XPost: sci.space.shuttle, sci.space.history, rec.aviation.military   
   From: jeff.findley@ugs.nojunk.com   
      
   "H2-PV NOW"  wrote in message   
   news:1140249804.179957.184170@f14g2000cwb.googlegroups.com...   
   > Ian Woollard wrote:   
   >> In   
   >> addition, because it spends more time to reach orbit, the gravity   
   >> losses are higher; although they are offset by the higher efficiencies   
   >> of wings at supporting the vehicle.   
   >   
   > There is no such thing as "gravity losses" as long as a vehicle is   
   > ascending. Gravity losses kick in when you can't go higher and you are   
   > still burning fuel. Using one 50th of the Shuttle's fuel to go to   
   > 100,000 feet is no loss if you still have enough fuel at 100,000 feet   
   > to get your air-launched vehicle to orbit   
      
   You're showing your ignorance here and are handwaving away a very basic part   
   of the equation.  There most certainly are gravity losses even if the   
   vehicle is ascending.  Essentially, the slower you accellerate to orbital   
   altitude *and* velocity, the higher your gravity losses will be.   
      
   > The fuel is not the problem. The oxidizer is the problem because it   
   > weighs so much. Oxygen weighs 16 atomic weight units for ever 1 of   
   > Hydrogen. NASA's Shuttle expends a million pounds of fuel and oxidizer   
   > to get the first 100,000 feet, the same altitude they got with 28   
   > horsepower of electric motors turning propellers shovelling air,   
   > powered by solar cells.   
      
   But the shuttle is moving at considerably higher velocity at 100k feet.   
      
   More importantly, spending time in the atmosphere to "save" on the mass of   
   LOX is silly if your goal is to get to LEO, especially considering that LOX   
   is one of the cheapest fluids on the planet since it's literally made from   
   air.   
      
   > Wings are cheaper than fuel. Before last year's oil price gouging   
   > carbon-fiber fabric was down to $0.94 square foot for 6kx6k 2,000,000   
   > psi, wholesale in volume lots. The cost of 10,000 square feet of wings   
   > in material costs was less than buying a Piper Cub used. Now Exxon got   
   > their price raise and it costs a NEW Piper Cub.   
      
   You're showing your ignorance again.  $0.94 per square foot for carbon fiber   
   fabric isn't what's expensive.  It's the cost of the machines, labor, and   
   time it takes to turn that into a wing that kills you.  More than one friend   
   of mine used to work for a US company that makes carbon fiber tape laying   
   machines.  Just writing the programs to lay the tape isn't easy...   
      
   > There's a lot of pnoney baloney on the internet about how cheap H2 and   
   > O2 is. Some say NASA pays $0.08 a kilogram for LOX, but that doesn't   
   > add up. Just trucking it from Mississippi to KSC in 4,000 gallon   
   > tankers has to cost $1/gallon for shipping, or do you believe in the   
   > "fuel fairy" giving away fuel below costs?   
      
   Look again at launch prices (i.e. $ per lb to LEO) and compare them to the   
   price of fuel ($ for fuel to get 1 lb to LEO).  It's not the high price of   
   fuel that is keeping launch costs so high.   
      
   > Somebody needs to do a price breakdown on the price of a Shuttle   
   > launch: prices from $1.2 billion to $55 million are tossed around, with   
   > $500 million per launch being the favorite of more people. NASA   
   > themselves says that the cost of payload is $10,000 per pound. Five   
   > kilos of drinking water for the ISS would buy 10,000 square feet of   
   > wing material. There's probably more than 10,000 square feet of wing   
   > material in that big External Tank they throw away each launch.   
      
   The ET's LOX tank holds about 20,000 cubic feet of LOX.  A quick search says   
   LOX weighs 64 lb per cubic foot, giving you 1,280,000 lbs of LOX in the ET.   
   If a shuttle launch costs $500 million, LOX would need to cost you about $4   
   per lb to make up just 1% of the total cost to launch the shuttle.  Actual   
   cost for LOX production (minus transportation costs) is reportedly pennies   
   per pound.  Even rocket grade kerosene costs you less than $4 per lb.   
      
   Here's part of an old (1996) posting from Henry Spencer:   
      
      
      
   If using LOX/kerosene, you need about 20 pounds of mix to lift a pound   
   into orbit, and maybe, oh, a fifth of those pounds are payload, so you   
   need 100 pounds of fuel+oxidizer.  Now, LOX costs about 4c/pound, and   
   is about 3/4 of the mix.  Kerosene costs depend on grade, but expensive   
   rocket-grade stuff is maybe 25c/pound.  So the average mix cost is   
   circa 10c/pound, and total propellant costs are about $10 per pound of   
   payload.   
      
   Figuring me at 200 pounds, that's $2000.  Not quite as cheap as London to   
   New York, agreed, but not much more than what I paid for a round trip from   
   Toronto to Australia some years ago.   
      
      
      
   In other words, the high cost of fuel isn't what makes spaceflight expensive   
   when launch costs fare more than the cost of fuel for the launch.   
      
   Now tell us again how the high price of LOX is making launch costs so high.   
   :-)   
      
   Jeff   
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