Steerable drogue chute?

[BABAR]

The problem isn’t just wind speed. With long burn rocket motors, there’s a larger component of the gravity deceleration vector turning the rocket’s flight to horizontal.

Even without high velocity altitude winds to carry the rocket downrange, a 200mph+ horizontal velocity at apogee with have already carried the rocket quite far by the time the drogue deploys.

Completely agree, you may NOT be able to get the rocket back to the pad.

I was concurring with the @Richard Dierking post 18 that if I had a choice of directional control of one portion of flight, drogue vs main, I think you’d get more bang for the buck with the drogue portion.

Not likely any such device is going to replace a good tracker/locator system for rockets with high altitude flight profiles, but it may make the drive at least a little bit shorter!

 

[Dan Griffing]

Completely agree, you may NOT be able to get the rocket back to the pad.

I was concurring with the @Richard Dierking post 18 that if I had a choice of directional control of one portion of flight, drogue vs main, I think you’d get more bang for the buck with the drogue portion.

Not likely any such device is going to replace a good tracker/locator system for rockets with high altitude flight profiles, but it may make the drive at least a little bit shorter!

Thanks!

That was my idea completely for asking this question at the start of the thread.

As a thought experiment, I’d venture that the outer limit is like a “steerable lawn dart“ that comes down really, really fast but can flare horizontally towards the launch site when close to the ground, stall to loose the last horizontal velocity, and then deploy the main chute. But this is only a thought experiment and not something that could seriously work, unless you were developing a space shuttle like vehicle with a NASA budget.

 

[BABAR]

Thanks!

That was my idea completely for asking this question at the start of the thread.

As a thought experiment, I’d venture that the outer limit is like a “steerable lawn dart“ that comes down really, really fast but can flare horizontally towards the launch site when close to the ground, stall to loose the last horizontal velocity, and then deploy the main chute. But this is only a thought experiment and not something that could seriously work, unless you were developing a space shuttle like vehicle with a NASA budget.

Hmmmm...... not sure why you need to stall the horizontal velocity. Unlikely the horizontal velocity of your controlled drogue is going to hold a candle to the downward vertical velocity. Even if you could only get 5% converted to horizontal (in the right direction, of course) you might significantly decrease your pad to touchdown distance.

Meanwhile, from the standpoint of dual deploy main chute deployment, I was thinking (perhaps wrongly) that the added horizontal vector would likely have a negligible impact on successful deployment of the main. Put another way, does it matter whether the rocket under drogue is falling straight down or slightly sideways when it activates main chute deployment? If not, why bother to attempt to “stall” the horizontal velocity? Will the net velocity vector amplitude be that much different compared with an uncontrolled drogue?

 

[BABAR]

FWIW, also agree that the importance of getting the rocket DOWN from Apogee to acceptable main deployment altitude as fast as possible (within tolerance of what the harness/cord/main chute can handle, of course) trumps importance of directional control. Even if you could get a 20 mph forward speed, you’re still potentially urinating into a 50 mph headwind, if you get my drift (sorry, it’s late.)

I imagined your theoretical directional drogue as NOT slowing the descent any more (or less) than a conventional drogue, simply using some of that humongous surplus of energy of the falling rocket to provide some directional control TOWARD a safe nearby recovery area.

 

[ksaves2]

Steerable drogue under GPS control is intriguing. I had a long necked converted Jerry Irving rocket that I added a coupler and extra body tube length just because I wanted to and make it dual deploy and long necked. Only a 29mm motor hole but could stuff ”H” and “I” motors up there. This stupid rocket when the drogue deployed would “glide” down to main chute deployment height. I kid you not! It would circle horizontally with the drogue deployed, butt end aft and the butt end of the rocket would rise up, stall out and continue the spiral descent In a near horizontal fashion! It would come down in a horizontal spiral which is one of the darnedest recoveries I’ve ever seen. It did it consistently too!

Until I screwed up the main charge and the main chute didn’t come out. Did a repair and the rocket doesn’t fly like it did before. Oh yeah, it comes down under drogue fine to main deployment, but no more entertaining spiral descents like it used to do! Had to do a coupler repair and I guess the weight screwed up the unique aerodynamics that allowed a “gliding” return under drogue.

The weird thing is the fins are quite small on this rocket but yet the chute and aerodynamics were such that it had a tendency to “glide” in a horizontal fashion under drogue. I couldn’t have planned that in a million years.
I wished I would have had video back then to prove it but alas I only had my eyes.

