explosive approach to chute deployment

[Seldom Seen Slim]

Man o man, see what happens when I try to help?  No, I can't implant that little bit of tissue.  The control board I have lets me get rid of spambots and ban FR -- but not reconfigure your sweetheart.  Saltfever's right, though -- in the process of fixing some stuff on his registration -- he lost his posts.  Really.

[Tman]

Careful Tman. That one's totally legitimate, plus Saltfever's a really active participant on the forum. Read the whole thread.

Pete

Little on edge here, there has ben a concentrated effort by spammers in the last few days and we have been dealing with them on other boards. Miniscule post count at the time of his posting made me think that. Purely coincidence. I would rather call out spam and be wrong. Which I was on this count.

[Peter Jack]

Spammers hit this board pretty regularly too but between Slim and Stainless they disappear almost as quickly as they appear. Keep up the good work Guys.

Pete

[Jonny Hotnuts]

Thats where you have the main chute that failed to deploy but is open, and you deploy a reserve on top of it. Now some resistance is better than no resistance but at this point your going to create unwanted side forces.

It is my plan that the only reasons this emergency chute was deployed IF the split tail 'air brake' failed to open OR in the event of a tip over (potentially also disabling the split doors, not to mention they could not react fast enough) to prevent a pencil roll condition. If there was the condition that it was used would mean the primary chutes were not released. (*I guess you could if they both failed but not even considering that. Also the same principles of multiple chute release applies to all vehicles with multiple chutes).

I used the term 'burst panel' but that may be the wrong thing to call it. The panel would be 'soft spots' un obstructed with structural elements in the ends of the tail section that would allow the chute to blow though without opening.


-Clearly the cute itself is not a suitable projectile-


I was going to solve this by using an aluminum 'shell', capped on one end and would fit inside the main tube (the open end faces rearward and contains the packed chute). The charge would be behind the shell. The shell itself, containing the chute would entirely eject rearward and once out the chute would pull out of the shell, in similar fashion to the kids fable of tying a string to your tooth and attaching it to a door and slamming the door to painlessly removing a loose tooth.

~JH

[DocBeech]

I like the Idea but I recommend that you link the system to eject the main chutes when used. I also don't recommend this as an airborne device. You will have less impact if you allow the vehicle to reach the ground in a roll than if you open the chute in mid air and throw the vehicle into the ground violently.

Same concept as in parachuting. You "tuck and roll" when you hit the ground on a T7A parachute. This should only be used when you are very close to the ground.

[krusty]

How about stuffing the chute in an old 8" howitzer brass and cutting the charge at only 1 white bag    :-D (I think, been over 40 years since I had to calculate a fire mission). Sorry, I couldn't pass this up. I have nothing else to offer.      vic

[Saltfever]

(edit . . . ) The charge would be behind the shell. The shell itself, containing the chute would entirely eject rearward and once out the chute would pull out of the shell, ~JH

I assume you will contain the shell with the car? (e.g. your "tooth" example). I doubt tech will allow debris on the track even though deployment is to prevent an accident which might add even more debris.

Jonny, have you had experience with air-bag explosives? I think your idea is very interesting as a source of energy. There could be other applications but I have personal reservations only due to my inexperience with them. I would like to learn more.

[DocBeech]

I hope you paid attention in math and chemistry:

Inside the airbag is a gas generator containing a mixture of NaN3, KNO3, and SiO2. When the car undergoes a head-on collision, a series of three chemical reactions inside the gas generator produce gas (N2) to fill the airbag and convert NaN3, which is highly toxic (The maximum concentration of NaN3 allowed in the workplace is 0.2 mg/m3 air.), to harmless glass (Table 1). Sodium azide (NaN3) can decompose at 300oC to produce sodium metal (Na) and nitrogen gas (N2). The signal from the deceleration sensor ignites the gas-generator mixture by an electrical impulse, creating the high-temperature condition necessary for NaN3 to decompose. The nitrogen gas that is generated then fills the airbag. The purpose of the KNO3 and SiO2 is to remove the sodium metal (which is highly reactive and potentially explosive, as you recall from the Periodic Properties Experiment) by converting it to a harmless material. First, the sodium reacts with potassium nitrate (KNO3) to produce potassium oxide (K2O), sodium oxide (Na2O), and additional N2 gas. The N2 generated in this second reaction also fills the airbag, and the metal oxides react with silicon dioxide (SiO2) in a final reaction to produce silicate glass, which is harmless and stable. (First-period metal oxides, such as Na2O and K2O, are highly reactive, so it would be unsafe to allow them to be the end product of the airbag detonation.)


