Parachutes seem simple, but space organizations spend a lot of time and money developing and testing them. Why is it so hard? @Eager_Space on Twitter Triabolical_ on Reddit / eagernetwork / eager-space-1038430522...
Took Boeing 10 yrs of testing? Apollo program didn't test their parachutes 10 yrs obviously since they had a Moon deadline. Random web surfing, I found NASA looked into a Helicopter Rotor System for Capsule Reentry but opted for parachutes to shorten development time. Maybe you could make a video about that? Just tossing ideas.
Haven't finished the video yet, but weird thought, despite rocket engines being way more complicated than parachutes, in practice a company can probably get propulsive landing reliable much more faster than parachute landing since parachutes will always have a small number of specialized tests whereas rocket engines get tested in real world conditions every flight on the way up and down. (So parachutes are a one and done thing every flight, but a rocket engine gets tested, for the most part, every second of the flight both on the way up then the way down) EDIT: Not to mention a company will get to test multiple engines at once all at the same time during flight, building up data on reliability that much more quicker.
I've had the same thought... Engines tend to be somewhat chaotic in how they start up and shut down and then quite predictable in how they run once started. They therefore get a ridiculous amount of testing for startup and shutdown. And some engines are really simple - the SuperDracos are just combustion chambers and some relatively simple valves. They are very reliable. It also tends to be easier to add redundancy to engines as they don't interact (much). Crew Dragon's move from 3 parachutes to 4 parachutes required a lot of retesting because it had the possibility to have many issues.
The thing about propulsive landing is you have to take fuel up to land with, including fuel for margin. I suggest that the relative weight of those two solutions is the most critical thing when they are of similar reliability.
It's not too often I watch a RU-vid video and think, "Wow! I never knew *all* that about x subject!", but this is one of those few videos! I mean, I usually learn something, but this really blew me away. I've been reading that parachutes add cost, mass, and complexity to space missions, but now I see just how complicated they are (and why they have to be so complicated).
Great video as always! It's quite often the case that the things which seem simple and easy at a cursory glance are the things which cause the most headache, and I think parachutes definitely fall into that category. Definitely a safety critical system if you ask the crew and/or payload though for sure! The channel spaceXcentric put together a nice documentary style overview video of parachutes in relation to space flight around 3 years ago as well if you haven't already come across it.
Great video. An interesting addition would cover unmanned parachutes, such as those used on Mars, Venus, and Titan. Also, not sure if it really happened, but the risk of frozen parachutes is mentioned in the movie Apollo 13, because they required electrical power to heat them and keep them pliable. This adds further complexity, especially for a deep space mission that lasts many years, such as the one to Titan.
Thanks, that's an area that I explicitly avoided because capsules already had enough complexity. I've added a "how to land on Mars" topic to my topic board.
A nice explanation of one of the huge additional costs associated with manned spaceflight vehicle development. Book: The End of Astronauts: Why Robots Are the Future of Exploration - Apr 19, 2022
I did't know much about parachuts and I never thought much about them. Wow, that was really interesting! Btw: you should ask people to hit the like button and subscribe. You have way too many views on your videos! And they are good!
I really really like the discussion of confidence and data and thought that was well articulated. But I suggest just because a number has been rounded off doesn’t necessarily mean it’s a guess, as it might be simply the number of significant digits in the data that you’re using to arrive at that number. I round off numbers all the time in the data I use for that reason, and I get the kind of pushback that you’re referring to all the time for no reason. Whereas if you give people a number that is a long string of numbers that appear to represent accuracy they take it to be a valid number to that accuracy. I think the red dots are a good idea and one should look at those values, but one should not assume that there any less justified than any other number on that page.
Fair point, and it's certainly true that people are very confused about precision and accuracy. Might be a video there... I'm pretty sloppy when I do calculations in my videos.
During the video I was wondering why the drogue chutes weren't used to deploy the mains, why did the mains use pilot chutes. I then figured it might be a redundancy issue; if the drogues failed then the mains could still be deployed, albeit with the danger of not being damaged by a high speed opening. Then you got to Dragon, which dispensed with the pilot chutes. Eliminating them and the cover release chutes* fits with their mantra of "the best part is no part." But if they can do it without my supposed redundancy reason, why didn't everyone else? NASA approved this, though. If a redundancy was indeed eliminated how was NASA OK with it? My mind of course immediately went to Dragon's propulsive landing capability. SpaceX has been maddeningly elusive as to whether that capability is still present. Afaik the only problem is, is there enough propellant? A fair amount is used to raise & lower the orbit. Also, was the original propellant amount reduced once the switch to parachutes was made. That depends on how it compares to the launch abort amount. So many factors go into this question - sorry to go on so long. *How does Dragon blow the side covers away without risking them being caught in the turbulence and bashing into the capsule? I'd think the risk would be greater than with a top cover.