The rocket can still fly with a little maintenance to the ebay but albeit in a rather conventional fashion.

Kurt Savegnago

 

[Not Quite Nominal]

The problem with the steerable drogue seems to be body drag. Most rockets coming down in a proper "inverted V" configuration have half the drag coming from the rocket itself. This drag is uncontrolled, and the steerable drogue will not only have to steer into the wind, but also do so resisting the flailing/turning induced by the body parts.

If you make the drogue larger, you gain control but come down slower and be exposed to high level winds longer.

If you make the drogue smaller, your drogue is now a smaller fraction of the drag and you lose control authority.

I think the best solution would be to drop fast through the high level winds (minimizing exposure) and then deploy a steerable main at a higher than normal altitude.

Once the expected wind speed is below the glide speed of the main, deploy the main and let it fly back.

A further thought here is that the average descent speed of a separated rocket, drogue or drogueless, might not be high enough, and deploying speed brakes (probably not steerable) to allow a fast but stabilized and controlled tail-first descent is probably better than separating the rocket.

 

[Dan Griffing]

Hmmmm...... not sure why you need to stall the horizontal velocity.

In July I saw a high altitude launch (20,000 feet?) where the horizontal velocity component (reported by a Multitronix “Kate” telemetry system) was in excess of 200mph — similar to a rocket’s velocity when falling as a “lawn dart” from an altitude of 2,000 feet. The result of deploying a drogue chute at this velocity will destroy all but the strongest rockets and recovery systems. (The launch I saw was a very strong rocket and recovery system but the recovery system almost failed when a 3/8” SS Quick Link opened up and nearly straightened out.)

This is why “stalling the horizontal velocity“ can be very important, especially for high altitude launches with slow-burn motors.

While a rocket is under the boost phase, the downward vector component of gravity is an unavoidable force that (without vertical fin control) bends the trajectory towards the horizontal. This is in addition to, but compounding the effect of weather-vaning due to wind.

 

[VernK]

While a rocket is under the boost phase, the downward vector component of gravity is an unavoidable force that (without vertical fin control) bends the trajectory towards the horizontal.

I have heard this said before and it is usually referred to as a "long burn motor gravity turn". However, I have never understood why gravity would turn a rocket any more while under thrust than while just coasting after burnout. Is there really a difference? And if so, what causes it?

 

[BABAR]

In July I saw a high altitude launch (20,000 feet?) where the horizontal velocity component (reported by a Multitronix “Kate” telemetry system) was in excess of 200mph — similar to a rocket’s velocity when falling as a “lawn dart” from an altitude of 2,000 feet. The result of deploying a drogue chute at this velocity will destroy all but the strongest rockets and recovery systems. (The launch I saw was a very strong rocket and recovery system but the recovery system almost failed when a 3/8” SS Quick Link opened up and nearly straightened out.)

I think we are envisioning two completely different systems.

In the above you refer to “deploying a drogue” at a horizontal velocity “in excess of 200 mph.” So I guess you are talking about a PRE-drogue deployment steerable system. Such horizontal velocity is NOT imparted by the drogue which by your discussion hasn’t been deployed yet. I am not sure what the source of such a 200 mph non-vertical velocity would be, I am thinking weather cocking or wind, but it CANNOT be attributed to a drogue which has yet to be deployed.

Sounds like what you want is not a steerable drogue but a steerable (and STALLABLE) lawn dart.

I was envisioning a “hang glider” configured drogue, very small and very tough, that could survive deployment at standard apogee conditions (not sure ANYTHING is gonna survive at 200mph velocity in any direction, but then I am L-0.). At drogue deployment, the rocket itself should be unstable, so left to its own devices it will tumble but not lawn dart (HPR equivalent of LPR “nose blow” recovery, nonstable and slows BY ITS OWN DRAG, better than a lawn dart anyway), with the drogue contributing little if any to reducing descent rate, but if STEERABLE could nudge the rocket back toward launch site adjacent safe recovery area (not the pad or spectators or parking lot!). On descent, the rocket is dangling and bouncing around from the shock cord attached to the hang glider drogue, it the shock cord is long enough and has some elasticity, the Downward pull on the draggy flying drogue may not be CONSISTENT in net force, it’s gonna bounce a lot, but should be relatively consistently DOWN (gonna take a heck of an updraft to make it bounce UP, and likely the same draft would hit the drogue too.) So IF you can get the hang glider drogue safely deployed, oriented, and steerable (controlled by on board GPS or by first person video or by some sort of combination of GPS location and on board compass?), you should be able to favorable alter the ground track of the descent compared to a non-directional (dumb) drogue system.

