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Ares I
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Ares I is the crew launch vehicle being developed by NASA as a component of Project Constellation. NASA plans to use Ares I to launch Orion, the spacecraft being designed for NASA human spaceflight missions after the Space Shuttle is retired in 2010. Ares I was previously known as the Crew Launch Vehicle or CLV. The larger, unmanned Ares V is being designed as a complement to the Ares I; it will be the cargo launch vehicle for Project Constellation.
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Ares I is the crew launch vehicle being developed by NASA as a component of Project Constellation. NASA plans to use Ares I to launch Orion, the spacecraft being designed for NASA human spaceflight missions after the Space Shuttle is retired in 2010. Ares I was previously known as the Crew Launch Vehicle or CLV. The larger, unmanned Ares V is being designed as a complement to the Ares I; it will be the cargo launch vehicle for Project Constellation. Ares I and V are named after the Greek deity Ares, who is identified with the Roman god Mars.
Ares I’s role in Project Constellation
Ares I is the crew launch component of Project Constellation. Unlike the Space Shuttle, where both crew and cargo are launched simultaneously on the same rocket, the plans for Project Constellation outline having two separate launch vehicles, the Ares I and the Ares V, for crew and cargo, respectively. Having two separate launch vehicles will allow for more specialized designs for the different purposes the rockets will fulfill.
The Ares I rocket is specifically being designed to launch the Orion Crew Vehicle. Orion is intended as a crew capsule, similar in design to the Project Apollo capsule, to transport astronauts to the International Space Station, the Moon, and eventually Mars.
Design
First stage
The first stage is a more powerful and reusable solid fuel rocket derived from the current Space Shuttle Solid Rocket Booster (SRB). Compared with the current SRB, which has four segments, the most notable difference is the addition of a fifth segment. This fifth segment will enable the Ares I to produce more thrust and burn longer. Other changes made to the SRB are the removal of the Space Shuttle External Tank (ET) attachment points and the replacement of the SRB nosecone with a new forward adapter that will interface with the liquid-fueled second stage. The adapter will be equipped with solid-fueled separation motors to facilitate the disconnection of the stages during ascent.
Upper stage
The upper stage is to be propelled by one J-2X rocket engine fueled by liquid hydrogen (LH2) and liquid oxygen (LOX). The J-2X is derived from the J-2 engine used on the Saturn IB and Saturn V rockets. On 16 July 2007, NASA awarded Rocketdyne a sole-source contract for the J-2X engines to be used for ground and flight tests.
Originally, NASA was to use a Space Shuttle Main Engine, but due to the high costs (~US$55-60 million per engine), the need to redesign the engine to start up in both the air and in vacuum, and that the Ares I upper stage is expendable, the engine was dropped in favor of the J-2X, which is significantly less expensive (~$20 million USD), and was designed from the beginning for high-altitude use.
Although its J-2X engine is derived from an established design, the upper stage itself is wholly new. Originally based on the internal structure of the Shuttle's External Tank, the original design called for separate fuel and oxidizer tanks, separated by an "intertank" structure. Using a concept going back to the Apollo era, the "intertank" structure was dropped to decrease mass, and instead, a common bulkhead would be used between the tanks. A recent design, currently under review, uses the savings to increase propellant capacity: with the common bulkhead, total propellant capacity would be . The increase in fuel mass is expected to decrease the initial acceleration of the second stage to around 0.6 G.
The upper portion of the upper stage includes an adapter assembly to mate with the Orion Crew Vehicle, and the lower section includes a thruster system, similar to that used on the Saturn IB and Saturn V rockets, to provide roll control for both the first and second stages of the vehicle during flight.
The only part of the Shuttle's External Tank on the Ares I upper stage is the spray-foam insulation. This will protect the cryogenic propellants from the warm, moist conditions found at Kennedy Space Center. This is the same insulation that broke off the Space Shuttle Columbia on launch, damaging the shuttle's re-entry shield and causing it to burn up on re-entry. The same risk does not exist in a rocket as there are no delicate components below the second stage that could be struck and damaged by a falling piece of insulation.
The upper stage of Ares I is to be built at the NASA Michoud Assembly Facility, the current location of the fabrication and construction of the Shuttle's External Tank, and the former construction site of the Saturn V's S-IC stage. On 28 August 2007, NASA awarded the Ares I Upper Stage manufacturing contract to The Boeing Company. Boeing built the S-IC stage at Michoud in the 1960s.
Development
Advanced Transportation System Studies
In 1995 Lockheed Martin produced for the Marshall Space Flight Center a report of work done under an Advanced Transportation System Studies (ATSS) contract. The executive summary for the ATSS report describes several possible vehicles much like the Ares I design, with liquid rocket second stages stacked above segmented SRB first stages. The variants they considered included both J-2S and SSME engines for the second stage.
Exploration Systems Architecture Study
On 29 April 2005, after President Bush had announced the Vision for Space Exploration in January 2004, NASA chartered the Exploration Systems Architecture Study to accomplish a number of specific goals:
- determine the "top-level requirements and configurations for crew and cargo launch systems to support the lunar and Mars exploration programs"
- assess the "CEV requirements and plans to enable the CEV to provide crew transport to the ISS"
- "develop a reference lunar exploration architecture concept to support sustained human and robotic lunar exploration operations"
- "identify key technologies required to enable and significantly enhance these reference exploration systems"
A Shuttle-derived launch architecture was selected by NASA for the Ares I. Originally, the vehicle would have used a 4-segment Solid Rocket Booster (SRB) for the first stage, and a simplified Space Shuttle Main Engine (SSME) for the second stage. An unmanned version, identical with the current design, would have used the 5-segment booster, but with the second stage using the single SSME.
