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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?

uhoh
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    I suppose that unless there is another engine that produces exactly the same Isp, their performance is unmatched. – Organic Marble Aug 15 '21 at 01:40
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    @OrganicMarble Yep! Mass enters also: an engine that produces one tick higher in Isp than another but is 20 times the mass doesn't excite propulsion engineers. I can't find any specs on the web but my search was admittedly brief. – Tom Spilker Aug 15 '21 at 02:05
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    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. – Tom Spilker Aug 15 '21 at 02:09
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    Wikipedia has an article on this subject. – David Hammen Aug 15 '21 at 07:40
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    This sounds like a fat load of "marketing speak" to me... – Dragongeek Aug 15 '21 at 13:24
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    “hundreds of hours of testing and design” – Russell Borogove Aug 15 '21 at 13:34
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    @RussellBorogove and before that, they probably needed to spend weeks in education to get the necessary background knowledge... – leftaroundabout Aug 15 '21 at 14:36
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    @leftaroundabout There are some very knowledgeable and very smart people who work at Intuitive Machines. Several of the people who worked on NASA's Morpheus Project (which not coincidentally used LOX/methane engines) moved to Intuitive Machines. I know this as a fact because I worked for IM for a while. They went through a rough patch five years ago or so. The rough patch ended when they were named a CLPS contractor a bit less than three years ago. I wish them all success. – David Hammen Aug 15 '21 at 21:05
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    From looking at their website, (1) it looks like IM has hired some awesome website developers, and (2) it looks like IM has gone all-in on their CLPS contract, plus a few related items. Gone, for example, are any links to the non-aerospace projects I worked on. Also gone are any links to this cool drone project (which I did not work on). Cutting projects that don't look massively profitable is what startups do. – David Hammen Aug 15 '21 at 21:59
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    Startups also expect people to be able "to work outside normal schedule and adjust schedule to meet peak periods and surge requirements when required." (This is straight from several of IM's job requirements.) My personal record was a 21.5 hour workday, followed by a 12 hour work day, followed by a nearly normal 9 hour workday, followed by a weekend where I mostly slept. Others outdid me. – David Hammen Aug 15 '21 at 22:09
  • One of my former co-workers works there. He's not able to be very forthcoming about what they do. – Organic Marble Aug 16 '21 at 00:36

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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.

uhoh
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