Magnetic Parachute Deployment Mechanism

[PTrockets]

Hi,
Here's my simple parachute system.
[youtube][/youtube]
How it works? (See these pictures)

[Brian]

This is an interesting design of a gravity deployment system. Have you tested it in flight, because the problem with gravity deployment is the stage of flight after the water is expelled, the rocket decelerates, causing the trigger weight to move forward.
You may find it only works on slow, heavy rockets that dont decelerate much.

[U.S. Water Rockets1]

This is an interesting design of a gravity deployment system. Have you tested it in flight, because the problem with gravity deployment is the stage of flight after the water is expelled, the rocket decelerates, causing the trigger weight to move forward.
You may find it only works on slow, heavy rockets that dont decelerate much.

There is also a chance that the rocket will encounter a greater negative gravity force at burnout than it will encounter in free fall. Since the rocket is falling after apogee, the only negative-G force it will experience is due to drag. The same drag force can much greater when the rocket has just finished thrusting. There should be a system that can overcome these issues, but it may be too complex or too hard to easily fabricate to be practical.

[Brian]

There is also a chance that the rocket will encounter a greater negative gravity force at burnout than it will encounter in free fall. Since the rocket is falling after apogee, the only negative-G force it will experience is due to drag. The same drag force can much greater when the rocket has just finished thrusting. There should be a system that can overcome these issues, but it may be too complex or too hard to easily fabricate to be practical.

I've been trying since I joined the forum, with little success.

[PTrockets]

If i'm correct, after apogee, the nosecone (wich is heavier) rotates and faces down. I don't see any problem here.
Well, I didn't test it in flight because the rocket is not finish yet.
Thank you for replying my post

[Brian]

You are, but, a similar force also occurs earlier in the flight which could deploy the recovery system too early.
When the rocket begins its decent its acceleration is slowed by air resistance, but the trigger mass inside the rocket is not, causing the mass to move forward. This also happens after the rocket stops thrusting as air resistance slows down the rocket but the trigger mass tries to continue forward, which in most cases, can overcome the current direction of gravity.

[PTrockets]

You are, but, a similar force also occurs earlier in the flight which could deploy the recovery system too early.
When the rocket begins its decent its acceleration is slowed by air resistance, but the trigger mass inside the rocket is not, causing the mass to move forward. This also happens after the rocket stops thrusting as air resistance slows down the rocket but the trigger mass tries to continue forward, which in most cases, can overcome the current direction of gravity.

Aaaaah! Now I get it
Yes, you are complety right. When I test it in flight, I will publish the results.

[U.S. Water Rockets1]

You are, but, a similar force also occurs earlier in the flight which could deploy the recovery system too early.
When the rocket begins its decent its acceleration is slowed by air resistance, but the trigger mass inside the rocket is not, causing the mass to move forward. This also happens after the rocket stops thrusting as air resistance slows down the rocket but the trigger mass tries to continue forward, which in most cases, can overcome the current direction of gravity.

If you watch the movie "Apollo 13" you can see this effect reproduced as it happen in real life. When the mighty Saturn V launches, they shut down the engines as the rocket stage separates... you see the astronauts thrown forward in their seats when the engines stop thrusting, and then when the next stage fires, they get thrown backward in their seats as the engines kick in. The part where they are thrown forward is the physical action that plagues every gravity actuated water rocket parachute system.

[bugwubber]

You are, but, a similar force also occurs earlier in the flight which could deploy the recovery system too early.
When the rocket begins its decent its acceleration is slowed by air resistance, but the trigger mass inside the rocket is not, causing the mass to move forward. This also happens after the rocket stops thrusting as air resistance slows down the rocket but the trigger mass tries to continue forward, which in most cases, can overcome the current direction of gravity.

If you watch the movie "Apollo 13" you can see this effect reproduced as it happen in real life. When the mighty Saturn V launches, they shut down the engines as the rocket stage separates... you see the astronauts thrown forward in their seats when the engines stop thrusting, and then when the next stage fires, they get thrown backward in their seats as the engines kick in. The part where they are thrown forward is the physical action that plagues every gravity actuated water rocket parachute system.

