Canceling the Orion Crew Exploration Vehicle (CEV) makes no sense if the government is serious about a “Flexible Path” approach for lunar fly-bys and visits to asteroids and Mars.
If Americans want to venture beyond low Earth orbit (LEO), a heavy-lift launch vehicle is necessary. But a vehicle just like Orion will also be needed to safely return the crew to Earth, using an Apollo-type re-entry after surviving a mission lasting up to several years. Atmospheric entry from lunar missions occurs at nearly escape velocity, and exceeds escape velocity for missions to the asteroids or Mars, resulting in significantly higher peak temperature, heat flux and heat load imparted to the spacecraft than entry from LEO. Missions beyond LEO are of long duration, with up to six months planned for lunar missions and up to three years projected for Mars missions (not including time for vehicle assembly in LEO).
Requirements for life support, communications, navigation, guidance and control, propulsion, radiation shielding, and thermal protection for manned vehicles on long-duration, deep space missions are much more stressing than those for manned LEO-only spacecraft like the Russian Soyuz and Chinese Shenzhou. In addition to being designed for LEO operations, the Orion is being designed to survive long-duration missions into deep space and high-speed Earth re-entry. The ability to design and develop a deep space-capable CEV is very challenging and requires a national team effort. This has been done before by only one nation — the United States, with Apollo. The development of Orion draws on that successful heritage and knowledge base and expands our capabilities.
The nation should invest in a heavy-lift launch vehicle to enable human exploration beyond LEO, but one cannot seriously contemplate sending crews into deep space without also having a CEV to return them to Earth. A CEV is a critical and integral part of any deep space mission, whether it be to the Moon, Lagrange points (e.g. for servicing the James Webb Space Telescope), near-Earth asteroids or Mars.
In canceling Orion, the nation runs the risk of losing the technical expertise and industrial base needed to produce such a vehicle. The Orion national team will move on to other work if there is no continuity in our manned space program. The nation cannot afford to throw away the already significant investment in Orion when a vehicle just like Orion is an essential part of any “beyond LEO” manned exploration architecture.
The name of the letter writer, a Boeing engineer, has been withheld by request.