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Void

Member

Registered: 2011-12-29

Posts: 7,819

The use of filler mass in propulsion. Could it help?

I am putting this here, because I think that there could be some who would resent it if I put something so wild into the transportation sections.

I have been wondering if any good can come from injecting non combutsible or non traditional substances into a cluster of rocket plumes.

I would start with the worst case notion, that of injecting just plain moon dust, from our Moon, or Phobos or Demos.

I had thought about injecting it into a rocket engine but intution told me that that is a no no. 

I am thinking if you had a cluster of engines, at least 3, and you could inject a slury of dust and C02 for instance into the area between the exhaust plumes, could that serve any purpose?

Similarly of course is dry ice and water.

The thing Dust, Dry Ice and Water have in common is that they might be obtainable at far locations with less fuss, and they are rather storable.  Turning dust into a slury for injection could be a problem.

I understand that for the solid rockets the space shuttle used, it was considered a good thing that it had soot and particles in the exhaust somehow it promoted thrust?

Ignorant wondering. 

Of course it might be quite possible to obtain C02 and Reduced dust from an astoroid of certain types by subjecting the dust to concentrate solar heat.  In that case the dust could actually be a fuel of sorts.  (Think grain elivator explosions).

Last edited by Void (2012-06-13 19:52:55)

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orionblade

Banned

From: Hampton Virginia

Registered: 2003-01-14

Posts: 60

Re: The use of filler mass in propulsion. Could it help?

Adding a noncombustible means you're sapping thermal energy from the exhaust stream. Injected after the nozzle throat, it may help to cool the nozzle and add to total mass flow, as water injection was used to increase mass flow rates on jet engines back in the 60's and 70's before high-bypass turbofans were developed.

Carbon black is added to solid rocket fuel to alter the burn rate and enhance combustion stability, as are a few other inert compounds, but you'll find these in concentrations well under the 1-2% mark by mass. Carbon black can make an otherwise infrared-transparent fuel grain opaque, so the whole thing doesn't soften, melt, and splort out the nozzle before it's supposed to be burned. Other modifiers keep the fuel grain from simply detonating as surface area increases and pressures go up in a core-burning grain, and there are other plasticisers that aren't the best for "fuel" that can keep the grain from cracking or aid in thermal gradient management. Keep in mind the color of the exhaust plume on the SRB's, too - damn near white.