Rocket belts and such

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cudabean
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Rocket belts and such

Post by cudabean » Wed Mar 01, 2006 12:31 am

In this recent PopSci article:
http://www.popsci.com/popsci/aviationsp ... drcrd.html
The inventor has been working since 1975 to develop his own rocket belt, building on the progress of the Bell Rocket Belt. He spent 20 years perfecting his Hydrogen Peroxide purification system. The thing I'm wondering is why are they basing their progress on using H202? What would be the drawback of using Hybrid rocket motors, anyone? One possible drawback to hybrids and other types of rockets is they eject gases and materials that are combusting whereas H2O2 ejects only steam. Plusses for hybrids though are the hybdrid motor is throttlable and I suspect it might provide a higher power-to-weight ratio (but not sure really).

Marlin

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re: Rocket belts and such

Post by Bruno Ogorelec » Wed Mar 01, 2006 12:57 am

Isn't the duration of thrust for a rocket simply too short? The peroxide apparatus of the original flying belt could keep a man up for a few minutes.

I have long been thinking of pulsejets instead. Rather bulkier, but the flight duration could be multiplied.

BTW. I have seen a video of this guy making practice flights. His stability problems are so acute that the thing is very dangerous to use -- and extremely funny to watch.

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re: Rocket belts and such

Post by El-Kablooey » Wed Mar 01, 2006 2:26 am

If we're thining of the same video, a link to it is posted in this forum in a thread titled "don't try this at home". It is pretty funny, and I'm suprised he ever put the thing back on.
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re: Rocket belts and such

Post by marksteamnz » Wed Mar 01, 2006 8:00 am

http://www.tecaeromex.com/ is where the full details are. Juan has updated his site in the last few months including a link to the Popular Science article. It's huge and slow to load on a dialup but very impressive. The display of 3 rocket belts ready to go is startling. The site implies he hasn't actually free flown yet. Neat training rig.
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Re: re: Rocket belts and such

Post by Bruno Ogorelec » Wed Mar 01, 2006 8:59 am

Ben wrote:The peroxide apparatus are rockets
Of course they are. I should have written, 'solid fuel or hybrid rockets'.

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Re: re: Rocket belts and such

Post by pezman » Wed Mar 01, 2006 12:23 pm

El-Kablooey wrote:If we're thining of the same ....
I'll do the thining around here, Baba Looey!

Sorry, couldn't resist the Quick Draw McGraw reference, given your handle ;)

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Re: re: Rocket belts and such

Post by Bruno Ogorelec » Fri Mar 03, 2006 10:28 am

Ben wrote:
Bruno Ogorelec wrote:
Ben wrote:The peroxide apparatus are rockets
Of course they are. I should have written, 'solid fuel or hybrid rockets'.
In that case, the answer is still no. Hydrogen peroxide as a monopropellant has a maximum ISP of 161 seconds. Using hydrogen peroxide and a fuel in a bipropellant system can net you an ISP as high as 350 seconds.

In other words, adding a propane tank and an ignition system to the Bell rocket pack could more than double flight time.
So, why do you figure the flying belt was made with a peroxide monopropellant rocket? Safety? Simplicity?

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re: Rocket belts and such

Post by cudabean » Fri Mar 03, 2006 5:56 pm

So the drawback of the monopropellant really is the power-to-weight ratio. But the great advantage is it's fine controllability.
Here's an idea:
Build a rocket belt with both monopropellant and a hybrid motor where the hybrid motor is providing 90% of the required lift as a constant thrust, then use the monopropellant for the fine-tuning. Then maybe you could beat the world record duration for a rocket belt flight which I think is about 1 minute. I guess it's not really a new idea, it's sort of what they do with large rocket boosters, this is just on a smaller scale.

Marlin

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Re: re: Rocket belts and such

Post by Bruno Ogorelec » Fri Mar 03, 2006 8:39 pm

cudabean wrote:So the drawback of the monopropellant really is the power-to-weight ratio. But the great advantage is it's fine controllability.
Here's an idea:
Build a rocket belt with both monopropellant and a hybrid motor where the hybrid motor is providing 90% of the required lift as a constant thrust, then use the monopropellant for the fine-tuning. Then maybe you could beat the world record duration for a rocket belt flight which I think is about 1 minute. I guess it's not really a new idea, it's sort of what they do with large rocket boosters, this is just on a smaller scale.
I don't think a rocket belt is the answer. A jet belt would be so much better. Especially a pulsejet belt. Put my Constant Flow engine pack on top of your backpack -- http://www.pulse-jets.com/phpbb2/viewtopic.php?t=2752

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Re: re: Rocket belts and such

Post by Fricke » Sat Mar 04, 2006 3:28 am

Bruno Ogorelec wrote:I don't think a rocket belt is the answer. A jet belt would be so much better. Especially a pulsejet belt. Put my Constant Flow engine pack on top of your backpack -- http://www.pulse-jets.com/phpbb2/viewtopic.php?t=2752
Humm...

