High speed reserve concept

[billvon 2,396]

Throwing this idea out:
Currently, freeflyers have a problem when selecting their gear. Few rigs are certified for operation above 150kts, and I don't know of any reserves that are. The problem is not the speed itself - any competent canopy manufacturer could design a reefing system on a reserve to withstand a 200kt deployment. The trick is to do that and still have a reserve that opens in time if you cut away at 800 feet, or if your cypres fires at that altitude during normal RW.
One way to do it is to reinforce it like crazy, so it withstands the greater opening shock. Many BASE canopies are built like this, to withstand even near-terminal sliderless deployment. The problem is, as a few BASE jumpers have discovered, is that it's no good to design a system that holds together if the deceleration kills you. In fact, as Bill Booth has pointed out, you sometimes _want_ part of the system to fail just before the deceleration force kills you, because being alive under a damaged canopy is better than being dead under an intact one. (He was talking about main risers, but I think the same idea applies.)
So here's my idea. I'll break inadvertent reserve deployments down into two types - cypres fires and plain old premature deployments.
First, the cypres fire scenario. The jumper is using a modified rig. The reserve is similar to a standard reserve, but designed such that, if the brakes are stowed, it opens normally. If the reserve is packed with the brakes unstowed, the deployment is a lot slower - slow enough to survive a 200kt deployment. (PD does a similar trick on some of their larger sabres to reduce opening shock.) The cypres has two sets of cutters. The first one or two cutters cut the loop on the reserve, same as most cypreses. The second two cutters cut the brake-stow loop on the reserves. The cutters themselves are mounted on the reserve risers.
If the cypres detects normal freefall (say, 78-160mph) it activates the reserve normally at 750 feet, and the reserve opens with the brakes stowed as always. If the cypres detects high speed freefall (say, 160 or higher) it activates the reserve at 1200 feet and simultaneously cuts the toggle stow loops on the reserve risers, freeing the brake lines to their "high speed opening" position. The canopy opens, the 1200 foot deployment altitude allowing more time to decelerate from the higher speed.
An alternative to this is to use two toggle stow loops, one the normal position and one the "high speed" position. The cutters would cut only the normal stow loop, leaving the "high speed" stow loop to set brake line length upon deployment.
Second scenario - high speed inadvertent deployment. This one is tougher, since it needs a new device in the cypres - an accelerometer. If the jumper is going faster than 160mph for more than a few seconds, a flag is set in the cypres. If the flag is set and the accelerometer detects a deceleration greater than 10G's, the cutters on the reserve toggle stow loops fire. This isn't as ideal since you essentially have to begin deployment _before_ the brakes are set to their slow deploy position. Another alternative is a simple light sensor on the cypres. If that high speed flag is set, and the cypres unit suddenly sees light (normally it's pretty dark in that reserve container) then it's likely that the reserve has begun deployment and the reserve toggle stow loops need to be cut. This will cut the loops before the reserve is out of the bag.
Anyway, my idea for the day.
-bill von

[quade 3]

Another idea that has been bouncing around is the concept of a Cypres fired drogue.
At some speed/altitude it would fire and put the skydiver belly to earth slowing the skydiver down enough for a "normal" Cypres reserve fire.
Obviously this isn't a perfect idea either since the drogue bridle could become entangled with the skydiver.
quade
http://futurecam.com

[freeflir29 0]

Good luck designing that and getting it to work..."It's the cans..they're defective. Stay away from the cans"-Steve Martin
Clay

[riggerrob 558]

Bill,
Your suggestion for a high speed reserve has merit, and it reminds me of two other options.
Your suggestion reminds me of some testing that was done at Naval Air Weapons Test Station China Lake, California during the early 1980s. This program - led by Manley Butler - proved that they could deploy a square parachute from an ejection seat at high sub-sonic speed and survive the opening. To moderate opening shock they used a sail slider plus two or three reefing ropes.
If you can't remember what a reefing rope looks like, dig your old 1970s vintage Strato Cloud out of your closet and examine the reefing rope strung around the tail, stabilizers and lower leading edge. The China Lake project used a series of explosive cutters - similar to Cypres cutters - to cut the reefing ropes at various air speeds to allow the canopy to spread gradually. You could probably develop a modern version with two or three modified Cypri. In the low speed scenario, all the Cypres cutters would fire when the pack opened. In a high speed scenario, the Cypri would fire in sequence, with a few seconds delay between each firing.
A much simpler option would be to complete the drogue research that Airtec started last year. Again you would have two Cypri: the first Cypres releases the drogue. After you have slowed to less than 150 KIAS, the second Cypres allows the reserve container to open.
George Galloway has been bragging for years that he could build a high speed reserve any time the FAA relaxes the 3 second requirement in the TSO.
The other alternative is to use multiple cutters. Unfortunately few skydivers are willing to pay for the extra cutters or haul around the extra bulk. Therein lies the dilemma.

