Steerable drogue chute?

[Alan15578]

Lots if intersting stuff in this thread, dead horse not with standing. For another approach, after apogee, point the nose down and start lining up on the target. Allow the speed to to build up until you approach Vne, then deploy the speed brakes. At the critcal time start a 12g pull out, or as much as you can bear, without hitting the ground. Regain some altitude and try looping until enough energy is bled off to to effect a mundane parachute landing.

 

[GrouchoDuke]

Dead horse...

I worked a little bit on a somewhat similar problem back in the 90s at NASA. It's definitely fun to chew on this stuff. Reading through some of the papers on it might be worth doing before buying stuff & writing code:

https://www.nasa.gov/centers/armstrong/news/FactSheets/FS-045-DFRC.html

 

[Dan Griffing]

Lots if intersting stuff in this thread, dead horse not with standing. For another approach, after apogee, point the nose down and start lining up on the target. Allow the speed to to build up until you approach Vne, then deploy the speed brakes. At the critcal time start a 12g pull out, or as much as you can bear, without hitting the ground. Regain some altitude and try looping until enough energy is bled off to to effect a mundane parachute landing.

RockSim says that some of my design configurations will have over 25Gs of motor acceleration with some more combinations.

While this isn’t the same as fin forces for a high G pull out, it does give a picture of the forces that a rocket might be subjected to.

 

[AZ_Ron]

I'd love to see someone attempt a SpaceX Starship recovery system on an HPR...
You'd only need a main chute, but would need two upper and two lower fins that could be folded
to keep the airframe roughly horizontal but steerable and using an onboard GPS to essentially have it glide back
to a predesignated spot at the launch site... pop the main at 1,000ft.

Then again, I can imagine someone could use this setup in a BAD way as well.

 

[Richard Dierking]

I haven't been following lately, but when the original thread began I started looking into a way for steerable recovery, at least for the nose.

I created a model based on the HL10 lifting body and had it scanned yesterday. The outboard fins are missing on the model. These fins fold in for packing in the aeroshell. The lifting body will be approximately 12" long and I'm starting to work on the stabilization and guidance system for recovery. It will glide back and deploy a parachute at about 500'.

I'm also working on the lifting rocket (image with aeroshell). The aeroshell is 7.5" diameter. This is made to be a sustainer. The booster is done and I need to make a 5.5" to 4" ISC. I estimate the whole project will take me a couple years to complete. So, at least one person has begun a project from this discussion.

 

[Not Quite Nominal]

What are you using to fly it home? It looks like many of the commercial autopilot solutions have relatively low accelerometer G limits and would suffer from gyro saturation.

 

[Richard Dierking]

I'm not quite ready to post the project. (And, I expect that I will need some help because I just don't have the complete skill set for something like this.). I'm doing the first 3D print today and it's a small one. I need to print using a water soluble filament, add structural components and fiberglass, then remove the printed material. That alone will be a complicated process.
I know that an Arduino-based control system is probably not going to work; I tried a couple. I need to develop a system that works with Spekrum. I would like to take over control if the lifting body is within visual range. I would like to flare before parachute deployment.
The next system I'm going to try is based on OpenPilot CC3D. But, this one is relatively old because these systems are developing rapidly. Mostly because of the quad copter market.
The objective of this project is to develop something that has cross-range capability and also some control over range.
The system will have elevators and a rudder (photo). Lift to drag at the correct angle of attack and high velocity will be airplane minimal at best. The thing is going to drop like a minimally controlled rock.

 

[AlexBruccoleri]

Okay, I think that helps. So with no gravity, the motor thrust will be acting exactly aligned with the long axis of the rocket and AOA will be zero. Therefore, no turning and a straight flight results. When gravity is applied there is a slight reduction to the vertical component of thrust and consequently the net trust is no longer exactly aligned with the long axis of the rocket. That causes a non-zero AOA. The fins then correct the AOA so that the long axis of the rocket is now flying at zero AOA but the net thrust is still not aligned with the long axis so the trend continues. This will cause it to pitch over into a more and more horizontal orientation. The longer the motor burns the more horizontal it gets. If it continues long enough, it will even pitch down. Eventually, when it is going straight down, the thrust and gravity vectors will both be exactly aligned to the long axis of the rocket. At that point it is flying at zero AOA so it will maintain that orientation from then on. Until impact.

If it was flying in a vacuum then there would be no gravity turn. It would just go in a straight line at a non-zero AOA.

I apologize for the diversion to this thread but I learned something today. Thanks.

I have been thinking about this and came across this thread. I believe VernK is correct that in a vacuum there would be no gravity turn. At least not without active guidance. Space-based gravity turns require some control to maintain a zero angle of attack. Hypothetically a rocket launched off a rail at an angle on the moon, would just fly at a slightly lower angle (due to the gravity vector summing with the thrust vector) for the entire burn without turning. The moon flight would maintain a positive angle of attack. Thoughts?