Re: Re: Re: starship-design: Bugs and Peformances

[KellySt@aol.com]

In a message dated 10/14/98 12:39:07 PM, ajcrowlx2@ozemail.com.au wrote:

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>-----Original Message-----
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>From: KellySt@aol.com <KellySt@aol.com>
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>To: starship-design@lists.uoregon.edu <starship-design@lists.uoregon.edu>
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>Date: Tuesday, 13 October 1998 13:23
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>Subject: Re: Re: starship-design: The Way ahead & Bugs
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>>>
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>>>Check out Cerulean Freight Forwarding Company for an idea of how cheap it
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>>could
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>>>get. They think they can build an orbiter for $1.5 million, and for ten
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>times
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>>more
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>>>they think they can scale it up to a manned satellite launcher. Just uses
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>>CH4/LOX
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>>>but it just might happen. They have some other chemical engines that get
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>Isp
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>>~
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>>>+600 s, but DoD wanted to slap a ban on their system - can't have the
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>>neighbours
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>>>getting such technology, can we?
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>>
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>>These guys sound like BS artists.  Unless your talking airbreathing you
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>don't
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>>get 600s with chemistry.  Also the "someone baned our tech" conspiracy
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>story
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>>echos old urban myths of 100mpg carburators.
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>>
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>The Isps are legit. They're possible because of the tri-propellent approach
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>they use. 

NO you can't get that much energy out of chemical reactions.  Tri propelant
has been studies, and can save tank space, but not get you 600 isp!

>But as you say they're un-necessary for cost-reductions in launch
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>costs. What's needed is a reusable vehicle/s with low overheads and lots of
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>business...

Agreed

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>>On the other hand there are some commercial research programs that are
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>>building and testing commercial launchers that could do similarly
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>spectacular
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>>cost improvements (space Access' ejector ramjet prototype for example) IF a
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>>market was large enough to support and operation with enough scale to
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>operate
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>>a system that cost effective.  Market scale is vastly more important then
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>>technology for low cost launch access.  Current normal tech could provide
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>>launch services for less than 1/100th current costs with little difficulty.
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>>>>
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>If only NASA had undertaken the Mars/Moon/LEO program in the 70s, and
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>half-a-trillion bucks hadn't been blown on Vietnam.

They were interested, but no one else was.  Apollo was a race with the
Russians, it was considered silly to keep racing after you won.



>>>> Oh, personally - I'm real dubious about Mars colonization.  A chemically
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>>toxic
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>>>> planet with high rad and low G is not a great realestate value.
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>>>
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>>>Chemically toxic? You try living without CO2 for very long. Our lungs need
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>it
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>>just
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>>>like they need O2 - we don't metabolise it, but it does play a role in
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>>diffusion.
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>>>As for the rest of Mars, AFAIK there's NOTHING toxic there that isn't
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>found
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>>roving
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>>>about here. The soil isn't "super-oxidising" as some claim - that's
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>>>thermodynamically and photochemically unlikely. Much of it is probably
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>salty
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>>or
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>>>clayey.
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>>
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>>That wasn't the final judgement of the analysis of the Viking data.  The
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>said
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>>the only explanation for the reactions with the soil samples would be a
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>super-
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>>oxidizing chemical reactino that breaks down organic molecules.
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>>
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>Like I said there's no evidence for any such reactions. The guys who
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>research the cause of the those Viking results ultimately found no evidence
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>of super-oxides, especially since they're photochemically unstable.
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>>
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>>>> >I'd really like to see Stephen Baxter's Saturn mission. See his book
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>>>> >"Titan". It'd be a great way to use all that 1960s and 70s tech that is
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>>rusting
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>>>>
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>>>> >around the US.
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>>>> >
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>>>
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>>>Would still like to see it happen. Could think of a better thing to do
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>with
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>>the
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>>>Shuttles and the old Saturns.
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>>
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>>Shuttles cant, Saturns are pretty much scrap metal.
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>>
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>Stephen actually researched it and you'd be surprised what's still possible.