Bruno...

If I had the chioce... I´d go wit h the rocketbelt... A PJ usually glows red on the brink to white... = HOT...

And most PJ I´ve read about is not that reliable yet! - Some day there will be a PJ that outperforms any other engine...

A rocket is a rocket a PJ is a PJ... like a Gasturbine (DIY) is the worst case in reliabillity...

Just my 2 cents... Don´t feel the need to discuss it further... =)

//Fredrik...

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Re: re: Rocket belts and such

Post by Bruno Ogorelec » Sat Mar 04, 2006 8:11 am

Fricke wrote:If I had the chioce... I´d go wit h the rocketbelt... A PJ usually glows red on the brink to white... = HOT...

And most PJ I´ve read about is not that reliable yet! - Some day there will be a PJ that outperforms any other engine...

A rocket is a rocket a PJ is a PJ... like a Gasturbine (DIY) is the worst case in reliabillity...

Just my 2 cents... Don´t feel the need to discuss it further... =)
Don't feel the need? Fredrik, you obviously don't know me! :o)

Glowing yellow hot is the consequence of no airflow. We are testing our engines stationary. The intakes and tailpipe ends, which are alternatively bathed by hot gas and cool air, do not glow hot.

Any sensible application of a pulsejet will include cooling air flowing around the combustor. Indeed, as I have been preaching for ages, the waste heat will be used to increase thrust in a Meredith-style passive ramjet duct.

As for reliability, well, this is certainly the least of the pulsejet worries. Valveless pulsejets must rank among the world's most reliable engines. There's nothing to go wrong if the components are engineered properly.

Perhaps you are confusing the starting problems with reliability, but that is a separate issue, which seems to be the question of primitive methods used by enthusiasts, rather than any inherent problems of the pulsejet. People who approach the engine building really seriously have starting systems that do not look at all problematic. This is especially true for big engines, which fire at will. It is usually small, model-size engines that have problems.

From what I can see from the sidelines, rockets are the opposite case -- they must rank among the least reliable, even when built by the big boys in the industry. Carrying an operating rocket on your back is very, very close to madness in my book.

The really big problem of the pulsejet is the noise. Everything else is a cinch, in comparison. Now, once we discover the Secret of the Canucks, even that will become manageable. I am very optimistic, but I have good grounds for that.

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re: Rocket belts and such

Post by Greg O'Bryant » Sat Mar 04, 2006 10:22 pm

Any sensible application of a pulsejet will include cooling air flowing around the combustor. Indeed, as I have been preaching for ages, the waste heat will be used to increase thrust in a Meredith-style passive ramjet duct


This is exactly what I intend to do with my pipewood( first I have to get it running). Not that much thrust, but a proof of concept project. I want to use an internal valvless pulsejet to create heat and presure waves. The pipewood is going to be inside of a larger valved duct with the tail pipe pionted toward the valves and the pipewood intake just outside of the tailpipe of the larger duct. My plan is to tune this larger duct to the pipewood. This way when the pipewood runs the larger duct will ingest more air and force it along the length of the hot pipewood until it gets to the CC which will act like a nozle for the larger duct adding heat and thrust. If----this works it should use the radient heat given off of the pulse jet to make more thrust add mass to the exhuast and quite the engine a bit.

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re: Rocket belts and such

Post by cudabean » Sun Mar 05, 2006 3:17 am

I guess these are a very complex problem due to reliability, controllability and usability.

At least I can fly one on my XBox in Grand Theft Auto, San Andreas!

The difficulty in flying these things reminds me of something funny I saw at the rodeo a couple of nights ago. A bare-back bull riding contestant got thrown off the bull within 3 seconds and then the bull started trying to wildly stomp on the hapless rider. The announcer said "This is NOT user-friendly"

Marlin

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re: Rocket belts and such

Post by marksteamnz » Sun Mar 05, 2006 5:09 am

Hi This talk of rocket belts reminded me to look at the chap in Germany who was/is building a jet belt. A wonderfull piece of work and a huge step up from the peroxide belts. Vectoring nozzles, Turbo fan I think.
BUT! I can't find the link in my bookmarks. I'm sure it was posted in the past on the forum. Can anyone help me out with the link. Pretty please with sugar.
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re: Rocket belts and such

Post by Bruno Ogorelec » Sun Mar 05, 2006 6:43 am

Mark, I can't find it either. I know it was hidden behind something else -- I think it was a page on peroxide rockets, and it was in there somewhere among myriad other things. An incredibly ambitious structure made in carbon fiber with four vectoring nozzles. Overkill in my book, but nevertheless fascinating. I wonder what happened to it, for I have never heard of it running, much less flying, yet it's been on the web -- looking near complete -- for ages.

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