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Thread: Question about H2O2 as a combination propellant/reaction mass

  1. #1
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    Question about H2O2 as a combination propellant/reaction mass

    Regardless of whether you're using H2 and LOX, LOX and kerosene, or another fuel, even solid fuel, is there any benefit to stream H2O2 into the mix in order to provide for some oxygen, but more importantly, reaction mass?

    What about with a hybrid nuclear/chemical rocket that would have a nuclear pile to heat up the reaction mass, but it would also use a two-part reaction mass that's both a fuel and an oxidizer?

    At what point does combining these elements reach temperatures/pressures our best materials science can't handle any more?

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    It's not that uncommon for gas turbine engines to have sections of their hot ends operating where gas temperatures are above the material's melting point; that's why all modern gas turbines use cooling and thermal shielding layers for the vanes and blades in their turbines.

    A conventional, that is solid-core, reactor is probably limited to fuel temperatures of about 2600K by fuel-element melting, which means that its maximum exhaust temperature (before expansion) would be somewhat less, probably no more than about 2300K. The maximum adiabatic flame temperature for a hydrogen-oxygen mixture is about 3200K, which would require the oxygen be preheated. Adding dilutants, like the water vapor from hydrogen peroxide decomposition, would reduce that. Somebody would need to do a systems engineering study to see if adding oxidizer to the exhaust stream is a net benefit. Sometimes it may be; sometimes it won't. I suspect that the largest benefits would accrue with reactors that are operating under more conservative conditions that 2600K fuel element temperatures.
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    You have to be really careful with HTP. It is now thought that Kursk was destroyed not by the Sqvall supercavitation rocket torpedo (which has a smaller thruster in the nose) but by HTP. HTP/Kerosene is the only storable propellant combo that isn't hypergolic, outside of cold gas thrusters and the like. Beal was going to use a pressure-fed first stage engine with more thrust than an SRB. That was the idea at any rate...

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    Thanks! I've been reading up on it. Hydrazine is preferred due to a higher specific impulse, but H2O2 is still used on some older satellites (maneuvering thrusters).

    Still can't find any information about hybridizing it with nuclear as a potential pre-heater for the HTP and fuel.

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    I believe that some satellites are moving from hydrazine to hydrogen peroxide because of the former's toxicity and environmental problems. Hydrogen peroxide is also probably easier to handle than a lot of the other fuels -- like the hypergolics used in the Titans -- although it is certainly not as easy to handle as RP-1.
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    No doubt. I'm still trying to get feedback on the nuclear hybrid aspect. Sort of a tangent with this thread.

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    In the March 19/26 issue of Av Week, we see the move to all electric satellites.

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    No thrusters? I guess they could use long wires to interact with Earth's magnetic field, and gravity-gradient stabilization...
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    It has electric thrusters, just no large amounts of liquid hypergolics. That liquid fuel makes up a lot of weight.

    spysats need a lot of fuel--to throw off orbit calculations for folks spying on them in turn.

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    Quote Originally Posted by publiusr View Post
    It has electric thrusters, just no large amounts of liquid hypergolics. That liquid fuel makes up a lot of weight.

    spysats need a lot of fuel--to throw off orbit calculations for folks spying on them in turn.
    And maybe to modify their orbits so they can keep people from hiding.
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    Exactly. Man I wish anti-gravity were real. Believe it or not--I hate rockets. I wish there were a way to directlt convert nuclear power to kinetic energy so spacecraft had naval like endurance and flexibility. I don't ever see that coming...

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    Quote Originally Posted by publiusr View Post
    It has electric thrusters, just no large amounts of liquid hypergolics. That liquid fuel makes up a lot of weight.

    spysats need a lot of fuel--to throw off orbit calculations for folks spying on them in turn.
    You mean ion?

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    At least mathematically, it should be possible to alter a vehicle's orbital parameters by passing passing a current through a coil, which will interact with the Earth's magnetic field to produce a force: thrust without reaction mass.
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    Quote Originally Posted by DoggerDan View Post
    You mean ion?
    There's a wide variety of electric thrusters, ion thrusters are only a specific type.

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    My reading tells me that most rocket engines, at least for earth-surface liftoff, are run rich anyhow, so adding oxidizer would defeat the purpose.

    For a nuc, the two things that matter most are core temperature and molecular weight of the working fluid. That's why hydrogen is best, even though I believe other working fluids (e.g., ammonia) have been tested.

    I recently finished a story where the craft used solid core nucs with water working fluid. Disadvantage lower Isp, advantage water is easier to store in lighter tanks than liquid hydrogen.

