Conference 7.286::space

    I'm not sure, but I think you _need_ the SSMEs for steering purposes.
    
       Detlef.
    

RE:    <<< Note 747.1 by HAMSUP::MARXSEN "Univ.Milky.Sol.Earth.FRG.Hamburg" >>>

Could be, though I believe that the SRBs are gimblable to a degree (likely not
to the degree that the SSME's are, which have travel limits of about 10 degrees
all around, but I don't know).
						-- Tom

The SRB nozzle can gimbal through 8 degrees along any axis.

- dave

  The shuttle cargo bay might not be big enough to take advantage of the extra
lift provided by 4 SRB's. If you were to remove the shuttle and replace it
with a throw away cargo pod, you would save so much weight that you might
not need the extra thrust.

  Also, that would be that much extra thrust pounding away at the pad on
launch.

  Lots of things to consider

  George

        A bigger problem would be the increased loading on the vehicle.
        Both the SRB and the SSME throttle down when going thru max-q, and
        the SSME again throttles down before shutdown to remain under the
        3G design limits. Adding any additional SRBs to the stack would
        likely push things WAY over these limits, unless a LOT of payload
        were added. 
        
        Where would these SRBs be attached?

    Re .-1 (Kaplow)
    
    I don't think that adding payload would be a problem. I mean people are
    desperate to get their stuff in orbit. If nothing else, they could take
    water, as an investment in the future...
    
    So your problems with max stresses (due to lack of payload) would never 
    come up.
    
    As for were to attach the extra boosters, around the main tank of course.
    That would mean a bit of a resdign of the shuttle stack, but then that is
    exactly what we are talking about.
    
    Since each shuttle launch is so darn expensive, it makes sense in sending
    up as much payload as possible in each one. Adding 2 SRBs would not 
    increase the cost per launch that much while it may increase the payload
    by as much as 60% ???
    
    Gil

  But where would you put the payload? I believe the TDRS/IUS is one of the
heaviest payloads and it takes up pretty much all of the cargo bay. Adding two
more boosters would almost double the thrust at take off. Where would you put
cargo equal to a TDRS/IUS, Shuttle, and loaded main tank? 

  Might be good if you wanted to launch a payload of gold or plutonium.

  Perhaps you could strap a 2nd Shuttle or pod on the other side of the tank.

  George

Plus with that much thrust, it would be important to have it symmetrical.  You
might be able to fit three around the tank symettrically (with the shuttle
between two of them) but I bet not 4.  Plus there is the thrust structure of
the tank and shuttle.  They would have to be beefed up considerably in order
to take the extra force (regardless of the payload mass).

Burns

Article: 45096
From: [email protected] (Brett Kottmann)
Newsgroups: sci.environment,sci.space
Subject: NASA launches and the environment (numbers provided)
Date: 23 Jun 92 09:56:25 EST
Organization: Logicon Technical Services, Inc.
 
	Space launches are less polluting than industrial and natural
sources.  Industry is sometimes less and sometimes more than natural. 
 
        (Oh, it's from Aerospace America, and not Aviation Week...)
 
	"Current and projected launches have insignificant impact on
the global environment." 
 
	Excerpts from _Aerospace America_, May 1991.
 
	Chemical Rockets and the Environment
	====================================
 
	Shuttle solid and liquid rocket motors inject more exhaust
products into the atmosphere than any other launcher, yet studies
indicate no significant impact on global environment. 
 
	Stratospheric O3 is continously produced in the upper
atmosphere by photolysis of molecular oxygen (O2), and is continuously
destroyed by both natural photochemical processes and by chemical
reactions with a number of species, including atomic chlorine (Cl),
atomic hydrogen (H), hydroxyl radicals (OH), and nitric oxide (NO). 
These chemicals processes are interrelated, so that changes in the
concentration of any one ozone-destroying species can affect the other
processes, but all processes are catalytic; that is, the active
species emerge intact so that many ozone molecules can be destroyed by
a single atom/molecule of Cl, H, OH radicals, or NO. 
 
	Rocket exhausts produce hydrogen chloride (HCl) from solids
and water (H2O), hydrogen (H2) and nitrogen oxides (NOx) from solids
and liquids.  Although HCl, H2O, and H2 do not react directly with ozone, 
they can be converted into reactive species, so both liquid and solid 
rocket exhausts do have the potential of destroying stratospheric ozone. 
 
	The bulk of the HCl exhausted from the Shuttle's solid rocket
motors, about 65%, is deposited in the troposphere, where it is
removed by rainfall.  It is not an ozone concern because it never
reaches the stratosphere.  The remaining HCl, which can react with OH
in the stratosphere to produce ozone-destroying Cl atoms, is only a
small percentage of the stratospheric Cl burden when compared to
industrial and natural sources.  Indeed, it would take a launch
schedule rate of 54 Shuttles and 36 Titans per year to produce 1% of
the current statospheric Cl burden. 
 
Annual contributions (in kilotons) of statospheric Cl, H2O, H2, and
NOx by rocket launches (9 Shuttles and 6 Titans) and by other sources
(chlorine data are global, other data for nothern mid-latitudes): 
 
Source		Chlorine	Water		H2		NOx
==============================================================================
 
Industrial	300
 
Volcanoes	100-1,000
 
Natural		75		15,600		340		280
 
Rockets		0.79		3.25		0.2		0.016
 
==============================================================================
 
Relative importance of some ozone-depleting cycles from all sources
and from rocket launches: 
 
Species			% Ozone removal		% due to rockets
==============================================================================
 
Nitrogen oxides		32			0.00005
 
Oxygen			23			0
 
Hydrogen/hydroxyl	26			0.0012
 
Chlorine		19			0.032
			_________		__________
 
Total			100			0.034
==============================================================================
 
Relative contributions of 9 Shuttles and 6 Titans to deposition of
particulates in the stratosphere and their effects on ozone depletion
in the northern low to mid-latitudes: 
 
			El Chichon	Natural Background	Rockets
===============================================================================
 
Integrated surface      17,500,000	540,000			763
 area (microns/m3)
 
Est. ozone depletion	10-17%		0.5-0.2%		0.0004-0.0007%
===============================================================================
 
	The article was written by Allan J. McDonald (AIAA Technical
Committee on Space Transportation), Robert R. Bennett (Research Labs,
Morton Thiokol), Jerry O. Hinshaw (AIAA Technical Committee on
Atmospheric Environment) and Michael W. Barnes (Marketing Dept.,
Atlantic Research). 
 
	The above is only part of the article.
 
Brett---------------------------------------------------------------------------
	"Why the courts don't tell a husband who has been living off his wife
to go out and get a job is beyond my comprehension."--Joan Lunden
--------------------------------------------------------------------------------