Airship lifeboats, design alternatives

Question

At sea lifeboats are a pretty straightforward affair, a small seaworthy boat that one uses to get away from a doomed vessel. In space the same basic principles apply although the requirements are far more strenuous. In between, in the air, things are conceptually a bit more difficult, I think. In space gravity is generally not trying to kill you and while at sea it is water goes some way to mitigating the effect admittedly while introducing problems of its own.

The question I want to pose is this: if the mode of lift, be it magic or otherwise, being used by an airship is too big, too complex, or too expensive to be used for the ship's life-rafts and the terrain being traversed is too rough and inhospitable for individual parachutes, (specifically I'm thinking either dense forest like this or "bladed" Karst like this) how can you get people safely from an airship in flight to the ground in an emergency?

The Forest and Karst environments are just the more extreme examples of places you don't want to parachute into, the more different landings a solution can make the better. For the purposes of scale etc... use the Hindenburg as your guide. Lifeboats need to be small and light enough that a reasonable number can be on board without compromising flight capability. Lifeboats cannot have powered flight or be lighter-than-air but anything else you can think of goes.

Obviously, passengers need to Survive the landing. Some ability to choose a landing point will help but is not required.

Whoever edited this before thank you but no, you added complexity and confusion to a difficult problem.

Answer 1

The safest place is still aboard your airship.

Unlike seagoing vessels, airships do not traverse a medium that is potentially deadly for humans. When a ship sinks, people need to still be able to float in water. Water is cold, wet and obstructs your respiratory passages if you breath it in. To stay safe in water you need to either swim or be on a floating surface. Even if you had unlimited air-supply, getting deeper in water means higher pressure and will eventually kill you. None of these things apply to air. The only danger of air is being high-up, which means we need a way to get down more or less safely.

An airship that breaks will still come down - And down is where you want to go. The only danger is the airship going down too fast, and even that can be mitigated without getting out of the airship.

In order to keep people alive, have a padded room either central to the superstructure or on top of it (depending on your ability to keep the ship level in case of sudden descent). For additional safety, pack people tight and layer with padded materials. People might get badly bruised - but that's it.

If you feel this is not secure enough you could additionally eject this chamber on impact, getting it away from the crash-site.

The case of hydrogen: Should the airship be using a highly volatile/combustible means of lift, such as hydrogen, your best bet is to insulate the chamber with asbestos or any other effective fire-retardant available. You could even shield it with water tanks used for ballast or drinking water to additionally keep the heat at bay. But in any case, a ship designed to fly with such a high fire-hazard would be designed around it, maybe trading cargo-capacity for additional means of fire-proofing, or adding mechanisms to 'shear-off' a burning section.

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This answer is designed around the assumption of airships being mostly Hindenburg-y and any alternative mode of lift is mostly along the line of providing a higher percentage of lift over the helium employed in the planning of the Hindenburg.

Answer 2

Gliders.

It requires either a (better than current) ai or a competent pilot to land on an unprepared field, but having more horizontal freedom can be helpful in less than ideal locations like you mention.

They are also generally heavier than parachutes, so on an airship you'd balance how much you want everyone to live with how much extra cargo you could carry.

But the thing about airships is you might not save that many people by preparing to disembark in the air during an emergency. In the Hindenburg disaster people walked (ran) away when it got close to the ground. It burned rather than exploded so the lift was continually reduced making the crash much more survivable than if say the wings fell off a plane at similar height. Most people who died burned with nowhere to run, so even if they had viable escape craft somewhere it wouldn't have helped.

Answer 3

A large parachute or set of parachutes with a survival capsule attached is probably a reasonable good bet in most circumstances. Some rudimentary parachute guidance cables could be provided to help an on board crew member avoid some obstacles such as a sideways approach to a vertical cliff edge. If couches and basic shock absorbers were provided under each couch a substantial fall would still be survivable in many cases.

Sea landings would be OK If the capsule was watertight.

