Project Constellation
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In September, 2005, NASA decided to use an Apollo-like capsule for the CEV design, dubbed by NASA Administrator Michael Griffin as "Apollo on steroids." This is due to the fact that the new CEV design will use the crew and service module design principle, instead of a spaceplane-style lifting body used in the Space Shuttle system. The "Apollo" reference is reflected in the design of the modules, which is virtually identical to the Apollo Command Module. 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.
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CEV Crew & Service Modules
Template:Main 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 minaturized 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.
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. To allow the CEV to service the International Space Station, it will use a more simplified version of the Russian-developed docking ring currently in use on the remaining Shuttle fleet, but with the ability of being discarded upon the ending of the mission. The docking adapter will be covered over with a Launch Escape System identical in design to that found on the Apollo spacecraft.
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 and hydrogen tanks. Instead, the new SM will have tanks containing liquid oxygen (LOX) and liquid methane (LCH4), the latter being the fuel for both the onboard service propulsion system and reaction control system. The choice of liquid methane was simple: 1. It eliminates the hazards associated with the use of hypergolic system similar to that found on Apollo and the Shuttle, and 2. it can be mined on methane-rich bodies such as Mars, Titan, Pluto, and most of the trans-Neptunian objects in the Kuiper Belt. Also, liquid methane, which can be produced with normal liquified natural gas (LNG) methods, is cheaper to store on site and can be transported with normal transportation methods (trucks, trains, ships, or even by pipeline), while hypergolics require special hazmat permits.
The CEV crew/service module will be launched into low earth orbit using a new Crew Launch Vehicle (CLV). This Shuttle Derived Launch Vehicle (SDLV), based mostly on the solid rocket boosters (SRBs) and external tank (ET) of the Shuttle, will consist of a solid-fueled first stage, using a five-segment booster instead of the current four-segment version, with the second stage being a liquid-fueled upper stage using LOX and liquid hydrogen (LH2) and powered by an uprated Apollo J-2 engine (the Shuttle's main engine was originally proposed, but an air-startable engine was never produced or tested while the Saturn-based J-2 was designed from the beginning to start in mid-air).
An unmanned version, using a pressurized crew module stripped of all crew-required equipment, can be used for resupply mission to the ISS in a fashion similar to that of the Progress supply ships in current use, with old scientific and engineering equiment being sent back to Earth for ground analysis (the Progress spacecraft cannot do this as the entire ship burns up in the atmosphere).
Lunar Surface Access Module
Template:Main 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 equatorial or mid-inclinational orbit like that of Apollo, or in a near-polar orbit favored by NASA for future lunar base construction sites [1]. This "lunar orbit insertion" (LOI) technique is similar to the former Soviet Union's lunar mission profile in which the L-3 complex, consisting of the LK (lander), LOK (a modified two-man Soyuz), and "Block E" rocket stage would brake the entire L-3 into lunar orbit, and after an EVA transfer by a lone cosmonaut (this is not necessary with the CEV, which has a pressurized transfer tunnel), would split into the separate "Block E"/LK combination and LOK components, with the former descending to the lunar surface.
This use of the LSAM for braking the stack into lunar orbit will be accomplished by the use of rocket engines fueled by LOX and liquid hydrogen (LH2), which is more powerful and efficient than the LOX/LCH4 mixture for the orbiter, or the hypergolic systems used on the Apollo LM. But like the orbiter, the ascent stage will use the same LOX/LCH4 mixture for its ascent engine and reaction control system. Like the orbiter, the LSAM will have the same 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. The LSAM, like its Apollo predecessor, is not reusable and is discarded after use.
Earth Departure Stage
Template:Main The Earth Departure Stage (EDS) is the main propulsion system that will send the entire CEV lunar stack from low Earth orbit to the Moon. It is launched on the Cargo Launch Vehicle (CaLV), a Shuttle Derived Launch Vehicle, (SDLV) roughly based on both the Magnum (U.S.) and Energia (U.S.S.R./Russia) boosters, and will incorporate five Shuttle main engines (or three RS-68 engines) with assistance from a pair of five-segment SRBs. The EDS places the LSAM into LEO approximately 2 to 4 weeks ahead of the manned CEV. Like that of Skylab, the manned CEV will rendezvous and dock with the EDS/LSAM combination, and after configuring the system, 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 uprated J-2 (J-2S) engines similar to that found on the CLV. The EDS, while primarily being designed for its lunar role, can also support manned CEV flights to both Sun-synchronous orbit and geostationary orbit, along with providing the needed thrust to launch a larger version of the Hubble Space Telescope, and components to the ISS that cannot be launched with a Russian Proton rocket. 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 cancelled 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.