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Ares I is the crew launch vehicle being developed by NASAmarker as a component of the Constellation Program. The name "Ares" refers to the Greek deity Ares, who is identified with the Roman god Mars. Ares I was originally known as the "Crew Launch Vehicle" (CLV).

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 is intended to complement the larger, unmanned Ares V, which is the cargo launch vehicle for Constellation. NASA selected the Ares designs for their anticipated overall safety, reliability and cost-effectiveness.


Advanced Transportation System Studies

In 1995 Lockheed Martin produced an Advanced Transportation System Studies (ATSS) report for the Marshall Space Flight Centermarker. A section of the ATSS report describes several possible vehicles much like the Ares I design, with liquid rocket second stages stacked above segmented solid rocket booster (SRB) first stages. The variants that were considered included both the J-2S engines and Space Shuttle main engines (SSMEs) for the second stage. The variants also assumed use of the Advanced Solid Rocket Motor (ASRM) as a first stage, but the ASRM was cancelled in 1993 due to significant cost overruns.

Exploration Systems Architecture Study

President Bush had announced the Vision for Space Exploration in January 2004, and NASA under Sean O'Keefe had solicited plans for a Crew Exploration Vehicle from multiple bidders, with the plan for having two competing teams. These plans were discarded by incoming administrator Michael Griffin, and on April 29, 2005, NASAmarker chartered the Exploration Systems Architecture Study to accomplish 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 four-segment solid rocket booster (SRB) for the first stage, and a simplified Space Shuttle main engine (SSME) for the second stage. An unmanned version was to use the five-segment booster, but with the second stage using the single SSME. Shortly after the initial design was approved, additional tests revealed that the Orion spacecraft would be too heavy for the four-segment booster to lift, and 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 change from a four-segment first stage to a five-segment version would allow NASA to construct virtually identical motors (albeit with some interchangeable segments), the main reason for the change to the five-segment booster was the move to the J-2X.

The Exploration Systems Architecture Study concluded that the cost and safety of the Ares was superior to that of either of the Evolved Expendable Launch Vehicle (EELVs). The cost estimates in the study were based on the assumption that new launch pads would be needed for human-rated EELVs. However, the facilities for the current EELVs (LC-37 for Delta IV, LC-41 for Atlas V) are in place and could be modified. The ESAS launch safety estimates for the Ares were based on the Space Shuttle, despite the differences, but included only launches after Challenger, and counted each of the remaining launches as two safe launches of the Ares booster. The safety of the Atlas V and Delta IV was estimated from the failure rates of all Delta II, Atlas-Centaur, and Titan launches since 1992, although they are not similar designs. This meant, for example, that the failure rate of the Titan IV, which used strap-on solid rocket motors, did not count against the Ares, which has a main solid rocket motor, but counted against the Delta IV Heavy, which has only liquid propulsion.

In May 2009 the previously withheld appendices to the 2006 ESAS study were leaked, revealing a number of apparent flaws in the study, which gave safety exemptions to the selected Ares I design while using a faulty model which unfairly penalized the EELV-based designs.

Contractor selection

NASA selected Alliant Techsystems, the builder of the Space Shuttle Solid Rocket Boosters, as the prime contractor for the Ares I first stage. NASA announced that Rocketdyne will be the main subcontractor for the J-2X rocket engine on July 16, 2007. NASA selected Boeing to provide and install the avionics for the Ares I rocket on December 12, 2007.

On August 28, 2007 NASAmarker awarded the Ares I Upper Stage manufacturing contract to Boeing. Boeing built the S-IC stage of the Saturn V rocket at Michoud in the 1960s. The upper stage of Ares I is to be built at the NASA Michoud Assembly Facilitymarker, the construction site used for the Space Shuttle's External Tank and the Saturn V's S-IC first stage.

J-2X engines

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 Space Shuttle main engine (around $55 million). Unlike the Space Shuttle Main Engine, which was designed to start on the ground, the J-2X was designed from inception 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 Space Shuttle Main Engine, on the other hand, would require extensive modifications in order to add an air-start capability and to be able to restart in a near-vacuum. Near-vacuum restart capability is needed for the Ares I because it is intended to fly an Earth orbit rendezvous, and because the Orion spacecraft has limited fuel reserves. Due to these design issues, a modified Space Shuttle Main Engine would have to be "pre-fired" in a manner similar to the "Main Engine tests" conducted on the Space Shuttle Main Engines prior to the maiden flights of each NASA orbiter, including the STS-26 return to flight in 1988.

System requirements review

On January 4, 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 Constellation Program. 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 of the Space Shuttle External Tank, 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.

Analysis and testing

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. NASAmarker 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 stated that this is a completely new transport system, like the Apollo or Space Shuttle systems were during their development, and that it is normal for such problems to arise during the development stage. According to NASA, analysis of the data and telemetry from the Ares I-X flight showed that vibrations from thrust oscillation were within the normal range for a Space Shuttle flight.

