3 ms·

Propellant, in the form of liquid oxygen and kerosene, is about as expensive as milk. For a vehicle with 2% mass fraction, and assuming that the entire vehicle

Propellant, in the form of liquid oxygen and kerosene, is about as expensive as milk. For a vehicle with 2% mass fraction, and assuming that the entire vehicle is fuel in order to place an upper bound on fuel costs, that's 49 parts fuel to 1 part payload, by mass. If fuel and oxidizer are roughly the density of water, then each gallon weighs less than 8 lbs. (Closer to 5 or 6 for kerosene, and about 9 or 10 for oxygen.) This gives us about 6 gallons of propellant for each pound of mass, for a cost of about $22. The fuel cost to launch something into orbit is about $22/lb. The rest of the $1e3 to $1e4 per pound is engineering and paperwork. A typical aerospace part that has, for example, $700-$800 worth of actual materials and labor will have a verification and paper trail that costs about $30e3 to produce, due to the mission-critical nature of all the highly stressed and low-factor-of-safety parts. (Car parts have an FS in excess of 2.5, for example, and aerospace parts are typically 1.1-1.2.)

AnthonyMouse 12y ago
That would seem to imply that mass production could reduce costs dramatically.
- Solarsail 12y ago
  Many people have suggested as much. The issue then is finding a large enough volume of customers / missions to make use of frequent flights. I've also heard (tho I don't have a link ready) that past 50 - 100 flights per year on a given vehicle, some more exotic methods of flight into orbit (that have been impractical to date) become cost effective compared to expendables. Not a few studies have suggested reusable chemical rockets are cheaper than expendables, if you can fit at least 50 flights a year on them. I once read that number as around 70 a year for the Shuttle (possibly from Antonio Elias, maybe someone else). If you can manage hundreds, some of the really nifty / whacky launch concepts might become viable, like cannon launch, laser launch etc. etc. http://www.fourmilab.ch/documents/rocketaday.html http://www.fourmilab.ch/documents/rocketaday.html (I think Antonio Elias, on NSF made the argument that Kistler's now defunct K1 (COTS contract, along side SpaceX) rocket would have been viable at nearly the lowest possible launch rate for a reuseable, far sooner than the Shuttle.)
saganus 12y ago
Oh wow. Such a nice explanation. Thanks! Never would have thought propellant was that cheap. Or that paperwork and engineering would be that many orders of magnitude more expensive. Impressive.

AnthonyMouse 12y ago

That would seem to imply that mass production could reduce costs dramatically.

Solarsail 12y ago
Many people have suggested as much. The issue then is finding a large enough volume of customers / missions to make use of frequent flights. I've also heard (tho I don't have a link ready) that past 50 - 100 flights per year on a given vehicle, some more exotic methods of flight into orbit (that have been impractical to date) become cost effective compared to expendables. Not a few studies have suggested reusable chemical rockets are cheaper than expendables, if you can fit at least 50 flights a year on them. I once read that number as around 70 a year for the Shuttle (possibly from Antonio Elias, maybe someone else). If you can manage hundreds, some of the really nifty / whacky launch concepts might become viable, like cannon launch, laser launch etc. etc. http://www.fourmilab.ch/documents/rocketaday.html http://www.fourmilab.ch/documents/rocketaday.html (I think Antonio Elias, on NSF made the argument that Kistler's now defunct K1 (COTS contract, along side SpaceX) rocket would have been viable at nearly the lowest possible launch rate for a reuseable, far sooner than the Shuttle.)

saganus 12y ago

Oh wow. Such a nice explanation. Thanks! Never would have thought propellant was that cheap. Or that paperwork and engineering would be that many orders of magnitude more expensive. Impressive.