The hang glider drogue’s job isn’t to stall the rocket or even slow it down any more than a “dumb” drogue (my Dad used to talk about smart bombs vs dumb bombs [no deviation in course control possible once released]).

It is merely to

1) slow the rocket to an acceptable main deployment system velocity between apogee and main chute deployment altitude (same thing as a dumb drogue)

but also 2) steer the rocket closer to desired landing site rather than leave it at the mercy of the actual apogee site (which may NOT be straight up from the launch site as intended/hoped) and the prevailing winds.

But I agree it ain’t gonna fix your 200 mph horizontal predeployment scenario.

 

[Dan Griffing]

I have heard this said before and it is usually referred to as a "long burn motor gravity turn". However, I have never understood why gravity would turn a rocket any more while under thrust than while just coasting after burnout. Is there really a difference? And if so, what causes it?

First, gravity always act on a rocket’s center of gravity to pull it downward, even after motor burnout.

But second, during the boost phase, the total acceleration vector of the rocket is the vector sum of the rocket motor thrust acceleration vector, plus the downward gravity acceleration vector. The only time this doesn’t cause the rocket’s flight path to curve towards the horizontal is if its going straight up, which is quite rare.

As long as the rocket’s motor is putting out thrust, once the flight path starts to curve, it will curve even more and the horizontal component of velocity will increase.

After motor burnout there’s no thrust acceleration component summing with gravity to accelerate the rocket partially in a horizontal direction. Short burn motors don’t have this effect working on the rocket for as long a time so it isn’t as much of a problem.

Most of the vector mathematics that cover this are in an undergraduate level physics course, at least they were in the 70s when I took them.

 

[Dan Griffing]

In the above you refer to “deploying a drogue” at a horizontal velocity “in excess of 200 mph.” So I guess you are talking about a PRE-drogue deployment steerable system. Such horizontal velocity is NOT imparted by the drogue which by your discussion hasn’t been deployed yet. I am not sure what the source of such a 200 mph non-vertical velocity would be, I am thinking weather cocking or wind, but it CANNOT be attributed to a drogue which has yet to be deployed.

I was not referring to a pre-drogue deployment of a steerable system.

I was referring to an actual launch that I saw in July, but didn’t want to reveal the details ahead of those associated with the launch who had posted the information elsewhere.

I calculated the horizontal velocity from the information provided by a “Kate” narrated video that was posted elsewhere. There were also posted pictures of the 3/8” SS Quick Link that had come apart when the drogue chute deployed at apogee when the horizontal velocity was over 200mph and nearly caused a recovery failure.

The horizontal velocity component was not caused by the drogue. It was the result of a long-burn motor on a high altitude, near sonic launch that resulted in a gravity turn.

 

[Dan Griffing]

I was not referring to a pre-drogue deployment of a steerable system.

I was referring to an actual launch that I saw in July, but didn’t want to reveal the details ahead of those associated with the launch who had posted the information elsewhere.

I calculated the horizontal velocity from the information provided by a “Kate” narrated video that was posted elsewhere. There were also posted pictures of the 3/8” SS Quick Link that had come apart when the drogue chute deployed at apogee when the horizontal velocity was over 200mph and nearly caused a recovery failure.

The horizontal velocity component was not caused by the drogue. It was the result of a long-burn motor on a high altitude, near sonic launch that resulted in a gravity turn.

Here’s an update from my post. I found a July 11 Tripoli Rocketry Association Facebook group posting by it’s moderator, Steve Shannon.

I had mistakenly thought that I had calculated the horizontal velocity from Kate data as over 200mph, but the velocity was only 175mph, and it was in Steve’s post. My apologies for my misstatement.

“Not a rant or an announcement (for a change).
This is from our launch today. Here’s an example of what can happen to a quick-link when a rocket picks up a little horizontal velocity and then deploys. This quick link was screwed closed. Amazingly, the shock cord didn’t pull loose. The rocket came down together with the shock cord snagged on this broken quick link. I suggested that he buy a lottery ticket.

