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Re: starship-design: Infrastructure in space [was: FTLtravel...]

In a message dated 4/27/00 10:30:34 PM, lparker@cacaphony.net writes:

>> Anyway one good sized commet core in near earth orbit has
>> been identofied as
>> having nearly 1000 times as much oil as opec produced in its
>> best year.
>Not that I doubt you, but I would like to ask for more details. To wit:
>1) What was that good year worth in dollars to OPEC?
>2) What was the per barrel price of oil that year?
>3) What is the per barrel price of oil a the moment?
>4) What is the total value of that comet core?
>I suspect it is quite a bit of money and I can see several possibilities
>soft landing the oil....

Sorry, typo, it was thousands of years worth in NEO.

As to more specific numbers:

Near earth comet core  5 Kilometers in diameter

    20  billion tons of water ice
    20  billion tons of organic componds (crude oil / oil shale)
            (i.e. 20 OPEC max years of output.)
    20  billion tons of ceramic ores
    1   billion tons of carbon dioxide ice

>>> Oil value <<<
600 gal of fuel < 5000 lb ???
roughly 500 lb / barrel ??
20 billion tons = 80 billion barrels-ish
            = $800 billion

Note I'm not not sure if oils 300 or 500 Lb per barrel


Delta V needed to LEO 1-2 kilometer/sec
1,000,000 secounds = 11.6 days

for accel of .002 m/s2 for 1 e6 you get a 2km/sec Delta V
thrust about 12 e6 tons thrust

Spec impulse ?  (lox/LH = 300-500?  Fusion/elect 3,500-5,000 solar thermal 

Spec impulse 1000 Reaction mass  of 12 e9 tons
Spec impulse 2000  Reaction mass  of about 6 e9 tons

Calc using solar thermal numbers 
Delta-V 2,000 m/s               Spec imp 2000
you get a 2km/sec Delta V With


Below are parts of letter about a oil shuttle idea I was playing with.  Its 
kind of fragmentary, but I'll forward them now and if you have trouble I can 
sort things out later.  Sorry.==

One problem that came up when I was looking over the numbers for the “Steel 
Challenge” scenerio was how do you deliver the cargo to earth?  Now the major 
cost is to launch a craft to orbit, not to land it.  But the sale price of 
comodities on earth is very low per pound.  Oil weighs about 500 pound per 
barrel, and for crude costs about $16 a barrel.  The cost per barrel changes 
frequently.  Back in the OPEC days it was up to $36 a barrel for a bit (even 
higher if you account for inflation) afterwards it droped bellow $10 a 
barrel.  Now its $16, but it will decline as the deacades continue.  Buy the 
time of this senerio they could have to sell their oil for $10 a barrel, or 
about two cents a pound.  Steel and such usually doesn’t go for a lot more, 
even specialtiy alloies seldom go for dollars a pound.  So I wond up with 
trillions of dollars of materials in orbit, and no way to profitably bring it 
to market.

My first idea was an old one.  Wrap the cargo in a thick layer of foamed 
rock.  Then drop it into the ocean.  The foam rock would burn off and 
insulate the cargo during reentry, and would help it float once in impacted 
the ocean.  But I wasn’t sure what it would cost to wrap this stuff, nor did 
the idea of droping hundreds, if not hundreds of thousands, of tons of cargo 
toward a mid ocean impact.  In theory you could make stearable craft to land 
more gently, and maybe you could build them cheaply enough to be a throwaway, 
or make them out of valuble materials that can be profitably scraped out 
after the delivery, but it didn’t seem likely.  

All in all a reusable craft seemed better.  After all if you could build a 
throw a way drop ship cheeply enough to deliver cargo.  A reusable ship should
 be even more economical.  One advantage these craft would have is they would 
only need to launch themselves empty to orbit.  They would land with a huge 
weight in cargo, but empty would weigh much less for launch back to space.  
Hence the name Downloader, since its built to take cargo down, not launch it 
into space. 

Looking over aircraft data.  Some millitary bombers can lift 2.5 times their 
empty weight.  But the best design to lift heavy crago into the air is a 
flying wing like the B-2 stelth bomber.  It, as near as I can figure from 
unclassified info, can lift 8 times its empty weight.  The B-2 uses high 
streangth composites, but using foamed alloys I'ld think 20-30 times dry 
weight may be possible.  (I.e. its a metal plane with 1/10th the weight)  A 
flying wing should be able to do better.  

Now most cargo delivery has learned that big craft are proportionally easier 
and cheaper to operate then fleets of small craft.  One of the biggest cargo 
craft are the oil supper tankers.  They weigh in at one million tons fully 
loaded.  Obviously a big step up from a 200-300 ton airliner, but then you 
have about tweenty billion tons of cargo to ferry down to market, and you 
probably want to sell it fairly quickly.  (The investors want their money 

So how big would a million ton flying wing be?  The wing loading on a B-2 
flying wing is about 70 lb per square foot.  So to lift a million tons of 
cargo craft (or at least to hold it in the air long enough to land it) you’ld 

1,000,000 tons  = 2,000,000,000 pounds

2,000,000,000 (pounds) / 70 (pounds/square-foot) = 29,000,000 square foot of 
wing area, about a square mile.  

