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Hydrogen/Oxygen Rocket Exhaust Gases

01/02/2018 9:05 AM

Is it possible to "harvest" some of the exhaust gas/s from a Hydrogen/Oxygen rocket whist still generating a usable thrust?

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#1

Re: Hydrogen/Oxygen rocket exhaust gas's.

01/02/2018 9:27 AM

What exactly do you plan to harvest? Heat? Water?

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#2
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Re: Hydrogen/Oxygen rocket exhaust gas's.

01/02/2018 9:35 AM

Heat and water but mainly water, or more correctly the steam first then whatever condensate.

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#3
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Re: Hydrogen/Oxygen rocket exhaust gas's.

01/02/2018 9:36 AM

It's pretty difficult to capture water.

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#19
In reply to #3

Re: Hydrogen/Oxygen rocket exhaust gas's.

01/03/2018 10:29 AM

Especially in the "near vacuum" of space

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#4

Re: Hydrogen/Oxygen rocket exhaust gas's.

01/02/2018 10:06 AM

No. One obtains thrust by energetically accelerating material away and letting it leave. You cannot let things leave and capture at the same time. To harvest anything thrust must be reduced. It would probably be easier and safer to allow the chemical reaction to occur in another chamber than the rocket reaction chamber to harvest anything.

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#14
In reply to #4

Re: Hydrogen/Oxygen rocket exhaust gas's.

01/02/2018 8:05 PM

Exactly! GA. You spend a lot of energy putting as much momentum as possible into that water vapor in order to impart equal and opposite momentum into the rocket. Stopping it to collect it is highly counterproductive. If you collected it all, the rocket would have no thrust and would just sit on the launch pad.

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#21
In reply to #14

Re: Hydrogen/Oxygen rocket exhaust gas's.

01/03/2018 1:53 PM

I would think its like having a thrust reverser on a rocket engine!

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#5

Re: Hydrogen/Oxygen rocket exhaust gas's.

01/02/2018 10:21 AM

Possible? Yes. Practical? No way!

See #4.

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#6

Re: Hydrogen/Oxygen rocket exhaust gas's.

01/02/2018 10:38 AM

Yes, though impractical. The thrust is generated by the expanding exhaust gases pushing against the nozzle of the engine; an action-reaction sort of thing. If one were to capture some of it, the thrust would be reduced. Then there is the matter of condensing and storing it, using a "source of coolth" and the weight of the plant needed to do this; additional weight on a rocket is generally a Bad Thing.

So if water is wanted on board a rocket, it is more practicable to load it in liquid form before launch.

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#7

Re: Hydrogen/Oxygen rocket exhaust gas's.

01/02/2018 10:39 AM

gas's gases

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#8

Re: Hydrogen/Oxygen rocket exhaust gas's.

01/02/2018 10:50 AM

Yes, but not any significant fraction, or one would lose thrust. Once such a rocket is off the launch pad, the steam produced is hot enough still to melt most materials you might want to employ as a "suction/capture" tube. The point this cools low enough to produce a billowing cloud of condensate droplets/water vapor is far below the rocket.

In theory, if one had a relatively small rocket above a larger one, the larger one could fly into this vapor trail, and "scoop" up a significant amount, but the cost in terms of larger rocket boost/drag ratio would be horrific.

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#9

Re: Hydrogen/Oxygen Rocket Exhaust Gases

01/02/2018 1:02 PM

No not from the rocket...

The flame plume extends quite some distance from the engine....

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#11
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Re: Hydrogen/Oxygen Rocket Exhaust Gases

01/02/2018 1:36 PM

Flame velocity about Mach 8, as I see it.

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#13
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Re: Hydrogen/Oxygen Rocket Exhaust Gases

01/02/2018 2:23 PM
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#10

Re: Hydrogen/Oxygen Rocket Exhaust Gases

01/02/2018 1:32 PM

I'm just guessing here, but one possible "recovery" might be a propeller/fan mounted on a l-o-n-g shaft sticking back into the exhaust plume to recover some of the exhaust force as rotational force? Propeller should be smaller in diameter than exhaust plume width.

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#12
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Re: Hydrogen/Oxygen Rocket Exhaust Gases

01/02/2018 1:37 PM

no,... because the prop ...

can't stand or hold up to the heat and force,

and the extra drag... remember the prop would have to be attached to the rocket....

Not to mention, the additional risk of an already risky process of lifting a rocket.

One would be better off putting a some type of a intake similar to a pitot tube to run a small turbine generator.

To power a flash light... or an exit (or an abort) sign,..... or the light on the eject button.

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#15
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Re: Hydrogen/Oxygen Rocket Exhaust Gases

01/02/2018 9:44 PM

Ah, that's sorta where the grand kids were going but a turbine of sorts to drive a generator and maybe hydrolosise some of the steam back to fuel...
Hey. they think the word "engineer" is a one size fits all...I'm civil structural who can fly aircraft

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#18
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Re: Hydrogen/Oxygen Rocket Exhaust Gases

01/03/2018 8:28 AM

<...hydrolosise some of the steam back to fuel...>

One will never get the same energy out during burn 2 as the energy put in to hydrolysis processes using energy from burn 1; this universe doesn't work like that. So that, given also the extra weight for the plant that the rocket would need to drag about to carry it out, makes it not viable - one is still better off using tanked fuel once.

