlas V rocket, 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 the LSAM for both the LOI and landing stages of the lunar mission.

Like the orbiter, the ascent stage was originally planned to use an RL-10 type engine fueled by the same LOX/LCH4 mixture originally planned for the CEV, but this has since been replaced with a single RL-10 fueled by the same LOX and LH2 mixture. Despite the change in the type of fuel to be used for the LSAM, the vehicle will feature computer technologies, but will also have provisions for the module to be powered by either solar batteries or with fuel cells (using leftover hydrogen in the descent stage's tanks), eliminating the extra weight and space created by batteries needed for a seven-day lunar stay. It would also have an airlock, a feature not found on the Apollo LM, that would allow the LSAM to remained pressurized during a lunar EVA, and minimize the dust transfer from the lunar surface to the cabin. The LSAM, like its Apollo predecessor, is not reusable and is discarded after use.

Earth Departure Stage

Concept of the Ares V rocket shortly after liftoff.

The Earth Departure Stage (EDS) is the main propulsion system that will send the entire CEV/LSAM stack from low Earth orbit to the Moon. It will be launched on the Ares V rocket (formerly referred to as the Cargo Launch Vehicle (CaLV)), an in-line Shuttle Derived Launch Vehicle roughly based on both the in-line Magnum (U.S.) and piggy-back Energia (U.S.S.R./Russia) boosters. The Ares V will incorporate five RS-68 engines (Space Shuttle Main Engines were originally planned for the Ares V, but the RS-68 engines are more powerful and less expensive than the SSMEs) with assistance from a pair of five-segment SRBs. The Ares V will fly for the first eight minutes of powered flight, while the EDS will place itself and the LSAM into low Earth orbit while awaiting the arrival of the CEV. Like that of Skylab, the manned CEV will be launched separately (at least 2 to 4 weeks after the Ares V launch) and then rendezvous and dock with the EDS/LSAM combination. After configuring the system for the journey to the Moon, the EDS will then fire its engines to propel the CEV stack to the Moon.

Based on the S-IVB upper stage of the Saturn V rocket, the EDS is in essence an enlarged S-IVB with larger LOX/LH2 tanks and is powered by two of the same J-2X engines already being planned for the Ares I. The EDS, while primarily being designed for its lunar role (and eventual Mars role), it can also launch large modules (that cannot be launched with the Russian Proton booster) in support of the International Space Station or even a Skylab-class space station in an ISS-like orbit. It can also, with the LSAM removed and a docking collar added, allow a CEV to change its orbital inclination (either the standard 29-degree orbit or the 57.5-degree ISS orbit) to that of a Sun-synchronous, Clarke, or near polar orbit in a manner originally planned for the Apollo Applications Program. The EDS, teamed with a Centaur upper stage, could also be used to launch large space probes in the same weight class as Galileo and Cassini-Huygens to Uranus, Neptune, and Pluto without having to use the complicated Venus and Earth flybys used by most post-Voyager probes--instead going on direct flight paths using Jupiter and Saturn for any needed flybys. For instance, it could have easily launched the now canceled JIMO mission to the moons of Jupiter.

It could also support a Mars Sample Return mission with direct descent and ascent from Mars surface, without the complication and technical challenge of a rendezvous in Mars orbit.

Mission Profiles

Like that of the Apollo Program, Project Constellation will involve the CEV to fly on near-Earth orbit missions, with the emphasis on servicing the ISS, and lunar orbit and landing flights. Currently (as of 2006), there are no immediate plans on the type of mission profile that would be flown to Mars, a mission which will not take place until after 2030.

Near-Earth Orbit & ISS Service Flights

The CEV and Ares I are assembled on a modified Apollo/Shuttle-era Mobile Launcher Platform in the Vehicle Assembly Building (VAB) at the Kennedy Space Center in Florida. After the Ares I/CEV launch stack is assembled, it is transported to either Launch Pad 39A or 39B (currently envisioned to be LC-39B as it will be taken off-line in 2008, but both pads will be made identical to each other by placing the service tower on each MLP) where the CEV's service module and the Ares I second stage is fueled with liquid oxygen (LOX) and liquid hydrogen (LH2).

Once the crew is secured inside of the spacecraft and all systems are cleared for launch, the solid-fueled first stage of the Ares I is ignited, at the same time the access arms are retracted. This is followed by the detonation of the hold-down posts, allowing the Ares I to "spring" off of the pad, followed by a roll maneuver to place the Ares I in the proper trajectory, either on a due-east pattern for solo NEO flights or the 57.5-degree inclination for ISS flights.

Two minutes into the flight, the solid-fueled first stage, now completely out of fuel, is jettisoned to fall into the Atlantic Ocean for recovery and reuse, while at the same time, the single J-2X on the liquid-fueled second stage is fired and the launch-escape system is jettisoned to expose the docking adapter ring, as well as the crew's windows. The second stage burns for four minutes, than shuts off at 6½ minutes into the flight, placing the spacecraft into a roughly 80 km × 560 km (50 mi. × 350 mi.) elliptical orbit. The orbit is circularized with the second firing of the engine 45 minutes later. After the second firing, the CEV is separated from the second stage of the Ares I, which is allowed to fall back into Earth's atmosphere to burn up. Upon separation from the Ares I, the twin solar panels for the CEV will unfurl, and allow the spacecraft to collect the electricity needed to support spacecraft systems.

On solo flights, which most likely will occur early in the program, the onboard three to four-man crew will carry out Earth observation and other experiments reminiscent to that of the early days of NASA and all pre-ISS Space Shuttle flights. The CEV is designed to support a three-man crew for 20 days and a four-man crew for 14 days, but the usual flights will last approximately 8 to 10 days.

