On Wed, 2003-10-22 at 16:09, Jonathan A Goff wrote:
> True enough. That makes sense. How easy is it to get waivers though
> for the 15 second rule?
My impression is that it's not terribly difficult. We'll see how
Carmack's application goes.
> 200,000lbf-sec is probably enough to do quite a bit of
> VTVL testing, especially
> if it isn't time limited. That would be more than enough to get it up
> to a sufficient altitude that it'll
> hit terminal velocity on the way down, so you can get a semi-realistic
> test of your landing system.
Yes, up to substantial size. 200,000 lbf-sec is a lot of bounce. Even
if you can only get a small burn time waiver, (say 30-60 second) it
should be possible to test both automated landing and guidance.
I've been wrapping my head around the guidance/flight control stuff a
bunch lately as part of the modeling I've been doing for Gizmo & POGO.
Turns out the general form of the control system that POGO uses (i.e.
differential throttling with engine canting for roll control) has some
interesting properties that I don't understand quite well enough yet to
really write down. Much of this is because I am hard up against the
limits of my understanding of linear algebra and rotation sequences. One
thing that I have figured out is that canting the engines couples the
control axes in ways that cannot readily be gotten rid of.
> Come to think of it, you might be able to get enough thrust to send a
> relatively large VTVL system
> up to that altitude and land it without leaving the 200klbf-sec box.
> That lets you test almost
> everything difficult other than the TPS.
You also probably can't test the vehicle's aerodynamic and control
behavior at high speed. You'll need a launch license to be able to do
that. However, most VTVL concepts are very simple shapes that are easy
to model accurately, like cones.
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