SpaceX and Boeing Still Need a Parachute That Always Works | Hacker News Reader

SpaceX and Boeing Still Need a Parachute That Always Works

wired.com

107 pointsn0pe_p0pe77 comments

Interestingly, SpaceX (Dragon), Boeing (Starliner), and NASA/Lockheed (Orion) all use the same supplier/subcontractor for parachutes: Airborne Systems.

Parachutes are hard. They're super complicated. They'll figure it out, but this will always be tough.

> Parachutes are hard.

I'm surprised to hear this. I've not heard much about parachute failures in Soyuz landings, except Soyus-1 in the 60's. Nasa had a good track record with parachutes too before they started using the space shuttle.

Are there technical challenges unique to SpaceX or Boeing that other systems didn't have to deal with?

Soyuz has a reserve parachute. Also, because Soyuz only has one, large primary chute, you're less likely (by a factor of 3 or 4) to see any failures. And a reliability of 142:143 is not terribly high for a safety-critical system.

No US orbital crew fatalities have ever occurred due to parachute failure, but parachute failure has occurred on at least one of the Apollo missions (Apollo 15). One parachute failure out of 61 parachutes for the US[0] versus one (or two, counting the reserve) parachute failures out of 143 (144) parachutes for Russia/USSR. The statistics here are effectively indistinguishible in any meaningful measure.

The challenge is these are new, pre-operational crewed spaceflight systems being developed from the beginning. New systems ALWAYS have a higher rate of failure for complex things like this, and also because there are not yet actually crew on board, there's a little bit lower level of mission assurance (which I would argue is optimal!). Nothing in particular special about SpaceX or Boeing.

And in many ways, we got lucky that there weren't more parachute-related fatalities. We understand the dynamics significantly better now than in the past.

[0](1 parachute on each Mercury and Gemini mission, 3 parachutes on each Apollo capsule)

> And a reliability of 142:143 is not terribly high for a safety-critical system.

That's a 50+ years ago flight on a system which was being debugged - unfortunately, too hastily. Parachutes subsystem underwent major rework after that catastrophe, and the follow-up flight history attests to it.

One can call it "142:143" only as a first approximation.

Did Shuttle use similar chutes, or were those simpler drag chutes for braking?

(Like the F-22 and F-35 do) The Shuttle did aerodynamic braking, which is sort of like using the whole vehicle as a parachute, which reduced the speed at which it had to resort to its chute, enabling the chute to be much smaller than it would otherwise have been:

https://en.wikipedia.org/wiki/Aerobraking#Aerodynamic_brakin...

But even if it didn't do that, it would need a much smaller chute than a capsule of the same weight because gliding greatly increases distance traveled through the atmosphere, which enables the vehicle to bleed off a lot more kinetic energy as drag.

It’s worth noting that it’s not the parachutes that typically fail, rather, the deployment systems.

You’re packing (by hand) a large area of fabric and cord into a very small volume. You’re coating that fabric and cord with a variety of anti-stick substances, which have to be stable with extreme temperature and radiation levels, and huge vibrations.

Parachutes are deployed in several ways - springs, hydraulics, compressed gas, explosives, drogues, and combinations thereof.

For flight tests, parachutes are typically pre-stressed as though they’ve been to orbit and back. This wasn’t always the case.

So - there’s a lot of surface area to go wrong purely around the problem of getting it to eject and unfurl, before you even start to think about the parachute itself.

supersonic parachutes, in particular, are hard.

They spent a bit of time talking about this on a documentary about a Mars lander. Supersonic wind tunnels are spendy.

It's too bad NASA didn't let SpaceX test propulsive landing with the cargo Dragons. Without that, SpaceX scrapped the feature from the Dragon program as a whole. It seems like they might have been able to get more reliability with that than the parachutes. And even if not, if I was sitting in a capsule that had a history of parachute failures, I'd feel a whole lot safer if there was a backup propulsive system ready to kick in in the event of a chute failure.

They would still have had to work on parachutes because a Pad Abort uses up all the propellant... leading to a parachute landing just off the beach at the Cape.

