4 comments

• Tom Billings

  February 26, 2016 at 11:09 am

  “Tests indicated that Boeing’s mono-propellant had a tendency to explode.”

  Interesting, …that, …especially since a small company in Mojave, FireStar Technologies, had been working with Nitrous Oxide Fuel Blend monopropellants for the last 10 years, and had licked all the problems with stable combustion. They weren’t Boeing, though, and apparently Boeing didn’t want to spend any money hiring them. What was the difference?

  Well, FireStar, had developed and tested, and patented a number of NOFB mixtures that worked well when fired in a 100 pound thrust engine, and in May of 2012 this had been cleared to be tested on ISS. Then, in November of 2012, they disappeared from the flight manifest, without a word why. Then ALASA was announced, and the announcements included that Boeing would be using a Nitrous Oxide Fuel Blend monopropellant with acetylene alone as the only fuel. Notable in the wikipedia article is the URL for their propellant patent:

  https://en.wikipedia.org/wiki/Nitrous_oxide_fuel_blend#NOFBX, in the external links section.

  While the patent mentions 3 different hydrocarbon fuels, ethane, ethylene, and acetylene in several mixtures, it does not mention a mixture with acetylene as the only hydrocarbon fuel. I assume this is because acetylene is usually dissolved in another solvent to stabilize it. Dissolving it in *3* solvents (nitrous itself is a good solvent) apparently did the job for the FireStar patented mixtures. But since a mixture with acetylene alone was not patented, Boeing selected that alone to be mixed with nitrous in *their* monopropellant? Well, …apparently.

  The behavior of the government community (and as a major member of the cost+ contractor club, I consider Boeing D&S a part of that) towards NOFBX switched between May and November of 2012. I realize now I have not heard of FireStar in the since November of 2012, even though their site is still up. Anyone know what’s up?
• John Whitehead

  February 29, 2016 at 12:50 pm

  The reference cited in Tom Billings’ comment does not lead to a patent, only a patent application. Possibly there have been continued efforts by Firestar to turn the application into a patent. The latter might have been Boeing’s reason to not copy the recipe (assuming there really was no working relationship between Boeing and FireStar).

  I met Greg Mungas (FireStar) back in 2004 when we each were doing projects for NASA’s Mars Technology Program, but have not heard any recent news.

  There seems to be quite a bias in the propulsion research community, to the effect that new propulsion technology is primarily (or only) about seeking new propellants, rather than new ways to make rocket hardware lightweight. My guess is that this bias comes partly from academia, i.e. chemistry and combustion experiments can be done in a university lab, but not actually building rocket vehicles (meaning focusing on making the inert mass very low). People get PhD’s in rocket science for focusing entirely on the minute details of propellant mixing and burning, while that topic is only a single-digit percentage of the effort to create and build and fly launch vehicles.
• John Whitehead

  February 29, 2016 at 2:06 pm

  Three more thoughts.
  1. Did Boeing buy FireStar company?
  2. When liquid fuel and oxidizer are mixed together in a tank, is there really such a thing as proving that they will never explode under any circumstances?
  3. Nitrous oxide has a high vapor pressure at ambient temperatures (15 times typical launch vehicle tank pressures), so the tank has to be thick and heavy. Alternatively, a nitrous propellant tank could be cryogenic to obtain pressures and tank performance typical of launch vehicles (50-psi tanks weigh only one percent of water-density propellants). It is not easy to make cryogenic rocket stages for small launchers, because the relationship between volume and surface area works against us (more heat leak area for a given mass of propellant). If cryogenic, then there will be ice buildup on the vehicle (more inert mass a launch), and propellant loading with vapor bleed-off needs to be continuous up to nearly the moment of launch, not easy to do if I correctly understand that ALASA was to be launched from an airplane. So, the point is that the physical properties of a propellant can be no less important than chemistry and combustion.
• PeterF

  February 29, 2016 at 5:07 pm

  Apparently, UCLA Berkeley won’t be participating in the effort to create new propellants…