Ok, quick question. As I continue to ponder a tube launch for my finless 50" tall, 3" diameter rocket, it seems like an actuator that moved 1" per second would be too slow to propel the rocket from the tube, yes? Thoughts?
One Inch Per Second
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I'd imagine so. 1"/sec is 5 ft/min, not even 0.1 mph. One usually thinks in terms of 40 mph off the rod for a conventional finned rocket.
Hmmm...
Is there a reason you are using an actuator, instead of just igniting the motor at the bottom of the silo?
That is a great question -- and I willl probably do just that for the initial launch! But down the road, I would like to tube launch with an actuator and have an air start for the first stage once it clears the tube. Does that make sense?
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Your biggest issue is going to ensure the rocket has enough speed and stability to be facing up when you air start. If it starts tilting to the side your rocket may become dangerous
There is a guy on here that has done just what you want. He used compressed air with a ram. Search for Joe Barnard.
I don't know. Accelerating the rocket to a stable aerodynamic speed does take energy, and getting that energy from a source external to the rocket leaves more energy in the rocket to make altitude. But @les has an important note. Then, too, the energy you gain might be offset by the battery mass and whatever other hardware you need to air start (though momentum would be stored in the accelerateed battery, too). But if @JoeBarnard has done it, at least it can be done. Joe is way more accomplished than I am.
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I've seen Joe's, but he is much more complicated than I would like to be. I am going for mechanical. I suspect there will be alot of testing w/o motors before I get to the field and alot of demonstrating after I get to the field w/o motors to show that the rocket can be launched with enough speed and stability to work. This version will have the flip fin can.
Have you seen the Spin Launch system? And that is just a 1/4 scale version of what they think they need!
dr wogz
Fly caster
what about a flinging device like those for shotgun 'clay pigeons'?
Slingshot-based system?
I have actually been thinking about that as well. Could probably make it work, but getting the band to pull evenly is my concern.
I do not know a single RSO that would allow you to stand there and slingshot a rocket with an igniter installed and armed ready to fire.
Agreed. But I have a slingshot idea with no person in the loop and a safe distance standoff.
It would deserve to be called a complex rocket which automatically gets double the distance if memory serves me correctly. In the past I have even gone for larger factors, just in case.
ThirstyBarbarian
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One inch per second is way, WAY too slow.
Safe minimum launch speeds are usually considered to be around 45 feet per second, so around 540 inches per second. And that’s just the minimum speed for clearing the rail with the motor already burning and rocket actively accelerating. For air-starts, the rocket should be traveling much faster than that.
Some flight computers allow you to set the minimum speed for initiating an air start. It’s for safety so the rocket won’t be traveling too slow and arcing over when the air-start motor lights. I’m not sure what the minimum recommended speed would be, but I’m guessing it’s in the hundreds of feet per second. Maybe research minimum safe air start speeds and aim for that.
Also, you mentioned this is for a finless rocket? That definitely makes the question harder to answer. The idea of minimum speeds is based on the need for the rocket to be traveling through the air fast enough for the fins to stabilize the flight and keep the rocket flying straight. Without understanding how your finless rocket is stabilized, it would be hard to say what the minimum speed would be.
Safe minimum launch speeds are usually considered to be around 45 feet per second, so around 540 inches per second. And that’s just the minimum speed for clearing the rail with the motor already burning and rocket actively accelerating. For air-starts, the rocket should be traveling much faster than that.
Some flight computers allow you to set the minimum speed for initiating an air start. It’s for safety so the rocket won’t be traveling too slow and arcing over when the air-start motor lights. I’m not sure what the minimum recommended speed would be, but I’m guessing it’s in the hundreds of feet per second. Maybe research minimum safe air start speeds and aim for that.
Also, you mentioned this is for a finless rocket? That definitely makes the question harder to answer. The idea of minimum speeds is based on the need for the rocket to be traveling through the air fast enough for the fins to stabilize the flight and keep the rocket flying straight. Without understanding how your finless rocket is stabilized, it would be hard to say what the minimum speed would be.
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Okay, I have done a search under ”finless” and your TRF handle, coming up with nothing but this post.
Finless Rockets? Challenging but do-able.
Augmented launch? I will take others words for it that it is do-able, sounds at least as challenging as above.
Air Starts? Absolutely do-able but requires some experience. Have you done this before?
combining all the above in a single launch without testing each component individually? That’s challenging cubed (or put another way, probability of success cubed, say each component has an 80% success rate, puts combination at about 50%, essentially a coin toss.)
i am not trying to yellow tinge your cornflakes. I like the concepts, just would like to see each demonstrated reliably before combining them. Nobody likes a ballistic return of a low power rocket, but that kind of failure done out in the middle of no where with no dry grass or brush and only you watching it, likely no harm no foul. But a screwed up air start under the same conditions might hit you personally and cause you significant injury.
i remember reading an article, not sure if it was in peak of flight by apogee, of a school girl and an experienced rocketeer who built a very tall tower powered by a falling weight that got a rocket up to launch speed . tried a search of ApogeeRockets and couldn’t find it. Apparently it DID work. I think the tower was pretty tall, definitely over 10 feet, likely near 20.
i wish you a happy, successful, and safe new year!
