"Ram Air" Parachute w/slider recovery

The Rocketry Forum

Help Support The Rocketry Forum:

Event Horizon

Well-Known Member
Joined
Apr 17, 2019
Messages
156
Reaction score
58
Just theorizing here, and asking. Have you seen this technology utilized with rockets?

https://en.wikipedia.org/wiki/Slider_(parachuting)

Ram air parachutes (square for short) have been around for decades.

Imagine a canopy (what skydivers call their parachute) that would open slowly to lessen the shock cord stretch and resultant almost inevitable nose cone airframe collision when the shock cord retracts.

Imagine a square canopy, above the rocket, on it's return to Terra Firma, that you can steer with a radio control transmitter to make it land mostly where you want it to.
 

Nytrunner

Pop lugs, not drugs
Joined
Oct 15, 2016
Messages
6,392
Reaction score
1,819
Location
Huntsville AL
I'm positive I've seen someone offering 3 and 4 line chute sliders for rockets. maybe Skyangle?
 

Event Horizon

Well-Known Member
Joined
Apr 17, 2019
Messages
156
Reaction score
58
You guys certainly are informed.

Does any one here use them?

What are the results. Doe sit work ?
 

Steve Shannon

Well-Known Member
TRF Supporter
Joined
Jul 23, 2011
Messages
6,093
Reaction score
2,589
Location
Butte, Montana
I’ve never used one. I think a friend of mine tried the simplest form once. A solid metal ring slid up tight against the bottom of the chute is reputed to work by old rocketeers. I would try that before splurging on dedicated sliders like I linked from Giant Leap.
 
Joined
Mar 3, 2019
Messages
24
Reaction score
16
Just theorizing here, and asking. Have you seen this technology utilized with rockets?

https://en.wikipedia.org/wiki/Slider_(parachuting)

Ram air parachutes (square for short) have been around for decades.

Imagine a canopy (what skydivers call their parachute) that would open slowly to lessen the shock cord stretch and resultant almost inevitable nose cone airframe collision when the shock cord retracts.

Imagine a square canopy, above the rocket, on it's return to Terra Firma, that you can steer with a radio control transmitter to make it land mostly where you want it to.
Your post is two fold. First, sliders are used and available but are not really beneficial in hobby chutes to lower forces but are more suited to control lines and work out tangles and twist. The reason they are not really beneficial is that in order to restrict the canopy opening the slider would have to be a very large percentage of the canopy's cross section area. Most flyers in the rocket community are not deploying higher that 100-120fps. Rings only delay the canopy inflation until the lines are stretched. They really don't lower forces. There are much better ways to mitigate opening forces which include rubber bands, deployment bags, packing techniques, etc.

There are a few companies who have started in on guided recovery. The one who is furthest ahead is Apogee Components, but they are not using a square canopy. Rocketman made a comment about developing a paraglider canopy. And BAMA Recovery Systems has made some comments about a guided ram air parafoil. Hopefully within the next year there will be a commercially available system.
 

Arthur Brown

Member
Joined
May 10, 2019
Messages
6
Reaction score
0
There is a weight penalty with multi layer box shaped parafoil but they do fly nicely.
 

dhbarr

Amateur Professional
Joined
Jan 30, 2016
Messages
6,206
Reaction score
886
Hopefully in the next year there will be at least two competing designs :)
 

Handeman

Well-Known Member
TRF Supporter
Joined
Jan 18, 2009
Messages
7,580
Reaction score
191
Location
Stafford, VA
I built my 7 cell ram air chute to use with RC controls several years ago. The shock of opening was never the problem.

When jumpers use these chutes, they control their body position and thus how the chute deploys. It's packed flat in a pack on their back. In a rocket it's in a round shape so it deploys much differently and you don't have much control of the orientation at deployment. Getting a consistent deployment was something I was never able to achieve. It really didn't have anything to do with the speed of opening, it was all about tangles and interference with other rocket parts.
 

Event Horizon

Well-Known Member
Joined
Apr 17, 2019
Messages
156
Reaction score
58
Handeman,

Thanks for your input.

