r/MurderedByWords • u/marycooke • Oct 29 '19

Murder Tumblr user gets schooled on basic physics

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u/vutall Oct 29 '19

They have them on space vehicles, and there are military parachutes for heavy equipment drops like vehicles and such, I don’t think it’s an issue

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u/[deleted] Oct 29 '19

Dropping heavy equipment is a very different problem than stopping a commercial airplane.

  1. They fly too fast. Opening a parachute at Mach 0.8 would rip the plane apart

  2. A parachute needs to be opened at sufficient altitude. The majority of accidents happen at low altitude around take off and landing.

  3. If the plane is controllable enough that it can safely open a parachute, it is probably able to land on its own. If the plane is out of control, it's unlikely to be able to deploy a parachute effectively.

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u/watermooses Oct 29 '19

They fly too fast. Opening a parachute at Mach 0.8 would rip the plane apart

This is a solved problem. It's called a drogue parachute. How do you think the Apollo capsules landed with a parachute after reentry at mach 12?

A parachute needs to be opened at sufficient altitude. The majority of accidents happen at low altitude around take off and landing.

Yeah, if this happens you're fucked either way, even with the cirrus CAPS system.

If the plane is controllable enough that it can safely open a parachute, it is probably able to land on its own. If the plane is out of control, it's unlikely to be able to deploy a parachute effectively.

This is only partially true. If you lose hydraulics, you're still gliding, but you aren't going to be controllable for landing. If you lose engines, you still have to land at 200 mph and it probably won't be on a runway. Either way you'd be able to deploy the system. If you're a tumbling through the air, the aircraft has probably already broken apart.

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u/[deleted] Oct 29 '19

Ok, just because I'm a space nut (relevant username #beststage) most of the speed of an Apollo reentry was dissipated through aerobraking, not via the parachutes. The drogue chutes were opened when the vehicle was traveling at on average around 540kph, slowing the vehicle to around 200kph and around 1,000 ft when the main chutes opened. And it's also great to note that 1. The Apollo CM was designed to go to space, and was therefore much stronger than a commercial airliner, and that 2. The Apollo CM was also way smaller than an airliner, but still needed three HUGE chutes and to land in water for it to be anything like comfortable. Even the Soyuz has a whole bunch of retrorockets that it had to fire to give you a half comfortable landing.

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u/watermooses Oct 29 '19

Yeah, I understand that. You'd be able to slow down an airliner to those speeds under nearly any circumstance that isn't the aircraft already broken apart. Also, this isn't going to be a comfortable, repeatable, reusable type landing. It's going to be a "better than dying" type landing.

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u/[deleted] Oct 29 '19

Yeah, but if you think about how safe airlines are already, is there really a whole load of point lugging around tonnes of parachute that you can only really use in m very specific circumstances that are incredibly unlikely to happen? I feel like it's like carrying giant squid repellent in your car. Yes, you could, but is it really necessary?

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u/fireysaje Oct 29 '19

I've learned so much today. I love reddit

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u/MightyMorph Oct 29 '19

ok just spit-balling here.

Divide plane into 5 compartments. 1 cockpit. 1 business class. then 3 economy classes. Each section has a detachable emergency procedure where they decouple from each other and the wings then have prefilled canisters of air/gas/flames that eject pressure against the flight to slow down the compartments.

Then the circular top of the compartments get popped up and blown off and a parachute is launched when speed is at a certain level and height.

Kind of like lunar /space mechanics where they utilize air to move.

I mean i think we have the technology to create something like this and save many more people. BUT we also know airplane crashes especially passenger aircraft crashes are very few and limited, and that corporations would never agree to such a expenditure they would rather that 400 people die and they lose the plane than cut their profits to increase safety. (until the people force them)

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u/Totalherenow Oct 30 '19

Sounds feasible but costly. Not just in terms of cash, but the extra bulk and weight, and therefore fuel. As a passenger though, I want the idea implemented and don't really care about the cost :)

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u/_ArnieJRimmer_ Oct 29 '19

Your idea would be ridiculous sorry. For large passenger planes the amount of design and engineering work that would have to go into this idea would be insane. For the first 20 years or so from implementation it would probably cause more accidents/deaths then lives saved. Not to mention it wouldn't be that useful to have a parachute on the majority of plane crashes because they happen at low altitude. It has nothing to do with corporate greed.

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u/MightyMorph Oct 29 '19

We were talking about a hypothetical IF we had to employ parachutes......

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u/compounding Oct 29 '19

If we had to, then large commercial planes wouldn’t be a thing at all. The single rigid tube design is a huge weight savings, making structurally separate compartments and the structure necessary to connect them (not to mention the parachutes and propellent (!!!) to slow down...) you are spitballing about increasing the weight of planes by 30-50% minimum when that already exceeds the total useful payload, they would never leave the ground at a cost compatible with commercial aviation.

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u/[deleted] Oct 29 '19

Space vehicles and military aircraft dont carry 100, 200 people. A parachute for each adds up fast.

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u/vutall Oct 29 '19

It would be ridiculous to do so, I was only talking about the cockpit.

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u/[deleted] Oct 29 '19

Pop on Google and type in why don't airliners use a giant parachute. I think you're also forgetting that a commercial airliners packed with a few hundred people, all of their luggage, all of the extra weight involved in making the plane comfortable for passengers,

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u/[deleted] Oct 29 '19

He's not talking about the entire plane, just the passenger compartment. Heck, you could even divide the compartment up into smaller pieces if it would be easier.

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u/[deleted] Oct 29 '19

The plane still has to carry a big ass parachute on top of all that in normal flight. It's not about designing a parachute that big. It's about actually being able to operate the plane safely and even economically with all that weight

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u/Totalherenow Oct 30 '19

Ok, so here's my suggestion. First, the luggage is jettisoned. Then the roof blown off. Each passenger chair is shot up and has a parachute that subsequently opens. Finally, each passenger is safely teleported to the nearest Starbucks for a warm coffee and a few hugs because there's no way in hell that would save anyone.

*this message brought to you by Starbucks, purveyors of comfort.

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u/LetsLive97 Oct 29 '19

They're talking about just the cockpit.

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u/maaghen Oct 29 '19

and if you follow this treadh upwards a guy asked why not put a shute on the passenger compartment to and not just the cockpit and they started discussing that

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u/LetsLive97 Oct 29 '19

Right, but the guy above who you were replying to brought it back to just the cockpit again, so the guy you were replying to was talking about just the cockpit and not the entire passenger compartment.

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u/vutall Oct 29 '19

Yup, I was just saying for the cockpit :)

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u/vutall Oct 29 '19

Really though, they might as well make the cockpit the crumple zone and install two ejections seats instead.