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#16

Re: Hydrogen/Oxygen Rocket Exhaust Gases

01/02/2018 11:35 PM

Not productively.

The combustion chamber produces the exhaust and gives it momentum, producing counter thrust to move the rocket.

Recapturing the exhaust would require a receptacle connected to the rocket; and the momentum of the captured exhaust would work against the generation of the original thrust.

It's like playing catch with yourself, moving the " exhaust" ball from one hand to the other. Do you, the "rocket" experience any propulsion ?

This idea sounds like suspiciously like an attempt at perpetual motion.

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#17
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Re: Hydrogen/Oxygen Rocket Exhaust Gases

01/03/2018 6:30 AM

No it's not about perpetual motion.

They (the grand kids)were talking about long distance space flight - not getting up - the "travel" bit and were wondering about recycling HO/H2O and creating a reaction propelling the "ship" whilst recycling the fuel.

The idea came from reading about the Japanese satellite using a very weak ion drive and the steam from a rocket launch. They asked me and I asked here.

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#20
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Re: Hydrogen/Oxygen Rocket Exhaust Gases

01/03/2018 11:09 AM

Science fiction writers have had a version of a drive in literature for years called an ion ramjet or ion scoopjet where the space vehicle deploys a field in front of the ship that collects loose ions in the area. The ions are fed through an "engine" that accelerates the particles and shoots them out the back at high speed for propulsion.

I suppose that if you have a regular travel route with a plume of exhaust ions in it that you could potentially run an engine on the plumes of exhaust from the engines of other travelers. However, the effects of such a plume on following ships would be of declining benefit if all the ships were going the same direction. You would build a high velocity ion stream that would effectively slow down following ships with drag. I would also suppose that you could have one way travel lanes where engines are run in one direction and travel in the opposite direction could deploy sail structures to capture the wind of the ion stream, making the arrested ions available to engine craft on the way out.

So you could engine out and sail back, but not at the same time.

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#22
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Re: Hydrogen/Oxygen Rocket Exhaust Gases

01/03/2018 2:50 PM

That what urine recycling is for...haha, still want to an astronaut kids??

..."NASA's updated urine-reclaiming system is recycling even more water on the International Space Station, paving the way for long-duration space travel such as the journey to Mars.

Hauling tons of water to the space station is inefficient and costly. In 2009, NASA astronauts began recycling urine using the Urine Processor Assembly, which is able to reclaim 75 percent of water from urine.

Engineers at NASA's Johnson Space Center have since improved urine-recycling systems aboard the orbiting lab by incorporating a chemical solution called Alternate Urine Pretreatment (AUP). A few milliliters of AUP are dispensed when the toilet is flushed on the space station, allowing for a greater percentage of reclaimed water, according to a statement from NASA. [How to Pee in Space (and What to Do If the Toilet Breaks)]

"The goal is not to take large amounts of water with us to space, but to be able to take the water cycle itself to space," Dean Muirhead, an engineer with Barrios Technology, who works on water- recovery systems for the space station, said in the statement. "This project was another step in facing the water-cycle challenge and creating a closed life support system in space.""...

https://www.space.com/34688-recycled-astronaut-pee-boosts-deep-space-travel.html

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#23

Re: Hydrogen/Oxygen Rocket Exhaust Gases

01/03/2018 10:25 PM

Best to use e.g. a fuel cell to make electricity from the H & O - there is your water, and power.

But anything that reduces H & O to rocket will reduce thrust similarly.

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#24

Re: Hydrogen/Oxygen Rocket Exhaust Gases

01/03/2018 11:08 PM

There is no energy in Oxygen.

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#25
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Re: Hydrogen/Oxygen Rocket Exhaust Gases

01/03/2018 11:42 PM

That is wrong in so many ways.

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#29
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Re: Hydrogen/Oxygen Rocket Exhaust Gases

01/04/2018 9:32 AM

You need to elaborate, or wear the dunce cap.

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#33
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Re: Hydrogen/Oxygen Rocket Exhaust Gases

01/04/2018 10:09 AM

The nuclear binding energy is but one energy.

Then there's the thermodynamic energy for anything not at absolute zero.

I forgot to mention Gibb's Free energy. (Notice example 1.1. I don't believe the Nitrogen atoms are the only ones with energy.)

Just because it is difficult to get energy out of Oxygen in a useful format doesn't mean its not there.

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#36
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Re: Hydrogen/Oxygen Rocket Exhaust Gases

01/04/2018 4:12 PM

OK, no dunce cap for you today, you may return to your seat, but put the tray table up this time.

In fact, stars begin to fuse elements (at least are proposed to do so) such as C, N, and O, in the so-called C-N-O cycle (makes iron, as I recall). This is apparently near the end of the star's life cycle.

