Ars Technicha's Rocket Report: SLS has technical problems, Vector—yes, Vector—is back links to Vector restarting operations under new ownership which says:

One thing they did wrong was the technology the used for their engines. “They had some Achilles’ heels associated with their technical approach. They were trying to use a propellant combination that was untested in the industry,” said Chris Barker, who serves as Vector’s chief rocket scientist. “They were struggling with trying to get performance that they knew they needed for a small launcher to be successful, and ultimately their test program was unsuccessful.”

Vector had been developing engines that used propylene and liquid oxygen propellants. The new Vector plans to instead use engines powered by a more conventional combination of liquid oxygen and refined kerosene, or RP-1, propellants. Barker has been developing such engines since the 1990s for companies such as Space America and Earth to Sky.

Question: In this case, was propylene as a rocket fuel "failure to launch" not due to any fundamental reasons or impediments, but it's just the way things worked out1, or was switching to RP-1 required for technical reasons associated with the fuel itself, its performance, or its supply?

Propene Source

That looks absolutely delicious, we'll have that! said the oxygen molecules


Propylene mentioned

1similar in some ways to the story of Thorium's current non-use as reactor fuel

  • 2
    $\begingroup$ What comes to my mind is that increase of Isp comes with the significant increase in combustion temperature Propylene is a constituent of MAPP gas (14%) which is used for welding. Lowering of combustion temperature with fuel rich composition is not practical because it creates to much soot. It can easily polymerize in gas, slurry or liquid phase when temperatures are higher than 60C and pressure higher than 30bar. It's not useful for regenerative cooling. I think that they intended to use ablative cooling on their LP engines. Also there is a lack of experience in its application in rocketry. $\endgroup$
    – WOW 6EQUJ5
    Nov 8, 2020 at 22:54
  • $\begingroup$ @RussellBorogove I've made some edits; two missing question marks, one in the title and one in the body of the question, and labeled the actual question with bold font. I moved the reference to Thorium to a foot note way down at the bottom, but for those familiar with it it works so well as an analogy helping me to express my question that I'll keep it, but in a less-distracting place. $\endgroup$
    – uhoh
    May 21, 2021 at 2:09


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