Author Topic: Questions: Drag coefficients and nose cones  (Read 3135 times)

Offline Jason1701

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Questions: Drag coefficients and nose cones
« on: 01/25/2011 10:27 pm »
Hi everyone. I'm doing a project that involves modeling a flight through the atmosphere. As part of this, I have to pick a drag coefficient for my theoretical rocket. According to this site, sharp nose projectiles have substantially lower coefficients at high Mach numbers. But is there a large difference between very sharp noses, like the External Tank's, and less sharp ones like those of Dragon and the Delta IV?

I read that a blunt nose is much better than a sharp one for reentering the atmosphere. Would it be feasible for a reusable SSTO rocket to have a sharp nose cone during ascent that is jettisoned before reentry to reveal a blunt nose underneath?

Thanks for helping me. I'll be very grateful for your input.

Offline Proponent

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Re: Questions: Drag coefficients and nose cones
« Reply #1 on: 01/26/2011 02:02 am »
It's certainly possible for an SSTO, like many of today's expendables, to carry a jettisonable aerodynamic fairing on the way up.  I believe Bono's (no, not that Bono :)) SASTO design of the 1960s featured such a fairing, at least in some versions.  SASTO, however, was intended to re-enter base-first; the fairing, IIRC, was used to improve the aerodynamics on the way up, which otherwise would have been constrained by the fact that a Gemini spacecraft comprised the nose of the vehicle itself.

I suspect, though, that what you really want in an SSTO is not high drag, but high lift or, more precisely, a high lift-to-drag ratio.  That way, you get more maneuverability and more cross-range.  This might push the design toward a nose-first re-entry.  In this case, a low-drag nosecone would be desirable even on the way down.  I believe the DC-Y design was an example of this approach.

In any case, base drag is likely to be a large component of the total drag whenever the engine is not operating.

EDIT:  Removed redundancy.
« Last Edit: 01/26/2011 05:27 am by Proponent »