Matt Wronkiewicz's Weblog

The Review of U.S. Human Space Flight Plans Committee recently released a summary of their report. The contents of that report mostly reflects the documents they had previously released and their comments during the public meetings. The report lists the most promising of the combinations of different options for exploring beyond low Earth orbit (LEO). Several of the architectures that they recommended include a new heavy lift vehicle (HLV) called Ares V Light, also known as Ares V Lite. Very little information has been released about this HLV, so I’ll document here what I have learned about it.

Ares V Light is a simplification of the Ares V design, which itself is a derivation of the Cargo Launch Vehicle (CaLV) described in the 2005 Exploration Systems Architecture Study (ESAS) report. ESAS considered several combinations of existing hardware and extensions to that hardware that were considered low-risk. CaLV comprised a Space Shuttle External Tank (ET)-sized core powered by five Space Shuttle Main Engines (SSMEs) and two five-segment Space Shuttle Solid Rocket Boosters (SRBs). The SSMEs would be thrown away on every flight. CaLV would send about 55 metric tons (mT) to a trans-lunar injection (TLI).

CaLV eventually was refined into the Ares V design. Ares V was modified in several ways from the CaLV in order to increase payload and reduce per-flight cost. In particular it uses expendable RS-68B engines derived from the Delta IV, and it extended the SRBs to 5.5 segments. The payload capacity of Ares V is an impressive 159 mT to LEO and 71 mT to TLI. With these upgrades, Ares V deviates significantly from the Ares I components that it was intended to share. Also, it requires the development of a new SRB design and a new LOX/LH2 engine variant.

Ares V Light is closer to the original CaLV design in that it maintains the original 5 segment SRB. Another difference is that it trades the advanced RS-68B for the RS-68A, which is nearing operational capability on the Delta IV. Payload capacity is reduced to 143 mT. This limits it to sending the Orion space capsule to the Moon or the Altair lander, but not both at the same time. Thus, a mission to the lunar surface would require two launches of Ares V Light instead of one Ares I and one Ares V. An additional crew launch aboard a commercial vehicle may be required for this mission if Ares V Light is not man-rated.

Ares V Light has several advantages over the baseline Ares I + Ares V configuration. Primarily, it requires the development and operation of a single NASA-owned rocket instead of two. The committee found that operating both Ares I and Ares V at the projected budget levels would consume NASA’s entire exploration budget, leaving nothing for expeditions beyond LEO. Also, Ares V Light would require less development work. The five segment SRB has been successfully tested, as have the RS-68A engines. The downsides are that it would have less lift capacity in a single launch, and that it would render moot some of the development work that has gone into Ares I. Ares V Light development is projected to finish in the early 2020s. After the Space Shuttle is retired, NASA would have no in-house space launch vehicles for more than a decade. This would extend the “gap” during which NASA would be unable to fly its astronauts by about five years over the baseline case. However, this could be mitigated by encouraging the development of commercial alternative crew launch, which the committee estimates would be ready by 2016.

The Ares V Light configuration first appeared in Bo Bejmuk’s July 29 presentation of the LEO Access subcommittee. Information about this configuration seems to have come from NASA Marshall Space Flight Center (MSFC), as Ares V Integration Manager Steve Creech referred to it in his presentation that day. Ares V Light was included in three of the seven architectures retained after the August 12 meeting, and those options were carried forward in the final report. The summary stated “of these two Ares system alternatives, the Committee finds the Ares V Lite in the dual mode the preferred reference option.”

References

• “Launch Vehicles and Earth Departure Stages“. Exploration Systems Architecture Study. National Aeronautics and Space Administration. November 2005.
• Bejmuk, Bo. “LEO Access Subgroup“. Review of US Human Space Flight Plans Committee. 29 July 2009.
• “Transcript: Constellation Architecture, Part 6b“. Review of US Human Space Flight Plans Committee. 29 July 2009.
• “Integrated Options for Human Exploration Discussion“. Review of US Human Space Flight Plans Committee. 12 August 2009.
• “Summary Report“. Review of US Human Space Flight Plans Committee. 8 September 2009.

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Tags: ares v light, heavy lift, hlv, human space flight, launch vehicle