I have a few questions, which I’d love folks to address after reading the OP:
Is what I describe plausible and practical?
If so, what would be the best form for it?
Is anyone currently working on–or even using–something like this?
What other cool uses could this technology be put to?
So I was reading a news story about a rescue operation in Pakistan where 8 people are trapped in a broken cable car 900 feet above the ground. I was thinking about how to solve it, and the Superman Catch came up.
You know: kid falls from great height (e.g., cable car), plummets screaming toward the ground. Five feet from impact, Superman swoops in from the side and catches them. They stare into his eyes, say, “You’re my hero!” and music swells.
My understanding is that the reality would be a little different: Superman would be covered in gore and left holding maybe a severed limb or a torso. A catch like this would be equivalent to falling 900 feet directly in the path of a freight train. Less Superman, more The Boys.
But could drones manage a modified version of this catch? Here’s what I’m imagining:
-Three or more decent-sized propeller-powered drones zoom under the falling victim. There’s a net loosely stretched between them.
-When the victim touches the net, the drones fall with the victim. But their propellers provide constant, safe deceleration.
-Eventually the victim reaches a safe descent speed, and rides in the net to a safe touchdown.
It might also be possible to use a single drone with, essentially, a big sack to catch the faller and a parachute attached to the sack.
So: would this work? Is it practical? What would the best approach be? Is anyone doing anything like it? What other contexts could this technology be useful in?
The math is easy enough. Get directly under the person, match their (accelerating) descent speed, then begin slowing that descent once they’re in the net. We know that someone who falls off a high place will reach terminal velocity in a couple hundred feet of fall. So that suggests we could safely slow them back down to zero fall rate in a similar distance. And by applying a higher decel rate = G loading, slow them in a lot less distance.
It will never be a practical rescue tool for e.g. somebody unexpectedly falling off a building or a cable car cable suddenly snapping. Because the time available from the start of the problem to impact is far too short to set up, much less execute, the response.
It could be a solution to folks trapped in a malfunctioning stuck cable car. Or atop a burning tall building. But we can do that now with a helicopter and a rescue hoist. And if for Rule of Cool we did want to recover people using some drones + net gizmo instead of a conventional helo then …
Instead of having them jump into space then maneuver to catch them in mid-freefall, it would work a lot better to simply have the drone-supported net sidle up next to wherever the people are stuck. Then folks could step off into the net rather like boarding a life raft from a sinking small boat. Then the net flies away with the passenger(s), takes them to safety, then returns for another load as needed.
Sounds a lot like a gizmo with almost zero practical application. But fun to play with.
That’s how Superman would catch people, at least after the first few failures. This was a factor in Spider-Man; Gwen Stacy died because Spidey’s webs didn’t have enough give and snapped her neck/back. In the latest Spider-Man move Andrew Garfield saved Tom Holland’s Mary Jane and took care to avoid the violent shock, thus showing he learned and redeemed himself from his previous failure.
In the case above, it would be much better if you piloted the drone net to the door of cable car and have the people step into the basket/net in a controlled manner. That would make it much easier to control. Trying to catch a falling body with a drone would be difficult.
I think it would work but the tolerances are very tight, particularly for a drop from a low height. The weight and velocity of the person versus the tension in the net and velocity of the drones. They either make a quick guesstimate and risk being a bit too forceful, or start with minimum force and find there isn’t enough time to readjust.
Plus we’re likely talking about a force greater than the lift power of the drones; they partially must descend, so it’s a somewhat uncontrolled situation.
Definitely doable but not as easy as some might imagine.
Drones are definitely going to be widely used for rescue very soon, possibly in a range of different form factors. The simplest might simply deliver a parachute.
Thanks for the answers–really interesting! It sounds like the cable car rescue is almost complete using other means, but when I wrote the OP, they were having trouble with helicopter rescue (I think the downdraft was dangerously pushing the cable car around, but they were able to lower a sling from a greater height).
The other two uses I was toying with:
Deliberate jumpers. There’s the classic image of firefighters at the bottom of a building that someone’s jumping from, to avoid fire or to commit suicide. Could this be used in such cases, or for bridge-jumpers, with greater safety than a net at the bottom?
Fun. Could this allow for skydiving without a parachute, just freeform jumping? Could there be aerial sports with midair trampolines or the like?
The problem here is that the rotors can interfere with a structure if they get too close. An initial fall might be important if the drones need to keep a distance from the structure.
I reckon it might be better to have the drones stretch the net open, then the moment the falling person hits, one of the drones fires a ballistic parachute attached to a drawstring around the perimeter of the net - the net encloses the falling person and the chute decelerates them to a survivable velocity.
There’s going to be a minimum height from which it would be viable, and if the victim is already falling before you scramble the drones, it’s probably too late.
BTW I think Superman can magically alter the inertia of things he touches - this applies not only to the last-moment catching of falling persons, but also things like grabbing a stalled jet plane by the nose and gently putting it down on the tarmac, still grasping it only by the nose.
There was an earlier thread where someone asked what the ideal material was to stop a fall safely. I noted that, realistically, it could be an iron block. If you could take melted iron, pump it full of air bubbles, and get it to form a sponge-like structure 100s or 1000s of times greater in volume with nanometer thick tissue between the air cells, the whole thing might crumple up on impact just perfectly to bring the falling person to a rest after any particular chosen rate of deceleration. You would need to do some engineering to figure out just the perfect level of sponginess but, in theory, there’s nothing to stop you from accomplishing the goal.
