Cardboard/Plywood Parts to a 100k

The Rocketry Forum

Help Support The Rocketry Forum:

AlexBruccoleri

Well-Known Member
Joined
May 12, 2021
Messages
203
Reaction score
82
Hi All, I had an idea for a rocketry challenge. The goal would be to launch a rocket to 100,000 feet with the limit of using LOC Precision-style parts such as cardboard tubes and plywood fins. No fiberglass/carbon and minimal metal parts allowed. Bolts for the electronics bay and motor retention would be okay. Another rule would be Tripoli certified motors.

The rockets would likely need to be staged and the velocity low in the thicker parts of the atmosphere.

This challenge would require good design and use of the materials. It also would be fun since Cardboard and Plywood are easy to work with. I have read about many of the Tripoli-style projects that went to the edge of space, and many were essentially sounding rockets built with high-quality machine tools and/or composites. While those projects are indeed awesome, I am curious if rocketeers can push the boundaries with more accessible materials.

Cheers, Alex
 

jderimig

Sponsor
TRF Sponsor
Joined
Jan 23, 2009
Messages
4,183
Reaction score
1,974
What a challenge. I do not think its possible with current solid motors and with no active guidance.
 

manixFan

Not a rocket scientist
Joined
Feb 15, 2009
Messages
2,519
Reaction score
1,691
Location
TX
Hi All, I had an idea for a rocketry challenge. The goal would be to launch a rocket to 100,000 feet with the limit of using LOC Precision-style parts such as cardboard tubes and plywood fins. No fiberglass/carbon and minimal metal parts allowed. Bolts for the electronics bay and motor retention would be okay. Another rule would be Tripoli certified motors.

The rockets would likely need to be staged and the velocity low in the thicker parts of the atmosphere.

This challenge would require good design and use of the materials. It also would be fun since Cardboard and Plywood are easy to work with. I have read about many of the Tripoli-style projects that went to the edge of space, and many were essentially sounding rockets built with high-quality machine tools and/or composites. While those projects are indeed awesome, I am curious if rocketeers can push the boundaries with more accessible materials.

Cheers, Alex
{Edited}I also don't think it can be done, with any kind of motor. The stress on the fins alone would seem to rule out such an attempt. Plus the weight and stresses at the interstage couplers would be beyond what cardboard can handle.

Unless someone can make a magic motor that burns at a 5:1 thrust ratio for many seconds, it would seem to defy the 'physics' of ordinary materials.

Tony
 

AlexBruccoleri

Well-Known Member
Joined
May 12, 2021
Messages
203
Reaction score
82
Hi Tony, The key would be keep the velocity low below 30k or so. Above that, you could start to "punch it". 3/8 or 1/2" plywood is quite strong. Likewise couplers are a concern, however LOC sells stiffeners which are very thick solid-cardboard. I have not done any sims but a starting place would be a four stage rocket, not minimum diameter to allow for rigid joints. N1000 to start and then an M750 and the top two stages could be something like the LOC Laser Loc 313 and two staged. Another thought would be strap on boosters for the initial "kick" to get it stable.

For what it is worth, when I did contest rocketry. I was making airframes that weighed under 3 grams and the entire rocket under 7 grams for duration events. A priori they seemed extremely flimsy, however stiffened in the right spots and they were very airworthy.

Cheers, Alex
 

AlexBruccoleri

Well-Known Member
Joined
May 12, 2021
Messages
203
Reaction score
82
What a challenge. I do not think its possible with current solid motors and with no active guidance.
I am confused. For a flight to 100k, no active guidance is necessary. Are you referring to orbit? I should comment, I do not think orbit is possible with commercial motors on any realistic budget. The specific impulse and mass ratios on commercial motors are nowhere close to what it takes for a 10ish km/s delta v. You would need an absurd number of stages.
 

heada

Well-Known Member
Joined
Jan 18, 2009
Messages
5,072
Reaction score
2,467
Location
Indianapolis, Indiana
100k feet or 100km? Huge difference. I think 100k feet could be possible with some out of the box thinking but 100km is probably not possible without advanced composites.

Also, is PML phenolic allowed? It is owned by LOC now and it is a paper and resin matrix like traditional LOC tubes, just with a different resin.
 

