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Randall Clague | 25 May 2003 01:44

Re: Repost: RE: Beal Aerospace Shutdown

On Fri, 23 May 2003 18:38:35 +0100, Ian Woollard
<i.woollard <at> btinternet.com> wrote:

>Let's say somebody spins the cylinder on a gun, points it at someone and 
>fires it. That particular chamber was empty. Nobody died.
>
>The question is; what was the probability that somebody would have died 
>here? You're argument seems to be, more or less, that there was no 
>chance, since nobody died; average deaths is zero.

No.  That's very nearly the opposite of what I'm saying.

I dislike using the Russian Roulette analogy, on principle.  But it
should be a blunt enough instrument to make my point.

The scenario is that you are planning to go into a crowded stadium and
play Russian Roulette.  You should at that point do an EC calculation,
but you don't.  You just go do it.  Having survived, you go back and
do the EC calculation.  If it tells you your EC was 8000 people, you
know that something is seriously wrong with your model.

>>What
>>is the average value of a sample of one?  The sample value.  What is
>>the standard deviation?  There isn't one.
>>
>Actually, it's zero. But there's no standard deviation of the average value.

OK, yes, my error.  The Std Dev is zero.

>>  What is the confidence interval?  There isn't one.
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Randall Clague | 25 May 2003 01:45

Re: And yet even more various replies

On Tue, 20 May 2003 10:43:55 -0700, Pierce Nichols
<forkbomb <at> earthlink.net> wrote:

>         Stage stacking doesn't need to be a huge operation -- cranes 
>aren't exactly horridly expensive, and with some thought to rapid mating 
>put in ahead time, it can be done in a relatively quick operation on the 
>pad, just prior to fueling.

The new Atlas does a lot of this.  Parts count is way down.  The
manufacturer (I can't tell the difference between Lockmart and Boeing)
rep bragged about a recent scrub.  Black box went down on the Centaur.
Defuel, back to the barn, swap out the box, out to the pad, refuel,
and launch.  Missed the original launch window by 24 hours.  Not bad
for a BFM (big-ass missile); they're learning.

-R

--
Having just passed through Los Angeles, I can now state
that, "You can NOT be that stupid," is usually false.
Randall Clague
rclague <at> rclague.net
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Randall Clague | 25 May 2003 01:45

Re: Various Replies about the Beal shutdown thread.

On Thu, 22 May 2003 00:07:25 -0700, Pierce Nichols
<forkbomb <at> earthlink.net> wrote:

>mounting sacrificial anodes around the outside of the engine. They don't 
>have to be very big, because if you have done your recovery right, their 
>maximum immersion time is measured in hours, not days.

You base your design on optimal recovery operations, when you've never
done them?  (Mercury, Gemini, and Apollo don't count, for two reasons;
one, that was the Navy, and you cannot afford the Navy; two, no one,
not even the Navy, has ever recovered an RLV.)

Given the headaches associated with corrosion, the corrosion control
program is a place I'd use lots of margin.

-R

--
Having just passed through Los Angeles, I can now state
that, "You can NOT be that stupid," is usually false.
Randall Clague
rclague <at> rclague.net
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Randall Clague | 25 May 2003 01:45

Re: SSTO vs TSTO

On Wed, 21 May 2003 03:35:25 +0100, Ian Woollard
<i.woollard <at> btinternet.com> wrote:

>>         Except for a really good reusable TPS. TPS is something that 
>> could really cause an SSTO designer substantially more pain than it 
>> will cause a TSTO designer, because the SSTO has much more area to 
>> protect and much less mass to devote to the problem.
>
>Actually more area and less mass are both positive things in many ways. 
>Everything else being equal, you aerobrake higher and generate less 
>temperature.

More area = good.
Less mass = good.
Less TPS mass = very bad.

TSTO TPS is much easier, because only the second stage TPS has to
handle orbital velocity.

-R

--
Having just passed through Los Angeles, I can now state
that, "You can NOT be that stupid," is usually false.
Randall Clague
rclague <at> rclague.net
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Randall Clague | 25 May 2003 01:45

Re: H2O2

On Thu, 22 May 2003 10:06:04 -0700 (PDT), Bill Clawson
<billclawson <at> yahoo.com> wrote:

>If you have any more horses you'ld like beaten to
>death, please feel free to respond.

But do you ride them afterward?  That's the question.

-R

--
Having just passed through Los Angeles, I can now state
that, "You can NOT be that stupid," is usually false.
Randall Clague
rclague <at> rclague.net
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Randall Clague | 25 May 2003 01:45

Re: Various Replies about the Beal shutdown thread.

On Thu, 22 May 2003 06:38:59 +0100, Ian Woollard
<i.woollard <at> btinternet.com> wrote:

>>The tricks are to keep the development cost down
>>
>If you're worrying about that too much, you're not launching enough. 

