Re: SpaceShipOne and reentry heat

From: Daniel Walker (dw229_at_hermes.cam.ac.uk)
Date: 06/24/04 

To: sci-space-tech@moderators.isc.org
Date: Thu, 24 Jun 2004 17:23:40 +0100

Reading these postings about SS1's re-entry and from what we've heard
recently regarding the space shuttle's TPS and its problems, why have
spacecraft tended not to use engine-based deceleration to reduce the
thermal effect of re-entry? If the orbital velocity is a major factor in
re-entry speed, why not take this off and just drop in? Dropping in from
400km would give you a nominal speed of ~2.8km/s if you reached the
Earth's surface (assuming I've done my sums right!).

I imagine the answers will involve the excess fuel needed, manoeuvring,
restartable engines, etc., so at what point (what altitude) does the
weight of thermal protection tiles beat the extra fuel needed for an
orbital craft? I know there's lots of variables involved, but wondered if
anyone had considered this?

Dan