They didn't scrap it exactly, they just relegated its function to use as an emergency propulsive abort system. But the Dragon 2 still has the super dracos... and one of them exploded, causing the loss of a test vehicle, a few months ago, which has resulted in timeline setbacks to the program. It doesn't seem like reliability has been a walk in the park there either.

The super draco didn't explode fyi, it was the fueling system.

An interesting distinction, like saying "the engine didn't explode, the gas tank did" but one wouldn't be there except for the other. I suppose for properly fixing the problem it's important to say one vs the other, but in general conversation it could come off as a pedantic?

Well an engine explosion and a gas tank explosion are very difference failure modes, and in rockets, pedantics matter.

Well, yes. Pedantic as it may be, the fueling systems seem to be a recurring theme for SpaceX, not their motors. Remember Amos-6?

Both failures may have had something to do with "fuel", but they aren't in any way related.

The Crew Dragon abort test anomaly was caused by a problematic valve leaking oxidizer "backwards" into the helium tubes which are used to pressurize the system right before ignition. The second they pressurized, it sent a huge amount of oxidizer into the engine where there should have only been helium at the time which caused the explosion.

The AMOS-6 anomaly was caused by LOX pooling and working it's way into the liner of a COPV inside the LOX tank. The LOX got into the fibers, and a small amount of friction ignited the oxygen and caused the "boom".

They may seem similar in that they are both related to the oxidizers getting somewhere they shouldn't and igniting, but a rocket is pretty much just a tube of carefully controlled fuel and oxidizer and a nozzle to shoot it out.

Of course most problems are probably going to result in fuel or oxidizer getting somewhere it shouldn't, and when that happens they are going to explode. For laypeople the exact reason why the fuel and oxidizer mixed at the wrong time isn't really important, but don't fall into the trap of thinking that the 2 are related.

If I remember correctly, SpaceX totally could have gone for propulsive landing, but opted not to because certification would have been a lot more work.

I think it basically came down to NASA not wanting them to test it on NASA flights.

SpaceX would have had to do their own launches and landings to verify the propulsive landing system, but they wanted to test it out on "production" cargo missions they were already doing for NASA.

Wouldn't dragon need the rockets to land on Mars? Parachutes aren't gonna do jack in Mars atmosphere.

I thought that was the bigger reason for the retro rockets.

That's not true, Curiosity used a parachute for part of its landing - it just needs to be pretty large to have an effect in atmosphere so thin:

https://www.space.com/16878-mars-rover-landing-sky-crane-gui...

SpaceX pivoted to building an entirely new rocket for Mars called Starship.

SpaceX has no plans to send Dragon to mars

SpaceX had plans to send Dragon to mars, that were cancelled at about the same time propulsive landing was cancelled for commercial crew. It's likely that cancelling it for commercial crew also cancelled the mars plans.

I think they cancelled it because it was a hair brained scheme from the get go. You need a lot of juice to not only land on mars, but then to propulse back off of it.

Red Dragon was always going to be one way, as a lander for some notional science payload. It was still a bit harebrained because it wasn't clear how to deploy that payload, whether rover or other, through the hatch. (I think I once saw a slide that had a subsurface drill deployed from inside the capsule by drilling through the heat shield.)

If propulsive landing was a harebrained scheme, we'd have never had the lunar landings.

Propulsive landing is awesome if the surface can stand up to it. Propulsive landing on mars with only a crew capsule is a little bonkers.

It takes ~3,000 m/s of dV to slow down, and do a powered landing on the Moon.

It takes takes ~6.400 m/s of dV to slow down, and do a powered landing on Mars.

Thanks to the tyranny of the rocket equation, it takes ~5x more fuel to do a powered landing on Mars, than it does on the Moon. For the entire mission. That's five Saturn V rockets, if you want to get a similar payload to Mars and back.

Shaving most of the dV requirements of the 'land on Mars' leg of the journey will reduce that requirement, from ~5x to ~2x.

