Re: starship-design: How to build a station.

[Ben Franchuk <bfranchuk@jetnet.ab.ca>]

KellySt@aol.com wrote:
> 
> Ok, to try to be more constructive in this argument.
> 
> How would you get a small craft into space?
> 
> Well one option is hobbeist.  Their are folks building and flying homemade
> ejector ramjets.  The digging I attached seemed fairly comfortable with
> Ramjets/scramjets getting up to, maybe above mach  6.  With a bit of work
> getting a ejector ram or pulse get to funding as a rocket in hard vac is
> doable,
> so the engine weight penalty wouldn't be high.

A ram jet needs a rail launch,to get up to speed.
That saves a few kg of fuel.


> The bad nest is between there and the surface is hypersonic flight.  Slight
> problems at that speed get nasty.  You have a aerodynamics problem at 400 mph,
> you can probably nurse your homebuilt plane home.  At mach-3 you and ship will
> look like you were run through a chiper-shredder.  Also you need to make the
> hull out of high temp materials, especially for reentry.

How about a fractal wing? triangular pattern --  smallest shapes
hypersonic, middle pattern sonic, outer pattern sub-sonic.

  But the exotic
> material used back when are now on the hobbest market.  Pricy, but there.
> (Not
> to mention new stuff like graphite composites that the 50's aerospace
> engineers
> would have sold organs to get.)  Get a hold of a good aerospace scrounger and
> you can find left overs at surprising prices.  I've seen folks walk off with
> flight worthy titan engines and $.05 a pound scrap value.

Don't forget heat pipes,or open  vapor cooling.

> 
> How do you make a areo shape that can keep going in a straight line at those
> speeds?  Steal!  No blushing around.  Order copies of hull info from a SR-71
> or
> X-15 - or go talk to Burt Rutan who doing such work for Orbital Sciences.
> Find
> a hull shape that flew at those speeds and didn't try to fly sidewise.
> Reentry?
> Large wing and flat bottom and belly flop in.  Need some good high temp bottom
> stuff.

A lifting body is harder to design, but may not have any advantages
anymore over the simple design with better materials.
 
> If this is to much, piggyback on another group trying to build something like
> it.
> 
> What about a space station?
> Well you can't ship it up in a craft able to carry 1/2 ton loads.  You need
> more
> then that to build a garage.  Besides the economies of scale are terrible at
> that scale.  Say 5 tons and the volume of a UPS truck.

With a 40:1 mass/payload ratio 5 tons is a 200 ton space/craft,
a bit large for a first time design. How about 2.5 tons... 100 ton
space-craft.

  To make it simple
> build
> and check most of it out down here, and disassemble it for up ship and
> assembly.
> REAL embarrassing to ship it up and find things don't fit.
>

yea for prefab.

> 
> For the outer shell a inflatable bag with a doc port is good.  Take it out,
> pump
> it out, and do the rest of your work in full air pressure.  Spray a good
> amount
> of reinforced concrete in the inside for structure, shielding, and thermal
> mass.

A side trip to the moon for concrete? way to heavy for lift from the
earth. 

> Now you can bring up and outfit it pretty much like a normal building.  Air
> processors can be adapted from marine and scuba recycling systems.  need to
> keep
> brining up liquid ox to replenish, but that's not to hard.  You can get most
> of
> your water recycling by condensing it out of the air.  Pump filtered brown
> water
> out into reaction jets.  Use their evaporation into vacuum for attitude
> control
> thrust.  Solid waste you need to bag and bring down.
> 
> Power is a serious problem.  Batteries and stuff are not good to have in a
> life-support area, and solar power systems need to be outside and maintained.
> Ship it up in prefab modules to socketed into dock points on the outside of
> the
> docking module?

Solar panels are too expensive I guess. A small solar generator may be
better.
here the limiting factor is not weight but bulk.

> 
> How much would all this cost?
> Could be all over the map. Hobbest projects or ones done by small skilled
> teams
> can cost less then a hundredth of a industrial one.  Industrial firms have
> estinated it would take them about $4-6 billion to build NASA $30-80 billion
> dollar station.  So you possibly into the tens of millions in cost.  Launch
> costs are a big factor.  But  if you have a decent launcher you can drop up
> costs so much you can save a lot of launching, and station design.  Another
> big
> cost is all the exotic junk on the station there to show off NASA's ability to
> make exotic junk (no I'm not kidding, I was on the program).  If you just want
> some living space figure a few thousand a person for air and water processors.
> $10-$30,000?  NOrmal inflatable tables and charrs (everything non flamible!!).
> Bifg cost is just launching it up.  You probably looking a few tons per
> person.
> Now thats great compared to station, which is about  80 tons per person?
> 
> For 70 people, assuming 8 tons per person (just a guess) thats 540 tons.  At
> least a hundred flights of your 5 ton lifter.  As a rought guess thats $1-3
> million dollars worth of fuel.

  @ $.25 /lb fuel x 40:1 x 2,000 x 540 = 10.8 million

  So you built your launcher for a extremely
> cheap
> cost  ($20-$40 million?), and can get folks to service it for free.  You MIGHT
> be able to to get the stuff up there for $100 + a pound.  If you can keep that
> up, you could get funding to turn your platform into a hotel, and actually pay
> your staffs.
> 
> Ok, 100 flights for free servicing is rediculas, and a few industrial bargins
> for design and construction work and your $100 a pound jumps to $500 a pound
> real quick!  Also the station construction and design costswern't covered, and
> its unlikly you can get this many REALLY helpfull friends willing to put in
> all
> this time for free.  Course if your looking ar a hotel complex, a firm might
> be
> willing to drop a couple $billion to do it a bit larger and much less
> scroungee.

Note with  $.25/lb fuel cost and 40:1 ratio that is $10 lb or
20k per ton. 

> 
> For comparison, liquid oxygen/kerosene rockets typically
> get only 350 seconds of Isp. A ramjet typically gets 1,200-1,800 seconds,
>.

That will drop the mass ratio down abit.
-- 
"We do not inherit our time on this planet from our parents...
 We borrow it from our children."
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