How fast have you landed?

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Hal8472

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I know there have been lots of discussion about how fast your rocket descent can be but I have found people don't go into enough detail on their rule of thumb. I would like to know more about how fast you can come down with specific details on ground conditions and construction design because I think there is a huge variation. Whether you are coming down with a cardboard construct on pavement or carbon fiber onto long grass, there is a huge difference. I am assuming we need to talk at least about Fiberglass, or Carbon Fiber. Cardboard landings are anywhere near epic.

So, please tell me your good and bad examples of landing but be specific on the conditions.

1. How fast (feet or meters per second)
2. Rocket construction. Body tube and fin material would be the most significant. But there will be situational specific issues. Such as the fin broke off, but was it through the wall with fillets or stuck to the body? Or if you didn't have any problems was it because you over reinforced the body? Why did it not break when you landed at high velocity?
3. Ground conditions. I have been to Death Valley and have respect for how solid desert sand can be. Fields of long grass are very forgiving with thick earth providing excellent impact absorbency (experience from a core sample landing). Bushes can be great to land in if you can get your rockets out later.
4. Would you do it again or was it a fluke? After seeing the results would you put a larger parachute on or did you keep the rocket as is.

I would like to know your limits. Granted there will be different limits for different types of fields. The fastest landing on the desert is just as exciting as the fastest landing in a snow bank.

Thanks
Andrew
 
I'd be willing to bet most people don't maintain that kind of data. :wink:

General rule of thumb is 15 fps (or 10.2 mph). Soft ground (e.g., plowed fields where it rains regularly) can buy you a little faster descent. Upswept fins can get you a little more. Fiberglass, even more. So with an FG rocket with upswept fins on a plowed field, you can probably get away with 30 fps (20.4 mph).

Balsa fins on playa, especially if they are downswept, might require closer to 5 fps.

It is always a give-and-take between landing speed and wind. If your rocket lands gently but drifts two miles away, that may be more challenging than a harder landing where you have a fix a fin afterwards.

BTW, I have seen so many LPR come in with the chute tangled or unejected, and they just lay in the grass undamaged. Why use a chute at all?
 
Yeah, too many variables.. I aim for 15-18 fps, but...

I use the stock chute in most cases. I build stock in most cases. I've never really "looked at" decent rates for finished & weighed models.

Most LPR rockets I have, I cut out a good sized spill hole, and no damage.

I had one of my favorite MPR rockets (Binder Stealth Jr.) fly numerous times, only to have a fin break on landing at LDRS.. So, different ground conditions or some weird fluke of a landing..

I've had rockets come in ballistic, and fly another day.

I've even witnessed an L1 cert attempt, and the flyer purposely failed the flight because the chute didn't fully deploy. The rocket had no damage what-so-ever, despite a no-chute landing. The LCO said he would allow it, as it did meet the 'flyable after the attempting flight' rule.. (WM Darkstar Jr. if you're curious)
 
vertical or horizontal speed? pretty sure that 'I' have been in an airliner (or 2) where they landed at 130 kts horizontal :). nother variable is, is the ground frozen?
Rex
 
I really like the idea of the L1 without a chute landing. And low power that happen to tumble nicely. My OpenRocket is much less forgiving. Nasty warning messages when my chutes deploy at high speed or for landings. It wants me to buy bigger parachutes.
 
I tend to over - build, which allows me to get away with landing a bit harder. I am comfortable in the 25'/s range. That is unless it's a shiny new paint job.

The hardest I have hit is in the 50'/s range. This was with a failed main but deployed drouge from 10,000' and landing on hard compacted dirt. She bounced good and I cringed watching, but she just had minor scratches upon inspection.

This was on a CF MD airframe with a single 3K 2x2 twill T2T. That rocket has flown 9 times since that flight, with the max velocity being M2.3 if memory serves me, could be 2.4.

Sent from my ONEPLUS A3000 using Rocketry Forum mobile app
 
I know there have been lots of discussion about how fast your rocket descent can be but I have found people don't go into enough detail on their rule of thumb.

Slower (15-20 fps) is better for rocket integrity, but also implies much longer walking distances to recover. Sometimes, absurdly so.
Thus dual-deployment, or JL CR, to open the larger chute closer to the ground (~300 feet), at which point the descent rate is reduced from >50 fps to <20 fps.

My data comes from JL Altemeter 3 recordings. I usually only make an effort to install it into mid-power and HP rockets.
Low power rockets fly on the kit provided chutes (or similar), with whatever descent rate they provide (my guess is ~15 fps).

