Re: The Five-Billion-Star Hotel / propulsion

[Mark Reiff <markreiff@xxxxxxxxxxxxx>]

Jason,

A SRB as a safe propulsion system?  Apparently you are not old enough to 
remember the Challenger accident.
Solid propellant has fuel and oxidizer mixed together.  It is inherently unsafe, 
especially when you have the SRB segmented with o-rings sealing the joints 
between the segments.  Now if you remove the oxidizer and use a hybrid solid 
rocket, where liquid oxygen is pumped through the fuel core - that is an 
inherently safe rocket motor.  That is what Rutan's SpaceShipOne uses.

Using an SRB as the basis for a manned launch vehicle sounds like what a NASA 
contractor would propose, in order to keep their SRB production line open.  Not 
that man-rating the EELV will be a cheap or quick thing to do either.  Both are 
poor choices for a cheap, quick and safe manned launch option.

As for the capsule, it has some inherent safety features as well as drawbacks. 
It does allow relatively uncontrolled safe atmospheric re-entry and launch 
escape by using a tractor rocket.  Of course it necessitates the use of a 
parachute/parfoil to ensure a survivable landing.  The reliability of 
parachute/parfoil systems has it's limits.  And if you have ever seen a 
flight-like capsule up close, you will know that is quite cramped inside.  Also 
the landing targeting is problematic.

Mark Reiff

Jason wrote:
> Following up Patrick's comment about using existing propulsion systems,
> I've included some pertinent information from astronaut Scott Horowitz.
>
> "It started as an idea of safe, simple, and soon," NASA astronaut Scott
> Horowitz said during a plenary session of the Mars Society's annual
> conference in Chicago last month. "After the Columbia accident, a few of
> us in the office were thinking about how we can do this better. How do
> we get to the point where we can launch lots of people to and from low
> Earth orbit?"
>
> That philosophy of "safe, simple, and soon" led them to adopt a capsule
> design for manned spacecraft. Horowitz said they then turned their
> attention to a launch vehicle for that capsule. "I was thinking, 'What
> is one of the most cost-effective, safest pieces of hardware that we
> have to use as a lower stage?'" Horowitz recalled. "I said, 'Hey, what
> about a solid rocket booster?'"
>
> Combine it with an upper stage, proponents argue, and an SRB could carry
> CEVs into orbit sooner and less expensively than an EELV.
>
> The whole article can be viewed at
> http://www.thespacereview.com/article/226/1.  
>
> Jason Klassi

--
Mark Reiff <markreiff@xxxxxxxxxxxxx>

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