AlexBruccoleri

Well-Known Member
Joined
May 12, 2021
Messages
203
Reaction score
82
100k feet or 100km? Huge difference. I think 100k feet could be possible with some out of the box thinking but 100km is probably not possible without advanced composites.

Also, is PML phenolic allowed? It is owned by LOC now and it is a paper and resin matrix like traditional LOC tubes, just with a different resin.
100k feet, not km. Also I thought about the purchase of PML and my initial reaction is no phenolic or fiberglass from their shop.

For what it is worth, I am not advocating against fiberglass or other strong materials. I use them, love them and they are great in my opinion. This challenge is about going to the edge of space with "easy to work with" and accessible materials.
 

manixFan

Not a rocket scientist
Joined
Feb 15, 2009
Messages
2,519
Reaction score
1,691
Location
TX
Hi Tony, The key would be keep the velocity low below 30k or so. Above that, you could start to "punch it". 3/8 or 1/2" plywood is quite strong. Likewise couplers are a concern, however LOC sells stiffeners which are very thick solid-cardboard. I have not done any sims but a starting place would be a four stage rocket, not minimum diameter to allow for rigid joints. N1000 to start and then an M750 and the top two stages could be something like the LOC Laser Loc 313 and two staged. Another thought would be strap on boosters for the initial "kick" to get it stable.

For what it is worth, when I did contest rocketry. I was making airframes that weighed under 3 grams and the entire rocket under 7 grams for duration events. A priori they seemed extremely flimsy, however stiffened in the right spots and they were very airworthy.

Cheers, Alex
With all due respect, I don't think you understand the stresses involved in high power rockets, especially staged ones. If your experience is building 7 gram rockets, you underestimate the challenges in scaling up airframes, especially when you add the stress of a staged rocket.

It's an interesting thought experiment, but I don't see any practical way to build such a rocket. Do yourself a favor and try to sim a stack that will get to 100K' and look at the weights and velocities involved. If folks can't do it with years of experience with extremely strong aerospace style components, it seems even less likely it would work with cardboard and plywood.

Come to a BALLS rocket launch sometime. I think you'd have a very different opinion of the practicality of your challenge.


Tony
 

AlexBruccoleri

Well-Known Member
Joined
May 12, 2021
Messages
203
Reaction score
82
With all due respect, I don't think you understand the stresses involved in high power rockets, especially staged ones. If your experience is building 7 gram rockets, you underestimate the challenges in scaling up airframes, especially when you add the stress of a staged rocket.

It's an interesting thought experiment, but I don't see any practical way to build such a rocket. Do yourself a favor and try to sim a stack that will get to 100K' and look at the weights and velocities involved. If folks can't do it with years of experience with extremely strong aerospace style components, it seems even less likely it would work with cardboard and plywood.

Come to a BALLS rocket launch sometime. I think you'd have a very different opinion of the practicality of your challenge.


Tony
Why do you think my experience is limited to 7 gram rockets? And for what it is worth I can calculate stresses, and clearly trying to go fast initially is a bad idea with a cardboard rocket. And most rockets at Balls do just that. A good display of the opposite is Gary Rosenfield's Hamster Dance rocket. I believe he used basic cardboard tubing, 1/16 plywood fins and made it to around 22k. He is very clever and designed his motor well to give an initial thrust spike for stability and then a long slow burn to avoid friction losses. (He is the founder of Aerotech....and he knows what he is doing.) Your mention of sims is valid and I did a quick sim. Starting from 60k, a 3 inch LOC rocket can get to 100k on a K250. I should do a complete sim, but the idea is to stage and stay slow for most of the atmosphere.

Also I should note that my challenge is not "easier" than using composites or metals. If anyone tried this in practice, they would likely need to do a lot of test flights. I find this challenge interesting because the build could be done in most households or even apartments.
 