Not to take away from your point but I thought THAT was because the stage 1 retro rockets were fired too early and was not an expected occurance

The sims do show a projected -2.5 g event after burnout so that is not going to be easy to overcome. Maybe some kind of double action trigger that uses both the anticipated events, or maybe a time delay to activate?

[U.S. Water Rockets1]

You are, but, a similar force also occurs earlier in the flight which could deploy the recovery system too early.
When the rocket begins its decent its acceleration is slowed by air resistance, but the trigger mass inside the rocket is not, causing the mass to move forward. This also happens after the rocket stops thrusting as air resistance slows down the rocket but the trigger mass tries to continue forward, which in most cases, can overcome the current direction of gravity.

If you watch the movie "Apollo 13" you can see this effect reproduced as it happen in real life. When the mighty Saturn V launches, they shut down the engines as the rocket stage separates... you see the astronauts thrown forward in their seats when the engines stop thrusting, and then when the next stage fires, they get thrown backward in their seats as the engines kick in. The part where they are thrown forward is the physical action that plagues every gravity actuated water rocket parachute system.

Not to take away from your point but I thought THAT was because stage 1 retro rockets were fired too early and was not an expected occurance

The sims do show a projected -2.5 g event after burnout so that is not going to be easy to overcome. Maybe some kind of double action trigger that uses both the anticipated events, or maybe a time delay to activate?

This is not how it was depicted in the film (which was supposed to have been reviewed for technical accuracy). In the film, Jim Lovell seem to be telling the other astronauts to brace themselves because he knew what was about to happen from his previous experience on Apollo 8. If the issue was with the retro rockets on the stage 1 firing early, that seems like a big mistake of the sort that could doom a mission.

[bugwubber]

This is not how it was depicted in the film (which was supposed to have been reviewed for technical accuracy). In the film, Jim Lovell seem to be telling the other astronauts to brace themselves because he knew what was about to happen from his previous experience on Apollo 8. If the issue was with the retro rockets on the stage 1 firing early, that seems like a big mistake of the sort that could doom a mission.

Yeah, the film missed on a couple things, like the gates breaking away from the rocket in sequence instead of all together and starting the engines at the wrong time. They were well above most of the atmosphere by that point (stage 1 separation) so drag would have been much less than we Earthbound misfits experience here at ground level. One of the astronauts apparently had an impressive dent in his helmet from the event.

The other issue with magnets that I see- they usually aren't very light. how much does your mechanism weigh? Wonder if you could put a clockwork in somehow that would wind a string around the pin that slowly pulls a plastic door open to release the magnet? That way the door would keep the magnet locked up during deceleration and allow it to fall down once the rocket turns over. Could try different diameter wheels on the pin to get the right timing.

[U.S. Water Rockets]

Not to take away from your point but I thought THAT was because the stage 1 retro rockets were fired too early and was not an expected occurance

This is a very interesting article going into impressive detail about the Apollo 15 launch transcripts, with commentary interspersed through the entire sequence. This is really fascinating stuff.

http://history.nasa.gov/ap15fj/01launch ... _orbit.htm

There is a description of the S-1C staging sequence and commentary from the technical debrief where the shutdown of the 4 outer engines was described as "violent" and there was significant recoil. It is also discussed that at this point the center engine has already been shut down for about 23 seconds because the air is thinning and the fuel load is burning off and the acceleration is approaching 4G and if they left all 5 engines running the entire time the shock at shutdown would be too great.

There's a cool graph on the page as well:


Point (2) on the graph marks the center engine shutdown.
Point (3) on the graph shows outer engine shutdown.

The outer engine shutdown shows the rocket going from 4G acceleration to 0G acceleration in just a few seconds time.

The debriefing describes the fireball from the engines passing the rocket and visible out the windows of the command module. This strongly suggests that the movie got it technically right where the S-1C cutoff threw the crew forward, and not retro rockets on the first stage. The movie did miss the fireball being visible though.

The movie may have also gotten it wrong and was showing all 5 engines cutting off. This will have to be reviewed. But perhaps this center engine cutoff was part of the Apollo 15 launch that was not part of Apollo 13?

In any event, this is a fascinating read.

Enjoy!