Additional information:
The horizontal velocity was 257 FPS (175 mph).
Vertical velocity was 3 FPS.
His shock cord was 30 feet of Kevlar.
This was a moonburner in a four inch carbon fiber rocket, a Mongoose 98. A large fraction of the mass was motor. A video of the flight show it arcing over as it climbs. It flew to 22,000 feet and after motor burnout the rocket would have a significant distance between the Cg and Cp.

Another rocket with a similar flight profile had a very similar horizontal velocity, 225 FPS.

Whenever you see a rocket arching over you’re seeing an increase in horizontal airspeed. With a long burning motor that effect can be exaggerated because they may begin arcing over while still under power.

Edit 2: I’ve attached a picture of another of the same kind of quick-link:“

 

[VernK]

First, gravity always act on a rocket’s center of gravity to pull it downward, even after motor burnout.

But second, during the boost phase, the total acceleration vector of the rocket is the vector sum of the rocket motor thrust acceleration vector, plus the downward gravity acceleration vector. The only time this doesn’t cause the rocket’s flight path to curve towards the horizontal is if its going straight up, which is quite rare.

As long as the rocket’s motor is putting out thrust, once the flight path starts to curve, it will curve even more and the horizontal component of velocity will increase.

After motor burnout there’s no thrust acceleration component summing with gravity to accelerate the rocket partially in a horizontal direction. Short burn motors don’t have this effect working on the rocket for as long a time so it isn’t as much of a problem.

Most of the vector mathematics that cover this are in an undergraduate level physics course, at least they were in the 70s when I took them.

I agree that for a non-vertical flight, a long burn motor will go down range further than a short burn motor of the same thrust. Is that all we are talking about here? It is the "gravity turn" phase that has me confused because I don't think gravity is doing the turning. Gravity acts at the CG of a rocket. Therefore, it does not generate any torque around the CG and therefore it does not cause a rocket to rotate. This applies regardless of whether there is motor thrust or not.

Now on the other hand, the trajectory path can be affected by gravity but I still don't see how gravity alone would create a "continuous turning" of the trajectory path while a motor is burning. Here is a thought experiment. Assume we have a motor that will burn forever at exactly constant thrust. Assume the rocket is flying at a 45 degree angle with respect to the earth's surface. The motor's thrust is acting along the axis of the rocket but it can be decomposed into two vectors. One horizontal and one vertical. These two thrust vectors are equal since it is flying at a 45 degree angle. If there is no gravity, then everything just continues and the rocket travels in a straight line at 45 degrees forever. Now add gravity into the picture. Gravity is acting vertically downward so all it does is subtract an amount from the vertical vector component of motor thrust. Therefore, the net vertical vector is now some amount less than the horizontal vector. That means the trajectory is now going to be some amount less than 45 degrees. However, it will continue on forever in a straight line at the new angle. Gravity has been fully accounted for and does not cause the trajectory angle to continually become less and less vertical. To do that the vertical and horizontal thrust vectors would have to be continually changing and that is not the case here. They are in steady state even with gravity included.

If we now add drag into the picture, I still don't see how that changes anything since it is acting along the axis of flight. The flight angle should remain the same.

Once the motor burns out, there is no more upward or horizontal thrust from the motor. Gravity is acting downward and drag is acting along the line of flight. This creates the familiar ballistic trajectory we know so well.

All I know is, I seem to have talked myself into a corner and I can't get out. I still don't have a good intuitive understanding of what people mean by "gravity turn".

 

[Dan Griffing]

It is the "gravity turn" phase that has me confused because I don't think gravity is doing the turning. Gravity acts at the CG of a rocket. Therefore, it does not generate any torque around the CG and therefore it does not cause a rocket to rotate. This applies regardless of whether there is motor thrust or not.

The answer to your confusion is all in the physics which includes the mathematics of vector analysis and calculus.

The rocket’s overall acceleration vector can be calculated by the addition of the gravity and rocket‘s motor thrust acceleration vectors. The rocket’s overall acceleration vector then can be decomposed into perpendicular vertical and horizontal components.

If you start with the rocket being any amount of off-vertical, and solve the vector acceleration equations for the resulting rocket vertical and horizontal velocity components, a delta fraction of time later, you will see that the rocket’s direction of travel has increasingly tilted.