Joined
Jun 30, 2015
Messages
1,485
Reaction score
1,703
Location
Australia
I don't think there is a motor with a suitable thrust profile to get you there. There's a number of factors that would make this near to impossible.
If I launch something to 5 or 10 K ft, the airframe is under thrust and all the stresses for an amount of time. If you go to 100K ft those stresses will be significantly greater due to in part the potential for high altitude winds and also it gets pretty cold up there and the flight will be 10 to 20 times longer.
A motor would have to have an extremely long burn, low thrust just to keep all your stresses down to acceptable limits. It would be almost impossible to keep the flight sub sonic. Due in part to the fact that the speed of sound DECREASES with altitude. If you were just subsonic at sea level you would be supersonic at the same speed at 100K. So you'd have at least a trans and supersonic event on the airframe. Not impossible for cardboard but certainly way too challenging for most.
And let's assume I like the challenge (it's not really my thing), what's my incentive? Why am I doing this? I'm risking lets say $2000 in hard equipment. Dual GPS trackable dual deploy computers plus same again if it's staged plus tiltometer plus 1 or 2 motor casings plus reloads plus(do I need to keep going) The risks here outweigh any kudos you might get out of it.
Even if you were successful, most are going to suck air through their teeth and say, "mate, you got away with it, but let's not do that again". The whole proposal is a serious error in the choice of materials for that type of project and it's really a safety issue. Better materials are readily available.
Norm
 
Last edited:

AlexBruccoleri

Well-Known Member
Joined
May 12, 2021
Messages
203
Reaction score
82
I don't think there is a motor with a suitable thrust profile to get you there. There's a number of factors that would make this near to impossible.
If I launch something to 5 or 10 K ft, the airframe is under thrust and all the stresses for an amount of time. If you go to 100K ft those stresses will be significantly greater due to in part the potential for high altitude winds and also it gets pretty cold up there and the flight will be 10 to 20 times longer.
A motor would have to have an extremely long burn, low thrust just to keep all your stresses down to acceptable limits. It would be almost impossible to keep the flight sub sonic. So you'd have at least a trans and supersonic event on the airframe. Not impossible for cardboard but certainly way too challenging for most.
And let's assume I like the challenge (it's not really my thing), what's my incentive? Why am I doing this? I'm risking lets say $2000 in hard equipment. Dual GPS trackable dual deploy computers plus same again if it's staged plus tiltometer plus 1 or 2 motor casings plus reloads plus(do I need to keep going) The risks here outweigh any kudos you might get out of it.
Even if you were successful, most are going to suck air through their teeth and say, "mate, you got away with it, but let's not do that again".
The whole proposal is a serious error in the choice of materials for that type of project and it's really a safety issue. Better materials are readily available.
Norm
The incentive is "just for fun". It is a hobby and clearly fun is subjective. I think it is fun to push the boundaries with materials I can access. I live in a city apartment and I like "doing what I can" in a limited amount of space with limited equipment. I am not planning anything as ambitious as this challenge, but maybe someone out there wants to push it.
 
Last edited:
Joined
Jun 30, 2015
Messages
1,485
Reaction score
1,703
Location
Australia
The incentive is "just for fun". It is a hobby and clearly fun is subjective. I think it is fun to push the boundaries with materials I can access. I live in a city apartment and I like "doing what I can" in a limited amount of space with limited equipment. I am not planning anything as ambitious as this challenge, but maybe someone out wants to push it.
If you've got $2000 spare, let me know and we can go out on the town and have some fun guaranteed more successfully than any success rate for this challenge. :)
 

cerving

Owner, Eggtimer Rocketry
TRF Sponsor
Joined
Feb 3, 2012
Messages
5,031
Reaction score
2,762
"Wood" doesn't mean "balsa", you could certainly skin balsa with plywood, perhaps several layers with alternating grain directions to provide multidirectional strength. The fins would certainly end up being heavier than the CF equivalent, and thicker too, whether that's a show-stopper or not remains to be seen.
 

jderimig

Sponsor
TRF Sponsor
Joined
Jan 23, 2009
Messages
4,183
Reaction score
1,974
I am confused. For a flight to 100k, no active guidance is necessary. Are you referring to orbit? I should comment, I do not think orbit is possible with commercial motors on any realistic budget. The specific impulse and mass ratios on commercial motors are nowhere close to what it takes for a 10ish km/s delta v. You would need an absurd number of stages.
Alex, For a paper and plywood rocket you would need a thrust profile that is slow during the dense part of the atmosphere. Any rocket with current commercial motors do not achieve anywhere near 100Kft without exceeding about mach 2.5. I do not think its possible to make a plywood fin with a low enough drag profile that can go that fast. Its just not stiff enough. So you have to go slow through about 30Kft MSL at least.

Now if you can find a motor that will accomplish this in a minimum mass rocket (which I do not think there are any) a slow rocket will be very susceptible to gravity turn once the rocket goes of vertical (which it will if is slow and there is any crosswind). Hence the need for active stabilization.