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#28
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Re: Hydrogen/Oxygen Rocket Exhaust Gases

01/04/2018 9:31 AM

And there is no p in oxygen. By definition of heat of combustion, all combustions defined with oxygen as the oxidant, so, yes, by default, no energy of combustion in oxygen, but there is enough in hydrogen to go around.

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#26

Re: Hydrogen/Oxygen Rocket Exhaust Gases

01/04/2018 1:52 AM

I think it is possible. On one extreme you have a stationary plant burning hydrogen in oxygen and producing dry steam. On the other extreme you have 100% thrust from the combustion. It looks like sell so much thrust to collect so much dry steam. The question is what to do with the dry steam in the spacecraft and how to condense it into useful water.

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#27
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Re: Hydrogen/Oxygen Rocket Exhaust Gases

01/04/2018 8:56 AM

I am having trouble following the thoughts in your post. The two "extremes" make no sense to view as separate entities when discussing the processes at work in a rocket engine burning H2 and O2 with the express design and result of producing a very high temperature and pressure exhaust jet at a speed (as others have already said) over Mach 8.

I understand that some of the exhaust from the first combustion stage is reused to power the two pairs of turbo-pumps that supply the high pressure H2 and O2 to the main engine. --JMM

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#30
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Re: Hydrogen/Oxygen Rocket Exhaust Gases

01/04/2018 9:36 AM

Obviously you are right in saying that something my provide the fuel and oxidant pressure needed entering the De Laval nozzles.

Tank pressures as high as are required would explode the tanks.

The issue is when one turbo-pump does not produce sufficient pressure, and fuel squirts back into oxidizer line or vice versa, and a really bad day is had by all.

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#31

Re: Hydrogen/Oxygen Rocket Exhaust Gases

01/04/2018 9:42 AM

Dear Mr.sapling,

Rocket will work above atmospheric air zone which may be above 45,000 Metres from the ground and totally zero pressure and extreme low temp.

It will be practically impossible to collect the water and thermal shielding will be a problem and add to weight. Thrust developed will drastically reduce once the back pressure builds up for harvesting.

Theoritically yes, but in practice not possible and will not be economical.

DHAYANANDHAN.S

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#32

Re: Hydrogen/Oxygen Rocket Exhaust Gases

01/04/2018 9:52 AM

I would think trying to capture any of the exhaust would be counter productive to the thrust, which they've carefully calculated.

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#34

Re: Hydrogen/Oxygen Rocket Exhaust Gases

01/04/2018 10:42 AM

You can generate small amounts of electricity using thermoelectric generators (TEGs) taking advantage of the temperature difference between the rocket exhaust and space. The TEGs would have to be built into the profile of the nozzle such as to not impact thrust. This application of TEGs is far better suited for jet engines on airplanes because the heat transfer would be much greater with -50C air moving at 500 mph compared to radiation heat transfer in space. Of course one needs to look at weight changes associated with using TEGs.

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#35
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Re: Hydrogen/Oxygen Rocket Exhaust Gases

01/04/2018 4:09 PM

So I assume TEG units are already being used this way?

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#37
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Re: Hydrogen/Oxygen Rocket Exhaust Gases

01/04/2018 8:42 PM
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#38
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Re: Hydrogen/Oxygen Rocket Exhaust Gases

01/05/2018 9:20 AM

I wonder what the low wavelength light output of a rotor motor (hydrogen-oxygen) is, and how that might relate to certain PV cells operation? I expect they would not be able to take that heat, though.

My question: Could one put them just outside the plasma/hot gases of the rocket exhaust, and produce electric power sufficient to drive additional plasma thrusters? Power on board electronics? Charge up batteries? I realize there would be a substantial drag penalty for deploying the PV pods while still in Earth atmosphere at considerable Mach.

Another question: Since the rocket exhaust is hot enough to contain substantial plasma, has anyone looked into MHD generation? What about injecting some sodium into that to generate more MHD power? (Yes I realize that might cause an alkaline hazard in the atmosphere surrounding the general track of the launch vehicle.)

Then I saw this patent while searching for plasma content:

thermolysis patent and apparent closed cycle

This sounds like perpetual motion, unless there is excess heat produced somewhere in the mix, and in substantial amounts.

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#39
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Re: Hydrogen/Oxygen Rocket Exhaust Gases

01/07/2018 3:00 PM

thermolysis patent and apparent closed cycle

"... A self-sustained cycle is created because the hydrogen and oxygen (disassociated water) that burns provides the heat/energy to perform work, including the generation of electricity for the resistance electrical current or masers and/or lasers and electric arc or lasers, and to heat additional water in the thermolysis coil and enormous quantities of excess energy for any other useful purpose."

Great, it seems like our energy problems are over, unless, of course, that pesky "Conservation of Energy" thing gets in the way!

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#40
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Re: Hydrogen/Oxygen Rocket Exhaust Gases

01/08/2018 2:17 PM

Or thermodynamics in general. Heck, I cannot even figure what container to use!

Yeah, if you heat water higher than the temperature of molten silicon, something is bound to happen!

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