The black forest scenario should be fine as the parachutes would tangle in the trees and the capsule would protect the occupants from hitting the branches.

The karst landscape would be challenging but would also probably be survivable in many cases (but not all) as the parachute would snag it the rocks / vegetation or they would land in a gully or the crewmember could avoid the worst rock faces. Even if the parachute tore it would probably provide considerable resistance in the process and the shock absorption system would help a lot with small drops especially into vegetation.

Landing in Polar Regions or arid deserts would also be survivable as they would have some protection from the elements. An explosive release of the parachute cables would be useful in some cases such as these to prevent being blown around after landing.

I assume that rescue craft would be sent promptly and a distress beacon/flares would be carried.

Answer 4

The maker's of the movie, Mission to Mars, came up with a creative solution, but even they didn't claim that it would work very well. To get down to the surface of Mars (which is somewhat comparable to your airborne lifeboat scenario) they built a rugged capsule and then surrounded it with tough airbags to cushion its fall. Unfortunately, in the movie, the airbags did not survive the initial impact and that impact happened to be on the top of a mountain. When the capsule, with its slightly flattened airbags, subsequently rolled of the edge of that mountain top, then second plummet overwhelmed the capsule's design which lead to the death of one of the crew.

Answer 5

Have each ‘Lifeboat’ essentially be a shallow metal cone with straps and multiple parachutes around the edge. In an emergency multiple people strap in, the disk drops (with small parachutes to maintain alignment) away from the ship then the main chutes deploy. With any luck the lifeboat will be moving slowly enough by the time it hits your terrain that it will deflect the worst of the impacts, leaving your airmen mostly intact.

Some (but not much) control can be exerted by manipulating the chutes, but the main point of this design is to shield your airmen from dangerous terrain (a tree branch through the spine often offends) and then provide further options. If snarled in trees, it’s easier to climb around inside and could have stowed rope ladders for safe egress, if a water landing then floats can be deployed, and the lifeboat can have space for potentially lifesaving supplies.

Answer 6

I will second the suggestion of gliders proposed by @not store bought dirt, with some additional details and reasoning.

Gliders that only need to work for a short time in an emergency can be lighter and more basic than a modern sport or leisure glider, won't need hardware for towing, and won't necessarily even require landing gear (more on that later). Many leisure gliders are single or two-seater configurations, but there is no reason you couldn't make one that could seat a dozen or more at a time, since it only has to carry the passengers away from the doomed airship for a (reasonably) short distance.

Storage space is a problem on an airship, and gliders obviously need large wings to work effectively, so you would probably need some way of folding or otherwise stowing the wings in a collapsed state and deploying them after launch, but if your civilization is advanced enough (technically or magically) to make airships, this shouldn't be too much trouble.

The flight time/range is going to depend on the number of passengers and amount of cargo the glider needs to carry, the properties of the atmosphere, how high up the craft is when launched, how large you make the wings, and whether the pilot (an AI, passenger, or sophisticated enchantment) can harness thermals and wind to recover energy.

Lastly, landing is the bugaboo. As mentioned by @not store bought dirt, landing a glider conventionally on an unprepared surface is dangerous and will likely destroy the craft. But it's important to remember that we're talking about one-use emergency vehicles here -who cares if the glider gets smashed up as long as the passengers survive? Equipping the glider with a small parachute in the rear which can be deployed just prior to landing to kill speed and soften impact wouldn't add much weight or complexity but would drastically improve survivability. Such things already exist in some modern private planes. A long, stiff but hollow nose would provide a crumple zone to absorb the remaining force of impact. It probably wouldn't be pleasant, but it would be survivable.

One last note. Your airship is going down. If you're still aboard when it crashes, you will most likely be killed -either by the impact, being crushed by the airship structure as it collapses, burning, etc. No emergency escape system will work perfectly in all scenarios, but something is better than nothing!

Answer 7

Use one of These two layer inflatable Hamster Balls plus a parachute.