But I haven't modeled any of this so it may be possible. Go for it.
 

AlexBruccoleri

Well-Known Member
Joined
May 12, 2021
Messages
203
Reaction score
82
If you've got $2000 spare, let me know and we can go out on the town and have some fun guaranteed more successfully than any success rate for this challenge. :)
Do not equate easy success rate with fun. The challenge is a lot of fun to myself and many of my friends. Also being able to work in normal house or apartment is a big consideration.
 

AlexBruccoleri

Well-Known Member
Joined
May 12, 2021
Messages
203
Reaction score
82
Alex, For a paper and plywood rocket you would need a thrust profile that is slow during the dense part of the atmosphere. Any rocket with current commercial motors do not achieve anywhere near 100Kft without exceeding about mach 2.5. I do not think its possible to make a plywood fin with a low enough drag profile that can go that fast. Its just not stiff enough. So you have to go slow through about 30Kft MSL at least.

Now if you can find a motor that will accomplish this in a minimum mass rocket (which I do not think there are any) a slow rocket will be very susceptible to gravity turn once the rocket goes of vertical (which it will if is slow and there is any crosswind). Hence the need for active stabilization.

But I haven't modeled any of this so it may be possible. Go for it.
These are good points. A few comments.

The fins would need to be thick. Stiffness goes with the cube of thickness so going with 3/8 or 1/2" will make a big different to prevent flutter.

A single commercial motor is not feasible for this to work. It needs to be staged, or have strap-on boosters. In essence the thrust profile will be "built" from a collection of motors.

I did not understand your initial comment on guidance and now I get it. That is a very good point and could be a show stopper. While I am not opposed to an active guidance system, (as long as it is "apartment-build style), it could mean flying with an angle of attack, and that could add too much stress on the airframe. It would be interesting to calculate how far the turn would be if the rocket stayed at 500 mph until it reached 50k. One thought is to have the rocket start with an angle to allow it to finish close to the zenith. Good point!
 
Joined
Jun 30, 2015
Messages
1,485
Reaction score
1,703
Location
Australia
Do not equate easy success rate with fun. The challenge is a lot of fun to myself and many of my friends. Also being able to work in normal house or apartment is a big consideration.
The motors for these would not normally be stored in an apartment. Does this have to be launched from your apartment? Is this a new rule? Does it have to be broken down into bits that are not detectable with metal detectors? I'm out.... :)
 

manixFan

Not a rocket scientist
Joined
Feb 15, 2009
Messages
2,519
Reaction score
1,691
Location
TX
Why do you think my experience is limited to 7 gram rockets? And for what it is worth I can calculate stresses, and clearly trying to go fast initially is a bad idea with a cardboard rocket. And most rockets at Balls do just that. A good display of the opposite is Gary Rosenfield's Hamster Dance rocket. I believe he used basic cardboard tubing, 1/16 plywood fins and made it to around 22k. He is very clever and designed his motor well to give an initial thrust spike for stability and then a long slow burn to avoid friction losses. (He is the founder of Aerotech....and he knows what he is doing.) Your mention of sims is valid and I did a quick sim. Starting from 60k, a 3 inch LOC rocket can get to 100k on a K250. I should do a complete sim, but the idea is to stage and stay slow for most of the atmosphere.

Also I should note that my challenge is not "easier" than using composites or metals. If anyone tried this in practice, they would likely need to do a lot of test flights. I find this challenge interesting because the build could be done in most households or even apartments.
A challenge should have some possibility of success, otherwise it becomes an exercise in futility. I spent some time in OpenRocket just trying to come up with a three stage that gets to 100,000' without breaking Mach 2, and exactly as John says, it does not seem possible, at least not with the motors I tried. Worse, if your don't use MD rockets, the loss in altitude from the larger diameter becomes very hard to overcome.

But I honestly don't think it's possible to make an N-N or N-M 2 stage just using cardboard in the inter-coupler. The moment arm created by even a small amount of non-zero angle of attack would likely exceed the strength of the materials even at fairly low velocities. You agree it needs to be staged which is why I think it is not possible with the materials you suggest.

A more realistic goal would be to build a 54mm cardboard/plywood rocket that survives Mach 2+ to over 20,000'. My guess is with very careful thought and some creative laminating, it might be possible. That seems more in the spirit of the Hamster Dance than your original goal, and with a far more reasonable price point.

