My Dream Rocket

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NewEntity1

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I've only recently returned to model rocketry, and I don't even anticipate trying for Level 1 HPR certification until this summer. I doubt I would ever reach the point where I was doing actual experimental rocketry...I'll leave that to the experts.

However, my dream rocket (which I'll never build...but maybe somebody will ;) ) would go something like this:

CATS went unclaimed in 2000. This isn't surprising because even the most efficient hobby motors available don't achieve an Isp much over 200. Compare this to the Shuttle Main Engines, which start at around 450 Isp at sea level and rise to over 500 in the vacuum of space.

I believe that for anyone to reach the 200km mark of the expired CATS prize with a 3 stage amature rocket would require 1) Lightweight yet very strong construction, 2) no wasted space...not only 'minimum diameter' but 'minimum length' as well, and 3) improved hobby motor technology capable of producing an Isp of at least 250.

A Lox/Kerosene bipropellant engine can easily reach 250 and then some, but liquid moters are highly complex devices, especially the super-powerful gas-turbines used to inject the fuel/oxidizer mixture into the combustion chamber at the high compression levels required. I takes millions of dollars and a full team of engineers to make such an engine, so thats out.

I had toyed with the idea of a pulsejet/rocket combo for the first stage, but most of the information I could find showed that to be impractical for an amature rocket. However, THIS PERSON may have a more viable solution...

My idea would be to use a ramrocket like ukrocketman suggests for the first stage, to take it to Mach 1 with a minimum amount of weight. Then the second stage would use something like an Aerocon bipropellant engine . This would boost it clear up to Mach 3+ and over 50km. Finally the 3rd stage, using a traditional composite motor, would boost it to around Mach 5+ and around 100km at engine burnout.

There is at least one major flaw in what I described above: Namely...how to ignite the second stage :D. The 3rd stage could be ignited using an altimiter, but that would be very tricky, since it would be difficult to accurately predict the altitude at which the second stage would burn out. I'm sure others on this forum will be able to point out additional major problems with this concept as well, heh.
 

Rocketjunkie

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A simulation indicates a 3 stage rocket using a P motor in each of the first 2 stages and an O motor in the third stage easilly reaches 250 Km. I've attached the thrust curve of the P motor. With a carbon fiber case, the entire stage weight can be less than the weight of an aluminum cased motor. The Isp of the P motor is 220.
Use timers to ignite upper stages. In this simulation, I ignited the 2nd stage 20 seconds after liftoff and the 3rd stage 50 seconds after liftoff. The P motor is 6" diameter and the O motor is 4.3" duameter.
 

rocwizard

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I hope you do realize that since you have now mentioned this project, you are now bound to it for eternity:D You have no option in whether or not you will build it. YOU WILL build it! and take MANY pics. Or you can expect a visit from V and T. :D :kill:




Just kidding;)
 

rabidsheeep

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yeah like rocwizard says now your bound to end up doing this sometime...

also team Marsz is actually trying to go for an out of orbit launch... you could read up one what their doin...

or is it mars? marz? i dunno...
 

NewEntity1

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uh oh! Bound! :D

All I can say is...I hope ya'll are willing to wait a looong looong time then ;)

Thanks for the replies though!

As for the 2 Ps + O, I thats interesting (didn't know there were composite p motors available with an Isp that high...thats good to know).

However, I would really like to try something exotic for the first stage (since this is, after all, supposed to be a dream rocket ;). As I mentioned in my post above, I won't even get around to trying cert level 1 until this June, so I'm not in a hurry to buy the full version of Rocksim just yet. I will, however...in a couple of months, I hope.

Given Rocketjunkies input, I'm now wondering if this could be done with just 2 stages...An 'exotic' motor with 250 Isp and O total impulse in the first stage, and a plain 'ol composite AP motor in the second stage, with N total impulse. It looks like rocketjunkie has already put more thought into this than I have :D

Btw, I have seen the M.A.R.S. website...sound like an interesting group :cool:
 

MattEx

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A liquid motor can be built relatively easily if you use a self pressurising oxidiser like Nitrous. Combine NOx with a nice fuel like Kerosene or Alcohol and you've got yourself a motor with a nice high Isp, without all the weighty pumping and cooling paraphanalia :) . And you better do it... you must know that the folk at TRF here like pics :D .
 

NewEntity1

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From what I've read on other forums, Alcohol would probably be the preferred fuel for amateur rocketry (at least for now...). True, a Kerosene-based engine would have a higher Isp, but alcohol has the advantage of having a higher vaporization rate, making for easier ignition procedures. Also, in the event of a spill, alcohol just evaporates, whereas kerosine spills result in the fire department showing up dressed in scary-looking hazmat suits :D

My only concern with N20-alcohol is that the Ratt-works tribrid only has a listed Isp of around 200. However, they may not have optimized the motor yet.
 

MattEx

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Hhmmmm the thing you've got to remember is that the Rattworks tribrid is a tribrid :) the Isp will change when it transitions into N20-alcohol mode, thus running in liquid mode. When it is functioning in tribrid mode it would be running very fuel rich so it wouldn't be very efficent.

LOL yeah you don't want men in scary looking suits coming along :D . I suspect if Kerosene was spilled on the ground you would have to cancel the launch or move the other pads waaayy away from the spill.
 

bobkrech

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I think the CATS prize went unclaimed because none of the competitors bothered to see what NASA and the Air Force have done over the last 50 years with sounding rockets.

We model these rockets all the time, and to win for the CATS prize, all someone had to do was make one. No one had to reinvent the wheel.

Solids are the only way to go. They are cheap to make and simple to setup and operate. No ground support required. No moving parts to fail. That's why all current sounding rockets use solids exclusively.

To find out how the real ones are made and flown go to https://www.wff.nasa.gov/~code810/index.html

Bob Krech
 

Rocketjunkie

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Originally posted by bobkrech
I think the CATS prize went unclaimed because none of the competitors bothered to see what NASA and the Air Force have done over the last 50 years with sounding rockets.
The primary reason the CATS prize went unclaimed was not technical. It was bureaucratic. One of the requirements was to abide by all the conflicting regulations.
 

daveyfire

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FWIW, you can get an Isp of 250 if you work at it with composites. Either that or just use a really big motor :D
 

bobkrech

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The primary reason the CATS prize went unclaimed was not technical. It was bureaucratic. One of the requirements was to abide by all the conflicting regulations.
Some amateur rocketry folks think that there should no regulations restricting their activities. I can't agree with this.

The FAA AST website had a section on what regulations had to be complied with for CATS flights. (These pages are not currently available.) There were some hoops to jump through but they were not unreasonable and were the same for everyone flying to that altitude: CATS competitors, other private ventures, commercial corporation and the government. The Space Frontier bulletin board has resource information posted as well.

The X-prize groups have to deal with the same regulations and are doing so, Scaled Composites is a prime example. A group of Florida Insitute of Technology Students built a sounding rocket and flew it to 100 KFT (33 km) last May, and they too had to comply with regulations. I'm sure the the Rocket Reaearch Society also has to face the same regulations since they have launched to 280 KFT (85 km).

So in my opinion, getting the permit is just as important as building the rocket and separates the men from the boys.

Bob Krech

Web References.

https://ast.faa.gov/

https://www.space-frontier.org/cgi-bin/BBS/CP1/read/205

https://www.scaled.com/

https://www.fit.edu/projects/jamstar/index.html

https://www.rrs.org/
 
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