[bugwubber]

Not to take away from your point but I thought THAT was because the stage 1 retro rockets were fired too early and was not an expected occurance

This is a very interesting article going into impressive detail about the Apollo 15 launch transcripts, with commentary interspersed through the entire sequence. This is really fascinating stuff.

http://history.nasa.gov/ap15fj/01launch ... _orbit.htm

There is a description of the S-1C staging sequence and commentary from the technical debrief where the shutdown of the 4 outer engines was described as "violent" and there was significant recoil. It is also discussed that at this point the center engine has already been shut down for about 23 seconds because the air is thinning and the fuel load is burning off and the acceleration is approaching 4G and if they left all 5 engines running the entire time the shock at shutdown would be too great.



Point (2) on the graph marks the center engine shutdown.
Point (3) on the graph shows outer engine shutdown.

The outer engine shutdown shows the rocket going from 4G acceleration to 0G acceleration in just a few seconds time.

The debriefing describes the fireball from the engines passing the rocket and visible out the windows of the command module. This strongly suggests that the movie got it technically right where the S-1C cutoff threw the crew forward, and not retro rockets on the first stage. The movie did miss the fireball being visible though.

The movie may have also gotten it wrong and was showing all 5 engines cutting off. This will have to be reviewed. But perhaps this center engine cutoff was part of the Apollo 15 launch that was not part of Apollo 13?

In any event, this is a fascinating read.

Enjoy!

Fascinating. It's fun to read this stuff, which once was common knowledge is being lost to recent generations. This article printed back in 1995 in the NYT has perhaps a few "mistakes" of its own...

Quoted:
The sudden jolt at the separation of the first-stage rocket was completely unexpected, not a routine occurrence as portrayed in the movie. During the actual mission, small retro-rockets on the top of the first stage fired one second too early. This is what threw the astronauts forward as shown in the movie. Truth be told, the real Jim Lovell had several marks on his helmet from banging into the switch guards.

http://www.nitcentral.com/oddsends/apollo13.htm

[U.S. Water Rockets1]

Not to take away from your point but I thought THAT was because the stage 1 retro rockets were fired too early and was not an expected occurance

This is a very interesting article going into impressive detail about the Apollo 15 launch transcripts, with commentary interspersed through the entire sequence. This is really fascinating stuff.

http://history.nasa.gov/ap15fj/01launch ... _orbit.htm

There is a description of the S-1C staging sequence and commentary from the technical debrief where the shutdown of the 4 outer engines was described as "violent" and there was significant recoil. It is also discussed that at this point the center engine has already been shut down for about 23 seconds because the air is thinning and the fuel load is burning off and the acceleration is approaching 4G and if they left all 5 engines running the entire time the shock at shutdown would be too great.



Point (2) on the graph marks the center engine shutdown.
Point (3) on the graph shows outer engine shutdown.

The outer engine shutdown shows the rocket going from 4G acceleration to 0G acceleration in just a few seconds time.

The debriefing describes the fireball from the engines passing the rocket and visible out the windows of the command module. This strongly suggests that the movie got it technically right where the S-1C cutoff threw the crew forward, and not retro rockets on the first stage. The movie did miss the fireball being visible though.

The movie may have also gotten it wrong and was showing all 5 engines cutting off. This will have to be reviewed. But perhaps this center engine cutoff was part of the Apollo 15 launch that was not part of Apollo 13?

In any event, this is a fascinating read.

Enjoy!

Fascinating. It's fun to read this stuff, which once was common knowledge is being lost to recent generations. This article printed back in 1995 in the NYT has perhaps a few "mistakes" of its own...

Quoted:
The sudden jolt at the separation of the first-stage rocket was completely unexpected, not a routine occurrence as portrayed in the movie. During the actual mission, small retro-rockets on the top of the first stage fired one second too early. This is what threw the astronauts forward as shown in the movie. Truth be told, the real Jim Lovell had several marks on his helmet from banging into the switch guards.

http://www.nitcentral.com/oddsends/apollo13.htm

Some of the flights used "Ullage" rockets which were solid motors that would fire to force the upper stage propellants to the bottom of the tanks before ignition. Is it possible this is the motors which they are talking about?