But shortly after the initial design was approved, additional tests revealed that the Orion spacecraft would be too heavy for the 4-segment booster to lift. In January 2006, NASA announced they would slightly reduce the size of the Orion spacecraft, add a fifth segment to the solid-rocket first stage, and replace the single SSME with the Apollo-derived J-2X motor. While the switch from a 4-segment first stage to a 5-segment version would allow NASA to construct virtually identical motors (albeit with some segments being interchangeable), the main reason for the change to the 5-segment booster was the switch to the J-2X.
Both cost and functionality influenced NASA's decision to change to J-2X. At approximately US$20-25 million per engine, the Rocketdyne-designed and produced J-2X will cost less than half as much as the more complex SSME (around US$55 million). Unlike the current SSME, which was designed to start on the ground, the J-2X was designed from the start to be started in both mid-air and in near-vacuum. This air-start capability was critical, especially in the original J-2 engine used on the Saturn V's S-IVB stage, to propel the Apollo spacecraft to the Moon. The SSME, on the other hand, would have to undergo extensive modifications to be air-startable and to be able to restart in a vacuum (as the Ares I would fly a "direct-insertion" profile, and since the Orion spacecraft has limited fuel reserves), and would have to be "pre-fired" in a manner similar to the "Main Engine tests" conducted on the SSMEs prior to the maiden flights of each NASA orbiter and before the STS-26 flight in 1988.
NASA has announced that ATK Thiokol, the current builders of the Shuttle SRBs, will be the prime contractor for the Ares I first stage. Rocketdyne, a division of Pratt & Whitney, will be the main subcontractor for the J-2X rocket engine. Testing of the engine is currently underway at a facility south of Huntsville, AL.
On 4 January 2007, NASA announced that the Ares I had completed its system requirements review, the first such review completed for any manned spacecraft design since the Space Shuttle. This review is the first major milestone in the design process, and is intended to ensure that the Ares I launch system meets all the requirements necessary for Project Constellation. In addition to the release of the review, NASA also announced that a redesign in the tank hardware was made. Instead of separate LH2 and LO2 tanks, separated by an "intertank" like that on the Shuttle ET, the new LH2 and LOX tanks will be separated by a common bulkhead like that employed on the Saturn V S-II and S-IVB stages. This provides a significant mass saving and eliminates the need to design a second stage interstage unit that would have to carry the weight of the Orion spacecraft with it.
On December 12, 2007, NASA selected The Boeing Company to provide and install the Ares Instrument Unit Avionics for the Ares I rocket.
Schedule
On 4 January 2007, NASA completed the Ares I system requirements review. This review was the first major milestone in the design process of the Ares I rocket. Going forward, NASA intends to refine the project requirements through 2007, beginning project design later that year. Project design is to continue through the end of 2009, with development and qualification testing running concurrently, starting in 2008 and running through 2012. At the same time, flight articles are to begin production towards the end of 2009 for a first launch in June 2011. The first launch of a human is planned for September 2014.
Issues
In January 2008, NASA Watch revealed that the first stage Solid Rocket Booster of the Ares I could create high vibrations during the first few minutes of ascent. The vibrations are caused by sudden acceleration pulses due to thrust oscillations inside the first stage. NASA officials have known about the problem since fall 2007, stating in a press release that they had wanted to solve it by March 2008. NASA admitted that this problem is very severe, rating it four out of five on a risk scale. Still, NASA said they are very confident of solving this problem, referring to a long history of successful problem solving. NASA also outlined that this is a completely new transport system, like the Apollo or Space Shuttle systems were at their development, and that it is normal for such problems to arise during the development stage.
Criticisms
The proposed Ares I configuration has been criticized on several grounds. The production of a launch vehicle in the 25 tonnes (55,000 lb) payload class can be seen as direct competition with existing vehicles such as the Boeing Delta IV-Heavy. It can be argued that lower costs and improved safety are likely to result from the use of an existing vehicle, since it would have lower development costs, a proven track record, and would benefit from a higher flight rate. The NASA study group that selected what would become the Ares I concluded the opposite, however, and rated the vehicle as almost twice as safe as an Atlas or Delta-derived design.
The configuration chosen by NASA requires two derivative engine development programs—both a new five-segment SRB for the first stage with its associated $3 billion development cost, and a new J-2X for the second stage with its associated $1.2 billion development cost. The extra cost, longer development schedule, and higher safety risk of new, unproven flight hardware can all be argued to negate many of the supposed advantages of using 'shuttle-derived' hardware. In fact, critics say, the deletion of the SSME and four-segment SRB from the configuration removes the new vehicle from the class "Shuttle-Derived Launch Vehicles" entirely.
Multiple delays in the Ares I development schedule due to budgetary pressures and unforeseen engineering and technical difficulties continue to increase the gap between the end of the Space Shuttle program and the first operational flight of Ares I. , the first operational Ares I flight is scheduled for late 2015, a full five years after the last Shuttle flight.
Performance shortfalls with Ares I have resulted in a series of reductions to the capabilities, size, weight, and even redundant safety systems of the Orion spacecraft which will fly atop the Ares I.
Supporters of the Ares I claim that the vehicle is essential in ensuring the continued employment of the current STS workforce, as well as those involved in developing several critical components (like the five segment SRB and J-2X engine) of the larger Ares V vehicle. Critics claim that the continuing schedules delays will result in mass layoffs for much of the current STS workforce, similar to those that occurred between the Apollo and Shuttle programs, and that the continuing cost overruns will prevent Ares V from ever being built.
See also
External links
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