That comes out to a delta wing shape about a mile long with a 2 mile wing 
span.  REALLY big!  But their are ways to drop that down a bit.  First if you 
fly faster you have much more lift per wing area.  Tripple the flight speed 
and the lifting abilaties go up about nine fold.  Of course landing is a 
problem, but then their ground effect.  Ground effect is the interaction of 
the wings air and the ground.  Effectivly the air gets compressed between the 
wing and the surface underneiath it.  Some systems can lift 3-4 times their 
flight weights while in ground effect.  Given the huge wings were talking 
about, the Downloader could get into ground effect while hundreds of feet 
above the ground.  Once in ground effect it slow down to a far lower landing 

Now you can’t land to fast or your craft takes a real beeting.  So lets say 
the downloader flys with 4 times the wing loading of a B-2 flying wing, and 
needs a long slow down in ground effect.  

2,000,000,000 (pounds) / 280 (pounds/square-foot) = 7,000,000 square foot of 
wing area, about a half mile on a side square.  

This comes out to a craft with delta wings a half mile long and one mile 
wide. Presumably the empty weight of the craft would also scale down, making 
it even lighter at take-off.  

Certainly better, but still monsterous.  We almost certainly could build it, 
we’ve designed bigger things.  Could we afford to build it?  Well 
construction costs are hard to figure.  If you scaled the costs up linearly 
with the dry weight of the craft in comparison with a B-2 bomber, it would 
cost about a half trillion dollars.  But about half the cost of military 
aircraft is for their avionics and military needs.  Obviously this wouldn’t 
scale up at all in cost, and would actually be largely unnessisary for a 
comercial craft.  Also the B-2 is precisly made to extreamly tight 
tolerences, with expensive composites, to allow its stealth abilities.  This 
craft wouldn’t need anywhere near that degree of precision.  If, as was 
suggested for the Downloaders, you were runing off huge strips of the wing 
like slabs of metal in a steel mill.  Taking a hard temperature tolerant skin 
and reenforcing it with strips of foam metal crudly welded on (nearly poored 
on), and with a forest of foamed metal cross beems and trusses fused into 
place by robots.  Costs would be dramatically lower.  More like the costs of 
a skyscraper or ship.  Even lower given the high levels of automation my 
Jones-Sinclair emphasised.  Instead of costing two three hundred billion 
dollars, it might cost only a few hundred million to build.  Given it lands 
with forty million dollars worth of oil each trip, it could quickly pay back 
that investment.

Could it function being that crudely made?  Could it last very long?  Given a 
large ship it could be made more robustly, and hence more damage tolerant.  
Also it could be made less precisely then a craft that needs to fly 
efficently for long distences, so even if badly banged up it could still do 
its job.  With its high wing loading it would have a high reentry heating.  
On the other hand given its size it could have a thick skin that could 
withstand the heat better, or it could cycle water through the hot spots for 
cooling and to feed steam powered retro and control rockets to help it down.  
So you have a craft thats more like a ship then an aircraft in many respects. 
 It should see years of service.

Fuel and reaction mass costs would be negligible for this craft.  Distiled 
sea water, or comet melt would feed its engines reaction mass requirements 
for free.  A few dollars worth of fusion fuel would feed each reactor for a 
year of continuous operation.

So what do we have so far?  The crafts empty weigh could be 20th or 30th of 
its loading landing weight, but we want it tough enough to take a lot of 
abuse.  So lets assume its landing weight was about 1/8th its loaded weight, 
or 125 thousand tons.  She’ld need about 40% that weight in water to launch 
herself into space as a pure rocket, but using the fusion motors to directly 
heat the outside air could drop that to 26%, but the boost to lagrage and a 
little reserve for emergencies would counter that.  Ad in about 25 thousand 
tons of other cargo and you are taking off with a fifth the weight you landed 
with.  Which should be a big help in getting this monster off the ocean 
surface.  Assume the wings are sweept back a bit for stability, and the wings 
about a half mile frount to back in the center, but the tips would hang back 
about a quarter mile back farther.  So:

Downloader stats
Wing span       1 mile
Wing root length    1/2 mile long
Craft length        3/4th mile
Craft height        120 feet

            weight      Speed
Landing     1,000,000 tons  300 mph to ground effect (?)
                150 mph surface landing (?)
Take-off       200,000 tons   80 mph (?)
  reaction mass 50,000 tons 
Cargo (t/o)       25,000 tons
Cargo (t/o)     875,000 tons
Empty            125,000 tons

So to land 500,000 tons would take a 20,000 ton craft.  

  But if we triple the landing speed, the lift should go up by a factor of 10 
(I think) needing a 900 ft by 900 ft.

Wing loading
B-2     70      Lb per square foot
Shuttle     75-82   Lb per square foot (lands at over 200 mph)
Venture Star    45      Lb per square foot

Maybe we could scale it up!!

