Get to space on less than $1000 of commercial reloads?

[Adrian A]

Active guidance could really open up the possibilities for multi-stage flight. For example, how high could a 54mm-54mm-38mm 3-stage rocket go?

I started with a 2-stage rocket I'm in the planning stages for, that has a Loki L1040 booster going to a Loki K627 38mm sustainer. This combination should be able to exceed 100,000 feet. I wonder what would happen if I add a a Loki M2050 booster underneath the stack and adjust some ignition times?



Yowzers! But what about aeroheating? Not really a problem:




The first stage only gets the stack to barely Mach 1. Not an aeroheating problem. The second stage gets it to Mach 2.5 at 17,000 feet. This is probably the stressing case for the fins, but also very survivable. The final stage ignites at about 70,000 feet, and even though it gets up to Mach 4.7, the drag force is only about 1/10 what it was on the second stage, because the density is so low.

The strategy on the active guidance would be to make an active-pointing coupler between the 2nd stage and the sustainer, and have small variable-exposure roll-control canards just behind the coupler. The system would be active during the first and second stage burns, and the sustainer pointing would be passive. The 2nd stage separation could be delayed to ensure that the sustainer is vertical after going through the jet stream, but the drag penalty for doing that is pretty high. Without that delay, the following set of reloads could get a rocket to space, according to OpenRocket (I will try this configuration in RASAero also, but I haven't yet)

L2050: $455
L1040: $346
K627: $170

Total: $971

 

[Cameron Anderson]

I vote yes

 

[Loki Research]

I second this.

 

[A-ron]

Adrian:

Your strategy to use active guidance only on the second stage makes a lot of sense, but gimballing the sustainer for attitude control sounds like a risky design choice. Think about the amount of torque it will experience and what would happen if that system failed for any reason. Unless you can somehow get the CP of the sustainer behind the gimbal, its natural tendency will be to go off-center, taking the rest of the rocket with it.

I would either make the canards bigger and use them exclusively, or use hinged flaps integrated into the second stage's fins. It's much easier to make these "aerodynamically stable" in the event of a mechanical failure.

Keep calm and go beyond.

 

[Adrian A]

This flight is at best a couple of years away for me. There will be lots of testing of different control actuators in the meantime. See the other thread in this sub for the different actuator concepts I’m considering. But both this one and the other mid-body bending concept have a lot going for them if they can be made to work, with almost no drag and the ability to work both aerodynamically and in a vacuum.

But I agree that if aerodynamic torque overpowers the servos there’s no recovery. The servos and mechanisms have to be sized to prevent that from happening. Options using a lead screw would be effective at preventing that, but theres a trade with response time that is another factor in stability.

 

[RGClark]

Active guidance could really open up the possibilities for multi-stage flight. For example, how high could a 54mm-54mm-38mm 3-stage rocket go?

I started with a 2-stage rocket I'm in the planning stages for, that has a Loki L1040 booster going to a Loki K627 38mm sustainer. This combination should be able to exceed 100,000 feet. I wonder what would happen if I add a a Loki M2050 booster underneath the stack and adjust some ignition times?

View attachment 549215

Yowzers! But what about aeroheating? Not really a problem:

View attachment 549207
View attachment 549208

The first stage only gets the stack to barely Mach 1. Not an aeroheating problem. The second stage gets it to Mach 2.5 at 17,000 feet. This is probably the stressing case for the fins, but also very survivable. The final stage ignites at about 70,000 feet, and even though it gets up to Mach 4.7, the drag force is only about 1/10 what it was on the second stage, because the density is so low.

The strategy on the active guidance would be to make an active-pointing coupler between the 2nd stage and the sustainer, and have small variable-exposure roll-control canards just behind the coupler. The system would be active during the first and second stage burns, and the sustainer pointing would be passive. The 2nd stage separation could be delayed to ensure that the sustainer is vertical after going through the jet stream, but the drag penalty for doing that is pretty high. Without that delay, the following set of reloads could get a rocket to space, according to OpenRocket (I will try this configuration in RASAero also, but I haven't yet)

L2050: $455
L1040: $346
K627: $170

Total: $971

Von Karman line with off-the-shelf motors. Cool! The biggest probem though might be the high altitude ignition, which has given even experienced amateurs difficulty.

