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From: Gary Hudson <>
Subject: Re: making the colonization of space cheaper
Date: Wed, 04 Mar 1998 13:35:35 -0800

Marcus Lindroos INF wrote:

> Another issue is TPS...airliners don't require this, and even the
> Concorde is only heated to 400 degrees Kelvin or so.  For RLVs, the
> current baseline is the Shuttle which requires 80,000 man-hours of
> TPS maintenance & inspection per flight. Future RLVs will use improved
> systems and benefit slightly from lower reentry heat loads (~1500K peak
> heating vs. 2000K for the Shuttle) because they will be lighter but I
> don't think the problem will go away at once. Gary
> Hudson plans to use water cooling; is there a reason why comparatively
> few base-first VTVL SSTO proposals use his approach?

Boeing proposed water-cooling on VTOL landers during the 1970s.  The
principal advantage is easy "refurbishment" compared to other TPS
options.  VTOL vehicles have an advantage with water cooling since the
heat pulse they see during entry is short and sharp, rather than
protracted due to higher L/D entries.  Water has been shown to be well
suited to that low L/D trajectory.

> Finally, you have propulsion. A jet engine operates at peak temperatures
> of 1300K or so (the turbin blades) with most parts enduring far less
> than that. A reusable rocket engine, on the other hand, is in a totally
> different world as far as temperature, pressure is concerned.

A properly designed resuable rocket engine should never see temperatures
even as high as jet engines!  The RL-10, for example has no component
heated more than about 600 F (the cooling jacket inner wall).  Pressure
is of course another matter, but temperature is the real killer.  That
and rate of onset of thermal shock.

Gary C. Hudson

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