I wonder if one of the large "G Series' hobby rocket engines would be enough to pull a pilot chute or even a very light canopy to full extension. Lots of things to go tragically wrong with that idea, but it would fill many Sundays with fun experimentation. It's nice to live in a place with a lot of wilderness . . .
NOT to encourage irresponsible experimentation or the misuse of hobby rocket engines. Just a back-of-the-envelope calculation:
Example parachute: Apco MD28UL: Weight 4.0 KG, max load 340 kg (750 lbs), 64m2 area. With a 750 lb load, Apco says the rate of descent is 6.3 m/s (21 fps, or 14mph). That's the same speed if you'd be at after a 7 foot fall--so good crush space under the butt will be important. (For comparison, the
Cirrus SR22 descends at 15-28 fps).
Example rocket motor: F67-4W: 61 N-s total impulse, 69 N avg thrust, 86 N (19 lb force) peak thrust, total thrust duration: 0.95 sec.
If one of these engines were lifting the entire 'chute pack at once, it would accelerate at about 3Gs and at the end of the the .95 sec burn time, the package would be 13 meters (42 feet) from the launch point (assuming a directly vertical launch). Now, in reality, our rocket won't be lifting everything at once. But there will also be the resistance of the unrolling canopy and lines and the air resistance of that nylon. If the rocket/slug drags the pilot chute up first and then the apex of the folded canopy, it seems quite possible that the rocket could get a pilot 'chute and maybe a good portion of the canopy out of the pack, away from the plane and well into the slipstream.
Since this is a "no-fail" project, using
two of these engines in parallel would help assure we got at least one timely ignition. If they
both ignited, we'd expect the acceleration to be 99 m/s2 (10g's). That's, again, assuming the whole parachute pack is lifted at once rather than spooling it out starting at the apex . If our rocket/"slug" drags our pilot chute+ lines, canopy, shroud lines, and bridle in trail and the whole thing totals 40 meters in length, they would be fully stretched out at 0.9 sec, just before the thrust ends (with the rocket "slug" traveling at 200 mph, in theory) . Again, air resistance, line drag, etc would slow things down in the real world.
The rocket engines come in a 2-pack for $35. The APCO MD28-UL lists for about $1100.
To get everything way from the plane a lot more rapidly, a larger rocket motor is needed. Engines with 5-10 times the thrust shown above are available.
To state the obvious: It would require a lot of work to actually develop a DIY setup that is reliable. Getting the canopy and lines out into the air is just one step in the process (e.g the APCO product has a max tested opening velocity of 90 mph. Anyone wanting more than that will have even more work to do--sliders, etc). Since a life depends on it, it's smarter to invest in a professionally engineered whole-plane parachute. There are a lot of scenarios where a botched 'chute deployment would give results far worse than an attempted landing.