Likewise, here, you could get the drones to fall with the body. But, likewise, you could make the net stretchy or have them rush down from above to grab the limbs of the person with little hands, traveling at the same speed as him, and decelerate slowly…
The only thing that matters is the change in velocity. So long as it’s kept below a certain threshold at all times up to coming to rest, any method is just as good as another. It’s only a question of budget and practicality.
If the jumper is already at a dangerous speed before they reach the net, then the drones must decrease their speed. In order to do that, they must be capable of exerting a greater upward force than the jumper’s weight. And if they can do that, then they can just pick up the jumper at the start, without needing the net or jumping.
Alternately, if the maximum force the drones can exert is just a little less than the weight of the jumper, then they might still be able to save the jumper, but only if they make contact before the jumper reaches dangerous speed. And the sooner (i.e., slower), the better. So in this case you’d still want the “jumper” to just grab ahold of the drone at the start, rather than actually jumping.
If you really want rescue drones, then you could have long poles dangling underneath the drones, so that when the poles hit the ground, the net is supported by them, and the jumper is decelerated in the net, as the net stretches to the length of the poles. The value of the drones, in this case, would be in positioning the net in the right place to catch the jumper (which might be most practically achieved by making contact in midair, and then falling together the rest of the way).
Sharing a favorite Youtube channel, The SCIENCE! which deals with how Impulse, Impact, and Time variables make a difference in final conclusions. It should be set to start at the appropriate point in the video.
Long story short, the longer period you decelerate over, the less impact you feel, from the same starting impulse. I have no desire to do the math to determine how much (in the OP’s scenario) the drones could safely decelerate the target with the same 5ft distance to impact, but it all helps.
But it’s that same 5ft that’s going to bone you in most scenarios, you only have a comparatively tiny amount of distance to apply that reverse acceleration (which must be within a reasonably survivable magnitude) in order to save our target. Someone who loves them some math or has an AI account could probably have them do the math though.
An even simpler use of drones in a different sort of rescue would be flying to the general area of missing people and providing a cell phone receiver/repeater that allows lost hikers, etc., to get a cell signal.
I thought of this years ago before the introduction of easy, cheap, and capable drones. At that time I envisioned using balloons. So darn easy to temporarily provide cell access to massive dead zones. Is this now a thing?
In a handful of years, most people will have access to satellite service good enough for texting on an emergency basis. The drone idea is an interesting one, but it probably has too short a lifespan to be useful.
Dang it! Too late again! I should have jumped on this 20 years ago with the balloon idea but I figured surely someone else had already thought of such a simple and obvious idea.
Sure, if that’s safe. My thinking is for scenarios where a drone can’t directly access, or where the person is falling already (admittedly it’s difficult to imagine that there’d be time to move the drone into position in that scenario), or where the person is suicidal.
Or where it’s fun.
That’s interesting, but it raises another question. The weight of the poles would need to be carried all the time from launch until landing, whereas the weight of the person would only need to be supported for a few seconds. Under what circumstances is it more energy-efficient to use poles?
What you need is controlled deceleration and it can be by any means. At NASA’s Zero Gravity Facility the drop vehicles fall over 400 feet and reach 113 mph. We stopped them in 12 feet with a catch tank filled with expanded polystyrene beads. The G vs time curve was a fairly straight ramp up to 50 Gs in about 50 milliseconds and dropped back down as I recall. That’s too much for humans but the basic system can be tailored for the application.
According to my math, (?) you would hit terminal 100mph (150fps) in 351ft.
Math is v^2=2ad. If you want, say, d=10 feet to stop from 150fps, then a=1125fps/s or 35g
Seems high, but apparently football players hitting the ground experince transientg forces higher than that.
Whatever is used to stop the person needs some lateral consistency, otherwise - as Spiderman knows - the more dense less supported parts, like the head, may travel too far compared to the rest.
My math is not great–are you calculating catching the person with 10 feet to decelerate, i.e., 10’ from the ground?
If so, that’s not my intention in this (admittedly frivolous) hypothetical. Rather, the question is about catching someone falling from a great distance, with sufficient room to decelerate. I think my mention of Superman gore may have been confusing here, and I apologize. A different analogy might be how we sometimes play with babies: we throw them high in the air and then catch them. When we catch them, it’s not stiff-armed, because that’d result in a broken baby; instead, we catch them above our heads and then bring our arms and baby down in a decelerating, gentle cradle.
A more interesting question might be, what’s the minimum distance to catch someone falling in this manner (if they’re at terminal velocity, not just a tossed baby) such that the deceleration can be safe? I think it’d start by figuring out the maximum g-force that’d rarely result in injury.
Yes, that. As you can see, 10 feet is iffy from terminal velocity. So I guess the question is, how many G? Depends too whether it’s the elderly aunt or a hardy stuntman.
Also, not discussed - parachutes need time to fully open. A net suspended between multiple drones, unless moving downward to allow a slow catch, will cause the drones to be pulled together with the impact of something hitting the net between them.
Right–which is why I didn’t intend that in the question. What I intended to ask is, instead of catching someone 10’ from the ground and turning them into hamburger, what if you use this method instead? In my mind it was clear that the “instead” included catching them at a much higher altitude; my apologies if that wasn’t clear.
Ooh, that is a really good and obvious point that nevertheless I didn’t think of. Good catch, pardon the pun! Even with a descending catch as intended, there will be a powerful force pulling the drones together. A semirigid frame around the net could prevent that, but it would also add significant weight to the operation.