As I understand the numbers something like 99.9% of that 6400 m/s dV is done via aerobreaking. Which makes it actually much easier to land on mars than on the moon energy wise.

The falcon heavy and dragon were almost definitely up to the task, given that SpaceX was for a short period of time actively looking for customers.

Source on the 99.9% is this talk (about starship, but I doubt red dragon would have been substantially different in terms of delta v): https://www.youtube.com/watch?v=bysu8XN5OfY

>99% is possible for the Starship because it has a lot of pitch control, and can fly a trajectory in the atmosphere where it maximizes lift for as long as it can.

A capsule doing a simpler landing generally needs to get rid of about 400m/s using other methods, based on NASA's past missions.

> It takes ~3,000 m/s of dV to slow down, and do a powered landing on the Moon.

With generous reserves, I guess. The speed on a low Moon orbit is about 1700 m/s, Apollo's LEMs had about (less than?) 2500 m/s delta-V for landing.

> It takes takes ~6.400 m/s of dV to slow down, and do a powered landing on Mars.

Seems too generous. Escape velocity for Mars is 5.027 km/s, so low orbital speed is about 3.6 km/s; more importantly, there is atmosphere - which maybe too thin to land safely on parachutes, but it definitely is going to reduce speed from orbital to some extent.

Propulsive landing on Mars doesn't take anywhere near that much. The atmosphere is thick enough that you can bleed 90% of your energy with a heat shield.

It seems like the minimal possible complexity of a sheet of fabric is always going to be higher than the minimal complexity of an engine simply because the physics of cloth are much harder to simulate accurate so you will never be able to find all the edge cases. Yes engines are initially more complex to build, but their minimum complexity once they are well understood should be lower -- even with the code needed to run them. You can't exact attach a debugger to the universe.

You simply cannot make a parachute that always works. My pal that works at SkyDive Perris has seen plenty of perfectly-packed parachutes fall prey to an errant gust of wind turning the chute inside-out mid-deployment and making it useless, requiring immediate deployment of the backup.

Now imagine this happening under supersonic conditions. Recovery would be almost impossible.

This is why skydivers wear multiple chutes.

The solution common to Boeing and SpaceX is the same: they have three (Boeing) or four (SpaceX) separate parachutes, each with their own drogue chutes, and they both can handle a single deployment failure without endangering the crew.

> Now imagine this happening under supersonic conditions.

Seems like even a big gust wouldn't make much difference at supersonic speeds in thin atmosphere.

This may just be conjecture but it's always seemed like they are solving the wrong problem. Why aren't they looking for alternatives to parachutes which to me seem like an archaic way of doing things. In saying that, the number of different maneuvers required in landing the space shuttle definitely shows how hard this problem is.

The tyranny of the rocket equation mostly - parachutes are light in comparison. They could use a burn to handle the deorbit or a but that would add more mass which requires adding more mass.

The "more modern" alternatives would be heavier and depend upon more systems. Even if dealing with futuristic assumptions like say electromagnetic in atmosphere flight and battery density/reactors good enough to handle reentey braking for a reduction of net reaction mass a parachute would have a place as a backup plan.

SpaceX originally planned to develop a [propulsive landing system](https://youtu.be/Cf_-g3UWQ04?t=90), but this was dropped due to several reasons:

* The additional risks of a relatively untested system * Starship development had begun, which would make Dragon obsolete

Propulsive landing of Dragon was therefore scrapped (and [Red Dragon](https://en.wikipedia.org/wiki/SpaceX_Red_Dragon), a plan to send uncrewed Dragons to the surface of Mars, along with it.)

The propulsive landing is still potentially a backup option to a parachute failure in the future.

Q: Are thrusters programmed as backup if chutes fail to deploy properly?

A: Most likely, but this is contingent upon NASA review & approval

https://twitter.com/elonmusk/status/1104510803313487872?lang...

Don't forget the biggest reason - the LES system used the same fuel as the propulsive landing system, and they only carried enough for one of the two. Which meant that landings after using the LES would require a parachute, and if you're carrying a parachute with you anyways why not just use it all the time?