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    Quote Originally Posted by mike alexander View Post
    My reading tells me that most rocket engines, at least for earth-surface liftoff, are run rich anyhow, so adding oxidizer would defeat the purpose.
    I'm going off of memory here, so I could be wrong, but I believe the best cryogenic engines (LH2/LOX) are run fuel rich to take advantage of the low molecular weight of the free hydrogen, but the best hydrocarbon engines (LOX/kerosene) actually run oxidizer rich instead.

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    Yeah, the Russian RD-170/180 family of staged combustion hydrocarbon engines are run oxidizer-rich, which is no mean feat.

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    Yes. I've been thinking LOX/LH2 for a while now.

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    I recall, from another thread, that certain molecules vibrate in different modes some of which are better for producing thrust, one of best of which is hydrogen.

    Also, I think I said it elsewhere recently, but there is a way to convert nuclear energy directly into thrust: Fission Fragment rocket.

    Maybe if get a theory of gravity, that will allow us to conceive of a way to amplify and/or negate it.
    Et tu BAUT? Quantum mutatus ab illo.

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    From what I remember, maximum thrust and maximum ISP have different fuel/oxidizer ratios for chemical rockets, depending on the molecular weight of the constituents of the exhaust. Which is chosen is a system engineering issue, but from what I've heard (from MIT's course on the Shuttle), hydrogen/oxygen engines are usually run fuel-rich, to reduce the combustion chamber temperature.
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    Quote Originally Posted by swampyankee View Post
    From what I remember, maximum thrust and maximum ISP have different fuel/oxidizer ratios for chemical rockets, depending on the molecular weight of the constituents of the exhaust. Which is chosen is a system engineering issue, but from what I've heard (from MIT's course on the Shuttle), hydrogen/oxygen engines are usually run fuel-rich, to reduce the combustion chamber temperature.
    Even if exhaust temperature isn't a consideration, the specific impulse scales (to a first approximation) as the square root of the quotient of the combustion temperature and the mean molecular weight of the exhaust. Because hydrogen is the lowest mean molecular weight of any gas, and combustion temperature is only weakly dependent on mixture ratio for ratios near stoichiometric, the maximum theoretical specific impulse occurs with a significantly rich mixture ratio. This is because the increase in efficiency from the lowering of the mean molecular weight of the exhaust from the excess hydrogen more than outweighs the downside of the slightly reduced combustion temperature.

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    Quote Originally Posted by Ara Pacis View Post
    Also, I think I said it elsewhere recently, but there is a way to convert nuclear energy directly into thrust: Fission Fragment rocket.
    Is this different from Zubrin's salt water nuke rocket? If so, how?

  23. #23
    Quote Originally Posted by DoggerDan View Post
    Is this different from Zubrin's salt water nuke rocket? If so, how?
    In about every possible way. The only commonality is they both use nuclear fission, a fission fragment rocket is essentially an ion drive that uses nuclear fission to accelerate the ions directly. The fuel elements are small enough that the daughter nuclei can escape with little energy loss, and magnetic mirrors are used to redirect them out the back of the spacecraft.

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    Quote Originally Posted by mike alexander View Post

    I recently finished a story where the craft used solid core nucs with water working fluid. Disadvantage lower Isp, advantage water is easier to store in lighter tanks than liquid hydrogen.
    It is always a hassle to deal with. Boiling water is about as close to ice in temperature as ice is to LH2. Its high volume and low density. It likes LARGE, simply shaped, metal tanks, and not multi-lobed conformal composite tanks (VentureStar). This is why it is always best to do all fueling on the ground--not in space--and to stage all of those liquids off as thrust. Once you swap liquids for inertia--that cannot leak--you are better off. Meteoroid hits an empty tank? Who cares? Now its just a meteorite bumper.

    Quote Originally Posted by GeorgeLeRoyTirebiter View Post
    Yeah, the Russian RD-170/180 family of staged combustion hydrocarbon engines are run oxidizer-rich, which is no mean feat.
    Nothing likes hot oxygen. This was why Glushko had that ugly, ugly fight with Korolov. He wanted hypergolics, so he and Chelomei hit it off better. Ironically, the RD-0120 hydrogen engines (channel wall IIRC) wound up being easier than the RD-17X series to develop, from what I have read over the years. Burn-throughs and all. Nasty.

    Its not that Glushko didn't want kerolox engines, he just didn't want to be rushed. His RLA series of rockets--scaled up versions of Falcon-9 if you will--were going to use kerosene and were to be even more powerful than the Zenit/Energiya strap-ons.

    With Korolov dead and Mishin a drunk (and Chelomei falling out of favor), Glushko centralized his power. He didn't want Energiya to have hydrogen in the ET-like Core stage, being a dense fuel fan. But the hydrogen engines wound up being easier all the same. Funny how things work out. This all explains why LVs look the way that they do.

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