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

[KellySt@aol.com]

In a message dated 4/20/00 2:45:48 AM, bfranchuk@jetnet.ab.ca writes:

>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.

Ejector ramjets can run from a standing start.


>> 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.

Not really since its harder to test and you want make lift drag for highest 
sppeds in rentry.



>  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.

Lots of stuff, even semirecyled life support is comercial area.


>> 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.

Lifting body isn't very high lift, nor very easy to get high drag on rentry.  
Also they fly teribly!


>> 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.

Why do you assume a 40 to 1 ratio?


>  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.

Yeah and since you don't want to ship up a full constructin crew, so you'ld 
want to prefab as much as possible.


>> 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. 

Cheaper to ship it up from earth then to ship it back from the moon.


>> 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.

Solar in general is expensive.  The panels however are simpler and more 
relyable.


>> 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

Why do you assume 40 to 1?  The ratio varies a lot depending on the design 
and engine systems.


>  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.

A LOX/Kero rocket based SSTO would use 14:1 fuel/craft ratio.  The air 
breather could cut that to 7-1 maybe less.  Given Kerosine is far more dence, 
it needs a far smaller and lighter tank.  

Kelly