I think the reason the lines tangle is because unlike most skydivers, rockets tend to tumble a lot right after the ejection charge blows the nose cone off and the chute almost always deploys mid tumble. Then like you mentioned rocket parts can cause interaction between the chute, lines and themselves.

Just curious, did you give up on the concept then?

I haven't had a rocket parachute that the lines didn't tangle up. I was thinking the square chute with slider might help prevent tangling as well.
 

Handeman

Well-Known Member
TRF Supporter
Joined
Jan 18, 2009
Messages
7,580
Reaction score
191
Location
Stafford, VA
Handeman,

Thanks for your input.

I think the reason the lines tangle is because unlike most skydivers, rockets tend to tumble a lot right after the ejection charge blows the nose cone off and the chute almost always deploys mid tumble. Then like you mentioned rocket parts can cause interaction between the chute, lines and themselves.

Just curious, did you give up on the concept then?

I haven't had a rocket parachute that the lines didn't tangle up. I was thinking the square chute with slider might help prevent tangling as well.
I haven't given up on it. But it's been shelved for a while.
The original concept was to deploy the drogue at apogee per std. DD. Then allow the RC control to activate a deployment charge to deploy the ram air at whatever altitude you wanted. The thinking was that you could drop through strong upper winds and then deploy in low winds at lower altitudes and still steer the chute toward your desired landing spot.

The issue was always the deployment of the ram air. It usually tangled with the line attached to the nose cone.
The whole point was to deploy at higher altitudes then a normal DD and then fly the rocket back to the pads. Using a pilot chute and d-bag attached to the nose cone would have probably solved the deployment issue, but who wants to replace the nose cone, d-bag and pilot after every flight because they floated off. You couldn't attach them to the top of the ram air like a pilot a sky diver would use because the ram air is so much smaller than a man rated chute relative to the pilot chute that this pilot would adversely affect the forward flight characteristics of the ram air. The problem with a pilot is that a skydiver is falling well over 100 mph and doesn't need much pilot to pull the chute out. A rocket is falling much slower and needs a relatively larger pilot to do the same work. Between the larger pilot and the smaller ram air, leaving the pilot attached to the top of the ram air isn't something that will work.

This put me back to a line from the rocket to the nose cone and tangle issues when the ram air deployed.

Hopefully one of the smart folks working with this stuff today will come up with a fool prove deployment method and I can copy that.
 
Joined
Mar 3, 2019
Messages
24
Reaction score
16
I haven't given up on it. But it's been shelved for a while.
The original concept was to deploy the drogue at apogee per std. DD. Then allow the RC control to activate a deployment charge to deploy the ram air at whatever altitude you wanted. The thinking was that you could drop through strong upper winds and then deploy in low winds at lower altitudes and still steer the chute toward your desired landing spot.

The issue was always the deployment of the ram air. It usually tangled with the line attached to the nose cone.
The whole point was to deploy at higher altitudes then a normal DD and then fly the rocket back to the pads. Using a pilot chute and d-bag attached to the nose cone would have probably solved the deployment issue, but who wants to replace the nose cone, d-bag and pilot after every flight because they floated off. You couldn't attach them to the top of the ram air like a pilot a sky diver would use because the ram air is so much smaller than a man rated chute relative to the pilot chute that this pilot would adversely affect the forward flight characteristics of the ram air. The problem with a pilot is that a skydiver is falling well over 100 mph and doesn't need much pilot to pull the chute out. A rocket is falling much slower and needs a relatively larger pilot to do the same work. Between the larger pilot and the smaller ram air, leaving the pilot attached to the top of the ram air isn't something that will work.

This put me back to a line from the rocket to the nose cone and tangle issues when the ram air deployed.