The airbag's acceleration (a) can be computed from the velocities and distance moved (d) by the following formula encountered in any basic physics text:
vf2 - vi2 = 2ad.

Substituting in the values above,

(89.4 m/s)2 - (0.00 m/s)2 = (2)(a)(0.300 m)
a = 1.33x104 m/s2.

The force exerted on an object is equal to the mass of the object times its acceleration (F = ma) ; therefore, we can find the force with which the gas molecules push a 2.50-kg airbag forward to inflate it so rapidly.  2.5 kg is a fairly heavy bag, but if you consider how much force the bag has to withstand (see Figure 5), it becomes apparent that a lightweight-fabric bag would not be strong enough.  Note:  In the calculation below, we are assuming that the airbag is supported in the back (i.e., all the expansion is forward), and that the mass of the airbag is all contained in the front face of the airbag.  

F = ma
F = (2.50 kg)(1.33x104 m/s2)
F = 3.33x104 kg·m/s2 = 3.33x104 N.

Pressure is defined as the force exerted by a gas per unit area (A) on the walls of the container (P = F/A), so the pressure (in Pascals) in the airbag immediately after inflation can easily be determined using the force calculated above and the area of the front face of the airbag (the part of the airbag that is pushed forward by this force).  Note:  The pressure calculated is gauge pressure.

The amount of gas needed to fill the airbag at this pressure is then computed by the ideal-gas law.  Note:  the pressure used in the ideal gas equation is absolute pressure.  Gauge pressure + atmospheric pressure = absolute pressure.

[Seldom Seen Slim]

Doc, you took the words right out of my mouth.

My experience with airbag detonators comes from when I was recycling metal (used oil filters) by taking the stuff to a local cupola furnace.  The main input to the furnace was defective airbag detonators and spent ones.  They'd be dumped into the top of the 50-foot tall thing -- looks like a fat chimney -- that was heated by natural gas at the bottom.  The metal would soften and melt, and in the meantime the detonators that weren't exploded would proceed to do so.  It made for a merry time when standing at the top of the thing -- "boom", "crump", "KA-pow!", and so on.  By the time the detonator was molten and reached the bottom, where it was drained into ingots -- the nasty stuff had been burned, detonated, and filtered through the baghouse.

Yes, the place was eventually shut down due to EPA/Dept. Environmental Quality violations.  No liability for me, though -- I was just a customer of the service.

Further deponent sayeth not.

[F104A]

In my lakester I use a kicker spring at the base of the canister that my parachute bag is stuffed into. I use a pilot chute to
begin the release of the parachute bag when the trap door opens. I've filmed the deployment action and it works very well.
On the NAE I use a Chevy steering wheel deployment canister, fired with a 12 vdc charge when I push the button. I also
open the trap door with a solinoid. There is a micro switch on the solinoid link that prevents the charge from going off before
the door is opened. I use a pilot chute to keep the bag oriented so the 150' riser line will deploy before the bag hits the end of the line and the bag strips off and allows the chute to stream out and open. I bundle the lines with rubber bands to keep things organized and in order. The parachute bag and line are all packed into one bag and the total weight is 30 lb. The charge will blow the bag about 30' in a static test. We've used that concept in most of our 30 test runs and it works very well. We've filmed the deployment with a high speed camera and are happy with the results. It works for us, it may not be something you would use but I'm happy with how it works on our car.

[Saltfever]

Very nice, DocBeech. There is more than gas laws involved and its nicely laid out which can help with other mechanisms.   

[kiwi belly tank]

So how did you plan to incorporate your "manual backup release" ?

[Jonny Hotnuts]

So how did you plan to incorporate your "manual backup release" ?

Kiwi, the ballistic chute would be deployed by inertia switch or manually by pushing a button and only used if the main chutes failed to open (and this could be a problem if the air brake doors did not extend, yet the vehicle remains upright).

The primary intent is to prevent a pencil roll condition but also could be used to slow the vehicle with minimal damage if all other slowing methods fail.

~JH

[F104A]

For a backup system, I use a completely redundant second parachute system. If the second one doesn't work, I look for
a brine pond.

[DocBeech]

Im not sure you could react fast enough for this to work. If you include the G forces involved in a failed parachute opening. It would need to be an automated system if you are trying to cut away a chute the only partially opened, or tangled. If this system is for the sole purpose of my main chute had no reaction at all, then you would be ok. But if your trying to prevent a roll from a tangled/partial opened chute then its a bad idea. You would need to have an incredible reaction time and strength if your chute opened funny and sent you into a side g pull.

Honestly I would only recommend this system as a reserve for a failed main. Not to prevent anything, or to try to counteract a chute that doesn't open properly.