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NASA has decided to pursue the design and construction of two new launchers, both based on technology and infrastructure developed for the US Space Shuttle Program . These launchers would replace the Space Shuttle and supply the launch services necessary to fulfill the Vision For Space Exploration . NASA has given the name " Project Constellation " for the manned Crew Launch Vehicle project. The derived launch vehicles are proposed to be called Ares. [http://www.nasaspaceflight.com/content/?id=4333 THE VEHICLES
CaLV Flight Profile At T-6.6 seconds, five Space Shuttle Main Engines (SSMEs) located at the bottom of the CaLV core stage are ignited, similar to the fire-up sequence on the Space Shuttle . At T=0, the onboard computers, having verified that all five SSMEs are operating at full thrust and do not have any problems, will then light the two five-segment Solid Rocket Booster s (SRBs). The CaLV will lift off from the launchpad similar to that of the Shuttle. At an altitude of 60 km (200,000 ft.), the SRBs are jettisoned and fall back to Earth for a parachute recovery (they are later refurbished and reused as either a CaLV booster or CLV first stage). At that point, the rocket, located above most of the atmosphere, jettisons the launch shroud to reveal the LSAM , which unlike the fragile Apollo Lunar Module , can withstand any outside pressures in the upper portions of the atmosphere. The SSMEs, powered at 104% rated thrust, continues to power the core system until just a little over 8 minutes into the flight. At that time, MECO (main engine cut-off) occurs and the first stage is then jettisoned to burn up in the atmosphere over the Indian Ocean . The Earth Departure Stage , powered by two J-2X engines, then maneuvers the LSAM into a circular orbit which will then be retrieved by a separately-launched CEV within a month. After the CEV docks with the LSAM/EDS, the EDS then fires its two J-2X motors again to thrust the CEV/LSAM stack towards the Moon. After shutdown, the EDS is jettisoned and goes into either a Heliocentric Orbit or like the S-IVB stages from Apollos 13 to 17 , can be delibertly crashed into the lunar surface to calibrate any future instruments left behind by the astronauts. The CaLV can carry up to 125 tons into a 28-degree Low Earth Orbit , making it suitable for launching very large payloads like the Skylab Space Station , or up to 100 tons into an ISS -type orbit, making the CaLV a viable heavy-lift launcher for possible ISS modules and repair parts after the retirement of the Shuttle in 2010. With a Centaur upper stage augmented with the EDS, it can launch heavyweight probes similar to the Galileo Spacecraft or the Cassini-Huygens probe to Uranus , Neptune , Pluto , and objects in the Kuiper Belt and Oort Cloud using direct-flight trajectories with gravity assists with either Jupiter , Saturn , or both. CLV Flight Profile At lift-off, the solid first stage would power the vehicle up to approximately 60 km (200,000 ft) and a velocity of about 2000 m/s (6,700 ft/s). At that point, the first stage is jettisoned and the liquid-fueled second stage would take over, burning for about 5 minutes to place the CEV on a suborbital trajectory with a 354 km (220 mi) perigee and then firing again about 45 minutes later to perform orbit circularization. The J-2X, the engine used for the second stage, would throttle to maintain 4 ''g'' (40 m/s&2) acceleration. This is nearly identical used in the "direct insertion" profile used on Space Shuttle flights. The first stage SRB could be in theory recovered and re-used as they are with the shuttle program, but the uncertain cost benefits of SRB recovery may preclude this. While the shuttle boosters are retrieved and re-used, the actual savings are negligible. Additionally, the lack of the nosecap would require the development of a new inter-stage assembly to hold the parachutes, adding expense and weight to the design. After allowing for a 9,000 lb (4000 kg) escape system, this variant could place about 59,000 lb (27,000 kg) into a 220×220 mi (350×350 km) orbit at 28 degree inclination. Approximately 45,000 lb can be flown on missions to the International Space Station , which is in a 51-degree inclination. Noteworthy is the relatively brief flight time, just over 6½ minutes, compared to the much longer burns characteristic of EELV derived launchers with their low-thrust, long-burn upper stages. ATK appears to be actively promoting this quick flight as minimizing the length of time during which a crew is at risk. The original planned re-engineering of the