- For mid-size fiber glass (FG) rockets (<1.5#), I've purposely flown on undersized parachutes to minimize recovery walks. Those things are nearly indestructible, so I'm landing them on farm and soccer fields at 30-50 fps without a scratch. The fastest descent recorded by Alt3 was 52 fps. Zero damage.
- For heavier, non FG-finned, and all HP rockets, I stick with 15-20 ftps.
- One time, my chute got tangled up on a 4.5#HP rocket, and failed to inflate, working as a streamer. Rocket landed at recorded 56 fps. One of the FG fins absorbed the bulk of the impact, earned a few paint scratches, and showed a 1" crack at the edge of the fin fillet. No other damage. I am not planning on repeating that.

HTH,
a
 
A few of mine that I can remember and have data. I wold prefer a slower descent than what I am getting but only to prolong the life of my rockets and because we have a few hardballs running through the launch site that wouldn't be good on my rockets coming in too fast.
Descent Data comes from Altimeter 3 on all but Tyrannosaur which is provided by an RRC3.

Rocket: Binder Design Tyrannosaur, paper/plywood
How Fast: 26 ft/s. Was going for around 20 ft/s. Stock chute wasn't big enough for the overbuilt rocket.
Field was a corn field that had been disked up and rained on a few times, still a little corn stubble.
1/4" plywood fins that don't extend below airframe. Plywood thrust plate. Internal fillets made from chopped fiberglass in US Composites epoxy
No damage

Rocket: Madcow 4" Cowabunga, paper/plywood
How Fast: 25 ft/s
Same field conditions.
Rear CR flush with aft end of air frame (helps prevent the damage to the aft end) Don't remember details on fillets, epoxy filled with something, probably baby powder
3 flights but one landed on a power line
All ground landings with no damage.

Rocket: Danger Close 2.6" fiberglass scratch build,
How Fast: 24 ft/s
Same field conditions
Aeropack retainer sticking out the back, fins don't extend past the aft end. Think I used talc baby powder on fillets. Foamed fin can
2 flights, no damage

And finally:
Rocket: Wildman Sport, fiberglass
How Fast: roughly 300 ft/s (using calculators) she came in ballistic and core sampled. Smashed up the Altimeter 3. That was the only damage, JLCR and RRC2+ survived. Good way to remove clearcoat from a nose cone BTW. Rocket experienced worse damage on a previous flight when the chute opened on the way up.
Same field conditions. Rocket buried about halfway up the body tube.
Built with five minute hobby store epoxy and foamed fin can. Some foam in the nose cone as well. No filler in the fillets, straight five minute epoxy.
Fluke, don't want to do that again. A sick feeling when you walk out to recover a lawn dart. I do have an E-tool now for just those types of recovery.

All but the lawn dart were perfectly acceptable recoveries, and the power line. The only one I have flown only once was the Tyrannosaur. I have a larger chute, a Rocketman, that is going in it to slow it down. It weighs 10 lbs and I don't want it to land that hard. The others are much lighter of course and the speeds are acceptable for now but I will likely up-size the chutes eventually just because I want them coming down slower.

I have seen two 4" paper birds come in under tangle mains or drogueless DD with the main not out. One BER, the other (I think) survived, I think I saw it fly again, but not positive.

BER = damaged Beyond Economical Repair

Mikey D
 
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Wow, those are some fast landings. Thank you guys. I do hear that sometimes there are lucky fluke landings however I am a little more confident about taking a chance with a strong rocket on good terrain.
 
I like the replies so far, "it depends" It really does. I've had rockets that hit on a tangle chute at 30 ft/sec or higher and had nothing but a few scratches. Then they landed under a full chute at less the 20 ft/sec but in a 15mph wind and the rocket was swinging just right at impact and it broke a couple fins.

Decent rate is a good ball park number, but you can break fins on a windy day with low decent rates and be fine with other landings with high decent rates. You can over build for all conditions and call it a static model. If you're really going to fly it, just go with something reasonable for the size and thrust.
 
I've even witnessed an L1 cert attempt, and the flyer purposely failed the flight because the chute didn't fully deploy. The rocket had no damage what-so-ever, despite a no-chute landing. The LCO said he would allow it, as it did meet the 'flyable after the attempting flight' rule.. (WM Darkstar Jr. if you're curious)

That should have failed certification. Both NAR and Tripoli require active recovery, recovery system to deploy, and a safe landing. In a no-chute landing its obvious that the recovery system failed. If you’re saying the flyer refused to allow it to be ruled successful, I commend that flyer.


Steve Shannon
 
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That should have failed certification. Both NAR and Tripoli require active recovery, recovery system to deploy, and a safe landing. In a no-chute landing its obvious that the recovery system failed. If you&#8217;re saying the flyer refused to allow it to be ruled successful, I commend that flyer.


Steve Shannon

I don't even know what this means: "purposely failed the flight because the chute didn't fully deploy." How is a failed chute deployment "purposeful?"
 