     There seems to be a confusion over my downloader Idea.  Namely, that 
     its impossibly with present technology to build a craft that large 
     that can fly.  That's not the case.  Such a wing has a couple of 
     quirks, but it also lacks a lot of the problems you'd assume.
     The structure of a mile wide flying wing is essentially a reinforced 
     box beam.  In English a thick walled tube with lots of internal cross 
     bracing.  With enough of this it could serve as a one mile wide 
     bridge.  Similar structures are used to build bridges.  However unlike 
     a bridge, or a normal aircraft wing, the load and support isn't 
     concentrated in particular points.  The cargo (1 million tons of it) 
     is assumed to be a liquid (or blocks of ore) which are scattered about 
     the full volume of the wing.  So the load for the wings structure and 
     cargo is only supported by the wing structure immediately around it.  
     (Also pumping cargo around can be used to trim for balance or maneuver 
     if your into that.)  Since this wing lands on water, no special 
     structure needs to be included to support the weigh from landing gear. 
       The wing does need to be stiff enough to keep from fluttering around 
     from turbulence, but that's not as big a problem, and if necessary you 
     can damp it out with local aerodynamic controls.  
     About all the heavy loads are front to back.  The engine thrust could 
     be scattered along the rear edge of the wing to even out the load, but 
     it doesn't seem worth the effort to worry about.  To think of the load 
     factors imaging the flying wing tipped up on its tail and only 
     supported in the center.  Each end is again a box beam a half mile 
     long and a half mile high.  The strength of such a structure is  
     related to the length vrs the highth at the supporting point.  A 5 or 
     10 to 1 ratio is good.  A one to one ratio with solid skin 
     reinforcement is fantastic!.  A half mile truss bridge isn't unusual, 
     and ours is way over designed.  Especially given the relatively light 
     thrust loads.
     Landing is a problem, but on the scale of this ship the ocean is 
     effectively glass smooth, and little turbulence can effect it.  
     Tipping the nose up at launch, or the nose slapping down when the 
     trailing edge starts to drag into the water is a high load, but 
     carefully landing can balance out about all of that.  Again, given its 
     size it will give a very smooth ride, with little ability to get 
     gossled off is course.
     The engines construction is assumed to be electric heating of water or 
     air as a reaction mass.  Not real complicated, and very effective!  
     However it assumes a lot of electricity.  I assumed beamed microwaves 
     or fusion reactors for the power source.  Given this isn't going to be 
     needed for a couple decades, and you'd need a big powerful energy 
     source to get enough cargo to fill this thing, one of the other 
     options are highly likely to be avalible at that time.   I used the 
     fusion reactor Bussard discussed in the papers I've already discussed.
     So all in all this is not pushing the technology envelope to a great 
     degree.  A bigger question is the cost of building it.  Since it is so 
     crude and heavy, it should be pretty cheep compared to a aircraft.  
     Also given that it isn't constrained by the harbors and ground 
     facilities of conventional ports and airports, Its economies of scale 
     should make it very attractive to bulk cargo shippers like oil and 
     ore.  Its the same logic that got us oil tankers and ore freighters 
     that dwarf aircraft carriers.

============ other lets =======

$ KW-h cost per Kilogram to orbit.  1cent per kw-h at spec imp 350 = $0.138
 $/kg to land with 10 to 1 lift capacity and asuming Power to orbit costs are 
1/3rd cost to orbit.    $0.041 kg

1 barrel of oil is 42 gallons, or 5.6145 cubic feet.  Oil weighs about 53 
pounds per cubic foot.  (http://pump.net/liquiddata/wdspecgrav.htm)  So a 
barel of oil weighs 298 pounds.  At $10 a barrel thats 30 pounds per dollar , 
or 3.3 cents per pound or 7.26 cents a kilo.  If the electric and maintenence 
costs can be kept down, it is commercially viable to sell crude oil to earth 
from space.  Or you could refine it in space for more profit.

As for a list of other delta V's of interest:

                                Table 1 Mission Velocity Requirements 

Earth surface to LEO    8.0 km/s
Earth surface to escape velocity    11.2 km/s
Earth surface to GEO    11.8 km/s
LEO to escape velocity      3.2 km/s
LEO to Mars or Venus transfer orbit     .7 km/s
LEO to GEO      3.5 km/s
LEO to HEEO     2.5 km/s
LEO to Moon landing     6.3 km/s
LEO to Near Earth Asteroid      approx  5.5 km/s
NEA to Earth transfer orbit     approx  1.0 km/s
Lunar surface to LEO (with aerobraking)     2.4 km/s
Phobos / Deimos to LEO      8.0 km/s

Given the NEA to LEO number of 1.0 k/s, its not going to add much to the drop 
costs.  I was asuming the bulk material would be in L-5 or some orbit between 
earth and moon.  That isn't listed, but I remember that LEO to GEO is higher 
then LEO to lunar orbit.  So I figure 3.5 km/s to get there is a good guess.