It seems to me that the parachute(s) you need for LES wouldn't need to be as complex and capable as landing parachutes.

The LES parachute(s) will be firing at quite low speeds, so they don't need to be too strong. The LES parachute(s) also don't need to be nearly as reliable or give nearly as soft a landing.

Ejection seats in combat aircraft show the same tradeoff -- it's considered acceptable to have ejection seats that fail sometimes and sometimes cause a landing injury. Hopefully you never have to use it, and so even if it fails or injures you say 10% of the time, it's much better than certain death in a pad explosion or similar.

Because landing on land allows for faster retrieval of the astronauts and cargo, and is better for the capsule.

All that really needs to be recovered are the astronauts. A backup system could be devised where the astronauts bail out and come down on their own parachutes.

Apparently the phrase should be "It's not parachute science" since that appears to be more difficult than "rocket science."

"Fly safe"

Supersonic parachutes are terrible. Notice that supersonic aircraft air intakes involve ramps (F-15, Concorde, XB-70, F-14), shock cones (SR-71, MiG-21), or diverterless supersonic inlet (F-35, FC-1 Xiaolong). Simple round openings, without a central spike, do not work well at all. It's bad news for parachute design before even thinking about the problems of parachute lines and the need to withstand shock waves as the geometry rapidly changes while unfolding.

The right solution is probably the ballute. SpaceX, Rocket Lab, Armadillo Aerospace, and Copenhagen Suborbitals have all been investigating ballutes in recent years.

https://en.wikipedia.org/wiki/Ballute

It’s a strange thing. I never expected parachutes to be the hard part when sending people to space. Any idea why this is causing such a headache?

How is the problem and solution different than the parachutes used in early NASA programs like Mercury?

> Since the design of Boeing’s parachute system is so similar to NASA’s, the company had to perform fewer tests to demonstrate the system’s safety compared to SpaceX.

This doesn't seem like a good habit for Boeing.

> This doesn't seem like a good habit for Boeing.

While I like to bang on Boeing for being fucking dumb about 737MAX, the habit of copying an existing well-tested, approved design is something that should NOT be discouraged.

Re-use of existing validated solutions / components leads to faster development cycles and increased agility (financially) . This is achieved by making more critical components COTS (Commercial Off The Shelf - not one-off / custom) and re-usable as self-contained "modules" or "packages".

Reinventing the wheel for reinventing the wheel's sake is in most cases not a good use of resources.

That said, if the original design has issues, my above commentary is invalidated somewhat - you need to modify the design to fix the root cause, which should trigger a fresh round of validation and testing at the original specification levels or greater. And of course, you should always do fully integrated tests, even if all of the components were previously validated and approved. You pretty much always find stuff (maybe only in solution-integrated combination) - I believe that's what happened in this case.

I don't think he means existing designs shouldn't be reused. I think he means that you shouldn't lessen testing because you are using an existing designs.

Boeing reused the 737 design to produce the 737 Max; however, because it was a reused design, Boeing did not go through the same certification process or testing that would have been done for a new airplane. Skipping testing because you have a reused design is the bad habit he is referring to.

Using old tech is why Boeing lost space though.

"Lost" space? I'm not following you. Unless you're referring to how up-start SpaceX has dominated the launch industry in the past 5 to 10 years?

From a quick Googling, the heaviest Mercury capsule launched weighed 3k lbs, while Crew Dragon is 20k lbs dry. That extra mass makes the problem significantly more complicated.

As for later programs like Apollo that are more comparable, I'm not sure. Maybe they were comfortable with heavier systems or worse safety margins. Also, I expect that working out the parachutes for Apollo was not easy.

Apollo also had parachute issues, e.g. see Apollo 15.

> This doesn't seem like a good habit for Boeing.

Using pre-existing proven designs for components is essential for building safe systems.

It sounds like the old-style parachute is not the best solution for this problem, but I'm sure they must have come up with other ideas and ruled them out. Why not hundreds of small parachutes? Why not wings or rotors to stabilize it? I'm curious to know.

Anything non-fabric would weigh too much. Many smaller parachutes means many more lines, which would weigh too much.