I challenge you to post a 3 or 4 stage non-minimum diameter rocket that hits 100,000', without breaking Mach 2 while under 30,000'. It can be made using unobtanium for this exercise.

Good luck,


Tony
 

AlexBruccoleri

Well-Known Member
Joined
May 12, 2021
Messages
203
Reaction score
82
The motors for these would not normally be stored in an apartment. Does this have to be launched from your apartment? Is this a new rule? Does it have to be broken down into bits that are not detectable with metal detectors? I'm out.... :)
Okay not sure how to respond to this. As anyone who builds rockets knows, especially complex ones, the build can take a lot of time. You do not need the propellant while building, the propellant can be kept at a suitable location. The cases are all you need for the build and some weights to test the cg.
 

AlexBruccoleri

Well-Known Member
Joined
May 12, 2021
Messages
203
Reaction score
82
A challenge should have some possibility of success, otherwise it becomes an exercise in futility. I spent some time in OpenRocket just trying to come up with a three stage that gets to 100,000' without breaking Mach 2, and exactly as John says, it does not seem possible, at least not with the motors I tried. Worse, if your don't use MD rockets, the loss in altitude from the larger diameter becomes very hard to overcome.

But I honestly don't think it's possible to make an N-N or N-M 2 stage just using cardboard in the inter-coupler. The moment arm created by even a small amount of non-zero angle of attack would likely exceed the strength of the materials even at fairly low velocities. You agree it needs to be staged which is why I think it is not possible with the materials you suggest.

A more realistic goal would be to build a 54mm cardboard/plywood rocket that survives Mach 2+ to over 20,000'. My guess is with very careful thought and some creative laminating, it might be possible. That seems more in the spirit of the Hamster Dance than your original goal, and with a far more reasonable price point.

I challenge you to post a 3 or 4 stage non-minimum diameter rocket that hits 100,000', without breaking Mach 2 while under 30,000'. It can be made using unobtanium for this exercise.

Good luck,


Tony
Okay I agree getting this right in a sim is a good place to start. I have not put in the time to design this and it is a fair thing to do. I suspect a two stage rocket will not work. It will need to be 3 or 4, or use a collection of strap-on boosters. My gut tells me it needs to stay below Mach .8ish until 30k or even 40k.

Also its is worth mentioning that Gary posted his data for his Hamster Dance flight to 22k and I believe it only reached Mach 0.9.

I also suspect strongly minimum diameter is not the way to go. A little extra thickness to allow for a better structure will probably be a better trade off, especially given the low speeds.
 
Joined
Jun 30, 2015
Messages
1,485
Reaction score
1,703
Location
Australia
Okay not sure how to respond to this. As anyone who builds rockets knows, especially complex ones, the build can take a lot of time. You do not need the propellant while building, the propellant can be kept at a suitable location. The cases are all you need for the build and some weights to test the cg.
I keep half my propellant in my house. It's a rod of ABS...... Never goes bad.

You're L3 certified. You've put together a full L3 submission document and passed. If you had put together a similar submission document for this proposal, we all might stop yanking your chain. Until then, this is not in the realms of plausibility. I also do not think it would pass a high altitude flight safety review. So again, not plausible.
 

AlexBruccoleri

Well-Known Member
Joined
May 12, 2021
Messages
203
Reaction score
82
I keep half my propellant in my house. It's a rod of ABS...... Never goes bad.

You're L3 certified. You've put together a full L3 submission document and passed. If you had put together a similar submission document for this proposal, we all might stop yanking your chain. Until then, this is not in the realms of plausibility. I also do not think it would pass a high altitude flight safety review. So again, not plausible.
I am posing a question, not posting a detailed design. I do agree it is worth putting together at least one or two plausible sims.

Regarding reality, if I were to try to pull this off, I would start with testing the first stage and having the rest of the "stages" be dummy weights. After getting that to work, I would try two stages and so on. Such an approach would be important from both an engineering and safety respect.
 
