Re: starship-design: Re: Re: debate

[kuo@bit.csc.lsu.edu (Isaac Kuo)]

Kelly St wrote:
>In a message dated 12/9/97 11:55:52 AM, kuo@bit.csc.lsu.edu wrote:

>>>>>Beyond that plannig on such systems in the next 50 years is highly
>>>>>conservative even by the standrads of commercial investors.

>>>>Commercial investors take amazing risks all the time.  They need to
>>>>do so in order to make their overall profits.  That is the nature
>>>>of investment.  Given the current profitability of the stock market
>>>>compared to bonds, I would have thought that obvious.

>>>Commercial investors never take amazing risks.  Their entire focus
>>>is to avoid amazing risks.

>>Untrue.  They regularly invest large sums of money on speculations
>>which may fail, and when it's other people's money it can make big
>>news when the bet fails.

>All investments are risks.  "amazing risks" suggests an unusually high risk

They are unusually high, in that the average middle income investor
can not afford to take them.

>>The larger the sums of money, the more risk investors take.  On one
>>end of the spectrum are personal savings, which require a low risk
>>strategy in order to save up retirement funds safely.  On the other
>>end of the spectrum is Bill Gates, who has so much money to spare
>>that he can afford to risk most of his eggs in one basket--his own
>>company--because it is the most profitable place to put it.  There's
>>maybe a 5% chance that a some "disaster" will cripple Microsoft
>>stock--that's too much of a risk for anyone to put their entire
>>retirement savings into Microsoft stock alone, but Bill Gates can
>>afford to put the vast majority of his money in Microsoft stock
>>because even in the worst case what remains is plenty.

>No, thats not what risks mean.  Gates invests in MS stock because it gives him
>more control in his company and because (as you stated above ["There's maybe a
>5% chance that a some "disaster" will cripple Microsoft"]) its a very low risk
>investment.

I state 5% as a bare minimum, because that's already an unacceptably
high risk for the average investor.  Do you want to have a 1 in 20
chance of losing all of your life savings, as well as your job
(which is what investing in the company you work for is risking)?

Bill Gates is extremely paranoid and cutthroat in his business
practices because he's seen first hand how volatile the computer
industry is and how no one is assured to stay on top.  He's well
aware that a single slip up could be all it takes to permanently
cripple a computer company, like IBM or Apple.

Microsoft stock is a high risk investment, but it has a very high
expected return.

>>>>>>Something _might_ be discovered in the next millenia which will lead
>>>>>>to fantastic increases in space propulsion beyond the theoretical
>>>>>>anti-matter rocket.  If so, I'll bet it won't look anything like
>>>>>>anything we've imagined.

>>>So your comment that "Something _might_ be discovered in the next millenia
>>>which will lead to fantastic increases in space propulsion..." is
>>>statistacally far to conservative.

>>No, I don't think so.

>>Sure, something will lead to fantastic increases in space propulsion
>>compared to TODAY's technology.  But look carefully at what I say.

>>I say, "Something _might_ be discovered ... which will lead to
>>fantastic increases ... beyond the theoretical anti-matter rocket."

>>Beyond the theoretical anti-matter rocket.

>>I have great confidence that for interstellar travel something on
>>the level of a theoretical anti-matter rocket or less will remain
>>the best we can hope for in the next millenia.  The physics of
>>relativity and conservation of energy strongly suggest this.

>The physics of relativity and conservation of energy have only been developted
>in the last century.

Conservation of energy has been around for longer than that, and the
physics of relativity did not invalidate most of the predictions
made by classical mechanics.

What relativity did was it explained a lot of phenomena which didn't
quite fit classical mechanics.

The critical difference between classical mechanics and general
relativity is that there were a lot of natural phenomena which
didn't fit classical mechanics, and there are NO phenomena (natural
or manmade) which don't fit general relativity.  We might observe
some phenomena which don't, but we've pushed the bounds to near
light velocities and haven't found anything inconsistent with it yet.

>They are not the end of physics research, nore are they likely to
>be the ultimate form of power or rocket physics.

I disagree.  I think general relativity and conservation of energy
will stand forever as limiting factors to technology.  The degree
to which we understand the motion of heavenly bodies is fundamentally
different from any period in history, because with general relativity
we acquired for the first time the ability to explain _all_ observed
motion.

The principle of conservation of energy is a principle which has
less direct predictive power, but it's one which has stood the
test of time despite changes in our understanding of physics.

>Research into
>newer physics, capable of far greater power, performance, etc (zero point
>energy, inertia/mass damping, etc) has progressed to the degree that NASA is
>funding some conferences and studies on them.

We will always look for ways around what we know, and research into
zero point energy and cold fusion is very inexpensive to conduct.

That doesn't mean there's any credibility to any of it.

>So I would estimate that the odds that current physics (like
>the physics of relativity and conservation of energy, or mass
>conversion rockets) will not be greatly surpassed in the next
>century, are about nil (assuming no colapse of civilization).

If you honestly think so, then why do you care at all about this
starship design list's concept?  According to your thinking, there
is no chance that anything we come up with will be anything even
remotely like what would be worth sending to the stars.