SSME to be restartable was to be significant, but with the decision to use the J-2X, the problems of developing a restartable engine was significantly reduced, as the original Apollo-Saturn J-2 was designed to restart from the beginning. Crew Exploration Vehicle Currently, NASA has selected a conical spacecraft for the crew exploration vehicle (CEV). When attached to its cylindrical service module, it is visually similar to a squatter version of the Command / Service Module (CSM) combination used in Project Apollo . The CEV is somewhat larger to house more crew (four to six) and will be capable of accepting a Launch Escape Tower, much like previous rocket stacks. The service module will have deployable solar panels for power much like the Russian Soyuz spacecraft capsule, eliminating problematic Fuel Cells used in Gemini , Apollo, and on the Space Shuttle . To avoid splashdowns and costly naval retrievals as seen in the Apollo program, the CEV will be equipped with parachutes and airbags similar to those on recent Mars Missions such as Mars Pathfinder . This airbag landing technology was originally developed for a prototype Viking lander that was never used, and redeveloped for the X-38 CRV, which was cancelled. After slowing its initial descent with drogue parachutes, airbags underneath the CEV will deploy while it continues to descend on parachutes. Just before impact rockets between the parachutes and spacecraft will fire to slow the spacecraft further before touchdown. NASA estimates that this will not incur more than three gravities on the CEV or its crew and are designing retro-rockets that will not cause ground fires. Advantages to this system include being able to land anywhere on Earth and not needing a long prepared runway or large pad for landing. Proposed landing sites, located mostly on the West Coast, will include Edwards Air Force Base, California , White Sands, New Mexico , Utah , Arizona , and even western Texas . Alternate sites may include the Everglades National Park in Florida and even Alaska , with emergency landing sites being proposed in Europe , the former Soviet Union , and even sparsly populated areas of North Africa and Saudi Arabia . REQUIREMENTS In an April 29 , 2005 memo, the following four requirements were given to shape the end-result.
CRITICISMS A shuttle-derived vehicle would utilize support personnel who currently work on the shuttle program. However since the large support crew constitutes the major component of the Shuttle's operational cost, some feel that an architecture not tied to the Space Shuttle would be significantly less expensive. Instead of a single heavy lift cargo launcher, it's possible that smaller rockets (though with smaller Mass Fraction s) would allow lower up-front fixed expenditures (development costs, infrastructure, etc.) that would be spread out over more launches. Although more fuel would be used per kg of payload launched in a smaller rocket, these are marginal expenses compared to the costs of other aspects of the program. From this standpoint a smaller rocket might be more adaptable to future missions, as well as more cost-efficient. RISK REDUCTION One of the primary benefits of the proposed system is that it is estimated to be ten to one hundred times safer for CEV crews than the present Shuttle system. This is for two main reasons, that are reflected in the two causes of the Columbia and Challenger disasters: # The CLV does not have a SRB positioned next to a liquid fuel tank, as is the case with the Shuttle, so any future incidents of O-ring failure and "blow-by" (a term coined by Morton-Thiokol engineers for any hot gases that escape through the field joints) could not trigger a catastrophic explosion and would be detected soon (by means of lower internal pressure) enough for the CEV escape system to pull the CEV capsule off of the booster. This would negate the form of failure seen in the Challenger accident and demonstrated by Nobel prize winner Richard Feynman on national television when he participated in the accident investigation committee chaired by William Rogers . # The CEV, besides being of the capsule configuration proven to be so reliable through both the American and Russian space programs, is positioned above any cryogenic fuel tank architecture, so the chance of damage to reentry systems or pressurization systems by ice or foam falling from fuel tanks is eliminated entirely. Although not in the current design, the CEV could be covered with a Fiberglass "boost protective cover" similar to one used on Apollo. EXTERNAL LINKS
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