In Space Engineers, Hydrogen is employed as a fuel for both propulsion and for electrical power (via the Hydrogen Thruster and Hydrogen Engine, respectively). This feels unrealistic to me, and I am considering creating a mod for the game that alters these pathways to more accurately represent real-world chemistry and physics.

Therefore, I'm curious if this is a simplification for the purposes of game development/balance, or if there are valid, viable means to extract work from a feedstock of pure H2.

The behavior is thus:

  • Thrust - Thrusters consume small amounts of Hydrogen while idle, and then much more to generate thrust. No other input to the system is required (not even electrical power, though because of the below scheme, it could be assumed that the same thing is being done here to generate power). The consumption of H2 is luminescent and sufficient to cause damage if one is close enough to, and inline with, the exhaust nozzle so I assume this isn't simply venting pressurized gas to space.
  • Electrical Power - Hydrogen is consumed to produce electrical power, the hydrogen engine itself looks like a reciprocating internal-combustion engine, which is obviously not the modeled behavior (that would require oxygen), but is there any legitimate hydrogen-only pathway? Hydrogen itself can be extracted from ice using 10% of the energy that the resultant hydrogen yields in this engine.

Assuming I'm correct that neither of these make any real, physical sense, what is the highest mass-efficient pathway for production of power in both forms, using any (or any combination) of the following available materials either as reactants or catalysts?

  1. Oxygen
  2. Iron
  3. Cobalt
  4. Silicon
  5. Nickel
  6. Magnesium
  7. Silver
  8. Gold
  9. Platinum
  10. Uranium
  11. Gravel (waste rock, let me know what common material you're assuming this to represent for your purposes)
  12. Electricity
  13. Heat
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    $\begingroup$ It works, but requires compact modular hydrogen fusion tech. Not even D-T fusion, but P-P fusion! $\endgroup$
    – PcMan
    May 25, 2021 at 15:50
  • $\begingroup$ @PcMan My understanding is that starting a fusion reaction should require a fair amount of electrical power to kick start it, no? Or is that cost trivial against the energy released in the first moments of the reaction? $\endgroup$ May 25, 2021 at 15:52
  • $\begingroup$ What is the unrealistic part? Hydrogen can both be burned (oxidation processes that can generate thrust), or used for electricity in a reverse electrolysis in hydrogen cells. The thrust isn't much as far as I know though. Edit: a quick google search andvaccording to NASA burning can put a rocket into space. $\endgroup$
    – Trioxidane
    May 25, 2021 at 15:56
  • $\begingroup$ There is some research that suggests metallic hydrogen may be stable and could be used as an immensely powerful monopropellant, e.g. iopscience.iop.org/article/10.1088/1742-6596/215/1/012194 However, since metallic hydrogen hasn't been successfully synthesized yet, it isn't known if this is true. $\endgroup$ May 25, 2021 at 15:57
  • $\begingroup$ @Trioxidane Oxidation process requires oxygen. The system, as it stands, burns pure hydrogen and nothing else. If it needed Oxygen as well, I would agree with you. $\endgroup$ May 25, 2021 at 15:59

3 Answers 3


Long ago (in the 1950s), Robert A. Heinlein used "single-H" -- stabilized monatomic hydrogen (usually stored as a liquid, presumable at cryogenic temperatures though this was never mentioned) in a number of his novels and stories set in the same universe as The Moon is a Harsh Mistress, The Rolling Stones, etc. He used it mainly because it was the ultimate reaction mass for a fission thermal rocket -- the lightest possible exhaust particle and no energy sink for dissociation, hence highest possible exhaust velocity -- as well as (he posited) being capable of catalyzed recombination to work as a "chemical" monopropellant for attitude thrusters and the like.

Obviously, this latter could also spin a generator via a turbine, or provide energy for a heat engine to drive a generator to produce electrical energy. Single-H would also make a good input for a catalyzed fusion system, in that there would again be no need to provide the activation energy to dissociate the molecules before they can be fused -- and catalyzed P-P fusion would produce enough neutron flux to make being too close to the reactor quite hazardous (not to mention being very bad for materials, but games often don't cover such details). "Burning" hydrogen by fusion is a long-standing shorthand from SF in any case, going back at least to Larry Niven's Known Space stories starting in the 1960s.

  • $\begingroup$ In reality mono Hydrogen is not possible on large volumes is it? The moment it reaches another Hydrogen atom, it'll combine into H². If it finds anything else it'll try to bind to it. It seems highly unstable to me, as the slightest change from absolute zero would set off a chain reaction. Although I'm not sure if H¹ has electrons to give? Isn't the lack of one forcing it to combine? $\endgroup$
    – Trioxidane
    May 25, 2021 at 19:49
  • $\begingroup$ That's why that's a science fiction solution, @Trioxidane $\endgroup$
    – Zeiss Ikon
    May 26, 2021 at 11:11
  • $\begingroup$ Heinlein in the 50's was NOT "long ago".I read him in the 50's. $\endgroup$ May 27, 2021 at 22:06
  • $\begingroup$ @JustinThymetheSecond Anything before I was born (late 1959, just after Hawaiian statehood was celebrated) is "long ago"... $\endgroup$
    – Zeiss Ikon
    Jun 1, 2021 at 11:10
  • 1
    $\begingroup$ @Zeiss Ikon When I taught history, I told my students 'When I was in high school, I never had to learn about the Cuban Missile Crisis or the Cold War or landing on the Moon in history class." They asked 'Why?" I told them 'Because it hadn't happened yet." Ask your grand kids what 'ancient history' is. (No capitals 'a', 'h') It's all relative. $\endgroup$ Jun 1, 2021 at 13:44

Hydrogen ion fusion. This accounts for the glow. Radiation! Your engine generates power thru hydrogen fusion. That is not particularly exotic sci fi. https://en.wikipedia.org/wiki/Fusion_power#Deuterium,_tritium

Hydrogen ion thruster. Nothing too edgy here either. https://en.wikipedia.org/wiki/Ion_thruster Your fusion engine likes the heavy hydrogen isotopes which leaves you with 99% of the regular hydrogen. Bust it into ions, magnetically accelerate them to 0.9c using your energy, and huck it out the back! Woo! Zoom!



(...) what is the highest mass-efficient pathway for production of power in both forms, using any (or any combination) of the following available materials either as reactants or catalysts?

Oxigen is used both for burning and generating electricity. In both ways the hydrogen combines with the Oxigen and is able to release an electron because of the bond. Although the result is the same, water, the way it's done releases the energy differently. Oxigen is the lightest of the bunch that Hydrogen can combine with, so it makes most sense in mass to energy ratio. With the burning you obviously need heat as a "catalyst".

  • 2
    $\begingroup$ Am I correct in assuming that in order to efficiently use H2+O2 reaction to make energy, you need to add back exactly the O2 that was electrically separated to isolate the H2? Making the process both energy negative in the round-trip (though greatly reducing the size of the equipment that needs to move around), and necessitating some other source for life support O2? $\endgroup$ May 25, 2021 at 16:56
  • 1
    $\begingroup$ @WilliamWalkerIII you are correct sir. A riund trip willbalways be energy negative, whatever you use. The Hydrogen is meant to store energy temporarily. Much like Uranium was once produced, storing part of the energy of the sun in it's complex bonds. If you create Hydrogen, you need to put the exact amount of O2 back with a perfect oxidation. So much like with other sources some extra O2 for life support is needed. Although you could look into Hydrogen 3. That might be a monofuel, but it's not certain to me. $\endgroup$
    – Trioxidane
    May 25, 2021 at 17:37

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