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Thinking about LEGO astronauts

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Jeff Lassahn

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I'm toying with the idea of having an interesting payload challenge:
A little module (maybe 40mm diameter or so) with a LEGO astronaut and some supporting electronics including a data logger, an altimeter and an accelerometer.
It would have some pretty strict rules about how it can fly, something like Can't exceed 6 Gs for more than 1 second, and Can't exceed 10 Gs ever.
The electronics would keep a permanent log and would declare the astronaut deceased if the limits are exceeded.

Then it might be fun to run a little toy space program with a few astronauts, competing for maximum altitude, flight duration etc. while trying not to kill any of them.

I was originally thinking this would be mostly a reliability engineering challenge, trying to figure out how to reduce the rate of rocket failures to the point where I wouldn't be worried for the safely or the model crew. But now I've realized that flying a payload with limited G tolerance is actually an interesting design challenge, with typical model rockets experiencing much higher G forces than would be OK for a crew mission.

Does anyone have any thoughts about how you would design a rocket for maximum altitude but with a tight limit on maximum acceleration?
 

Funkworks

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The ejection charge messes things up. It’s required in model rocketry but an issue if you want to sustain life (or simulate doing so). Not only because of the g-force but because from so close, it might hurt the astronaut’s ear drums.

So one could either consider it, or simply ignore it.
 

Peartree

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The ejection charge messes things up. It’s required in model rocketry but an issue if you want to sustain life (or simulate doing so). Not only because of the g-force but because from so close, it might hurt the astronaut’s ear drums.

So one could either consider it, or simply ignore it.
The astronaut would necessarily have to be contained/enclosed in a capsule to protect him/her from ejection gases. Designs to mitigate the g forces of ejection/separation could be worth bonus points.
 

Scott_650

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The astronaut would necessarily have to be contained/enclosed in a capsule to protect him/her from ejection gases. Designs to mitigate the g forces of ejection/separation could be worth bonus points.
Sort of a reverse egg loft - don’t break the astronaut! To keep the design complexity down I think ignoring the recovery event is probably an option the goal being to launch successfully without exceeding typical human g tolerance.
 

Jeff Lassahn

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I'm not sure how I feel about ignoring the recovery event. If this were a real rocket program, the mission objective is the mission objective and "that sounds hard let's not do that part" isn't really an option. It's kind of like making the goal of the Apollo program "We will land a man on the moon within the decade, and it would be a nice bonus if we could also get him back".
 

mooffle

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I just launched a rocket like this a month ago, good to see someone trying to top my previous ambitions :p
I would think the best way to do this would be very careful engine selection.
 

Funkworks

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I'm not sure how I feel about ignoring the recovery event. If this were a real rocket program, the mission objective is the mission objective and "that sounds hard let's not do that part" isn't really an option. It's kind of like making the goal of the Apollo program "We will land a man on the moon within the decade, and it would be a nice bonus if we could also get him back".
A problem is that we can't control the recovery charge energy (at least not unless we're in dual deployment systems). A proper way to do this might be to have much smaller charges that merely pop off some bolts, instead of a "huge" one that blows away the entire nose cone. That's an important difference between models and human-size systems: the charge is proportionally huge compared to the payload.

In any case, maybe there's away to release the astronaut before the ejection charge goes off. Drag, trap door, glider, separate chute, something.

Using radio to open a hatch and let the wind drag out a parachute-fitted capsule?
 

mooffle

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In any case, maybe there's away to release the astronaut before the ejection charge goes off. Drag, trap door, glider, separate chute, something.
Some sort of nose that has a retaining pin would let the payload 'drop' instead of 'pop'. Think side ejection coming after a nose ejection. G forces could be near zero that way
 

Funkworks

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1. Electronics detect approaching apogee.
2. Electronics opens hatch before apogee, wind drags out astronaut, who falls with own chute..
3. Ejection charge goes off after apogee and rocket comes down conventionally.

Without electronics, i have nothing so far.
 

Jeff Lassahn

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I can imagine a version that uses electronics and motors, with no ejection charge at all.
I can also imagine a system with baffles and vents that limits the force of the ejection charge, but that would require a lot of testing because I don't think ejection charge energy is a well controlled as main motor impulse.
 

mooffle

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You could use the ejection charge as the release mechanism then rig your payload with a rubber band arm. The rubber band alone would determine your g force. Since you mentioned lego the whole thing could be rigged with technic parts.
 

Scott_650

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When John Beans of Jolly Logic did an episode of The Rocketry Show podcast he talked about a recovery system based on opening fairings/hatches with altitude sensors connected to servos - similar to the Chute Release I would assume. And iirc there was an article in Apogee’s Peak of Flight newsletter about someone using pop open hatches for recovery. Fascinating stuff all around!
 

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That's the beauty of having a competition. You don't have to have all the answers. Just offer points for solving the problem, and you unleash a hundred teams to explore, experiment, and discover ways to get there
 

Funkworks

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There could be a mechanical winding mechanism timed to release the occupant before (pre-apogee) the ejection charge goes off (post-apogee).
 

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