Your airship lifeboats need to address 2 problems. Deceleration and rough terrain. A Parachute will take care of the deceleration part to some extent, but your people trying to get safely away may not know how to land and can be severely injured even on good terrain. That is where an inflatable hamster ball comes in.

It doesn't exactly have to be like the one I linked to, but the concept is the same. The ball can be inflated by a relatively small tank of compressed air. The person jumps into the already inflated ball and is pushed out of the airship. The parachute deploys. The parachute slows the whole thing down to a point where the impact of the ball on the ground is not too harsh and is spread out over a substantial surface area. The parachute also maintains the alignment of the object in the air.

On bad terrain, the tough materials of the outer ball will protect the people inside even on a very bad landing, falling through branches, hitting sharp rocks and so on. Even if the outer ball bursts a large amount of the impact should be absorbed to the extent that the person inside will only suffer from minor injuries.

In addition, these kinds of balls will serve as flotation devices. They can be made out of high visibility materials to aid search and rescue efforts. You could reinforce the outer sphere with lightweight ribbing material. It would increase the overall strength of the structure without sacrificing too much in the way of space on the airship. You could further use the material and ribbing for a shelter on the ground.

It isn't absolutely perfect, and would only hold a few people per unit, but it's better than nothing.

Answer 8

Since magic is in this system:

How about a magical potion/orb/stone that when smashed into the ground instantly form a jelly like substance around the user (dispersing the deceleration across the whole body) creating a cushion that then dissipates in 10-30(breath deep) secs.

Kind of like a magical ODST concept, which it could also be used for.

But practically

no real world parallel is going to be fool proof in a forest. Parachuting is currently the best real world method here but as you mentioned, it's not without risk.

Edit out the magic

Ok so a capsule with a long nose, when the nose impacts the ground, a compound lining the nose and walls of the capsule is provided an electric shock causing it to rapidly react with the air enveloping the passenger in a foam that cushions their descent. 1 sec after reaction, a catalyst is released above the passenger as part of the top compartment that then dissolves the foam.

This method has been theorized many times before. The reason it hasn't YET come to fruition is the chemistry and engineering is incredibly complicated when the cheap and easy solution of a parachute works just fine.

-add more science-

instead of a nose, a large pad (increase surface area to increase drag to slow descent). on the down ward face of the pad have a distance measuring sensor(probably an array of lasers) and a turret that will shoot a canister of the compound at the ground when a target distance has been reach, of course the capsule still dissolves into more foam.

perhaps some fins or a parachute to stabilize the capsule (keeping going straight downward and not flipping).

Answer 9

The decent can be controlled horizontally by using either a ram-air parachute or some type of inflatable air-foil wing. This would allow the escapees to choose the safest landing place. It takes some skill to operate so it would be best if they had some type of computer control to make them easier for untrained passengers to point-and-shoot their target.

Even with horizontal control, it is likely that there won't be an ideal landing place within range. The escape pod would need some sort of landing protection such as an airbag system or even just a solid floor.

Larger pods are probably better that smaller ones because they are more weight-efficient and they give you a lift raft or shelter after you land. You can save weight by reusing some of the structural elements. What is a passenger seating area in normal operation can break off to be an escape pod in an emergency (eg this concept).

Answer 10

Simplest most basic glider would be a Rogallo Wing. In the early 1960's that was going to be the system used for capsules, esp. the Gemini. In it's most basic form it is simply three poles joined at one end, a crossbar & fabric. NASA used inflatable rods, which meant the entire thing could collapse into a smallish parachute like package for storage in an external compartment of a space capsule.

Answer 11

First, is your airship going straight down, at free falling speeds?

If it is free falling we have to solve that problem first.

1. Deploy a parachute for the plane (as someone else suggested)
2. Fill one or more helium/hydrogen balloons
3. Both

You also need to deploy parachute(s) behind you to slow your vertical speed.

Hopefully this has slowed your decent to a gentle rate.

At this point you either need control of the rudder so you can point the plane at a reasonable safe, or safer than the other options available to you.