And furthermore, if you repeatedly solve these equations you will see the curving of the rocket’s flight path. What I’ve described here as the delta fraction of time approaches zero is called vector calculus, and it takes two years of college courses to cover, so I cannot provide more of an explanation of the gravity turning phenomenon than I already have.

 

[boatgeek]

Saying the same thing as Dan but translated from the engineer:
Where you analysis breaks down is the assumption that the rocket stays at 45 degrees elevation relative to the ground. Let's say that it started out at 45 degrees elevation. After a little while with gravity pulling on it, it will be 44 degrees elevation from the original launch site. That means the airflow isn't perfectly aligned with the rocket anymore, so it will turn so it's headed at 44 degrees as well. Then more time passes, the rocket is at 43 degrees elevation from the original launch site and the rocket has turned a little more, etc.

 

[kalsow]

boatgeek is right. The fins are working as expected. The rocket is turning to align itself with the air stream (AOA = 0).

 

[OverTheTop]

https://en.wikipedia.org/wiki/Gravity_turn

 

[PayLoad]

Studied a little physics & fluid dynamics when I was younger - Doesn't the fact that the rocket being steered back to earth weighs (relatively) nothing it is close to impossible for to steer a chute? (The chute would be steering the rocket just as much) 20lb+ rocket I can see, but I flay max 1 kg

 

[VernK]

boatgeek is right. The fins are working as expected. The rocket is turning to align itself with the air stream (AOA = 0).

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.

 

[jadebox]

Another slight diversion, but the discussion of gravity turning makes me wonder how difficult it would be to use guidance technology during the flight so that the rocket's position at apogee allows it descend back to a point near the launch site without guiding the 'chute. I guess the trick in doing that would be knowing what the wind speeds and directions are throughout the flight and descent paths.

 

[Dan Griffing]

Saying the same thing as Dan but translated from the engineer:
Where you analysis breaks down is the assumption that the rocket stays at 45 degrees elevation relative to the ground. Let's say that it started out at 45 degrees elevation. After a little while with gravity pulling on it, it will be 44 degrees elevation from the original launch site. That means the airflow isn't perfectly aligned with the rocket anymore, so it will turn so it's headed at 44 degrees as well. Then more time passes, the rocket is at 43 degrees elevation from the original launch site and the rocket has turned a little more, etc.

The gravity and motor thrust vector component don’t have anything directly to do with airflow, the fins or their angle of attack.

Instead its because when a rocket isn’t going straight up, the rocket’s motor thrust acceleration and the earth’s gravity deceleration vectors (think of “arrows” visually) aren’t completely aligned.

This means that for a rocket with a 5:1 thrust to weight ratio, the 1.0g gravity deceleration “arrow” is pulling the rocket a little in the direction of the existing tilt to increase it, and away from the direction of the rocket’s long axis where its 5.0g motor would be otherwise accelerating it.

The progression you describe is correct, but it would even happen on a planet without atmosphere to cause any airflow.

Instead think of the gravity “arrow” pulling the rocket slightly more towards the direction of increased tilt.

 

[Dan Griffing]

https://en.wikipedia.org/wiki/Gravity_turn

Thanks!

Never rely on an engineer to mess up and explanation when there’s Wikipedia to do it with hundreds of people!

 

[OverTheTop]

Never rely on an engineer to mess up and explanation when there’s Wikipedia to do it with hundreds of people!

I am an engineer too .

 

[Dan Griffing]

FWIW, also agree that the importance of getting the rocket DOWN from Apogee to acceptable main deployment altitude as fast as possible (within tolerance of what the harness/cord/main chute can handle, of course) trumps importance of directional control. Even if you could get a 20 mph forward speed, you’re still potentially urinating into a 50 mph headwind, if you get my drift (sorry, it’s late.)

I imagined your theoretical directional drogue as NOT slowing the descent any more (or less) than a conventional drogue, simply using some of that humongous surplus of energy of the falling rocket to provide some directional control TOWARD a safe nearby recovery area.

The context I was assuming for originally asking about a steerable drogue at the beginning of the thread — was to take care of the residual distance of up to three miles back to the launch site — after a steerable fin control system had already taken care of any horizontal component of velocity before the rocket reached apogee.

This residual distance was mostly due to wind. I agree that you want to come down to the main chute deployment altitude as fast as safely possible to prevent the wind from blowing you farther away. But the whole point of asking about a steerable drogue was whether this situation could be improved upon.