Bob Clark

 

[RGClark]

Could you post the OpenRocket sim so we can confirm this altitude?

About the active guidance, amateur Joe Bernard was able to do engine gimbaling on a rocket:



This would not need spin-stabilization. But this is at relatively slow speed. I imagine it would be a more difficult proposition at supersonic and hypersonic speeds.

Another possibility would be to do spin stabilization but have a stable platform that would not spin through which you can use control jets that would direct the rocket. Joe Bernard was able to demonstrate the stable platform idea with a camera platform on a rocket:



The issue with spin-stabilization while doing active guidance, is, with either gimbaled engines, control jets, or vanes in the exhaust, the rocket is spinning so rapidly it's hard to only direct the rocket in one direction only. For instance with gimbaled engines you could only tilt it for a tiny fraction of a second before the spin would make the rocket veer towards the wrong direction.

Member Jim Jarvis has approached this from rather the opposite direction. He has attached a "spin can" to which the fins are attached. Here the spin can and the fins would rotate but the rest of the rocket body would be still. This would have the advantage that all the methods of active guidance, engine gimbaling, exhaust vanes, control jets, could now be used.

Bob Clark

 

[Loki Research]

Better order those motors soon or you'll have to re-title the thread. Just sayin.

 

[Walter Longburn]

Better order those motors soon or you'll have to re-title the thread. Just sayin.

Is there a way to order motors that aren't in stock? I've been wanting to get a K627 for some time but it seems like it's always out of stock.

 

[wclaybaugh2]

(I will try this configuration in RASAero also, but I haven't yet)

Adrian:

I have given up on trying to model high velocity flights on the current (v. 15.03) version of Open Rocket (I'm open to trying the new version after it is out of beta).

I have found OR to significantly overestimate the forward movement of Cp with velocity. That in turn leads to oversized fins and much higher drag then actually required for the mission.

Checking this design on RAS Aero might get you a much higher--and likely much more accurate--result with smaller fins.

Bill

 

[Adrian A]

Could you post the OpenRocket sim so we can confirm this altitude?

About the active guidance, amateur Joe Bernard was able to do engine gimbaling on a rocket:

Yes but that wasn't a minimum diameter rocket. The idea I'm going to follow up on once I release the Blue Raven is to split the rocket into two pieces and gimbal the whole airframe. Use a spherical bearing on the centerline to take all the motor thrust and then either 2 ball linkages or 2 lead screws to control the alignment of the 2 parts of the rocket in pitch/yaw. Plus a variable-exposure roll control tab.

The issue with spin-stabilization while doing active guidance, is, with either gimbaled engines, control jets, or vanes in the exhaust, the rocket is spinning so rapidly it's hard to only direct the rocket in one direction only. For instance with gimbaled engines you could only tilt it for a tiny fraction of a second before the spin would make the rocket veer towards the wrong direction.

Agreed. That's why I'm going to work on zero out roll first, and then pitch and yaw control will have a chance to work.

Member Jim Jarvis has approached this from rather the opposite direction. He has attached a "spin can" to which the fins are attached. Here the spin can and the fins would rotate but the rest of the rocket body would be still. This would have the advantage that all the methods of active guidance, engine gimbaling, exhaust vanes, control jets, could now be used.

Yes, Jim has done great work over a number of years that has turned out very successfully. My goal is to get similar performance in a smaller package and with less drag. Not sure if it will be possible, but it will be fun and interesting to try.

 

[Adrian A]

Adrian:

I have given up on trying to model high velocity flights on the current (v. 15.03) version of Open Rocket (I'm open to trying the new version after it is out of beta).

I have found OR to significantly overestimate the forward movement of Cp with velocity. That in turn leads to oversized fins and much higher drag then actually required for the mission.

Checking this design on RAS Aero might get you a much higher--and likely much more accurate--result with smaller fins.

Bill

Yes, RASAero is my go-to for the final work in simulation. I have been pleased that OR has converged toward the RASAero solutions a lot over the last few years.

 

[Adrian A]

Better order those motors soon or you'll have to re-title the thread. Just sayin.

Get the L1040 back in stock and I'll take you up on that.