Joined
Jun 30, 2015
Messages
1,485
Reaction score
1,703
Location
Australia
Keep us posted. I'm sure we'd all like to be proven wrong. But the structural integrity of this whole project over, as you say, years rests on no-one spilling a cup of coffee on it.
We've all tried to dissuade you from it. Now prove us all wrong and Good luck with the project.
 

manixFan

Not a rocket scientist
Joined
Feb 15, 2009
Messages
2,519
Reaction score
1,691
Location
TX
Okay I agree getting this right in a sim is a good place to start. I have not put in the time to design this and it is a fair thing to do. I suspect a two stage rocket will not work. It will need to be 3 or 4, or use a collection of strap-on boosters. My gut tells me it needs to stay below Mach .8ish until 30k or even 40k.

Also its is worth mentioning that Gary posted his data for his Hamster Dance flight to 22k and I believe it only reached Mach 0.9.

I also suspect strongly minimum diameter is not the way to go. A little extra thickness to allow for a better structure will probably be a better trade off, especially given the low speeds.
The Hamster Dance rocket is irrelevant to this discussion.

There is no way to get to 100k’ with a max velocity of .8 Mach while under 30,000', unless you have some magic motor with a crazy regressive profile that can burn for far longer than any available commercial motor. It’s just simple math: 30,000' / .8 Mach = 33 seconds. (30,000ft/900ft/sec=33.33 seconds) Now imagine trying to do that with a staged rocket, even with strap-on boosters. And you still have 70,000' left to go.


Tony
 

AlexBruccoleri

Well-Known Member
Joined
May 12, 2021
Messages
203
Reaction score
82
The Hamster Dance rocket is irrelevant to this discussion.

There is no way to get to 100k’ with a max velocity of .8 Mach while under 30,000', unless you have some magic motor with a crazy regressive profile that can burn for far longer than any available commercial motor. It’s just simple math: 30,000' / .8 Mach = 33 seconds. (30,000ft/900ft/sec=33.33 seconds) Now imagine trying to do that with a staged rocket, even with strap-on boosters. And you still have 70,000' left to go.


Tony
The Hamster Dance rocket is a data point of a high altitude, sub Mach flight which very much fits into my "apartment build" fantasy. I think it was an extremely impressive display of what good engineering can do with low-strength materials.

I am going to play with some sims. Recall, the goal of the first two stages is to get out of most of the atmosphere. They do not finish the job! Once cleared of the thick air, the next stages "punch it".
 

manixFan

Not a rocket scientist
Joined
Feb 15, 2009
Messages
2,519
Reaction score
1,691
Location
TX
The Hamster Dance rocket is a data point of a high altitude, sub Mach flight which very much fits into my "apartment build" fantasy. I think it was an extremely impressive display of what good engineering can do with low-strength materials.

I am going to play with some sims. Recall, the goal of the first two stages is to get out of most of the atmosphere. They do not finish the job! Once cleared of the thick air, the next stages "punch it".
The Hamster Dance rockets do not use commercial motors. As a starting point, see if you can find a commercial motor that can mimic that flight.


Tony
 

AlexBruccoleri

Well-Known Member
Joined
May 12, 2021
Messages
203
Reaction score
82
The Hamster Dance rockets do not use commercial motors. As a starting point, see if you can find a commercial motor that can mimic that flight.


Tony
I just did a sim and it was not perfect but a good starting point. N1000-L400-K250, 5.38" tubes and then 3". That got to 112k, but it went too fast too soon. Mach 1.3 around 20k. Rocksim will not allow 4 stages and I need to figure out air starts and strap-on boosters. This is close enough where I am pretty confident my idea is quite possible from an engine selection. I suspect strap-on boosters are a better approach to keep the aspect ratio of the rocket lower.

Regarding the Hamster Dance, I mentioned in a previous post that Gary cleverly designed his motor. No motors with a thrust profile like that are available commercially. I suspect the casing temperature would get too hot, but that is a guess. Regardless Gary showed the Balls crowd a much more gentle approach to 20k+. His rocket could literally be built on an office desk with very basic hand tools. That to me is *awesome*.
 

manixFan

Not a rocket scientist
Joined
Feb 15, 2009
Messages
2,519
Reaction score
1,691
Location
TX
I don't mean to discourage you, only to provide what I feel are real-world obstacles to your challenge.
The Hamster Dance rocket is a data point of a high altitude, sub Mach flight which very much fits into my "apartment build" fantasy. I think it was an extremely impressive display of what good engineering can do with low-strength materials.

