Rocket motor

How powerful does a rocket motor have to be to lift a human?

You mean like Rosie O'Donnell...

Maybe we should refer this to the Mythbusters.

Not to take away from those having fun, but in case this was a serious question...

Normally 'power' in rocketry would be equated to impulse, or N-sec. That doesn't really directly relate to what a rocket can lift though. What you would care about there would be how much thrust does it need to produce. The answer is the motor must produce more thrust (N or lbs) than the weight of the person it's lifting plus the weight of the motor and any other attached structure (like say a rocket airframe, fins, nosecone, etc.). However, if your talking about flying a stable rocket, then it probably needs quite a bit more. For model rockets, I think the rule of thumb is about 5:1 thrust to weight ratio. Not sure about human rated rockets.

There are some commercial (L? and up impulse) motors that could lift a human, but I sure wouldn't want to sit on one.

Here are a few examples, so you can Google the specs ...

Mercury Redstone (1 man, sub-orbital)



Mercury Atlas (1 man, orbital)



Gemini Titan (2 man, orbital)



Saturn V (3 man, lunar)



Greg

BTW, TRFfan, why don't you tell us a little about yourself.

I think a K750 would lift me - a bit over waist high.

Before calculations can be made, criteria must be gathered. Here is some raw data to chew on if you can stomach it:

https://www.howtallis.org/rosie-odonnell-height-weight-measurements/

I think Steve Eaves 1:10 Saturn V should be more than ample, assuming Rosie's head and torso would fit inside the upper stage. Can you imagine the screams? :rofl:

tmacklin said:

Before calculations can be made, criteria must be gathered. Here is some raw data to chew on if you can stomach it:

https://www.howtallis.org/rosie-odonnell-height-weight-measurements/

I think Steve Eaves 1:10 Saturn V should be more than ample, assuming Rosie's head and torso would fit inside the upper stage. Can you imagine the screams? :rofl:

Click to expand...

I would not expend good propellant to throw Rosie.
(wow, that sounds dirty, doesn't it?)

mrichhcirm said:

I would not expend good propellant to throw Rosie.
(wow, that sounds dirty, doesn't it?)

Click to expand...

Y'all are no fun...

[video=youtube;RGlpF9bimpo]https://www.youtube.com/watch?v=RGlpF9bimpo[/video]

s6

OK, to provide a semi-serious answer:

Person: 200 lbs
Chair: 100 lbs (for a decent shock-absorbing chair that will let you take 5G and not be too messed up, but definitely not a fighter pilot's seat)
Other stuff: 100 lbs (motor mount, chute, etc.)

Total: 400 lbs
5:1 thrust: 2,000 lbs or 10,000N
So a Cesaroni N10000 VMax should just about do the trick. Neglecting air resistance, that gets you to about 65 feet of altitude under power if my math's right. I wouldn't expect to get much more than about 100 feet, so expect a rough landing.

boatgeek said:

OK, to provide a semi-serious answer:

Person: 200 lbs
Chair: 100 lbs (for a decent shock-absorbing chair that will let you take 5G and not be too messed up, but definitely not a fighter pilot's seat)
Other stuff: 100 lbs (motor mount, chute, etc.)

Total: 400 lbs
5:1 thrust: 2,000 lbs or 10,000N
So a Cesaroni N10000 VMax should just about do the trick. Neglecting air resistance, that gets you to about 65 feet of altitude under power if my math's right. I wouldn't expect to get much more than about 100 feet, so expect a rough landing.

Click to expand...

I would say that is a good answer. The original question never stated how high or specified a survivable flight and landing.

boatgeek said:

OK, to provide a semi-serious answer:

Person: 200 lbs
Chair: 100 lbs (for a decent shock-absorbing chair that will let you take 5G and not be too messed up, but definitely not a fighter pilot's seat)
Other stuff: 100 lbs (motor mount, chute, etc.)

Total: 400 lbs
5:1 thrust: 2,000 lbs or 10,000N
So a Cesaroni N10000 VMax should just about do the trick. Neglecting air resistance, that gets you to about 65 feet of altitude under power if my math's right. I wouldn't expect to get much more than about 100 feet, so expect a rough landing.

Click to expand...

OK, I'll do the math and see if we come out the same.

Starting from the 400 lb (181.4 kg) mass and 2000 lbf (8.9 kN) thrust required for a good flight, rounding the thrust up to 10 kN sounds good. The N10000 gives 10347 Ns impulse. Ignoring air friction, the peak speed would be (10347 Ns) / (90.7 kg) = 57 m/s. It's peak thrust is 11564.5 N, giving a peak acceleration of (11564.5 N) / (90.7 kg) = 127m/s², or 6.5 gees. Ouch.

The average thrust is not much less at 10219.3 N, so the average acceleration during the 1.01 s burn is 56.33 m/s². Altitude at burnout is thus 1/2*(56.33 m/s²)*(1.01 s)² = 28.7 m, or 94 feet.

Additional altitude from there is v²/2g = (57 m/s)²/2/(9.81 m/s²) = 165 m. The total altitude is then 194 m, or 636 feet. Reducing that for drag, I'd still expect to get at least 400 feet, and probably 500.

Can we have these figures done again by a third person to resolve the discrepancies, please?

Also, to TRFfan: DON'T TRY IT!

As a guy who never flew anything larger than a C motor, I definitely won't try this but I was just curious about how much today's motors can lift.

I think the discrepancy is that it's been too long since I did basic mechanics of materials and I was too lazy to look up the equations.

Given that my weight allowance doesn't really cover a nose cone, body tube, or fins, I think it's a fair guess that we'd see a bunch of tumbling after burnout if not before. While I agree with your equations, I stand by my altitude estimate in the real world. Maybe we can get the oddroc folks to do a mindsim.

The FAA frowns on this sort of thing. . .

§101.23 General operating limitations.

(a) You must operate an amateur rocket in such a manner that it:

(1) Is launched on a suborbital trajectory;

(2) When launched, must not cross into the territory of a foreign country unless an agreement is in place between the United States and the country of concern;

(3) Is unmanned; and

(4) Does not create a hazard to persons, property, or other aircraft.

(b) The FAA may specify additional operating limitations necessary to ensure that air traffic is not adversely affected, and public safety is not jeopardized.

Click to expand...

jqavins said:

OK, I'll do the math and see if we come out the same.

Starting from the 400 lb (181.4 kg) mass and 2000 lbf (8.9 kN) thrust required for a good flight, rounding the thrust up to 10 kN sounds good. The N10000 gives 10347 Ns impulse. Ignoring air friction, the peak speed would be (10347 Ns) / (90.7 kg) = 57 m/s. It's peak thrust is 11564.5 N, giving a peak acceleration of (11564.5 N) / (90.7 kg) = 127m/s², or 6.5 gees. Ouch.

The average thrust is not much less at 10219.3 N, so the average acceleration during the 1.01 s burn is 56.33 m/s². Altitude at burnout is thus 1/2*(56.33 m/s²)*(1.01 s)² = 28.7 m, or 94 feet.

Additional altitude from there is v²/2g = (57 m/s)²/2/(9.81 m/s²) = 165 m. The total altitude is then 194 m, or 636 feet. Reducing that for drag, I'd still expect to get at least 400 feet, and probably 500.

Can we have these figures done again by a third person to resolve the discrepancies, please?

Also, to TRFfan: DON'T TRY IT!

Click to expand...

So basically you're saying that...

It would take at least two N10000's...

To lift Rosie to an acceptable altitude...

Might want to check the drag figures again...:grin: