Rules that Prohibit Propulsive Landing of Rocket or Lander?

wyattjohnson35

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So I am competing in the Battle of the Rockets 2019 competition, and although propulsive landings aren't allowed, I did the math and really want to build a test bed just to get the experience and learn a bit about this subject. I've seen model rockets do propulsive landings in the past with composite motors, but I am wondering if there are any rules that prohibit propulsive landings from landers ejected from the rocket near Apogee (with a backup parachute system of course).
 

Ben Martin

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So I am competing in the Battle of the Rockets 2019 competition, and although propulsive landings aren't allowed, I did the math and really want to build a test bed just to get the experience and learn a bit about this subject. I've seen model rockets do propulsive landings in the past with composite motors, but I am wondering if there are any rules that prohibit propulsive landings from landers ejected from the rocket near Apogee (with a backup parachute system of course).
Landing vehicles from apogee is similar to what Joe Barnard is attempting to do. If you are attempting to do it with low powered motors you should not have any issues. Having a backup parachute system makes it that much more safe. I don't believe there are any serious regulations about model rocketry propulsive landings.
 

Bat-mite

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Never seen a rule against it. Would take some serious engineering, and would most likely be cost-prohibitive for standard hobby purposes, but would be way cool, too.
 

Zeus-cat

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Every part of your recovery system is dead weight on the boost part of the flight. Using a motor to land the rocket means you need a bigger motor to launch it. Plus the engineering to monitor the rocket's descent and then fire and control such a system is way beyond most hobby rocketeers. I'm sure most people here would be fascinated to see how your research progresses.
 

wyattjohnson35

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Every part of your recovery system is dead weight on the boost part of the flight. Using a motor to land the rocket means you need a bigger motor to launch it. Plus the engineering to monitor the rocket's descent and then fire and control such a system is way beyond most hobby rocketeers. I'm sure most people here would be fascinated to see how your research progresses.

Well, I was thinking that a small test-bed unit no more than a few inches across could be built for sub $100. I did the calculations and could do tests with C motors to get a feel for the stability factors, and then improve the design to using 29mm motors.
 

Rex R

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a big challenge in getting it past the RSO is the fire hazard of flaming hot gas impacting the ground. you will need to ensure that a) all combustibles are cleared from the landing area and b) that the rocket lands in the landing area.
Rex
 

wyattjohnson35

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a big challenge in getting it past the RSO is the fire hazard of flaming hot gas impacting the ground. you will need to ensure that a) all combustibles are cleared from the landing area and b) that the rocket lands in the landing area.
Rex

This is a problem I didn't foresee, but you could do some testing to measure the flame length of the motor you're planning on using, then time the motor to cut off at that height(let's say .5m), and then the lander can free fall the remaining .5m or however long the distance is, which isn't going to cause a great increase in impact velocity.
 

Bat-mite

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This reminds me of a story. Bear with me; it has a moral.

Brian May of Queen invented his own electric guitar he called "the Red Special." It provided that classic Queen sound. When they were recording the song "Crazy Little Thing Called Love," they decided to give it a 1950s rockabilly sound. May experimented with his Red Special over and over again, trying to make it sound like a 1950s Fender Telecaster. He tried flatwound strings, he tried different amps, he tried equalizers ... but no matter what he did, it didn't sound right.

Finally he went to his engineer and said, "I don't know what to do. I don't know how to get that Telecaster sound."

The engineer said, "Why don't you play a Telecaster?"

Smart people (May has an honorary PhD in astronomy) very often overthink problems and miss the most practical solutions. Parachutes are a simple, cost-effective, successful way to land rockets. Your experiment, while I'm sure it would be fun and educational in a lot of ways, is really just reinventing the wheel. Have fun, but don't be surprised if you are the first, last and only hobbyist to try it.

Honestly, what would be far more useful is a guidance system that brings your rocket down closer to the pad; but there is already another thread about that.
 

DAllen

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a big challenge in getting it past the RSO is the fire hazard of flaming hot gas impacting the ground. you will need to ensure that a) all combustibles are cleared from the landing area and b) that the rocket lands in the landing area.
Rex

This is an excellent point. And it isn't just a flammability concern you sure don't want it to land on your fellow fliers car, LCO table, club trailer, etc or anything like that while under thrust.
 
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wyattjohnson35

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"
This reminds me of a story. Bear with me; it has a moral.

Brian May of Queen invented his own electric guitar he called "the Red Special." It provided that classic Queen sound. When they were recording the song "Crazy Little Thing Called Love," they decided to give it a 1950s rockabilly sound. May experimented with his Red Special over and over again, trying to make it sound like a 1950s Fender Telecaster. He tried flatwound strings, he tried different amps, he tried equalizers ... but no matter what he did, it didn't sound right.

Finally he went to his engineer and said, "I don't know what to do. I don't know how to get that Telecaster sound."

The engineer said, "Why don't you play a Telecaster?"

Smart people (May has an honorary PhD in astronomy) very often overthink problems and miss the most practical solutions. Parachutes are a simple, cost-effective, successful way to land rockets. Your experiment, while I'm sure it would be fun and educational in a lot of ways, is really just reinventing the wheel. Have fun, but don't be surprised if you are the first, last and only hobbyist to try it.

Honestly, what would be far more useful is a guidance system that brings your rocket down closer to the pad; but there is already another thread about that.

This is a good example, but the problem came about because I was thinking about problems with a lander. If the parachute was the land on the lander and cover it, it would cause issues. Also, how do you get the "John S. ---- NAR #96911 ---- TRA #15253 ---- MDRA #067
L1, 3/15/14: Aerotech Sumo, CTI H133BS
L2, 6/21/14: Giant Leap Vertical Assault, CTI J240RL
L3, 3/12/16: MAC Performance Radial Flyer, CTI M1101WH
Altitude: 13,028', L3 flight; Speed: Mach ???, L3 flight"

stuff under each post?
 

Oberon

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Probably not feasible with hobby rocket motors. A truly propulsive landing requires a precise amount of impulse delivered at exactly the right time - rockets like Falcon and New Shepard use throttleable liquid motors.

With hobby motors, the variability in impulse and ignition time are going to be way too large to do this reliably (not to mention the short burn time).

What you could maybe do is something like the Soyuz recovery system - a somewhat undersized set of parachutes with a set of solid motors that fire just before landing to slow the spacecraft a bit.

But you're still likely to have issues with getting multiple motors to light instantly and simultaneously.
 

neil_w

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Horizon Hobbies had a model that kind of did something like this. Can’t dredge up the name at the moment. I recall reading that it was pretty dicey.

Personally I think this would be very iffy based on safety considerations.
 

Bat-mite

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"

This is a good example, but the problem came about because I was thinking about problems with a lander. If the parachute was the land on the lander and cover it, it would cause issues. Also, how do you get the "John S. ---- NAR #96911 ---- TRA #15253 ---- MDRA #067
L1, 3/15/14: Aerotech Sumo, CTI H133BS
L2, 6/21/14: Giant Leap Vertical Assault, CTI J240RL
L3, 3/12/16: MAC Performance Radial Flyer, CTI M1101WH
Altitude: 13,028', L3 flight; Speed: Mach ???, L3 flight"

stuff under each post?
Add a signature block in your profile.

Sent from my Moto E (4) using Rocketry Forum mobile app
 

Steve Shannon

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boatgeek

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I think this would be doable with a few "ifs" resolved if you have a lander that falls straight and true under a parachute or streamer. I'd follow the process below:

Experiment a little on paper with a LPR lander. What's your weight balance and ideal descent speed under chute for a standard A, B, or C motor?
Do a little testing with an altimeter to trigger the motor well above the ground. Did those calcs work out pretty well? Adjust weights and/or chute size so that the lander is basically stopped at motor burnout.
Wash, rinse, repeat. When you're happy with results, determine the stopping distance from when the altimeter triggers the igniter.
Set up the flight computer you are using (probably a custom Arduino based system?) to trigger the motor at the ground height plus stopping distance plus a little bit

This is the really important part.
Fly the rocket on an arcing trajectory (rod angle maybe 10 degrees or so) well away from anyone else or anything that could be damaged by the landing motor into a green field that preferably still has morning dew on it. That way you don't have fire danger or risk of injuring someone.

all that said, what I think isn't that important. What the RSO and landowner think are far bigger issues.
 

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Use a small chute on a long kevalar line and use something like a fixed but underpowered escape tower so that it is self stabilising. This will keep the engines away from the ground. You’re going to need a very good altimiter that can fire accurately low to the ground. Above all you need to do many ground tests and flights adding complexity till you can prove that your rocket can ignite the motor reliably at the right height (will need some external lights to show firing times). You might also consider a remote arm switch so only when you confirm it is decending over a safe area, then it will be armed. Also make sure you document this process and engage your club in it so they can see you have the safety aspect worked out, don’t show up unannounced one day with the completed rocket they will be skepticall.

