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The Sierra Nevada Corporation's "Dream Chaser" is one possible contender for NASA's future crew transport to the space station. (Sierra Nevada Corp.)

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Planning to operate a taxi service for NASA astronauts? Here’s what’s required.

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But I would say that the abort system, from a systems design standpoint, could be very complex. And I believe that most of our partners in [commercial crew] are very much seeing that the abort system is driving some of their key components and key drivers of their overall design. So it is definitely a driver, a huge driver. But I cannot necessarily say it's the most complex. That depends on the actual system itself.

Chaikin: Let me just broaden the question then. For a vehicle that has not flown crew before, what do you need to see? Is it a question of saying, you've done X number of tests and the results are within X percentage of reliability? For these brand-new vehicles, how will you know when it's okay to put NASA astronauts on them?

Mango: Very good question. There are a number of things we are going to require in order for us to certify the vehicle. For an abort system, we are going to have a reliability number that says that when you push the ‘big red button,’ the system will actually work, and you get the crew back to the surface safely. Whatever that abort system is, whether it’s parachutes, or you’re going to a landing strip, or whatever. We are going to declare we've got to have 95 percent reliability, which is pretty high for an abort system that you’re hopefully never going to use in the life of your program. But it’s got to be there.

Now, how do you get there? What we will request during the next phase of our program is a proposal from the bidders [describing] what they plan to do to verify that their system can meet our certification requirements. I always get this question: “How many abort tests do companies gotta go do?” And there isn't a right answer. Because it depends a lot on all the other variables. How many component tests are you doing? How much are you making sure the reliability of those components are up to speed and ready to meet the requirement? …. I believe at some point we will have to have some level of demonstration that says you have met the capability of your abort system.

Chaikin: What you're saying is there's no prescribed test sequence or flight test plus ground test sequence. It could be a whole matrix of tests that would then give you an acceptable result.

Mango: Correct.

So that's the abort system. The rest of the vehicle is really kind of done the same way. We, NASA, already have in our requirements sections that say, for this particular requirement we suggest that the company do the verification of that particular certification requirement by test, analysis, demonstration, or inspection…. All those kind of things we will work with the contractor to put together [into] a good plan that NASA will buy into.

Chaikin: When do you think this next round of requesting proposals will happen?

Mango: Before the end of [2011] we will have a request for proposals on the street; that’s our plan. And we hope to award the Integrated Design Contract (IDC) in the summer of 2012. And then that will go for about two years. Throughout that process we will begin to work with the contractor on what that certification plan will be. And by the end of that contract, we will have what's called the Critical Design Review, which is our key design milestone.

Chaikin: That's the point at which you say the design can be finalized.

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