Author Topic: Pumping Cycles for Rocket Engines  (Read 47313 times)

Offline Jim

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Re: Pumping Cycles for Rocket Engines
« Reply #80 on: 03/10/2013 07:58 pm »
Jim, if you're interested in rocketry,

Here is some practical rocketry experience.
« Last Edit: 03/10/2013 10:03 pm by Jim »

Offline R7

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Re: Pumping Cycles for Rocket Engines
« Reply #81 on: 03/10/2013 08:20 pm »
... wasn't recently test-fired Blue Origin's BE-3 hydrolox thrust chamber pressurefed?
their chamber pressure is between 30 and 100b, which precludes pressure-feeding hydrogen in a rocket.

Both the vessel and the remaining gaseous hydrogen are too heavy to make efficient hydrogen stages if pressure-fed.

I wasn't referring to the final engine but the test setting itself. IIUC just the chamber was tested, not the pump. Is it even known what cycle is going to be used?

30bars isn't so bad for pressure fed system anyway, solid motors go considerably higher and still do their jobs. Sea Dragon pressurefed hydrolox US was supposed to run at 7bar, and the design was vetted by aerospace professionals as doable.
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Offline Enthalpy

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Re: Pumping Cycles for Rocket Engines
« Reply #82 on: 03/12/2013 04:58 pm »
I think you'll find most satellites that use hypergolic AKM's do so because their station keeping thrusters are also hypergolic.
So if you want to introduce LO2/LH2 to comm sats you'll need to replace hypergolics for both uses.

Ionic thrusters for station and attitude control exist already and work. They save propellants better than a hydrogen-oxygen thruster would. So if a satellite designer abandons storable fuels, he'll go directly to ionic thrusters where possible.

That's why I don't consider storing hydrogen for a decade on satellites - just for the 10 hours needed by the apogee kick, for which the thermal inertia suffices.

Long-term hydrogen storage must be developed for other uses, like space probes or manned missions to planets. There, small thrusters stronger than the attitude control of satellites are needed for trajectory and attitude control, and these thrusters would benefit from hydrogen-oxygen, provided this couple is already justified by a planetary capture or departure for instance.

For such thrusters, a positive-displacement pump must fit better, possibly adapted from the screw pump I describe for the apogee motor.

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