Details on Starliner changes

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This article provides some details about the design changes being made to Starliner that have caused its first test flight to be delayed until 2018.



  • John Kross

    Kind of late in the game isn’t it? Didn’t Boeing conduct aerodynamic tests before this? Troubling.

  • Edward

    John Kross,
    Yes. It is late in the process, but the tests were months ago. The solution is only now being announced, now that further testing indicates the solution works.

    Congress’s choice to reduce funding delayed this kind of testing and may have reduced the amount of resources available to find the solution, as other aspects need to also move forward as well, spreading scarce resources among too many areas.

    This is the kind of surprise that rears its ugly head after the engineers think that they have a good design, and why testing is performed to verify that the design is as good as thought. When this kind of surprise comes up, they figure out why and how the design is inadequate and what needs to change to make a working design.

    The disappointing part is that we have had capsules on top of rockets before, so we would think that we know how to do it successfully. Without knowing what the aerodynamic problem was, I am going to guess that the service module is shorter than for earlier capsules (perhaps to save weight), and that the shorter section resulted in unexpected aerodynamics.

  • John Kross

    Yes, I agree with most of your post, but surely aerodynamic tests (or at least detailed CFD models) should have been performed years ago when the first designs of the CST-100/Atlas V stack were envisioned. It still seems very late to discover “unexpected” aerodynamic loads.

  • Edward

    John Kross wrote: “but surely aerodynamic tests (or at least detailed CFD models) should have been performed years ago when the first designs of the CST-100/Atlas V stack were envisioned.

    Vision is not design. The vision is the perfect condition that is seen by the designers and artists making the concept drawings. Eventually reality rears its ugly head (that is where the surprises come in) and changes have to be made. A seemingly harmless, minor design change can turn into a nightmare. Because of the costs of tests and computer modelling, these are not done constantly but are saved until the design has settled down a bit.

    My research shows that they performed early wind tunnel testing — without the Atlas V as part of the model — in December of 2011. I did not find out when they included the Atlas V in their tests and analyses, but the service module was already short.

    The following article talks of two problems. One was weight (it grows during design, because of reality’s ugly head) and the other was the aerodynamic problem, but they had been working on these two problems before May:
    They had one issue, a non-linear aerodynamic loads issue, where they were getting some high acoustic loads right behind the spacecraft.

    Solving the problem may have taken a long time, because they need to understand why and how the problem occurred and what is happening aerodynamically in order to figure out how to solve it. When you run into trouble, return to the fundamentals and work from there.

    After all, what got them into this trouble in the first place was relying on the similarity to Apollo and other proven capsules. Guessing at a solution without understanding the problem can cause even further delays as it is discovered that the guess was wrong. As Gene Kranz said, “work the problem, people. Let’s not make things worse by guessing.” (1 minute)

    From the linked article: “The good news is there are no additional large problems that have arisen in the last six months, so maybe we’re at the point where we’ve investigated everything, and we finally have a design we’re confident in.”

    Robert may have your answer, though:
    Robert commented: “This delay for Boeing is not really a surprise. Unlike SpaceX, the company had done very little actual development work on the capsule before winning its contract from NASA. They therefore have a lot more to do to become flight worthy.

    It looks like, for Boeing, the serious work started after the contract was signed in 2014.

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