Hybriddyne Forum - Rocket Back Pack

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	Sep 7^th, 2010, 6:54pm
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Rocket Back Pack (Read 3941 times)

rocketdev

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Rocket Back Pack
Dec 19^th, 2004, 9:20am

Well into a design and testing for a rocket back pack motor. This has special requirements since it is strapped to a person's back!

The exhaust temperature has to be lowered a great deal to be usable.

It needs a warning system for case temperature and for oxidizer level.

The thrust vector/body dynamics relation is very complex.

The liability is extreme!

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Dynasoar New Member Load. Push. Zoom. Coast. Pop. Drop. Repeat. Posts: 11 Gender:	Re: Rocket Back Pack Reply #1 - Jan 29^th, 2005, 12:50am I seem to recall a chemical that burned at so low a temp that it could be held in the hand. Nitroguanadine? Maybe nitrosoguanadine.
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rocketdev

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Re: Rocket Back Pack
Reply #2 - Jan 29^th, 2005, 9:03am

True, the back pack could be operated with a solid, but difficult to throttle.

The balancing act (pun intended) in a back pack motor with regard to temperature of the exhaust products is in the contrary effect on specific impulse of lowered temperature. Where it might take 70 lbm of propellants for a 30 second flight with an Isp of 200 seconds, it takes 90 lbm for 150 seconds Isp (both figures include a 10 lbm margin).

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Dynasoar

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Re: Rocket Back Pack
Reply #3 - Jan 30^th, 2005, 10:31pm

I've no doubt the device could be made to work, but the human body is a horrble design to try to fly around. Making it assymetrical with a backpack thruster just seems to make the problem harder than it needs to be. Yes, I've seen it done -- I saw Captain Keds fly one at Superbowl I. It just seems the design would be wasteful. Wouldn't a front-and-back pack with say, a pyramidal array of 4 thrusters, be easier to control and therefore more efficient?

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rocketdev

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Re: Rocket Back Pack
Reply #4 - Jan 30^th, 2005, 10:48pm

This is a retro-fit to the hydrogen peroxide system. H2O2 is so difficult to get in this post 911 period that most back-packer's either distill it (a hazardous procedure) or have given up. We are creating another system that has the same performance with accessible propellants.

Yes, Bell had fits designing and testing their original design. Largely the problems were due to the human body dynamics when laterally accelerated.

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rocketdev YaBB Administrator Posts: 626 Gender:	Re: Rocket Back Pack Reply #5 - Feb 6^th, 2005, 10:29am Latest tests with HTPB/Urea show temperatures of 250F to 500F 18 inches from the nozzle exit. Variation is due to unknown factor, probably misalignment at ignition of the TC or some such. Used TC amp and load cell amp from http://tinyurl.com/6ewna Very sweet system.
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to_orbit

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Re: Rocket Back Pack
Reply #6 - Oct 29^th, 2007, 3:02am

Have you considered NOX as a mono-propellant , it can be decomposed using Iridium based catalysts. I think the temp might be around 750 deg from memory, perhaps that could be cooled by injecting an inert shield gas (nitrogen/ argon). Carbon Fiber tanks like those made for life support would allow lightweight high pressure storage?, self pressuring system would reduce complexity.

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rocketdev

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Re: Rocket Back Pack
Reply #7 - Oct 29^th, 2007, 10:41am

HTP is the perfect propellant for back-packs. We finally gave up on the hybrid system. Having separate thrusters opens up the possibility of assymetry of thrust, a very bad situation so the single combustor with manifolded nozzles is the better approach. But this means having conduits for the hot gas.

So it is better to use a monoprop or propellant combination which has an innately lower combustion temperature which eliminates the possiblity of an errant O/F ratio burning out the conduits.

Many, many factors to consider in a man-rated device and better to have it innately safe than to pile up a bunch of safety measures on a potentially unsafe system.

N2O is a potential monopropellant. Right now, until the SS-2 failure analysis comes out, it seems like less of a choice for manned flight.

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to_orbit

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Re: Rocket Back Pack
Reply #8 - Nov 1^st, 2007, 3:50am

Quote from rocketdev on Oct 29^th, 2007, 10:41am:

HTP is the perfect propellant for back-packs.

Yep I am big fan of HTP, just need to get past the distillation issue. Not sure if you have seen this patent or not for a new technique developed at NASA.

http://patft.uspto.gov/netacgi/nph-Parser?Sect1=PTO1&Sect2=HITOFF&d=PALL &p=1&u=%2Fnetahtml%2FPTO%2Fsrchnum.htm&r=1&f=G&l=50&s1=7122166.PN.&OS=PN/7122166&RS=PN/7122166

It allows for point of use low temperature distillation of Peroxide using osmosis type methodology, we are looking at producing a prototype to experiment with but the NAFION film doesn't look to cheap Sad

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rocketdev YaBB Administrator Posts: 626 Gender:	Re: Rocket Back Pack Reply #9 - Nov 1^st, 2007, 10:37am This is an old concept, the material to do so was not available in the 90's when it was discussed. (Many patents now are re-patented or are based on public domain concepts, unfortunately) But it is good that it has been developed.
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r2k_in_the_vortex New Member Posts: 32	Re: Rocket Back Pack Reply #10 - Feb 1^st, 2009, 3:51pm as far as i have heard all todays jetpacks work with h2o2 monopropelant engines, silver is the catalysis of choise usually iirc. using any hybrid/solid/bi-liquid propellant rocket for a booster there is plain insane.
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r2k_in_the_vortex New Member Posts: 32	Re: Rocket Back Pack Reply #11 - Feb 15^th, 2009, 12:49pm heres a very nice backpack alternative, almost as fun and 100X less likely to kill you http://www.metacafe.com/watch/2358035/you_can_fly_using_this/
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