Now I don't know how much steel cable weights, but you could probably have several 1000ft or greater spools on the airship.

Maybe something like this or a bit thicker.

http://www.fehr.com/all-steel-cable/5-16-x-5000-ft-7x19-galvanized-aircraft-cable-2g9312-05000

The cable above is 5000ft and claims its weight is only 173lbs/mft and the minimum breaking weight is 9,800lbs.

Each passenger would put on a vest similar to a life preserver, but would have a mechanical breaking device that would attach to the cable so they could control their decent rate. So attach your self to the cable and start sliding down.

The weight of 5 or more people should keep the line from bucking too much.

Another thing you can do is use the end of the steel cable to lasso an object and basically zip line down to it, much more practical with a blimp than plane.

Tying a weight onto the cable to use as an anchor, to help stop your plane the best possible location.

Your example uses a blimp as an example, for that case you could slide down the cable to the ground, and give you time to run away before the main body hits the ground. That way you would not be hit by the blimp or caught in an explosion after the blimp hits the ground.

If its an actual airplane, you may have too much forward momentum to land safety on the ground.

This would also be useful if the plane lands on a forest of tall trees. Some areas the trees are 100ft+ high, and these cables would get you safely to the ground.

If you landed on a tall cliff, they would also be great for the final decent to the actual ground.

Answer 12

just saw 1930 movie "Madam Satan" last night on TCM that had parachutes in long outboard tubes along the side of the air ship. Passengers were given a harness and hooked these on to the chute rope as they jumped. Dont know if this was just a Hollywwod prop or a real thing. Good idea tho. Movie was OK.

Answer 13

Parachutes are the best option. A commercial ship is required to have at least one parachute for each passenger by law, much like aircraft today are required to have at least one life-vest for each passenger.

How are they used? They can be either required to be worn throughout the flight or be spread out over the ship so they are easily accessible. Parachutes are compact, weight very little in relation to their performance. How to deploy one when exiting the airship if the person is inexperienced? Simple, altimeter or proximity sensor. This is all based on that the ship is at sufficient altitude for the parachutes to deploy.

The altimeter would be used in the sense that a person falls and when they reach a certain altitude, the parachute auto deploys. A proximity sensor would work similarly. There should be a sensor system on the ship and if the parachute is too far from any of the sensors (Translates sufficiently far outside the ship) the parachute deploys automatically.

Parachutes and be steered to land as normal. If over water, a simple inflatable life-vest can be attached to the parachute bag. This is too simple and easy to cook up. Especially since this is WorldBuilding. Add features and mechanics to your taste.

In OP's case of terrain, the Karst will be rough to land on but much softer with a parachute than with a glider that needs relatively a lot of speed to remain airborne. A parachute when flared and more or less land vertically and thus be able to set down softer. In dense forest, I'd rather get tangled in a tree and bruise myself badly than pilot a glider and crash straight into the canopy.

Answer 14

According to one on-line terminal velocity calculator, an 80 kg mass with a cross-sectional area of 81 m² (9 meters x 9 meters) and with a drag coefficient of 1 (which is what a person has, a smooth ball has 0.1 or would need ten times (10x) more area, although the relationship between area and terminal velocity isn't linear with the Coefficient of Drag) would have a terminal velocity of 8 mph.

Since I've survived several bike crashes with nothing more that some (fairly serious) abrasions at similar velocities, that's about the fastest I'd want to hit a random point on the ground.

Here's the problem with that: (9 x 9) is a huge area. We're basically talking about a parachute (opening after escape). I can see some inflatable suit which could protect from penetration injuries, but I can't imagine anyone willingly wearing such a awful thing for extended periods, nor can I imagine that in an emergency, anyone would have time to put something like that on.

You should consider the (blatantly obvious, to anyone over 40) idea that if something better than a parachute was feasible, we'd be using it. Seems to me kevlar body panels, and a helmet would be about optimum. The elephant in the room is that if they have time to evacuate, you have to explain (credibly) why they don't have time to crash land.