Ares I

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This article is about the Ares I launch vehicle. For other uses, see Ares (disambiguation).

Ares I

Artist's impression of Ares I launch
Fact sheet
Function	Man-rated orbital launch vehicle
Manufacturer	Thiokol
Country of origin	USA
Size
Height	309 ft
Diameter	5.5 m
Mass	TBC
Stages	2
	Capacity
Payload to LEO	25,000 kg
Launch History
Status	In Development, ready for test on LC-39B
Launch Sites	Kennedy Space Center, LC-39B
Total launches	0
Maiden flight	Scheduled for 2009
First Stage
Engines	1 Solid
Thrust	TBC
Burn time	~150 seconds
Fuel	Solid
Second Stage
Engines	1 J-2X
Thrust	TBC
Burn time	TBC
Fuel	LH2/LOX

Ares I (formally known as the Crew Launch Vehicle or CLV) is the crew launch component of Project Constellation. Ares I will launch the Orion Crew Vehicle, the spacecraft currently being designed to replace the Space Shuttle after it is retired in 2010. 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.

[edit] Ares I’s role in Project Constellation

Ares I is the crew launch component of Project Constellation. Unlike with the Space Shuttle, where the crew and cargo were 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.

[edit] Design

Comparison of the Saturn V, Space Shuttle, Ares I, and Ares V.

Ares I is a two-stage rocket designed to launch an Orion crew capsule into Low Earth Orbit (LEO).

[edit] First stage

The first stage is a reusable solid fuel rocket derived from the Space Shuttle Solid Rocket Booster (SRB). Compared with the Space Shuttle SRB the most notable difference is the addition of a fifth segment to the rocket. This fifth segment will enable the Ares I to produce more thrust, burn longer, and attain a higher orbit than a standard four-segment SRB. Other changes made to the SRB are the removal of the Space Shuttle External Tank (ET) attachment points and the addition of a newly designed forward adapter replacing the nosecone. The adapter will be equipped with separation motors to disconnect the stages during ascent.

[edit] Second stage

The second stage will be propelled by one J-2X rocket engine fueled by liquid hydrogen (LH₂) and liquid oxygen (LOX).^[1] The J-2X is derived from the J-2 engine used on the Saturn IB and Saturn V rockets.

Although its J-2X engine is derived from an established design, the second stage itself is wholly new. Originally, separate fuel and oxidizer tanks were to be employed. Using a concept going back to the Apollo era, the separating "interstage" was dropped to decrease mass. Instead, the second stage will use a common bulkhead 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 297,900 pounds.^[2] The increase in fuel mass is expected to decrease the initial acceleration of the second stage to around 0.6 G.

The second stage also includes an assembly to mate with the Orion Crew Vehicle.

[edit] Design History

Engineering concept illustration of NASA's new Ares V (left) and Ares I (right) launch vehicles. The Ares I will have a five-segment solid-rocket booster first stage (replacing the four-segment Shuttle SRB shown here) and a shortened second stage.

After President Bush announced the Vision for Space Exploration in January 2004, NASA chartered the Exploration Systems Architecture Study on 29 April 2005 to determine: the "top-level requirements and configurations for crew and cargo launch systems to support the lunar and Mars exploration programs"; to assess the "CEV requirements and plans to enable the CEV to provide crew transport to the ISS"; to "develop a reference lunar exploration architecture concept to support sustained human and robotic lunar exploration operations"; and to "identify key technologies required to enable and significantly enhance these reference exploration systems." ^[3]

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, with a simplified Space Shuttle Main Engine (SSME) being used 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 to be lifted with the 4-segment booster, so in January, 2006, NASA announced that the Orion spacecraft would be slightly reduced in size, a fifth segment would be added to the solid-rocket first stage, and that the single SSME would be replaced 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 need of the 5-segment booster was the need to adopt the J-2X.

At approximately US$20-25 million per engine, the Rocketdyne-designed and produced J-2X is less than half that of the complex SSME (≈$55 million), and 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, and was critical, especially the original J-2 engine used on the Saturn V's S-IVB stage, to propel the entire Apollo spacecraft to the Moon. The SSME, on the other hand, would have to undergo extensive modifications to be air-startable, be able to restart in a vacuum (as the Ares I would fly a "direct-insertion" profile, and that 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^[4]; ATK is also bidding to become part of the consortium that will build the Ares I upper stage. Rocketdyne, a division of Pratt & Whitney (formerly under the ownership of Rockwell International and Boeing's North America division), will be the main subcontractor for the J-2X rocket engine. Testing of the engine is currently underway at a facility north 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.^[5] 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 LOX 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 will allow NASA to construct a shorter and lighter second stage, along with eliminating the need to design a second stage interstage unit that would have to carry the weight of the Orion spacecraft with it.

[edit] Design Problems

On November 11, 2006, Spaceref.com reported that the current design is underpowered by a metric ton or more.^[6] The lack of power would make it so the Ares I would not be able to put the current Orion Crew Vehicle design into the orbits needed for missions to the International Space Station or the Moon. However, Project Constellation’s program manager, Jeff Hanley, claims that the latest set of analyses indicate that the Ares I can lift 58 thousand pounds of mass (klbm), more than the Orion mass of 48.4 klbm.^[7]

[edit] Development Schedule

See also: List of Constellation missions

On 4 January 2007 NASA completed the Ares I system requirements review.^[5] 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 will 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 will begin production towards the end of 2009 for a first launch in June 2011. ^[8][9]

[edit] Criticisms

The proposed Ares I configuration has been criticized on several grounds. First, the production of a launch vehicle in the 25 tonnes (55,000 lb) payload class can be seen as direct competition with existing vehicles, e.g. 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.^[10]

Second, the configuration chosen by NASA requires a new 5-segment SRB with its associated $3 billion development cost; this negates many of the supposed advantages of using 'shuttle-derived' hardware. In fact, critics say, the deletion of the SSME and 4-segment SRB from the configuration removes the new vehicle from the class "Shuttle-Derived Launch Vehicles" entirely.

Third, technical objections may be raised over the aerodynamic stability of the proposed configuration. The tall, slender 'stick' configuration leads to a forward center of pressure and an aft center of gravity. Thus, the Ares I will continually tend to turn around, being most stable if flying backwards. The thrust vector control system on the SRB will have to constantly cope with this instability, which may lead to increased mechanical loads on the airframe. NASA has ongoing wind tunnel studies to address this problem.

However, 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 developing several critical components (like the five segment SRB and J-2X engine) of the larger Ares V vehicle.

[edit] See Also

• Project Constellation
• Orion (spacecraft)
• Ares V
• Saturn V

[edit] References

Wikimedia Commons has media related to:

Project Constellation

v • d • e  Project Constellation
	Main Article: Project Constellation
	Components: Orion | Ares I | Ares IV | Ares V | Earth Departure Stage | Lunar Surface Access Module | J-2X | RS-68
	Launch Sites: Kennedy Space Center LC-39
	Misc: Vision for Space Exploration | Exploration Systems Architecture Study | Abort Modes | Missions | In-Flight Aborts and Rescue Options

v • d • e  J-2 Rocket Engine
	Main Article: J-2		Technologies: Bipropellant | Gas-generator cycle | LOX | LH2
	Historic Spacecraft: Saturn IB (S-IVB) | Saturn V (S-II, S-IVB)
	Future Spacecraft: Ares I | Ares IV | Ares V | Earth Departure Stage
	Other LOX & LH2 Engines: SSME | RS-68 | RL-10 | Vulcain