Conference 7.286::space

    Not so silly a question.  I just got back from the KSC and LOTS
    of people were asking the same question.
    
    The answer lies in the power/weight ration.  Solids give a lot more
    of a bang per pound than liquids [or so they said].  Normaly they
    also wouldn't have to worry about fuel tanks rupturing [we all know
    where that argument goes, dont we].                         
    
    It's also much cheaper to have solid rockets.  Just look at the
    model roceting hobby.  They're ALL solids because people can't afford
    to buy one-shot liquid rockets that don't exist or HIDEOUSLY expensive
    re-usables that don't exist [in that size].

NASA was pushed into using solids on the shuttle for cost reasons.  In
1970-71, when the Space Transportation System was being defined, there was
great pressure on NASA from the Office of Management and Budget to reduce
development costs.  Originally, the Shuttle was comprised of a manned,
reusable liquid-fuel booster stage and a manned orbiter with internal
tankage.  Unfortunately, OMB informed NASA that President Nixon, never a
big fan of manned space flight, would only support the Shuttle if its
development costs were kept under $5 billion, about half of what NASA
believed would be necessary.  NASA went through a series of gyrations
during that period, trying to develop a cost-constrained Shuttle, and
justify it to an increasingly anti-space Congress. 

Various configurations, including an orbiter with over-wing fuel tanks
mounted on a Saturn V first stage, were examined.  The Air Force had
developed some advanced solid rocket technology, including demonstrated 5
million lb. thrust motors.  NASA examined this technology and felt that it
could save money by building on some already-developed systems. Eventually,
the kludgey configuration we know today was adopted. 

NASA was lucky to get the Shuttle.  The four part Post-Apollo program 
(Shuttle, space station, moon base, manned Mars mission), was chopped back 
to the Shuttle, with the space station pushed into the future, and the 
other programs (including the nuclear engine program) canceled.

>    President Nixon, never a
>    big fan of manned space flight,  

My understanding is that Nixon *was* supportive of the manned space
program but neglected to instruct the OMB to give high priority to
NASA funding.  See note 232.0 in this conference.  BTW, send me mail
if you'd like a copy of the article mentioned in that note.

    The SRBs came about by a sort of forced evolution as shuttle
    requirements and budget constraints changed during design. For cost
    reasons, a recoverable booster was scrapped in favour of a cheap
    expendable. The S-IC from the Saturn V was considered but its LOX/RP-1
    engines were not efficient enough. NASA then shifted to a parallel burn
    concept where the orbiter's engines were ignited on the ground and
    provided much of the thrust for the initial ascent. Choices then were
    cheap pressure fed liquid boosters or solids. The solids were chosen
    because USAF and UTC had already developed the 120 inch solids for the
    Titan III program, which had already been man-rated and would be
    cheaper than expendable liquids. The ability to reuse the solids was a
    bonus. 
    
    If they had started with similar design constraints they may have
    ended up with a different design.
    
    To correct a couple of comments earlier...
    
    Solid propellants are not more efficient in terms of power/mass
    (specific impulse) than most liquid propellants but they are often more
    volume efficient, especially when compared to LOX/LH2. This is an
    important constraint in the early part of the flight. This is one of
    the reason you rarely see LOX/LH2 in the first stage of launch
    vehicles. 
    
    Also, thrust cutoff is possible on solids. It was in the original
    design of the SRBs and I guess it got dumped for budget reasons.
    The idea was to explosively open vents at the top of the SRB that
    cause a sudden pressure drop in the combustion chamber. When the
    pressure drops below a certain critical value the propellant
    extinguishes itself and thrust drops to zero.
    
    gary

        In regards to Reply 256.2 - 
    
      	Why are POLITICIANS the ones who approve and disapprove space
    projects?!             
    
    	These people (especially this Administration) know next to nothing
    about space technology, or how to properly plan our exploration
    of space, yet they are the ones who decide - and they usually cut
    everything that doesn't have some national "muscle-flexing" involved!
    
    	For example, many books on space history are finally starting
    to emphasize the role that Shuttle-type vehicles played in our early
    space program, and how if politicians hadn't decided to start a
    virtually dead-end project to get Americans on the Moon first, we 
    could have had a Space Shuttle where all the bugs and most of the 
    inevitable accidents occured years ago, and by now we'd have at least 
    a permanent space station in Earth orbit, and probably a manned lunar 
    base too, not to mention manned Mars expeditions!
                      
    	Please do not take this as a neive question - I know that NASA
    needs to get its money from somewhere, but why politicians who go
    on the equally ignorant whims of the general public?  It was the
    geenral public who "got bored" with manned Moon landings, and thus
    helped to cut any more missions - what do they know about lunar
    exploration?  And by God, that was EXCITING - we actually had men
    on the Moon for the first time!  History was being made right in
    front of us, and yet many people got bored!                 
    
    	I say, let big corporations fund NASA and the space projects;
    it may not be perfect, but when a big company wants something done,
    they do it!  
    
    	Larry
    

    re .5
    
    Poiiticians are (allegedly) the chosen spokespeople of the public,
    who ultimately (and allegedly) hold the purse strings. Get the majority
    of the public sufficiently excited about a purposeful space program,
    and it will happen, quickly.
    
    That's exactly how Kennedy's moon prophecy came true.

    	But that is my point - the public gets all excited about a manned
    Moon mission, yet they really don't know what's going on, and their
    ignorance and unrealistic expectations make their "sense" of direction
    for the space program like following a ship navigator without any
    navigation equipment in the dark!  Eventually they get frustrated
    and want to give up, and you're stuck in the water with a big ship
    and nowhere to go, and you know it's dangerous just to sit there!
                                        
    	And the polititians would support spending money on watching
    grass grow if it would keep them in power, so they certainly aren't
    any help with their lack of real concern and understanding.
                                                               
    	How one of the most important projects in the history of humanity
    ever got this far off the right path, I'll never know!
    
    	Larry
    

Walter McDougall's book, _The Heavens and the Earth: a Political History of
the Space Age_, talks extensively about Nixon's attitudes toward the space
program, both as VP under Eisenhower and as President.  There's no question
that in 1960, Nixon shared Ike's view that any crash program of manned
space flight would amount to nothing more than "a raid on the Treasury." 
Nixon's 1960 election platform proposed termination of the Air Force LUNEX
(Lunar Expedition) and Army/JPL Apollo programs, Nova, and much of the
planning for post-Mercury manned missions.  (He did support the X-20,
however.) 

After he was elected in 1968, he expressly rejected his own Vice
President's Space Commission proposals for a large post-Apollo program and
implemented the budget cuts that terminated the lunar exploration program
after Apollo 17, terminated Saturn V production, and reduced the Apollo
Applications Program to a single Skylab facility.  Nixon supported the
Shuttle, claims McDougall, for two reasons: it would gain support in the
layoff-stricken aerospace industry and thus improve his re-election chances
in California and elsewhere, and it would provide a launching capability
for large military satellites. 

I'm sure Nixon was sophisticated enough to feign interest in a program that
his Administration was about to ask Congress to fund. 

>    I'm sure Nixon was sophisticated enough to feign interest in a program that
>    his Administration was about to ask Congress to fund. 

     I've been reading "Prescription For Disaster:  From the Glory of
     Apollo to the Betrayal of the Shuttle," by Joseph J. Trento
     (this is not the book mentioned in note 241 -- this book is worth buying).
     I've changed my mind about Nixon  -- he *was* a stinker when it
     came to the space program.  I guess I was politically naive in those
     days (even more so than I am now  :-)...