Sounds like a great project to me.
 

Rex R

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I'm picturing a curiosity lander type setup, it descends under chute until about 3' agl(above ground level) at which point 1/2 the shroud lines are released and a co2 thruster 'fires' to land the lander via the 'soft landing rockets'. no hot gases to burn people or things (freeze maybe :)).
Rex
 

georgegassaway

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As mentioned earlier, Joe Barnard (BPS Space) is working on doing this. He's already perfected vectored thrust launches. Even a Falcon-Heavy where all three cores have independent vectored thrust guidance (programmed to work in conjunction with each other without any electrical communications with each other, very impressive in videos the way the outer two gimbal for roll control as well as pitch/yaw). The two outer boosters separate, the core fire a bit longer, and then stages with an upper stage with vectored thrust (yes, at launch the whole rocket has four sets of independent guidance/control systems).

For landings, he's now going at it in increments to concentrate just on the landing issues. Using a Quadcopter to carry it up and drop it, then the guidance system determines when (what altitude and Velocity) to ignite the engine. A big issue with trying to do this, is that unlike the SpaceX Falcon cores, there's no throttle. Although perhaps he will come up it a throttle of one type or another to reduce the thrust (I've suggested a servo-driven heatproof sliding sleeve to telescope below the nozzle area to use the Krushnik effect to reduce thrust). He's flying from a site with low-risk, no non-participants around. Obviously not the sort of thing to fly at the edge of a weedy field on a windy day. Wind is another big enemy of trying to stick the landing, a 1/50 scale model of a Falcon-9 landing in 10 mph wind would be like the real thing landing in 500 mph wind. I've noticed most of his flights, particularly the landing tests have been with low wind. Highest wind a real Falcon-9 apparently landed in was ballpark around 25 mph (Barge landing at sea in less than ideal weather... which IIRC may have been the first successful barge landing)

https://motherboard.vice.com/en_us/...lding-self-landing-replicas-of-spacex-rockets

This first test, IIRC, he purposely had it fire early enough to stop well above ground, the chute system activated but did not deploy. Obviously for the final version of his rocket to launch on rocket power and then to also stick the landing (using a 2nd motor), the fixed fins at top will be replaced by deployable fins such as the Falcon-9 booster uses to help stabstabilize it tail-first (perhaps not grid fins, may not be as effective at model size and relatively slower velocities


In this test, a real landing attempt, ignited a bit late (too low and or too fast decent). But this video also has post-flight analysis / description by Joe.

 
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MikeyDSlagle

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Interesting idea. I've daydreamed about it myself on occasion.
Rather than rocket motors maybe use CO2, and then the thrust could be throttled a bit. Proximity sensors to detect when the vehicle is close to the ground. Have an altimeter to arm the thrusters at say 100' and the proximity sensors start firing sometime after that. The Co2 would probably be weight prohibitive but one canister could feed 4 thrusters.
 

wyattjohnson35

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I think this would be doable with a few "ifs" resolved if you have a lander that falls straight and true under a parachute or streamer. I'd follow the process below:

Experiment a little on paper with a LPR lander. What's your weight balance and ideal descent speed under chute for a standard A, B, or C motor?
Do a little testing with an altimeter to trigger the motor well above the ground. Did those calcs work out pretty well? Adjust weights and/or chute size so that the lander is basically stopped at motor burnout.
Wash, rinse, repeat. When you're happy with results, determine the stopping distance from when the altimeter triggers the igniter.
Set up the flight computer you are using (probably a custom Arduino based system?) to trigger the motor at the ground height plus stopping distance plus a little bit

This is the really important part.
Fly the rocket on an arcing trajectory (rod angle maybe 10 degrees or so) well away from anyone else or anything that could be damaged by the landing motor into a green field that preferably still has morning dew on it. That way you don't have fire danger or risk of injuring someone.

all that said, what I think isn't that important. What the RSO and landowner think are far bigger issues.

That's actually exactly what I'm planning on doing. Make a bunch of cheap low-powered prototypes and scale up. Start with something I can control and get my head around the mecanincs of how this thing is going to work.
 
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