[ExI] Eyes on the Solar System

spike at rainier66.com spike at rainier66.com
Sun Sep 4 16:57:21 UTC 2022

-----Original Message-----
From: spike at rainier66.com <spike at rainier66.com> 

>...However... hydrogen has always been crazy hard to handle: tiny atomic
radius, super cold, dangerous as all hell, and you know the thing...spike

BillK and other non-yanks here, we have a way to subtle reminder of "you
know, the thing" meme: 


Of course what I meant by "you know the thing" in this case was a reference
to a day on which an image is burned into my retinas, 28 January 1986, a day
which changed my life forever.

We space guys have been second-guessing ourselves and second-guessing NASA
ever since that day.  For instance... one of the options for the shuttle,
rather than hydrogen fuel is kerosene or methane, or even methanol (maybe on
that last one) with the advantages being denser safer fuels.

A calculation I did many years ago suggested that had the exact solid rocket
booster failure happened with a forward tank LOX and aft tank kerosene,
would the explosion had destroyed the orbiter?  According to my best
estimates, no it wouldn'ta destroyed that orbiter and might not have even
had any explosion analogous to what happened in the Challenger accident.  

Reasoning: the aft mount of one of the solids was burned thru, the front end
of the booster pivoted around and struck the tank which contained liquid
oxygen forward and probably also ruptured the hydrogen tank.  But what if we
were carrying a hydrocarbon fuel?  The kerosene (or methane or methanol)
would go forward, being the denser fuel (to move the CG forward (closer to
the center of pressure)) so that solid would have struck a kerosene tank and
probably ruptured the LOX tank.  But... that would likely not have resulted
in an explosion, or if so, not one likely to break up the orbiter.

OK then.  Suppose there was a sudden torque and the abort flight procedure
kicks in.  The orbiter is detached from the main tank/solids (those three
are jettisoned together) and now the orbiter is mostly intact (we hope.)  It
is altitude about 14 km, downrange about 11 km, which isn't that far, which
is why it was still in visual range to the horrified audience at Cape
Canaveral (and even from front yard in Titusville.)  

Had the orbiter remained intact, at that point, they had enough altitude,
speed and control authority to turn around and fly back to the landing strip
at Cape Canaveral.

Burning kerosene in the first stage has its performance penalties but it has
safety, reliability and cost advantages that pay it all back with change
left over.


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