[billvon 2,396]

>The China Lake project used a series of explosive cutters - similar to Cypres cutters - to cut the reefing ropes at various
>air speeds to allow the canopy to spread gradually. You could probably develop a modern version with two or three modified Cypri.
I thought about that, but the reliability issues with the additional reefing ropes, increased chance of tension knots and modification of reserve design seemed to be pretty formidable.
>In the low speed scenario, all the Cypres cutters would fire when the pack opened.
Hmm. I think the system absolutely has to fail safe, and in such a system, a dead cypres battery would give you a dangerously slow opening reserve.
>A much simpler option would be to complete the drogue research that Airtec started last year. Again you would have two Cypri:
>the first Cypres releases the drogue. After you have slowed to less than 150 KIAS, the second Cypres
>allows the reserve container to open.
How would that be accomplished? Would the drouge be detached after it slowed the jumper to a safe speed, or would the reserve have to open around it? Would it act as the reserve PC? Where would it be stowed? How would it be launched? Could the jumper launch it manually?
>The other alternative is to use multiple cutters. Unfortunately few skydivers are willing to pay for the extra cutters or haul
>around the extra bulk. Therein lies the dilemma.
I don't think the multiple cutters are the problem per se - having an additional cutter for the Racer reserve didn't seem to be a big deal. (Well, people complained, but skydivers complain about everything.)
-bill von

[nacmacfeegle 0]

I'm more interested in the "inherently safer" option of building a reserve to survive the high speed opening, and setting the Cypres higher. I appreciate it will take longer to deploy, but can't some proposal be made to the FAA to change their 3 seconds requirement? Surely the FAA have to re-assess their requirements to reflect the developments in our sport at some stage or another anyway.....
Or maybe I am off on the wrong track here, just 'thinking out of the box'.
Good thread though

• Quote

[DBTECH 0]

If one wants to put the money up, there is no question in my mind, that with 'today's technology,' a 'hydraulic reefing system' could be developed that would control a 'spider slider.' This system would guarantee a fairly flat 'dialed in' slider decent time, over a very wide range of deployment airspeeds.
Dave Brownell

[nacmacfeegle 0]

Hmmm, hydraulic reefing....reliability issues spring to mind.
I'm a big fan of the "keep it simple" philosophy.

[Engovatov 0]

Ice climbers (you know - the REAL crazies) face somewhat similar problem of limiting the shock on the ice protection. They use devices like Yates screamer (http://www.yatesgear.com/climbing/screamer/index.htm) that limit the maximum shock force transmitted to that little piece of metal in ice you life depends on.. though the experienced climbers, asked about how well it will hold just answer "you better do not fall".. but anyway..
Similar breakaway stitching can be put in between reserve risers and the harness. The one possible problem being that only one side may potentially activate, leaving you somewhat askew in the harness. Beats broken backbone for me, still..

[DBTECH 0]

'hydraulic reefing system'
I did say--'with today's Technology'
I'm aware of the 'working fluid' temperature/viscosity issues/problems, but I also believe there is an answer. Maybe the use of air as the working fluid?
I can envision a unit maybe-->Dia=2.5" X 4" long--mounted to the center rib's wide tape that runs from the bridle attachment point to the bottom skin. The slider control line would then pass through a grommet on the bottom skin. Ideally, the unit would self-retract the slider control line/slider just after landing--as apposed to having to wind the line back in to the unit manually, before packing, which we know for sure, skydivers would hate, big time.
As said--'is very possible with today's technology'
Dave Brownell

[DBTECH 0]

Just for the record-->
A constant change in velocity from 120 MPH to 0 MPH, over a distance of thirty feet, is 16 g's!
Dave Brownell

[Engovatov 0]

>Just for the record-->
>A constant change in velocity from 120 MPH to 0 MPH, >over a distance of thirty feet, is 16 g's!
>Dave Brownell
One can survive 16g's. You get killed by peak force, and also - at this level, human body can not be modeled as solid anymore - time of acceleration becomes very important.
Think of it - if you jump of a table - you get stopped with a fraction of an inch by the floor. If you just use the simplified math it would be 100's of g'ss

[tlshealy 0]

How about a bungee colapsble pocket on the slider? At normal or low speeds the slider would work normally but at high speeds the pockets would open up to increase pressure on the slider and slow the opening a little. When I was on the parachute team we used to dump at a full track from 12000 feet at 2000, never had a hard opening even at about 150kts. But I could do a hop and pop at 2000 and still open soft and quick. I realize our canopies back then were bigger and different than now, but I still think something can be done with slider size or design to make high speed openings better, without going to some complicated reefing system.( As I recall, people used used to chop ropes and rings a lot)
Thanks
Tad

[markbaur 0]

Is the Cypres TSO'd? Would it need to be if it were designed to alter deployment characteristics?
Mark