Wednesday, January 9, 2008

To land on land or not to land on land?

That is the question. Well, not really. That is really the noble answer that the Emperor, prodded by Queen Marsha, is handing to Orion.

With 6000 pounds of weight risk already identified, the program continues to look for ways of avoiding additional weight. Some hard choices had to be made to even get to that number. Orion was originally required to land on the dry lake bed in California. That hard floor, approaching at 16 feet per sec during the landing sequence, would require Orion to carry an attenuation system designed to cushion the Queen and her court upon contact. Airbags or retro-rockets, seats with shock absorbers, cushions, all weigh something. A handy way of avoiding that weight, at the expense of hiring a navy on occasion, is to let the more forgiving waters of the Pacific absorb the blow of contact. Exit airbags.

But there are still a couple of gotchas that caught the Queen's attention. What happens if Orion has to abort off the top of an Ares-1 somewhere in the vicinity of the launch pad? What happens if the wind is high enough to blow Orion back on land? What happens if a reentry trajectory doesn't work out as expected (e.g., de-orbit burn goes awry) and the capsule and its crew ends up landing long on top of Los Angeles? Doesn't Orion need a land landing contingency option anyway?

Skip Hatfield didn't think so. The Queen did. But was Skip wrong? It didn't matter. The Queen said, "Off with his head."

Such issues really should come down to good engineering ... and probabilities. Something that Skip was exercising and that the Queen is unfamiliar with. How does one minimize the probability of landing on land? Don't launch on really windy days! One can set a wind limit based on the amount of thrust the launch abort system can deliver as it pulls Orion off a failing stick (albeit, a more likely occurrence than, say, an abort off a Saturn V). Now, just don't launch if the winds are going to pull you back to shore.

But what about landing long after a nominal on-orbit mission? Just how does one attenuate a 16 fps landing with only the stroke available in a set of seat shock absorbers? Not easily. In fact, it is much easier to engineer the de-orbit system with appropriate redundancy to lower the probability of such an event occurring. Target the landing elipse far off off-shore to preclude the problem. Good engineering leading to a low probability of bad things occurring. That's what aerospace designers are paid to do. Unfortunately, that's not good enough for the Queen. She wants he precious rear end protected no matter matter what the weight penalty that is.

This issue really points out one of the Queen's personality traits. Its all about her. One could argue that the issue shouldn't be about protecting the crew at this point, but more about how will Orion be engineered to miss the boys and girls in their classroom at Redondo Beach Elementary? What's your answer to that one, Queen Marsha?

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