 

[wclaybaugh2]

Yes, RASAero is my go-to for the final work in simulation. I have been pleased that OR has converged toward the RASAero solutions a lot over the last few years.

Adrian:

A couple decades ago I took a bunch of the sounding rocket folks at Wallops out for drinks and quizzed them about “rules of thumb”…

They offered a couple:

Although they regularly do it, they strongly recommend against rockets with a length to (maximum) diameter greater than twenty. They said the weight of the interstages gets to be a very significant fraction of total weight as one makes the stack longer and has to deal with bending under acceleration and wind loading.

They also said that in addition to averaging thrust and aero asymmetry another important reason for spinning a sounding rocket was to maintain control under thrust above 75k feet where aero forces start becoming too weak to keep the pointy end forward. (I have designed my two stage to burnout below 75k feet.)

Lastly, they observed that when buying rockets, a big purchase is way lower cost per unit because of setup costs. I have directly confirmed this: one 9” nozzle of typical “amateur” design costs about $2200 but two cost about $1800 each and three drop to about $1650. This means that using the same stage twice in a multi-stage sounding rocket is much lower cost than two different stages.

As a side benefit it turns out that two identical stages, stacked, can use the same fins so long as those allow the upper stage to keep the canonical two caliber stability.

When I have modeled three stages, I have always used identical stages for the first two because of the much lower cost.

Bill

 

[RGClark]

Yes, RASAero is my go-to for the final work in simulation. I have been pleased that OR has converged toward the RASAero solutions a lot over the last few years.

By the way, I noticed even for rockets going supersonic and hypersonic OpenRocket has this odd quirk in that it will give higher altitude for short, squat nozzles, compared to long, pointed ones. See if you can get a higher altitude from OpenRocket using a short ogive nozzle.

Bob Clark

 

[Adrian A]

Adrian:

A couple decades ago I took a bunch of the sounding rocket folks at Wallops out for drinks and quizzed them about “rules of thumb”…

They offered a couple:

Although they regularly do it, they strongly recommend against rockets with a length to (maximum) diameter greater than twenty. They said the weight of the interstages gets to be a very significant fraction of total weight as one makes the stack longer and has to deal with bending under acceleration and wind loading.

They also said that in addition to averaging thrust and aero asymmetry another important reason for spinning a sounding rocket was to maintain control under thrust above 75k feet where aero forces start becoming too weak to keep the pointy end forward. (I have designed my two stage to burnout below 75k feet.)

I'm playing with the idea of actively controlling the pitch/yaw of the 2nd/3rd stage coupling to keep the rocket going straight whenever it has either thrust or airspeed. Doing this would require nulled roll, which I would be able to do with a separate variable-exposure roll canard up until the air gets too thin. I'm not sure how much roll disturbance there would be above that point.

Lastly, they observed that when buying rockets, a big purchase is way lower cost per unit because of setup costs. I have directly confirmed this: one 9” nozzle of typical “amateur” design costs about $2200 but two cost about $1800 each and three drop to about $1650. This means that using the same stage twice in a multi-stage sounding rocket is much lower cost than two different stages.

As a side benefit it turns out that two identical stages, stacked, can use the same fins so long as those allow the upper stage to keep the canonical two caliber stability.

When I have modeled three stages, I have always used identical stages for the first two because of the much lower cost.

Bill

Yes, an M to M to K would have more margin for getting to the VK line, but it would add to the concern about length and aeroheating on the second stage. And be over the clickbait $1000 reload cost.

 

[wclaybaugh2]

And be over the clickbait $1000 reload cost.

Adrian:

A fair point....

Bill

 

[SDramstad]

Has anyone tried to mount one of these in a rocket? https://www.gyroscope.com/d.asp?product=SUPER2

Mounted in the nosecone could it help keep the rocket straight? Also if you need nose weight for stability it couldnt hurt.

 

[Adrian A]

Has anyone tried to mount one of these in a rocket? https://www.gyroscope.com/d.asp?product=SUPER2

Mounted in the nosecone could it help keep the rocket straight? Also if you need nose weight for stability it couldnt hurt.

Spacecraft use reaction wheels. They are usually not the most mass-efficient actuators, but they are needed for pointing precisely enough for space telescopes (e.g. spy satellites). To get the incredible speed needed for orbit, all mass hurts, even in the nosecone.