spaceplane research: summary of responses

From:         naylor@research.canon.oz.au (William Naylor)
Date:         18 Feb 93 03:32:22 PST
Organization: Canon Information Systems Research Australia
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In a previous message, I asked:

>I have heard it suggested that long distance air travel could eventually
>be done by airliners which fly in low earth orbit.  Flying in low earth
>orbit could reduce travel time and reduce fuel consumption.
>
>I know almost nothing about this and I was hoping some of you could
>enlighten me.  Particularly, I would like to know:
>
>  1)  What are the difficulties and advantages of flying in low earth orbit?
>
>  2)  How much research has been done/is being done?
>
>  3)  What is the status of the research?
>
>Please e-mail replies to me; I'll post a summary.

This is my summary.


From: ak336@cleveland.freenet.edu (John Dill)

>I'm not very techincally involved with the "space plane" concept
>but I can say that the hurdles are huge! To reach a near earth orbit
>requires a speed of nearly 18,000 mph. The amount of fuel required with
>todays  technology is evidenced by the space shuttle (about 75% of it's
>gross take off weight is fuel and suplemental engines..the solid fuel
>boosters).
>Rumors are flying about a secret spy plane operating in the Nevada desert
>that can attain a speed of mach 8..about 5,0000 mph, and also can fly
>around the world non-stop. Check the sci.avaition. sig above this one
> for further details.
   

From: weiss@SEAS.UCLA.EDU (Michael Weiss)

>In article <airliners.1993.96@ohare.Chicago.COM> you write:
>>  1)  What are the difficulties and advantages of flying in low earth orbit?
>
>There are several, mostly related to the fact that atmosphere is 
>extremely thinat those altitudes:
> 1)  Turbojets/turbofans are not very efficient at those altitudes
> 2)  It is extremely difficult to garner lift from such a thin atmosphere
> 3)  Turbojets/turbofans cannot reasonably be used at above M2 without
>     exorbitant fuel costs (high speeds are necessary for two reasons: one
>     is that the whole point is to get there faster, and two is that in
>     order to maintain lift, the plane has to travel at extremely high
>     speeds)
> 4)  Materials able to withstand the high forces at those altitudes and
>     speeds for the lifetime that makes it economically feasible have not
>     yet been developed.

>  2)  How much research has been done/is being done?
> 
>Plenty.  It is being funded by both the US and EC.
>  
>>  3)  What is the status of the research?
>   
>Promising, but not soon to be complete.


From: drickel@sjc.mentorg.com

>>   1)  What are the difficulties and advantages of flying in low earth orbit? 
>Umm.  Some terminology, perhaps.  If you're in low earth orbit, you aren't
>flying (aerodynamic effects are insignificant).
> 
>Let's see.  Advantages.  Any spot on earth is within 50 minutes of any other
>spot.
>  
>Disadvantages.  Using current or projected near-term technology, craft must
>be about 90% by weight fuel.  Passengers are subjected to large g forces
>on take off (probably at least 2.5 g's).  Passengers are subject to long
>periods of zero gravity.  Passengers may be subject to fairly high negative
>g forces (-1.5 g?) on reentry.
>   
>This is assuming some sort of rocket; it is akin to the Single-Stage to Orbit
>proposals now being investigated (DC-X is one currently being funded).
>    
>It might be possible, using scramjets or some other technique, to lower the
>fuel requirements somewhat.
>     
>>   2)  How much research has been done/is being done?
> 
>Some.  Some more (but not much more) is being done in the hypersonic flight
>regime.  This has its own set of advantages and disadvantages.  It is
>slower (craft travel from one third to half as fast), skin heating is more of
>a problem (they stay within the atmosphere), there aren't any prolonged
>periods of zero gravity.  This is the so-called aerospace plane or orient
>express.
>  
>>   3)  What is the status of the research?
> 
>Ongoing, but not seriously.  Several people would like it, but nobody knows
>whether or not the market will be there.
  

From: drinkard@bcstec.ca.boeing.com (Terrell D. Drinkard) from Boeing:

>We've looked at the hypersonic transports, the Mach 25 stuff, and it
>doesn't make sense.  To make the accelerations bearable, one would have to
>go all the way around the world at least once.  At a minimum, fly the
>reverse course.  With current technology and economics, this is
>unthinkable.  :-)  Sorry.
 
-- 
Will Naylor               net:  naylor@research.canon.oz.au
                          mail: Canon Information Systems Research Australia  
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