Hopefully one of the smart folks working with this stuff today will come up with a fool prove deployment method and I can copy that.
A few quick thoughts. Deploying just after apogee is probably the optimal time since ram air parafoils need speed in order to align properly. The point of a pilot chute is to drag the main into clean air so we there it's increasing the riser length or increasing the bridle length or both should eliminate entanglement with the rocket. Use of a colapsable pilot chute allows to keep the pilot chute attached but does not change the airflow and drag is minimal. a lot of the issues you are addressing are relatively easy to overcome. The hardest part for commercial purposes is developing a system that is forgiving and works in a lot of different situations.
 

Handeman

Well-Known Member
TRF Supporter
Joined
Jan 18, 2009
Messages
7,580
Reaction score
191
Location
Stafford, VA
A few quick thoughts. Deploying just after apogee is probably the optimal time since ram air parafoils need speed in order to align properly. The point of a pilot chute is to drag the main into clean air so we there it's increasing the riser length or increasing the bridle length or both should eliminate entanglement with the rocket. Use of a colapsable pilot chute allows to keep the pilot chute attached but does not change the airflow and drag is minimal. a lot of the issues you are addressing are relatively easy to overcome. The hardest part for commercial purposes is developing a system that is forgiving and works in a lot of different situations.
I don't really want deployment right after apogee. I want it controlled by the RC at some point during the fall. There should be plenty of speed, but the direction the nose cone is pointing when it actually deploys is anyone's guess so entanglement with the line connecting the nosecone to the rocket is usually an issue.

How do you make a collapsible pilot? I had several ideas, but would like to hear the best way.
 
Joined
Mar 3, 2019
Messages
24
Reaction score
16
For a collapsible pilot chute, download the FAA parachute rigger manual for free. It is simply routing a kill line from the apex of the pilot to the connection point on the chute. This kill line can also be rigged to pull down the apex slightly in an inflated state which can provide up to 20% more drag.
 

Handeman

Well-Known Member
TRF Supporter
Joined
Jan 18, 2009
Messages
7,580
Reaction score
191
Location
Stafford, VA
For a collapsible pilot chute, download the FAA parachute rigger manual for free. It is simply routing a kill line from the apex of the pilot to the connection point on the chute. This kill line can also be rigged to pull down the apex slightly in an inflated state which can provide up to 20% more drag.
How does that kill line work? Is it something that can be automatic during the release or does someone have to operate it?
 

AfterBurners

Well-Known Member
Joined
May 8, 2012
Messages
7,307
Reaction score
273
Location
Dallas Texas
For a collapsible pilot chute, download the FAA parachute rigger manual for free. It is simply routing a kill line from the apex of the pilot to the connection point on the chute. This kill line can also be rigged to pull down the apex slightly in an inflated state which can provide up to 20% more drag.
Like an Iris chute from Fruity Chutes?
 
Joined
Mar 3, 2019
Messages
24
Reaction score
16
How does that kill line work? Is it something that can be automatic during the release or does someone have to operate it?
The kill line is automatic. right after the main is pulled out of the D-bag, the pilot inverts and collapses or kills itself. In the pictures you can see the pilot chute cocked or in a ready position and if I pull the kill line then the chute inverts. The kill line is anchored to the main and is slightly shorter than the bridle so the kill line bears all of the pilot's drag after the main leaves the bag and this forces the apex of the pilot down.
20190517_204753.jpg
20190517_204810.jpg
 

Handeman

Well-Known Member
TRF Supporter
Joined
Jan 18, 2009
Messages
7,580
Reaction score
191
Location
Stafford, VA
The kill line is automatic. right after the main is pulled out of the D-bag, the pilot inverts and collapses or kills itself. .... The kill line is anchored to the main and is slightly shorter than the bridle so the kill line bears all of the pilot's drag after the main leaves the bag and this forces the apex of the pilot down.
I'm thinking the bridle could be shorter and attached to the d-bag to pull the bag off the chute while the kill line is longer and feeds through the d-bag and attaches to the main. It would be long enough to ensure the bag is off the chute before it inverts the pilot. The inverted pilot and d-bag would then come down attached to the top of the ram air.

That could work well. I still need to figure out what to do with the nose cone and how to keep it's line from tangling or wrapping over the ram air.
 
Top