A study released in July 2009 by the 45th Space Wing of the US Air Force concluded that an abort 30–60 seconds after launch would have a ~100% chance of killing all crew, due to the capsule being engulfed until ground impact by a cloud of solid propellant fragments, which would melt the capsule's nylon parachute material. NASA's study showed the crew capsule would fly beyond the more severe danger. Wernher von Braun said in the early 1970s that no human should ride on a solid rocket as they were too dangerous.

The Ares I igniter is an advanced version of the flight-proven igniter used on the Space Shuttle's solid rocket boosters. It is approximately 18 inches (46 cm) in diameter and 36 inches (91 cm) long, and takes advantage of upgraded insulation materials that have improved thermal properties to protect the igniter's case from the burning solid propellant. NASAmarker successfully completed test firing of the igniter for the Ares I engines on March 10, 2009 at ATK Launch Systems test facilities near Promontory, Utahmarker. The igniter test generated a flame 200 feet (61 meters) in length, and preliminary data showed the igniter performed as planned. On September 10, 2009, the first Ares I motor was successfully tested in a full-scale, full-duration test firing.

The Ares I prototype, Ares I-X, successfully completed a test launch on October 28, 2009, at 11:30 a.m. EDT (15:30 UTC). The launch pad 39B was damaged more than with a Space Shuttle launch. During descent, one of the three parachutes of the Ares I-X’s first stage failed to open, and another opened only partially, causing the booster to splash down harder and suffer structural damage.


NASA completed the Ares I system requirements review in January 2007. Project design is to continue through the end of 2009, with development and qualification testing running concurrently through 2012. As of July 2009, flight articles are to begin production towards the end of 2009 for a first launch in June 2011. Since 2006 the first launch of a human has been planned for no later than 2014, which is four years after the planned retirement of the Space Shuttle.

Delays in the Ares I development schedule due to budgetary pressures and unforeseen engineering and technical difficulties have increased the gap between the end of the Space Shuttle program and the first operational flight of Ares I. The total estimated cost to develop the Ares I through 2015 has risen from $28 billion in 2006 to more than $40 billion in 2009.

Originally scheduled for first test flights in 2011, the independent analysis by the Augustine Commission found in late 2009 that due to technical and financial problems Ares I was not likely to have its first crewed launch until 2017-2019 under the current budget, or late 2016 with an unconstrained budget.

Role in Constellation program

Ares I is the crew launch component of the Constellation program. Originally named the "Crew Launch Vehicle" or CLV, the Ares name was chosen from the Greek deity Ares. 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 Apollo program capsule, to transport astronauts to the International Space Station, the Moon, and eventually Mars. Ares I may also deliver some (limited) resources to orbit, including supplies for the International Space Station or subsequent delivery to the planned lunar base.

Ares I has a payload capability in the class and is comparable to existing vehicles such as the Delta IV and the Atlas V. The NASA study group that selected what would become the Ares I rated the vehicle as almost twice as safe as an Atlas or Delta IV-derived design.


The rocket is making use of an aluminum-lithium alloy which is lower in density but similar in strength compared to other aluminum alloys. The new alloy is produced by Alcoa.

First stage

The first stage is a more powerful and reusable solid fuel rocket derived from the Space Shuttle Solid Rocket Booster (SRB). Compared with the Solid Rocket Booster, 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 Solid Rocket Booster are the removal of the Space Shuttle External Tank (ET) attachment points and the replacement of the Solid Rocket Booster 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, derived from the Shuttle's External Tank (ET) and based on the S-IVB stage of the Saturn V, is to be propelled by a single J-2X rocket engine fueled by liquid hydrogen (LH2) and liquid oxygen (LOX). The J-2X is derived from the original J-2 engine used during the Apollo program, but with more thrust (~294,000 lbf) and fewer parts than the original engine. On July 16, 2007, NASA awarded Rocketdyne a sole-source contract for the J-2X engines to be used for ground and flight tests. Rocketdyne was the prime contractor for the original J-2 engines used in the Apollo program.

Although its J-2X engine is derived from an established design, the upper stage itself is wholly new. Originally to be based on both the internal and external structure of the ET, the original design called for separate fuel and oxidizer tanks, joined together by an "intertank" structure, and covered with the spray-on foam insulation to keep venting to a minimum. The only new hardware on the original ET-derived second stage would be the thrust assembly for the J-2X engine, new fill/drain/vent disconnects for the fuel and oxidizer, and mounting interfaces for the solid-fueled first stage and the Orion spacecraft.

Using a concept going back to the Apollo program, the "intertank" structure was dropped to decrease mass, and in its place, a common bulkhead, similar to that used on both the S-II and S-IVB stages of the Saturn V, would be used between the tanks. The savings from these changes are being used to increase propellant capacity, which is now . The spray-on foam insulation is the only part of the Shuttle's ET that will be used on this new Saturn-derived upper stage.

See also

  • Ares IV, a heavy-lift variant of Ares I and V combined
  • Boilerplate
  • DIRECT, shuttle-derived launcher proposed as alternative to Ares I and Ares V.


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