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Comment by oooyay | Hacker News Reader

Naive question: Planes and helicopters do not have the ability to safely eject passengers mid-flight. We largely accept these conditions as a risk of those modes of travel. Why is LES/LAS a unique requirement for space shuttles?

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> Planes and helicopters do not have the ability to safely eject passengers mid-flight. We largely accept these conditions as a risk of those modes of travel. Why is LES/LAS a unique requirement for space shuttles?

That's a fair point, although my understanding is that parachute systems for small planes are becoming more common.

My view is that flight rate is the fundamental issue at hand. Airplanes and helicoptors fly many orders of magnitude more than these capsules, which means we know they are many orders of magnitude more reliable.

They've also generally been through a long process of refinement - the original airplanes were extremely dangerous compared to modern variants.

Additionally, aircraft can afford to have a lot higher margin of safety baked in to them. Because of how high gravity is on Earth and the nature of the Rocket Equation[1], it's just not possible to have a lot of margin in rockets of capsules. They need to be extremely svelt to launch at all.

And lastly, we have experience with human spacecraft without an LES/LAS - it was the Space Shuttle. And it killed 14 people - easily the most dangerous spacecraft ever created. No one has any desire to build on that particular legacy.

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1. https://en.wikipedia.org/wiki/Tsiolkovsky_rocket_equation

Also worth noting that test pilots of experimental aircraft generally wear parachutes, at least for higher risk tests. This includes tests of commercial aircraft.

> which means we know they are many orders of magnitude more reliable

No, it means we have orders of magnitude more reliability data. Same result, different point.

We have enough data to know that rockets are not as reliable as airplanes.

1) Commercial planes and helicopters are orders of magnitude safer than space flight. https://usafacts.org/articles/is-flying-safer-than-driving/

2) Both planes and helicopters have an ability to glide (or autogyro) to a relatively safe landing in the event of most failures. A spacecraft can also do that with wings or parachutes, but only if it gets far away from its exploding booster fast enough to survive.

3) Many military planes do have the ability to safely eject passengers.

4) astronauts dying live on stream is a really bad look.

Planes and helicopters do not frequently fail by exploding, but rather things like engines failing. An engine failure, even if it’s the only engine in a given airplane or helicopter, does not automatically involve a deadly crash. Airplanes can glide, frequently for very long distances, and helicopters can use the air moving across the rotors to effectively “glide” down. It’s not always possible, but they do have inherent redundancies that rockets necessarily do not.

Planes and helicopters burn, though.

https://www.smithsonianmag.com/smithsonian-institution/freak...

Here's an attempt to develop a jet fuel that wouldn't burn:

https://www.youtube.com/watch?v=Y33N0raKZBo

Helicopters are actually even safer than fixed-wing airplanes this way: as long as the rotor system is working properly (i.e., it's just an engine failure), the pilot can autorotate and land on any nearby spot of clear land large enough for the helicopter, and can achieve a safe landing with no or minimal damage. In fact, helicopter pilots frequently practice this maneuver while in flight training.

Airplanes need some kind of runway, by contrast, and this isn't usually available within the glide distance. So they can "land", but it frequently won't be a pretty landing.

The main dangers with helicopter engine failures are 1) it happens too close to the ground, so there's no time to react and enter a safe autorotation, and 2) the pilot is too slow to react (low-inertia rotor systems are more dangerous this way, so helicopters like Robinsons are worse).

You could go without an LES if you can convince NASA that you have sufficient contingencies to not need it (and, of course, you can do almost anything you want on a private flight). SpaceX has been entertaining the idea of not using an escape system on Starship and instead proving its safety through sheer number of flights. Although there also is just a general consensus that the flip maneuver would probably make that necessary even if they had an LES.

Startship will not have an abort capability either.

Neither did the Shuttle, unfortunately.

Unlike the Shuttle there will be a lot more uncrewed testing of Starship, so hopefully it will be more reliable.

I think rockets in this design space have frequently been closer to prototype quality rather than commercially deployment quality.

Those other systems have other redundancies and safety mechanisms.

Airline passengers are in the dime-a-dozen category of expendable. Investments in astronauts are significantly higher. You really want them to be re-usable more so than the rockets

planes/helicopters have a fuel source that is orders of magnitude less volatile, and are also able to safely land without power

What fuels do you mean in particular? If you’re talking about hypergolic propellants, those aren’t commonly used as a main propellant on manned rockets. Most planes and helicopters use kerosene, which is also the primary fuel used by the launch stages of manned rockets.

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