Authours "Researching" such topics is a slippery term, and one often that is
used to cove much poetic lisence.  ;)


>I was expressing my frustration with the whole NASA approach.
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>>
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>>>>
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>>>>  Anti-matter would be great for Sol space travel in smallish
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>>>> >quantities even. For IS flight, I'm not so sure.
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>>>>
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>>>> Big problem is holding the stuff stables for years in major quantities.
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>>Also
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>>>> I'm not sure if we could hold enough of it in a light enough tank.  I
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>mean
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>>it
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>>>> would be silly to replace a thousand tons of fusion fuel for a quarter
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>ton
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>>of
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>>>> anti-mater in a 3000 ton containment chamber.
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>>>
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>>>Come on! If we're gonna have fusion and mag-sails we'll need advanced
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>>magnetic
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>>>materials and field maintenance techniques - neural net control and
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>high-Tc
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>>>super-conductors. Else it's hopeless. With such antimatter will be easy!
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>>
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>>  ?!   Fusion needs none of those.
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>>
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>!? You sure? I've been watching fusion research fora while and that's the
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>kind of thing they're talking about. Really practical fusion needs to get
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>away from bulky magnetics and needs smart plasma control.

Thats the oppinion of the current DOE project team, not of many other academic
and commercial fusion researchers.  In many cases the relyence on super
conductors in the designs was considered a critical failure, and one dooming
the desighns to gigantic and useless scales.  Simple copper winding inside the
rad shields (superconductors don't like rad so then have to be kept way away
from the plasma) were sound to much more effective.

Assuming of course you use a magnetic compresion and confinement system,
personally I like Bussards voltage compresion systems.  ;)



>>>>
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>>>> Also the radiation levels are real bad.
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>>>
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>>>Neutrinos are the big worry. Who knows how much damage they can do in
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>>quantity
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>>>-
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>>>and no shielding stops them.
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>>
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>>Neutrinos do virtually nothing.  Nutron radiation is bad.
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>>
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>In sufficient numbers neutrinos are bad too. Assuming we use aneutronic
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>reactions we can eliminate one, but what of the other?

Even the sun doesn't put out enough neutrinos to bother anyone.


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>>>There's stuff in the deep that we've yet to encounter -
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>>>weird microbes that we can't imagine - but we've been pulling up nets for
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>>>centuries. Know of any pandemics from fish? From squid? No.
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>>
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>>They are far less alien then stuff from another star system, and many of
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>them
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>>have proven very deadly.
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>>
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>Such as? Though you may be right, I have trouble seeing just how. Some
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>people want to stop a Mars Sample Return on the basis that Mars might have
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>life. Personally I think the risk is lower than paranoia imagines.


But the stakes are very very high if your wrong.


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>>>So I think the threat is overblown.
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>>>
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>>>Remember, Ebola's reservoir is monkeys [our relatives] not some wholly
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>alien
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>>>lifeform. And we are a lot closer to every lifeform on this planet than we
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>>are
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>>>to
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>>>any exobiological entities.
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>>
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>>Actually the best guess is Ebola lives in Bats.
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>>
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>Typical. Always something I miss. If it's fruit "bats" they might still be
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>close[ish] relatives. Some say they're primates.
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>>
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>>>Adam
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>>
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>>Kelly
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>>
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>Adam
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>
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>PS
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>Engine performance... if it's a fusion system we're talking about then most
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>studies say 0.1 g would be amazing, unless it's pulse using BIG bombs. High
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>Isp fusion usually involves low thrust levels and low accelerations. We're
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>talking 0.01 - 0.001 g, or worse. I think we might find ways of doing
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>better, but 0.25 g would be great. Higher is getting into the ridiculous.
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>Really high accelerations [+100 g] becomes possible with externally
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>propelled systems, NOT with fusion or antimatter drives.
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>
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>Adam

The Bussard systems allow far higher thrust to weight ratios.  See the web
site for details and refs.

Kelly