Path: utzoo!utgpu!jarvis.csri.toronto.edu!mailrus!tut.cis.ohio-state.edu!ucbvax!agate!eos!steve
From: steve@eos.UUCP (Steve Philipson)
Newsgroups: sci.space.shuttle
Subject: Re: Aurora recovery by C-5
Message-ID: <2953@eos.UUCP>
Date: 21 Mar 89 03:33:14 GMT
References: <7.UUL1.3#5131@mvac.UUCP> <3412@aplcomm.jhuapl.edu>
Reply-To: steve@eos.UUCP (Steve Philipson)
Organization: NASA Ames Research Center, Calif.
Lines: 66

In article <3412@aplcomm.jhuapl.edu> jwm@aplvax.UUCP (Jim Meritt) writes:
>In article <7.UUL1.3#5131@mvac.UUCP> space@mvac.UUCP (Sci.Space netmail) writes:
>}    Now this seems a bit outrageous to me.  My volkswagon has enough trouble
>}    when following a truck due to the wind turbulance.  And that is in only
>}    two axis of motion.  I would imagine that a C-5 creates a pretty high
>}    amount of wind turbulance as well, and in the air one has three axis to
>}    worry about.
>
>You are extrapolating problems where they do not exist.

>The Air Force (and the Navy) have managed to come up VERY closely behind
>some very fast and very large aircraft with very small aircraft.

>Look for a picture of in-flight refueling.  Tough, but possible.

   The problem does exist, is a problem, and would make a "fly into fuse-
lage" system very difficult to implement.  The "extrapolation" is quite a 
reasonable one.  Every aircraft has a significant wake behind it, both
from disturbed airflow over the fuselage and downwash from the wing.  

   Close formation flight at high speed is an art, and requires in-depth
knowledge of the flow patterns around enach aircraft.  Aerial refueling 
systems and procedures are very carefully developed so that the receiver 
stays out of the worst part of the wake of the tanker.  Both flying boom 
and drogue and hose systems allow the receiving aircraft to remain in an 
area of reasonably smooth flow.  Even so, the tanker pilot has to adjust
his pitch trim as the refueling aircraft moves into position, as his "bow
wave" can produce an upward force on the horizontal stabilizer of the
tanker.  These procedures are regarded as fairly critical and somwhat 
hazardous.
  
   Remember the crash of the XB-70?  A chase plane moved into an area
of turbulent flow under and to the rear of the wing.  The flow pattern
forced the nose of the chase plane up into the wing of the bomber, 
resulting in collision and fatal crashes for both aircraft. 

   Just to set the record staight, a C-5 cannot open its front cargo 
door in flight -- the front "door" is the nose section of the aircraft 
(including the cockpit), which opens UP.  Thus, the only way to recover
an object would be (as Jim points out) to make secure attachments to it 
while it is in stable position, then bring it in.  This still would be 
very difficult with any large object, particularly one that develops 
lift, as forces would be large and change magnitude rapidly.  

>Way back when there were blimps (remember them, space jocks?) we had
>aircraft launched from and recovered from blimps.  ...

   Blimps are fairly modern airships, and we still have 'em.  I don't
think any ever were capable of retrieving fixed wing aircraft.  Some
DIRIGIBLES were capable of such operations, but they had a much easier 
task than would a C-5 recovering a jet -- the flight speed of the bi-
planes that were operated from them was fairly low (decreasing the body
wake problems), and there was no wing downwash to contend with.  

   Sure, this kind of recovery could be done, but it's not worth the
expense and risk given the number of other, more practical alternatives.


   This discussion is really in the domain of rec.aviation, but it is
clear that there is interest here.  If you really don't want to see
more of this, just use your "K" key.
-- 

						   Steve
					(the certified flying fanatic)
					    steve@aurora.arc.nasa.gov