A possibly ideal solution — assuming the same context of an existing steerable fin control system — would be to use the same fin control system to aim for a predetermined upwind point of apogee before going totally vertical — so that the quickest safe path to the ground with a small un-steered drogue — would be close to the launch point.

 

[BABAR]

A possibly ideal solution — assuming the same context of an existing steerable fin control system — would be to use the same fin control system to aim for a predetermined upwind point of apogee before going totally vertical — so that the quickest safe path to the ground with a small un-steered drogue — would be close to the launch point.

Agreed, that would be ideal!

Challenges:

Requires for-knowledge of directions of winds aloft, which may be capricious and constantly changing, even during the duration of the flight! We low power guys try to do this sometimes by angling slightly into the wind, with mixed success. The usual failure mode for me is the rocket weathercocks, go horizontal, and apogee is waaaaay upwind.

I think @JimJarvis50 or @blackjack2564 (apologies in advance, I am not in this section of the forum much, but the thread caught my attention) has found that just trying to keep a high power rocket VERTICAL via
controlled fins is tricky enough!

Thanks for letting me participate in your thought experiment, I like looking for “outside the box” solutions!

 

[jadebox]

A possibly ideal solution — assuming the same context of an existing steerable fin control system — would be to use the same fin control system to aim for a predetermined upwind point of apogee before going totally vertical — so that the quickest safe path to the ground with a small un-steered drogue — would be close to the launch point.

That sounds familiar.

I don't know enough about how guidance systems work to know if they can determine how to counter the wind without knowing what the wind speeds and directions are in advance.

 

[Dan Griffing]

Challenges:

Requires for-knowledge of directions of winds aloft, which may be capricious and constantly changing, even during the duration of the flight!

Many launches don’t occur in isolation. Estimates of the overall effects of the winds aloft might be had from other launches just before. I’ve seen quite a few launches where the rockets launched to similar altitudes come down in a similar direction and distance from the launch site.

All that’s needed is an estimate to improve over having no adjustments at all.

Imagine having two nearly identical vertical fin control system rockets. Launch the first one and use the measured direction and distance where it lands as the offset for launching the second one.

 

[boatgeek]

Many launches don’t occur in isolation. Estimates of the overall effects of the winds aloft might be had from other launches just before. I’ve seen quite a few launches where the rockets launched to similar altitudes come down in a similar direction and distance from the launch site.

All that’s needed is an estimate to improve over having no adjustments at all.

Imagine having two nearly identical vertical fin control system rockets. Launch the first one and use the measured direction and distance where it lands as the offset for launching the second one.

Or launch something relatively small (say half the altitude you'll go to) and program that offset in. Just getting a "go X miles on bearing YYY" would knock down your recovery time quite a bit. With some experience, you could probably get a decent guess off of early launches.

 

[Dan Griffing]

Or launch something relatively small (say half the altitude you'll go to) and program that offset in. Just getting a "go X miles on bearing YYY" would knock down your recovery time quite a bit. With some experience, you could probably get a decent guess off of early launches.

I totally agree. Good idea. Something like an inexpensive “sounding” rocket like an Apogee Aspire but with streamer to emulate a drogue chute descent rate.

We don’t need to solve all of the problems to get something we can build on to learn from the actual experience of things we hadn’t considered beforehand.

 

[Richard Dierking]

Here's an example of both gravity turn and weather cocking. I launched a two stage M685W to K550W at XPRS (Black Rock) in 2018. I made a mistake and used a long burn (11.5 seconds) for the boost. Surface wind about 10 mph. Launched straight up, until it cleared the pad, then immediately was under the influence of the wind. The profile would have been much better with a higher average impulse motor for the boost.

And, the criteria of velocity and altitude was met for the 2nd stage to ignite - and it did.
The sustainer was traveling about 300 mph at 24 K' when the two 9" drogues from side bays were deployed. They held, but the shear pins for the main failed and the rocket drag separated. Got pretty ugly after that. At that point, the rocket was 4.1 miles downrange from the pad.

The nose with the GPS drifted back 6 miles and I calculated the high alt wind at about 75 mph from the profile and how far it landed from deployment. The descent track is just the nose/GPS with a 18" parachute.

After that, I began thinking about rocket designs that could help correct for these problems. Glad to have some good company.