The predictive power of general relativity is simply too much
better than what came before, and too heavily tested and confirmed
by hostile scientists, to put it on the same level as what came
before.

>>>>>>You were looking to avoid a mere 160,000-1 fuel ratio?  In favor
>>>>>>of a 400-1 fuel ratio?  Just how lightweight did you think the
>>>>>>microwave satellites were going to be?  Show me numbers.  Power-weight
>>>>>>ratios.  Desired output thrust.  I'll bet that given any reasonable
>>>>>>numbers, you'll find that the mass of the microwave emitter satellites
>>>>>>will end up weighing more than 400 times the sailship.

>>>Mass comparisons are rather irrelavent.  The cost of an ore, vrs a
>>>manufactured systems vary wildly, and are not liniarly related to mass.

>>Yes, they vary wildly--but in all cases the cost of the manufactured
>>system is more than the cost of the raw materials used to manufacture
>>it.  This should be obvious.

>>The costs of various raw materials may differ, but fusion rocket
>>fuel (Deuterium and possibly Hydrogen; D-D fusion is trivial if
>>we have Li6-H fusion) will very likely always costs less than
>>the metals/composites used to manufacture beam satellites.

>Deuterium, He3 and other exotic issotopes is extreamly rare and difficult to
>aguire, so its cost per pound could be hundreds to thousands of times as much
>as Li-6, and likely to cost far more pound for pound they an equal weight of
>solar power sat, much less they the equivelant weight of silicon, iron, or
>aluminum (the major materials for solar power sats).

Deuterium is not rare.  He3 is, but deuterium is not.

>>Huh?  Advantage over what?  A dispersed phased array system can't
>>be adapted to longer range without significant modification.  What
>>_can_ be done is to increase it's efficiency by bunching it up
>>together as tightly as possible, ideally shoulder-to-shoulder.

>>The only thing you gain by dispersing them over a wide area is...
>>you don't gain anything, actually.  At every range, the beam
>>produced by the tightly bunched up array is superior to the
>>beam produced by the widely dispersed array.

>You gain increased range due to the larger virtual lens from the array.

NO YOU DO NOT!!!!!!!!

YOU DO NOT INCREASE RANGE BY EVEN A SINGLE MILLIMETER.

The larger virtual lens size is exactly counteracted by the reduced
efficiency.  In other words, if you get a spot which is 1/10 the
area, it will also have 1/10 the beam energy.  You haven't gained
anything.

OTOH, you have _lost_ 9/10's of the theoretical optimum beam (the
optimum beam is if the elements are bunched up shoulder to shoulder).

Kelly, try and comprehend this one fact, if nothing else.  The
widely spaced array gains you NOTHING.

>>>>The possible reuse of the lasers is particularly notable if it is
>>>>reused in a single mission (e.g. sequencially launching multiple
>>>>modules which provide deceleration fuel).

>>>>However, the possible reuse of lasers for marketable power generation
>>>>is, IMO, dubious.  First, there has to be a market for that amount
>>>>of power.  

>>>Presumably for large scale industrial operations in space, such as non near
>>>earth asteropid work and transport.  But agreed, this is speculative.

>>The only serious use for them I can imagine is for laser powered
>>rocket transport.  Assuming nuclear reactors remain expensive and/or
>>fission materials remain restricted, laser powered rockets offer
>>great potential savings in rocket costs.

>>For any sort of heavy industrial work where it's worth putting a
>>high power refinery on site, it's also worth putting its power
>>source on site.  Beamed power really only offers a potential
>>advantage in cases where the power is only needed a small fraction
>>of the time (which is the case for rockets).

>Since the refineries and propulsion platforms would need to relocate around
>asteroidal space, being able to buy a couple months powe without shipping a
>power plant to the site could make a lot of economic sence.

These refineries are likely to mass a lot more than their power
source, so if it's worth moving the refinery on site, it's not
much of a marginal cost to bring its power source along as well.
(The alternative is moving the asteroid to a refinery, which is
an example of rocket power--which I already describe as a valid
potential use for beamed power, if nuclear rockets are restricted.)

>>>>Third, in this example we
>>>>assume fusion power is available for the deceleration leg.  If that's
>>>>the case, then who's going to bother buying beam power?  

>>>I can't follow this bit.

>>The affordability of the powerful deceleration leg fusion rocket
>>(that we can afford it at all) suggests we have similar fusion
>>power generation capability which is relatively affordable.
>>Given the plentiful inexpensive energy everywhere, who's going
>>to need beam power?

>Saying you have fision power, does not mean its the cheapest form of power,
>nor the cheapest way to get power to a remote area.  We have nuclear powe
>plants, but still fire foundrys with coal.

It might not be the cheapest--but if it's not then something else
is the cheapest and it's cheaper than the relatively affordable
fusion power this starship design postulates.  Given that we can
afford the incredibly powerful deceleration leg rocket at all,
it suggests there's a lot of inexpensive energy from _some_ source,
if not necessarily fusion.
-- 
    _____     Isaac Kuo kuo@bit.csc.lsu.edu http://www.csc.lsu.edu/~kuo
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