I am going to play with some sims. Recall, the goal of the first two stages is to get out of most of the atmosphere. They do not finish the job! Once cleared of the thick air, the next stages "punch it".
I just did a sim and it was not perfect but a good starting point. N1000-L400-K250, 5.38" tubes and then 3". That got to 112k, but it went too fast too soon. Mach 1.3 around 20k. Rocksim will not allow 4 stages and I need to figure out air starts and strap-on boosters. This is close enough where I am pretty confident my idea is quite possible from an engine selection. I suspect strap-on boosters are a better approach to keep the aspect ratio of the rocket lower.

Regarding the Hamster Dance, I mentioned in a previous post that Gary cleverly designed his motor. No motors with a thrust profile like that are available commercially. I suspect the casing temperature would get too hot, but that is a guess. Regardless Gary showed the Balls crowd a much more gentle approach to 20k+. His rocket could literally be built on an office desk with very basic hand tools. That to me is *awesome*.
I admire your dedication to your challenge. But you'll note that you state in the first post your goal is to 'punch it' once through the lower atmosphere, yet in the second post once you do a sim your second and third stages are an L400 and a K250, which is the exact opposite of punching it. So already you've learned that your initial guesstimate on how to achieve your goal is probably incorrect. And I guarantee once you put some real world weights and 1/2" fins behind those sims, the numbers won't look so good. And the Hamster Dance does not fit into your goal in that is uses a non-commercial motor, which you certainly don't want to do in an apartment. So continually using it as an example just drives home the point that it seems unlikely commercial motors can meet your challenge.

In reality, you hit the answer in post #10, a ballon launched rocket. It's been done before and exactly as you state, if you start from 60,000 feet everything is a lot easier on the airframe. So it's possible a cardboard and plywood rocket could do it given that head start.

Good luck and keep us posted.


Tony
 

AlexBruccoleri

Well-Known Member
Joined
May 12, 2021
Messages
203
Reaction score
82
I don't mean to discourage you, only to provide what I feel are real-world obstacles to your challenge.

I admire your dedication to your challenge. But you'll note that you state in the first post your goal is to 'punch it' once through the lower atmosphere, yet in the second post once you do a sim your second and third stages are an L400 and a K250, which is the exact opposite of punching it. So already you've learned that your initial guesstimate on how to achieve your goal is probably incorrect. And I guarantee once you put some real world weights and 1/2" fins behind those sims, the numbers won't look so good. And the Hamster Dance does not fit into your goal in that is uses a non-commercial motor, which you certainly don't want to do in an apartment. So continually using it as an example just drives home the point that it seems unlikely commercial motors can meet your challenge.

In reality, you hit the answer in post #10, a ballon launched rocket. It's been done before and exactly as you state, if you start from 60,000 feet everything is a lot easier on the airframe. So it's possible a cardboard and plywood rocket could do it given that head start.

Good luck and keep us posted.


Tony
Okay it depends what you mean by punch it. I consider a K250 in a lightweight rocket punching it. An L1000 works well too, and certainly higher thrust is fine if the second stage can clear most of the atmosphere. Also my initial guestimate is right in line with the sims. "The rockets would likely need to be staged and the velocity low in the thicker parts of the atmosphere.", but that is not important. I agree a real-world rocket will not perform like this sim, but keep in mind a four stage (or air start) rocket is what I was thinking. If all the parts worked, such a rocket would reach extreme velocity in thin air and easily exceed 100k. I keep bringing up Gary's Hamster dance rocket because of how efficient it was. Yes no commercial motors match his thrust profile, but a collection of motors can in a relative sense.

Anyway the point John Derimiggio brought up about guidance is very valid. This rocket will turn badly as it hits the upper-air winds. A guidance system takes this to a whole new level of hard.

I should back up now and get to my original point. I think more can be done with LOC Precision style components than most think can be done. I also suspect higher speeds are possible than what I initially thought. It is a a fun space to explore.

Perhaps the takeaway from this discussion to anyone reading is optimism. You do not need a professional-grade machine shop or advanced composite shop to build some very capable rockets. Though a word of caution. Staging and air starts require lots of care to be safe, especially with big motors.

Finally I have no interests in trying this challenge myself. My challenges are much more down to earth such as convincing my wife a porta potty "isn't that bad" at a launch. All of my current projects are aimed at the fields/waivers I have access to, which are modest, but still great fun.
 
Top