Right, am I being stupid here? You sustain a massive G-force hit when you land, not while you are falling.

You reckon correctly! If you've reached terminal velocity, you're falling at a constant rate, and your net acceleration is zero.

Sum the momentum -> m*v1-(int)F dt = m*v2
-(m) your mass is constant
-(v1) your terminal velocity is constant (assuming you Have reached terminal. Rockets may not by the time they reach the ground)
-(v2) your final velocity after impact is zero (assuming you don't bounce for simplicity [modulus of elasticity =zero])
-simplify the integral to force of impact (F)*time it takes to come to rest (t) (assumption: back of napkin calculations sufficient)
-(t) is probably much less than a second

Divide your momentum by how long it took to stop to find the force [(m*v1/t)=F], divide the force by your mass, and you have your acceleration upon impact or "G's". [F/m=a]
Simplified- > (v1/t)=a
 
Right, am I being stupid here? You sustain a massive G-force hit when you land, not while you are falling.

I am just saying that the concepts of velocity (kinetic energy) and momentum-impulse probably best describe the ground hit problem. G's of acceleration, while easy to compute, don't seem useful to me.
 
-(v1) your terminal velocity is constant (assuming you Have reached terminal. Rockets may not by the time they reach the ground)

They most certainly do, at least after deployment events. Look at any simulation or altimeter plot. Terminal velocity occurs very quickly after the drogue/drougueless/or parachute deploys. Only takes mere seconds to reach terminal.
 
They most certainly do, at least after deployment events. Look at any simulation or altimeter plot. Terminal velocity occurs very quickly after the drogue/drougueless/or parachute deploys. Only takes mere seconds to reach terminal.

Very true, in ideal recovery chains, they will reach terminal very quickly.

For some reason the off-nominal case of low-altitude apogee event failure was running through my head. ** descending whistle.......crunch**
 
BTW, I have seen so many LPR come in with the chute tangled or unejected, and they just lay in the grass undamaged. Why use a chute at all?

Because that is half the fun of LPR. The chute adds to the flight time (enjoyment). It also takes skill to play the wind and stick the landing without drifting into the trees. Straight up and straight down - that's too easy!
 
I enjoy questions like the one posed by the OP - and I like the discussions they generate... That's how we all learn stuff. :y:

I always try to design / size my recovery system with the goal of 15 -20 FPS at touchdown. Have I landed faster? - unfortunately yes, but not by design. :y:

Remember that the landing speed - not only has an effect on the rocket/fins/etc. - the landing speed also has an "impact" on whatever might be under the "falling object". :y:

People have been known to bring stuff like cars with breakable windshields, children, even babies to rocket launches... That's the reason why I can't recommend a recovery system designed for anything more than about 15-20 fps at touchdown. ;)

https://topflightrecoveryllc.homestead.com/descent_rates.html



[h=2][/h]
 
My fastest "landing"? 32ft/sec^2 (less aerodynamic drag). I've had a few two stage rockets come in ballistic. The rockets were write-offs.
 
Of course if we don't want to get technical about things, we could go with the Flat Earth Society's explanation of gravity:
"The theory of gravity is patently false. Things just fall."
 
I enjoy questions like the one posed by the OP - and I like the discussions they generate... That's how we all learn stuff. :y:

I always try to design / size my recovery system with the goal of 15 -20 FPS at touchdown. Have I landed faster? - unfortunately yes, but not by design. :y:

Remember that the landing speed - not only has an effect on the rocket/fins/etc. - the landing speed also has an "impact" on whatever might be under the "falling object". :y:

People have been known to bring stuff like cars with breakable windshields, children, even babies to rocket launches... That's the reason why I can't recommend a recovery system designed for anything more than about 15-20 fps at touchdown. ;)

https://topflightrecoveryllc.homestead.com/descent_rates.html



[h=2][/h]

"Out of the mouths of babes..." Spot on, Wild Child. :clap:
 
My rear eject rocket hits the ground about 25 ft/s and is cardboard. It lands on the tip of a AT nose cone, hopefully on dirt for some shock absorption. It's about a pound empty and uses an 18" six-line chute.
 
I've even witnessed an L1 cert attempt, and the flyer purposely failed the flight because the chute didn't fully deploy. The rocket had no damage what-so-ever, despite a no-chute landing. The LCO said he would allow it, as it did meet the 'flyable after the attempting flight' rule.. (WM Darkstar Jr. if you're curious)I don'

Yeah, I don't understand the first sentence either. If the flyer purposely did not have full chute deploy and said so for his L1 attempt, then I give him credit for at least adhering to the flight plan! Though I would be pretty pissed if it was coming in hot (60+ ft/s) and landed on my head or my car!
 
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