interesting question: 2 rockets walked into a bar....

[shockwaveriderz]

Lets say you had 2 identical P size rockets.

Assume the rocket and motor is semi-optimized for maximum altitude in both cases.

The 1st you launch from the ground to altitude.

The 2nd you launch from 100,000 ft up.

What kind of altitudes can be expected in these two examples?

tia

terry dean
nar 16158n

 

[Adrian A]

O.k., I'll bite.

Rocket 1: Pretty darn high

Rocket 2: Not much higher than 100,000 feet, since it will probably tumble due to atmospheric pressure being about 1/100 the sea level value, so fins won't do much good. --Unless you had a REALLY long launch rod!!--

 

[heada]

You'd also have to seriously figure out how to ignite the motor at 100,000 as most have problems that high. I remember reading something about igniting a motor above 50k or 60k feet is very difficult. You have to basically seal the motor to allow it to come up to pressure but not seal it so that once it does come up to pressure that it will over-pressurize. sea-level = 100% atmosphere, 40,000 feet = 25% atmosphere and 80,000 feet = 4% atmosphere.

-Aaron

 

[plasticpaul]

Uh.....anybody want some sweet tea?? I'll go check on the grill....

 

[Handeman]

Interesting, but straight forward question if you make certain assumptions, motors on both rockets ignite and perform the same. Both rockets fly with the same stability. That would only seem to leave one question, how much higher would the second rocket go since it's starting at a much lower atmospheric pressure?

A quick check with identical rockets/motors in wrasp with base altitudes of 0 and 100,000 ft show the second rocket would go 280% higher.

 

[teflonrocketry1]

The one launched from the ground will make it to about 52,000 feet AGL in about 48 seconds. The one launched at 100,000 feet should go to 415,000 feet AGL in 166 seconds as per RockSim, not enough velocity to orbit, but enough height to go beyond the Earths atmosphere!

Bruce S. Levison, NAR #69055

 

[Chicagonative17]

I believe orbit is 8 kilometers per SECOND horizontally. It would take some SERIOUS power to get a rocket to get to that velocity before burnout. You need to realize that orbit is just freefall with the arc sin (I think) the same as the earths. That is a 5 meter drop for every kilometer.

(I think my numbers are correct, please correct me if I am wrong.)

Can't wait for a day an amateur rocket goes into orbit . The regulations would now have to be spacebound !

 

[darkhelmet]

Originally posted by teflonrocketry1
The one launched from the ground will make it to about 52,000 feet AGL in about 48 seconds. The one launched at 100,000 feet should go to 415,000 feet AGL in 166 seconds as per RockSim, not enough velocity to orbit, but enough height to go beyond the Earths atmosphere!

That's an excellent estimate! This is what was done with Loki and Deacon rockets launched from high-altitude balloons in the 50's and 60's. Rockoons. And two-staged Rockoon flights went to the 200+ mile range.

JP Aerospace made an HPR rockoon flight at Blackrock in the late 90's. 70K feet IIRC. They had to launch at lower altitude because the balloon was drifting outside the safety zone.

Project HALO (Huntsville amateur group) lanched a hybrid motor (made by Tim Pickins, now the owner of Orion Propulsion). Early failure of the balloon made them ignite the thing sooner than expected and they got 38 miles instead of the planned 70 miles. It was launched over the ocean. This was their last attempt at the CATS prize attempt in 1997.

 

[shockwaveriderz]

thanks for the replies guys... very interesting results.

My question was about the 'rockoon" idea as theres a company that has dveloped a computer controlled balloon system . They normally fly these balloon platforms at 80-100K ft.

SO knowing about rockoons experiments from the past I thought:

this balloon platformthat they have might be an idea rockoon platform to lauch rockets near the edge of space. 400K ft is definately "sub-oribital' . The significance of this question now is what if you took a max impulse FGHIJKLMO motor and launched from the same 100K altitude...what kind of altitudes could rocket of those sizes reach into the upper atomsphere?

thanks for your help


terry dean
nar 16158

 

[darkhelmet]

Originally posted by shockwaveriderz
thanks for the replies guys... very interesting results.

My question was about the 'rockoon" idea as theres a company that has dveloped a computer controlled balloon system . They normally fly these balloon platforms at 80-100K ft.

The biggest hurdles are not technical, but regulatory.

What company has a "computer controlled balloon system" and what is "controlled"?

 

[heada]

To further your max thrust question, what about the thrust profile? Would a rocket that has a 1 second burn time putting out a total of 500N (a number I pulled out of the atmosphere) go higher than a motor that burned for 10 seconds but had the same 500N? The atmosphere is so thin at that altitude that drag is almost non-existent so just about the only thing you're fighting is gravity and since we're assuming stable flight anyway, you don't have to worry about a very slow lift-off.

-Aaron