If you're worrying about it much at all, you're not launching yet
anyway.  You're still in development.

>>and keep the operations cost down.
>>
>Ok; you got me there slightly; there's a difference between launch rate, 
>and launch amortized person hours, but most of the costs currently are 
>the R&D and the vehicle.

And that will continue to be true given any forseeable market.
Remember market elasticity: three years ago Henry Vanderbilt pointed
out that even if launch costs dropped by half, the launch rate
wouldn't go up.  According to Lockmart and Boeing presentations at
COMSTAC on Wednesday, launch costs *have* dropped by half.  With no
perceptible effect on the market.

Extend that to dropping launch costs by 90%.  The market might triple.
Drop launch costs by 99%.  The market will grow, but will it grow by
the more than 100x you need to make money at that price point?  That's
not at all clear.

> Both are very much improved by increased launch rate.
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Randall Clague | 25 May 2003 01:45

Re: SSTO vs TSTO

On Wed, 21 May 2003 02:48:57 +0100, Ian Woollard
<i.woollard <at> btinternet.com> wrote:

>Nobody except Rotary, so far as I know, has ever tried to build an SSTO 
>[unless you are including lunar missions ;-) ].

Rotary did not actually try to -build- an SSTO.  They were still in
design when the company folded.  They did build and fly the ATV, but
that didn't demonstrate SSTO-like mass fraction.

BTW, Marty last-name-I-forget, Rotary's Chief Engineer, has an amusing
AIAA paper out, which says that winning the X Prize is impossible.
His reasoning seems to be based on the fact that no one has ever done
it.

-R

--
Having just passed through Los Angeles, I can now state
that, "You can NOT be that stupid," is usually false.
Randall Clague
rclague <at> rclague.net
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Ian Woollard | 25 May 2003 01:59

Re: Interesting analysis of X-Prize competitors launch modes

cpwinter <at> rahul.net wrote:

>    As reported in AW&ST for 19 May, find it at
>
>	http://mae.ucdavis.edu/faculty/sarigul/AIAA_2003_0909.pdf
>  
>
I found this to be good, if a bit lightweight and facile and prejudged.

For example, he dismisses VL because: "The resulting maneuver is 
extremely aggressive and unrealistic- the motors are not throttled up 
until the vehicle is 1000ft (300m) above the ground and the motors are 
fired for only 8 seconds as the vehicle slows from 260 ft/s (80m/s) to a 
hover. If the motors fail to throttle up, the vehicle crashes into the 
ground only 4 seconds later."

Basically, that's highly emotive language, he's trying to get you to 
imagine dying, and nobody likes that; it's a good sign that someone is 
trying to pull the wool over your eyes. Consider:

a) if the motors fail to throttle up- this implies that several of the 
motors have failed simultaneously, some sort of redundancy is guaranteed 
in any likely vehicle (assuming there is no catastrophic failure of 
course, but elsewhere he indicates that the chances of a catastrophic 
failure is about 0.2%, although it isn't clear if this is per flight or 
each time an engine is lit- I suspect the former is more realistic).
b) he describes the maneuver as 'unrealistic', that's very 
prejudgemental, and he doesn't then substantiate why it is unrealistic; 
it sounds like FUD to me
c) he gives a graph showing percentage of landing mass that is fuel, for
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Henry Spencer | 25 May 2003 02:48

Re: Interesting analysis of X-Prize competitors launch modes

On Sun, 25 May 2003, Ian Woollard wrote:
> So basically  he is left with VTHL...

Which is the poster child for flight profiles which lack intact abort
during crucial parts of the flight. 

                                                          Henry Spencer
                                                       henry <at> spsystems.net
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Andrew Case | 25 May 2003 04:55
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Re: Interesting analysis of X-Prize competitors launch modes


On Saturday, May 24, 2003, at 07:59 PM, Ian Woollard wrote:

> cpwinter <at> rahul.net wrote:
>
>>    As reported in AW&ST for 19 May, find it at
>>
>> 	http://mae.ucdavis.edu/faculty/sarigul/AIAA_2003_0909.pdf
>>
> I found this to be good, if a bit lightweight and facile and prejudged.

It's a sales job for the concept favored by their employer, SpaceDev. 
There are some good points in the article, but as you point out, there 
is enough shiftiness to throw the whole thing into question. I was 
initially taken in by the reasonableness of much of the discussion, but 
a closer reading indicates a troubling level of indifference to the 
merits of concepts other than hybrid powered VTHL.

> So basically  he is left with VTHL. Gee.

Fancy that. Also he fails to acknowledge the two huge failings of his 
concept: no immediate post-takeoff abort mode, and no way to dump fuel 
in an abort at altitude.

......Andrew

--
Dr. Andrew Case, PhD.
Institute for Research in Electronics and Applied Physics,
University of Maryland, College Park
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