ARES I

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

'Ares I' is the crew launch vehicle being developed by NASA as a component of Project Constellation. NASA will 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.

Contents

Ares I’s role in Project Constellation

Design

First Stage

Upper Stage

Design History

Design Problems

Development schedule

Criticisms

See also

References

External Sources

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 non-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, 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, the parachutes and other recovery equipment, 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 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. On 16 July 2007, NASA awarded Rocketdyne a sole-source contract for the J-2X engines to be used for ground and flight tests.^[2]
Although its J-2X engine is derived from an established design, the upper stage itself is wholly new. Originally based on the Space Shuttle External Fuel Tank, separate fuel and oxidizer tanks were to be employed. Using a concept going back to the Apollo era, the separating "intertank" structure 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.^[3] 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 assembly to mate with the Orion Crew Vehicle, and the lower section includes a thruster system to provide roll control for both the first and second stages of the vehicle during flight.
NASA announced the winner of the Ares I Upper Stage contract to The Boeing Company on August 28, 2007. The upper stage of Ares I will 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, which Boeing built back in the 1960's.

Design History

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." ^[4]
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. 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 change to 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 will cost less than half as much as 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. 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^[5]; 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 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.^[6] 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.
Ares I is a two-stage rocket designed to launch an Orion crew capsule into Low Earth Orbit (LEO).

Design Problems

On November 11, 2006, Spaceref.com reported that the current design is underpowered by a metric ton or more.^[7] 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, reports that the latest set of analyses indicate that the Ares I can lift 58 thousand pounds (26.30822 metric tons), more than the Orion mass of 48.4 thousand (21.95 Metric Tons).^[8]

Development 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 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. ^[9][10]

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.^[11] Reports of growing political pressure from Congress to cancel the Shuttle-derived system and instead use existing Atlas/Delta vehicles began circulating in mid-2007.
Second, the configuration chosen by NASA requires a new five-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 four-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.

See also

★ Project Constellation

★ Orion (spacecraft)

★ Ares IV

★ Ares V

★ Saturn V

References

1. Ares I Fact Sheet
2. NASA Awards Upper Stage Engine Contract for Ares Rockets
3. Ares I Upper Stage change - receives additional capacity
4. Exploration Systems Architecture Study -- Final Report
5. NASA closing in on naming new fleet Chris Bergin
6.
7. NASA Encounters Problems With Ares 1 Launch Vehicle Design Keith Cowing
8. NASA Internal Memo From Constellation Program Manager Jeff Hanley Jeff Hanley
9. Draft Launch Schedule For Ares Launch Vehicle Keith Stein
10. Constellation Program Overview
11. Part 6 of the Exploration Systems Architecture Study Final Report

External Sources

★ A Visual History of Project Constellation