It's not redundancy. If the drogues both fail, deploying the mains will likely just rip them apart - notice how the Ares I chute "streamed" when it opened just slightly too fast. My *guess* is that Apollo went with the pilot chutes because it will tend to pull the main chutes out to the side and deploy them with some distance apart and NASA wanted that. The drogue -> pilot -> main was also used on Gemini and they may have just wanted to stay with what worked. The SpaceX decision to go with a parachute bay meant that they didn't really have the option to do that - all the mains would be going in the main direction, and the bigger drogues are going to give a more solid deployment than the small pilots would. And they tested that and found that it worked fine. WRT Dragon's propulsive landing capability, I do not think it exists. You simply *do not ship* software features that are not required and tested thoroughly, because the downside of it being triggered when you do not want it to be triggered would be very significant. WRT how Dragon deploys the side covers, I couldn't find an answer to that question. I do know that SpaceX really likes to use pneumatics for that sort of thing as it can be tested in a way that pyrotechnics cannot.
The only thing I feel is missing from this video is what calculation leads to the different curves about certainty of reliability. It's beside the point, but I would've liked to see it in the corner so I could understand how the math works better.
I considered add in some of the math but I thought it would be distracting. The math is known as "success run theory" and you should be able to find some online references for it. Here's one: harishsnotebook.wordpress.com/2023/07/04/deriving-the-success-run-theorem
Oh hey a LOC IV. I got my NAR L1 on that rocket. If we're at the same launch, I'll have some stickers for you. Also, great video. Plenty of stuff to think about doing electronic dual deploy for high power model rockets, and why I try to fly with two altimeters from different vendors.
Alas for me, 3 months after I got my level 1 the site that was 25 minutes away from me (5K limit only) went away and the nearest site is now 3 hours away, which is just too far for the amount of time I choose to devote to the hobby.
Good question... Generally, there are self-contained reefing cutters - they are pyrotechnical devices with chemical fuses, so the parachute deployment essentially lights a fuse which burns down and then triggers the reef-cutting charge. This is all up in the parachute canopy so there's no required control from the capsule. Apollo used that system and I think it's still the approach used with the current capsules. There's a concept called "continuous dereefing" where a control line would be progressively unwound from the capsule, but AFAIK it's never been used. It would slowly unreef the chutes rather than doing it in very specific steps.
Wasn't there a starliner parachute test that failed because they forgot to hook up one of the chutes and the system was designed in such a way that you cannot inspect the connection?
Yes, that is exactly what happened. I decided not to include it because I didn't think it added much to the discussion and it was only a test flight. I had to include the Ares I flight because the failure of the chute because it opened too quickly was both cool and disturbing to watch.
Yes, although they didn't actually forget to hook up a link in the lines. The technician thought the connecters had engaged together but he couldn't directly see it because the design of that section included a sleeve and the connection was inside the sleeve; it had to be done by feel. IIRC the tech was alone, there was no one to confirm it at the moment. Protocol required a second person to be present for a flight article but this was skipped because "it was only a test."* And yes, once that mistake was made the next steps made it impossible to inspect. This is an example of a poor overall design concept that should have been ditched once they realized the assembly weakness and inability to be inspected. It was probably reached because of other design decisions for other parts of the system inadvertently required it. Good engineering practice would mean the upstream design decisions needed to be changed. Unfortunately Boeing is now notorious for poor engineering management. A redesign would have cost money. *Another example of Boeing ignoring the practice of "test like you fly." NASA complained in a different review that Boeing was still not supplying enough manpower to get various jobs done right. That review was done after the *second* test flight had several serious problems. Two bad test flights and Boeing was *still* skimping on resources on a crewed spacecraft. (The first failed flight's biggest problem was caused by their failure to "test like you fly," they didn't do an end-to-end test computer test of the software with all the computers hooked together because it would have cost more. Instead they relied on testing only segments.)
In the off-chance that this is a serious question: Because the astronauts have limited mobility in the pressure suits they wear during ascent/entry and, besides, they are securely strapped in their seats.
@@EagerSpace I didn’t realize it was all! Some are obviously fake, but the poster seemed cool enough it might be real. That makes the joke even better!
Returning from space using parachutes is so pathetic, uncivilized. What happened with the fancy space plane? Maybe it was just a fantasy fraud? We were not there then, not there even now.
@@EagerSpace Well, we cannot have them. How much does shuttle weigh? 120 tons with cargo and fuel? How much Falcon 9 Crew Dragon weigh? 12.5 tons. So, Shuttle weighs about 10 times more than Crew Dragon. How much Falcon 9 weigh? 549 tons. Then, just simple extrapolation, Shuttle + External Fuel Tank + Boosters should have weighed at least 5,490 tons (as it has less efficient solid boosters, probably 6,000 tons) But its spec says only 2,000 tons and it's already very massive. Which means, instead of 2 boosters and one ET, shuttle should have had 6 boosters and 3 External Fuel tank to match the weight ratio with more modern rockets. 28,000 km/h speed is not a joke.