The rocket equation is cruel.

Smaller parachutes would be larger surface area compared to one large chute also, right? More weight there.

Parachutes were supposed to be easy because they have plenty of heritage and other users. And in spite of the problems they likely still are easier. Any other system would need even more testing.

> 600 mph

Probably better to use km/h, especially for space related coverage.

Americans don't have an intuitive sense of metric units, and Wired is based in the US and has mostly US readership. I agree with you, and I'll bet the editor also agrees, but they'd probably get FAR more comments to use imperial units because 'merica, if metric was used instead.

That's one of the ways to develop intuitive sense - start using it everywhere. It will never develop if it's not used. Besides, officially US was supposed to switch to metric system anyway, so formally there is nothing wrong with using it and no one should be complaining. Except it takes ages and almost not moving anywhere due to complete apathy from the government about it.

When discussing speed of an object that is landing, m/s might in fact be even better for most of the world.

> Americans don't have an intuitive sense of metric units

I don't really believe that. American public schools have been teaching the metric system to middle schoolers for a few decades now. Every American I talk to understands the metric system. In some cases, particularly units of volume, they understand the metric system better than the imperial units (liters are easy, but I can never keep quarts/pints/cups/floz/etc straight in my head.) Coca Cola sells sugar water to Americans in liter-oriented packaging (.5, 1, an 2 liter bottles are ubiquitous), and Americans certainly don't balk at that. They drink it up.

Volume effort went well indeed. What's still lagging behind especially are temperature, distance and speed units. Lot's of people are still not comfortable when you are trying to use metric for them. Which probably only highlights that there should be a stronger push to use them.

Also, 24H time system is something people often don't get, and only know about it as "military time", due to army actually using it.

I think temperature is easily the most alien to Americans. Metric distances probably aren't quite as well understood as metric volumes, but I'd wager that knowledge only trails by a little. The rough equivalence between a yard and a meter is widely know by Americans, as is the rough equivalence between 100km/hr and 60mph (helpfully, American speedometers all provide this education.)

The distances you cite are pretty much the only ones (well, 2.54cm = 1 in as well) that are likely to be well-known. Yards are just not a heavily-used unit, people prefer 10s or 100s of feet instead of using yards. So when you go from tens to hundreds of meters, there is going to be no intuition about what kind of distance that actually is, and you have to mental math your way to familiar units of 100s of feet or quarter/half miles.

Meters to feet is easy, it's roughly just x3. Yards may not be common (yards are certainly common in sports, and sports are very popular), but three feet to the yard is definitely commonly known. Centimeters might be harder, but in my experience Americans suck at estimating inches too, one American's "half an inch away" is another American's "two inches away." And the average American off the street would be hopeless if asked how many feet are in a mile. They'd actually have a better chance of giving you a kilometer->feet conversion than miles->feet. At least, I certainly would (without looking it up: 1 kilometer = 1000 meters ~= 1000 yards = 3000 feet, +10% fudge, approximately 3300 feet to the kilometer.)

Anyway, my point in all of this is that if a pop-sci publication like Wired uses units like kilometers, it is unlikely that their American readers will be confused. They'll probably walk away from such an article with a casual understanding of the subject that is reasonably close to the casual understanding they'd have if the article used miles instead.

The only way to gain intuition is to use units straight, without doing mental translation.

Yep. Two years in Australia wasn't enough for metric temperature units to become instinctive for me.

Speed was easy, relatively. Even weight/height was alright, though Aussies tended to use imperial for those often anyway, including the whole 'stone' thing that threw me off at first.

I'm a late-20s American. I do have some basic understanding of metric units, although it is relative (a centimeter is about half an inch, a meter is a bit more than a yard, a kilometer is slightly more than half a mile.). That all goes out the window when you add a second unit, though - kilometers _per second_ means absolutely nothing to me.

Pardon me, the ignorant American... but this is who I am :D

In UK they managed to fix it, by stronger push to make it mandatory. In US somehow the government blew the effort that's why it's still like this today.

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