NASA isstudying a variant of its planned Ares 5 heavy-lift rocket that would enable anApollo 8-like trip around the Moon in the 2015 time frame, a top U.S. space agency official told reporters Jan. 25.
ScottHorowitz, NASA's associate administrator for exploration systems, said he askedengineers at the agency's Marshall Space Flight Center in Huntsville, Ala., tostudy a rocket design that would combine the Ares 5 main stage with the Ares 1upper stage to permit an around-the-Moon-and-back shakeout flight of the OrionCrew Exploration Vehicle [image] several years ahead of the first lunar landings.
"You coulddo an Apollo 8 kind of mission," he said during a roundtable discussion withreporters. "You could test out the capsule and the service module all the wayaround the lunar environment as a build up to the actual landing ... and youcould have the capsule re-enter at lunar velocities."
One keyobjective of such a mission, Horowitz said, would be to conduct a full-scaletest of a skip-entry technique that would give NASA greater control over wherethe Orion capsule lands when it comes back to the Moon.
Astronaut-carryingspacecraft to date, including the Apollo capsules, have used direct-entrytrajectories for their returns home, Horowitz said.
"Normallywhen you come back to Earth you hit the atmosphere and you just, whoosh, goin," he said. "You can get a lot more flexibility in picking your landing siteif you can hit the [Earth's atmosphere], skip out a little bit, and then re-hitthe Earth."
Horowitz saidthe direct-entry technique used on Apollo required NASA to carefully select thedate of return in order to have some control over the stretch of ocean wherethe capsule would splash down.
NASA wantsOrion to routinely land on terra firma inside the United States, preferablywithin the same landing zone it uses for trips back from the internationalspace station or other low-Earth orbit destinations.
Skip entrywould give mission planners more flexibility and control for lunar returns, hesaid.
"Dependingon when you leave the Moon and where you leave the Moon from, the Earth is notalways pointed in the right direction for you to target the landing site youwant," he said. "So you almost have to pick the day you depart from the Moon,if we did it like Apollo, before you take off. It's like a launch window fromthe Moon. With skip entry you get a lot more variability on that launch window.You get it to the point where you can basically go home any day you want."
Horowitzsaid there are a number of arguments for testing Orion at lunar-returnvelocities prior to the first Moon landing, not the least of which has to dowith sound program management. "Having the people who are designing andbuilding the rockets and operating the rockets doing one every so often initself is value added to the program just because you keep all the skills youneed sharp."
And whileskip entry promises "tremendous operational capabilities," he said, it "createsinteresting technical challenges for to the thermal protection system as wellas control and guidance."
NASA isdesigning an ablative heat shield for Orion that will be scrapped and replacedafter each flight. Skimming the atmosphere before plunging in creates uniquethermal stresses that NASA does not fully understand, and that could drive theagency to build more robustness than necessary into the heat shield.
"There issome risk associated with how well the thermal protection system will work,"Horowitz said. "If you can put some of that risk to bed early with a high-velocitytest and proper instrumentation on board and you can look at it after you getit back, before you go into production you may be able to knock a couplehundred pounds off because you say, 'hey, my unknowns are smaller, therefore Ican shave of an inch of thermal protection system because I don't have toprotect for unknowns because its not unknown any more.'"
Horowitzsaid the Ares 5 variant, referred to by some people as Ares 4, is just oneoption for enabling early high-velocity tests of Orion. NASA also is looking atwhether Ares 1 could be tweaked to enable Orion to demonstrate a skip-entrylanding without having to circle the Moon, he said.
"I'm askingthe program to look at all kinds of ideas ... for how to do this," he said.
SkipHatfield, NASA's Orion project manager, told Space News that a crewedskip-entry flight would be preceded by unmanned tests involving subscalespacecraft in the 2011 timeframe. He said a Delta 2-class rocket, for example,could kick a subscale Orion out far enough from Earth to achieve lunar returnvelocities without having to go as far as the Moon.
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