According to https://www.intuitivemachines.com/propulsion

LOX/Methane Engines

Our LOX/Methane engines are unique for in-space propulsion, in that they offer safety in handling and testing here on the ground, but crank out unmatched performance in the space domain, and enable our vehicles to fly more direct trajectories to the moon.

Why is that important?

Higher performance allows us to transit the Van Allen belts once, unlike our competitors, which greatly reduces the risk of damage to our vehicle avionics due to high energy particles.

Question: Why do Intuitive Machines' LOX/Methane engines "crank out unmatched performance in the space domain" allowing them to "transit the Van Allen belts (only) once, unlike (their) competitors"?

What is it exactly about their performance that is unmatched? Why do competitors have to (presumably) transit the Van Allen belts more than once? Which competitors might those be?

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    $\begingroup$ I suppose that unless there is another engine that produces exactly the same Isp, their performance is unmatched. $\endgroup$ Commented Aug 15, 2021 at 1:40
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    $\begingroup$ They might be setting up a "strawman" argument: if someone is proposing electric or some other low-thrust main propulsion system, then achieving a lunar transfer orbit would require multiple revs and thus multiple passes through the Van Allen belts. But if there is another proposal for a high-thrust system that can do it with a single burn, then the strawman argument is disingenuous. $\endgroup$ Commented Aug 15, 2021 at 2:09
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    $\begingroup$ Wikipedia has an article on this subject. $\endgroup$ Commented Aug 15, 2021 at 7:40
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    $\begingroup$ “hundreds of hours of testing and design” 😂😂🤣 $\endgroup$ Commented Aug 15, 2021 at 13:34
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    $\begingroup$ @RussellBorogove and before that, they probably needed to spend weeks in education to get the necessary background knowledge... $\endgroup$ Commented Aug 15, 2021 at 14:36

1 Answer 1


By "performance" they mean thrust, as opposed to ISP, as suggested in the comments. There are far more mass-efficient engines than theirs that are already in use eg: ion thrusters.

Their VR900 engine has 900 lbf thrust. Compare this with:

  • 99 lbf for Chandrayaan 1
  • 110 lbf for Clementine
  • 0.015 lbf for SMART-1

Their "competitors" are pretty much everyone else who launches a probe: Chandrayaan 1 made 5 passes of the Earth over 13 days to enter a trajectory that reached the moon, Clementine took 3 weeks and 2 passes to get to the moon, and SMART-1 spiraled out over 13 months.


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