For flights to the ISS, the CEV, after its orbital circularization burn and jettison of the Ares I, will fly for at least 2 days to catch up with the ISS, at the same time it will trim its trajectory to match that of the ISS. Upon reaching the ISS, the CEV will dock, depending on the mission, at either the main U.S. front docking adapter (currently in use by the Space Shuttle) or on the auxiliary (X-33) docking adapter that will either have a manned CEV (in the case for an emergency escape from the ISS) or an unmanned CEV supply spacecraft.

During the 7 to 14-day stay at the ISS, the U.S. crew elements are exchanged (a third person, either from Europe or Japan, will fly as a "guest" astronaut) and old experiments are loaded from the ISS to the CEV. Following the same precedence as Russia, the most recently-launched CEV will remain with the new U.S. crew members while the old CEV will go back to Earth with the old U.S. crew. If the new CEV is required to be moved due to the need for a reboost ship (an unmanned CEV with the pressurized crew capsule replaced with a docking ring attached to an enlarged service module), the spacecraft will then be "rotated" to the auxiliary adapter after the old CEV departs from the station.

Once the CEV undocks from the ISS, or at the end of a solo CEV flight, the spacecraft will then turn around so that the main propulsion engine faces forward. After the reentry burn commences, the service module is then jettisoned to burn up in the atmosphere while the crew module makes an Apollo-like entry, using the heat shield to both shield and to slow down the spacecraft from 28,000 km/h (17,500 mph) to 480 km/h (300 mph). After reentry is completed, the forward assembly is jettisoned to release a pair of drogue parachutes, followed at 20,000 feet by three main parachutes and airbags (which are filled with nitrogen (N2), as it does not combust in high-heat situations), allowing the spacecraft to touchdown at a landing site in the western United States, most likely Edwards Air Force Base in California or White Sands Missile Range in New Mexico. The CEV is then returned to Kennedy Space Center for refurbishing and reuse (it can be reused up to 10 times under normal situations) for a later flight.

Lunar Flights

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 and then transported to the launch pad, which will likely be LC-39A, although NASA may use LC-39B as a backup. 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, the EDS swing arms and Ares V core stage collect "chocks" will retract, and the booster will lift off from the pad.

After "clearing the tower," the Ares V will fly a trajectory identical to that of the Shuttle, which has the twin SRBs jettison at 2 minutes into the flight and the main engines shutting down approximately 8½ minutes into the flight, followed by the jettisoning of the core stage, allowing it to burn up in the atmosphere over the Indian Ocean west of Australia, and the launch shroud covering the LSAM. The EDS, powered by two J-2X motors, will then steer the EDS/LSAM combination into a stable orbit.

Approximately 2 to 4 weeks after the Ares V launch, the CEV/Ares I stack, on the adjacent pad, will then lift off, and following the same flight pattern as that on an ISS service mission, will dock with the EDS/LSAM stack in low-Earth orbit. After configuring the systems for lunar flight, the EDS will then fire for the five-minute Trans-Lunar Injection (TLI) burn, which will then increase the speed of the stack from 28,000 km/h (17,500 mph) to 40,200 km/h (25,000 mph). After the TLI burn, the EDS is then jettisoned to either enter into either a solar orbit or steered into a slightly different trajectory to crash the stage into the lunar surface (similar to that used on the S-IVB for the last five Apollo missions). During the trans-lunar coast, which will last 3 days, the four-man crew will monitor the CEV's systems, inspect their LSAM and the moon-walking space suits, and change their trajectory to allow the LSAM to land in a near-polar landing site suitable for a future lunar base.

Three days after TLI, the spacecraft, approaching the lunar far side, will orient the spacecraft stack so that the LSAM's engines point forward and then the Lunar-Orbit Insertion (LOI) burn is commenced. Once in orbit, the crew will then refined the trajectory to allow the LSAM to be separated from the CEV, only then will the CEV be placed under automatic ground control and the entire four-man crew transfers to the LSAM and undocks from the CEV, performing the same ballet maneuver as done in Apollo, except that ground controllers in Houston serves as the "eyes" previously done by Apollo CM pilots in the past. Once the separation maneuver is completed, the CEV is then placed in a 60 to 70-mile altitude circular orbit to wait for the LSAM's return.

After configuring the LSAM for landing and receiving approval from Houston, the four RL-10 engines on the LSAM's descent stage will then fire again, and like that of Apollo, the crew will then land their LSAM in a pre-determined landing spot that was scouted out before by unmanned spacecraft. Upon landing, the crew will then don their lunar spacesuits and commence the first of six to seven lunar EVAs collecting samples, deploying experiments, and most likely for the first landing, leaving memorials to the astronauts who died on the Challenger and Columbia disasters (Apollo 11 left a memorial for the three Apollo 1 astronauts and the lone Soyuz 1 cosmonaut, while Apollo 15 featured the Fallen Astronaut sculpture, made after the disastrous Soyuz 11 mission).

After completing their lunar deployment operations, the crew will then enter the LSAM's ascent stage and then take off from the Moon, powered by a single RL-10 engine and using the descent stage as a launchpad (and as a platform for future base construction), and then dock with the CEV. Once the crew transfer the samples and photographs over to the CEV, the LSAM will then be jettisoned to crash into the lunar far side, and the CEV 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 flying a special reentry trajectory designed to both slow the vehicle down from its break-neck speed of 40,200 km/h (25,000 mph) to 480 km/h (300 mph) and allow for a west coast landing, the CEV will then land on Earth in the same manner as that of an ISS/solo CEV flight. Like that of the ISS/solo missions, the CEV will then be flown back to KSC for refurbishment and reuse on another flight, while the lunar samples are flown directly to Houston for analysis at the famed Lunar Receiving Laboratory.