From: strider@acm.acm.rpi.edu (Greg Moore)
Subject: Re: 20 Questions About the Delta Clipper
Keywords: SSTO
Organization: The Voice of Fate
Date: Tue, 8 Sep 1992 14:44:13 GMT

In article <1992Sep1.144007.3396@iti.org> aws@iti.org (Allen W. Sherzer) writes:
>This was prepared as part of a packet of information on the SSRT project
>and the DCX and DCY vehicles. Permission is granted to reproduce and
>distribute any way you want.
>
>   Allen
>--------------------------------
>
>                  20  question about the Delta Clipper
>
>12>  Will it be able to fly to the Moon?
>     A Delta clipper derivative vehicle, re-fueled in Low Earth Orbit,
>would be able to fly to the Moon, land there, and then return to Earth.
>The modifications required, however, would be substantial.
>
	In other words, don't hold your breath.  When I read substantial
modifications, I start thinking "new ship".

>16>  Why should I believe all these claims for the Delta Clipper
>     when similar ones were made for the Shuttle twenty years ago?
>
>     The Shuttle's design was "frozen" in the 1970's.  Using the technology
>available then would have resulted in a SSTO that was extremely large and
>expensive. A Delta Clipper sized SSTO based on 1970's technology would not
>have ben able to reach orbit. In the 20 years since then, we have learned
>a lot about design, light-weight materials, trajectory optimization, avionics,
>computers, and engine design.
>
	This is all nice, but I think it is not really a good answer.  So
what if the shuttle's design was frozen?  And so what if the technology
available then would have resulting in a large SSTO.  No-one claimed the
shuttle wsa to be a SSTO.  This paragraph sounds more like an answer to
the question: "Why didn't we do this with the shuttle 20 years ago?"

	I think in general the real question being asked in this case is
how you plan to meet turn-around requirements and cost requirements.  The
above tells me nothing that relates to that.

>     In addition, the Delta Clipper is being designed with supportability
>and operability as priority considerations. For example, the engines
>on the Delta Clipper won't run at 110% of their design capacity, as the
>Shuttle's do, so they won't have to be torn down and repaired before each
>flight. If on-board diagnostic instruments indicate a problem with a
>Delta Clipper engine or any other component, it is designed so components
>(called line replaceable units) can be pulled and replaced quickly after
>landing.
>
	This is actually more to the point of answering the above question.
However, I now have a couple oif questions of my own.
	The point about not running engines to 110% is a good one.  And
I will grant that you probbaly won't have to tear them down after each
flight.  However, we have no real-world experience on this matter.  Yes,
the RL-10 has been fired for so long and refired so many times, but until
you build the DC-Y and fly it a few times, you have little idea of the
actual wear and tear on the engines.  You may find the atmospheric transit
has strange affects (look at the British Comet) that negatively affect
wear and tear, requiring more maintainance than required.  And this 
is assuming you use the RL-10.
	Also, what work is being done to develop the LRU's?  Or can they
in most cases simply be adapted from aircraft LRU's.  
          
>
>-- 
>+---------------------------------------------------------------------------+
>| Allen W. Sherzer | "If they can put a man on the Moon, why can't they     |
>|  aws@iti.org     |  put a man on the Moon?"                               |
>+----------------------234 DAYS TO FIRST FLIGHT OF DCX----------------------+