Sometimes Things Happen Exactly The Way They Should
It speaks well of @ElonMusk & @JimBridenstine & @NASA / @SpaceX that they can have a difference in opinion & then work to quickly resolve those differences and do so with openness and transparency – and speak to common goals, values – & dreams for space exploration. More please. pic.twitter.com/RLiMpEyKCu
— NASA Watch (@NASAWatch) October 10, 2019
It is interesting that Bridenstine and Musk brought out the situation with the recovery parachutes and the ongoing tests, and the need to obtain at least ten repeatable tests of the Mark 3, the apparently latest iteration of the chutes. This apparently is as much of a pacing item as the redesign of the escape system rockets for getting the Crew Dragon safely qualified to carry astronauts. It does appear that, while they would like to avoid having to buy more seats on the Soyuz, they are not going to rush the process! It does seem that NASA has come away from the “go fever” that caused the Challenger disaster…I hope.
(Just as an aside, I wonder if they looked at the design and data from the Space Shuttle Solid Rocket Booster Decelerator Subsystem (SRB DSS), which utilized three 136 ft. diameter main chutes to lower the boosters to the water. Of course, the rate of onset and the impact profiles of the boosters may have no relationship to the loads on the Crew Dragon.)
Go SpaceX.
AIUI the parachute test results for Dragon, Starliner and Orion were not matching NASAs models, so this was a much broader problem. It’s also why Musk said SpaceX is sharing their safety IP with the others.
That’s my understanding as well. So while SpaceX keeps catching headlines for its commercial crew delays, Starliner and even Orion are having the same delays due to very same parachute design/development issues.
Given the parachutes issues it really looks like SpaceX would have been better off staying with propulsive landing. Actually, unlike the Starliner and Orion, SpaceX still has that as a backup option if the parachutes fail.
But it also makes you wonder why after extensive use on Mercury, Gemini, Apollo and Dragon Cargo parachutes are causing such an issue. You would think they would be an well understood mature technology by now.
Could be another reason to diss on SpaceX all the while hiding the fact that Orion and Starliner are just as behind and Orion has had a lot more development time than either ships.
And don’t forget the very deep experience of the Soviets/ Russians as well.
I’ve looked around for more, and deeper, coverage of the parachutes with little success. What, for instance, IS the issue? Drogues? Drogue handoff? Main chutes opening, or not?
The one Dragon test failure that we know about is when they purposely failed one of the four parachutes, the other three are supposed to be able to still land within margins but for some reason that didn’t happen and it landed too hard. The problem wasn’t specified but my guess is the failed parachute interfered with the others somehow. I wouldn’t be surprised if all of them are having a problem passing that test, or maybe some other off-nominal tests.
I have no information on the failure mode of that test. If it was simply a matter of a blown canopy, then, if sized correctly, the remaining three chutes should be capable of landing…but the impact would definitely be more severe. On the Shuttle SRB DSS chutes we did have single chute-out capability, but the damage to the booster’s aft skirt was considerably greater. What that would translate to in terms of g’s and rate-of-onset of the g’s, I don’t know.
OTOH, if the failed chute wrapped around the riser lines of the other three, that would have been catastrophic with a crew onboard!
I didn’t hear what material was being substituted for nylon. Was it Kevlar? We had proposed 115 ft. dia. Kevlar chutes for the filament-wound SRB’s, but both those boosters and the chutes were cancelled. Definitely an interesting problem, but one which I expect to be solved…given enough time!
I think it was Zylon.
OK, I can see that, but the underlying question in my mind: with so many decades’ experience by so many agencies/countries, how exactly is it that failures still happen?
Are we asking exponentially more of these chutes than previously? or?
I don’t think there is as much experience with this very narrow application and combination of requirements, which is multiple parachutes which are opened at high speed, high altitude, and which must be human rated for safety. Watching some of these parachutes gradually unfurl has an almost ballet like quality to it, which highlights the complexity of dealing with a large range of speeds and air densities. And that’s for a nominal chute opening even before they start worrying about how to make off-nominal deployments survivable.
For a layman’s explanation of the issue, google “Commercial Crew Program Testing Fosters Improvements in Parachute Safety”, this should take you to a NASA commercial crew blog article about the issue, specifically:
For a more in-depth look at Asymmetry Factor, search for “CPAS Main Parachute Cluster Asymmetry: A Second Look”, it’s a presentation on NTRS.
Thank you.
I think part of it is trying to minimize the mass of the parachute system. The old Apollo era designs were pretty heavy. And Dragon doesn’t have people onboard. That makes everyone more comfortable with tests that worked but not exactly as planned. I can’t see either NASA or SpaceX shrugging an iffy test for the crew version as “good enough.”
I also don’t think Dragon 2 can land on its rockets if the parachutes fail. I think the earlier concept still used parachutes for part of the descent, and I don’t know if the current version has all the necessary guidance, navigation and control capabilities for a landing. Once they decided against propulsive landing, why develop and test all that.
But, if misery loves company, we do have some. The ESA/Roscosmos Exomars 2020 lander/rover is also having parachute problems. Those sound serious and the mission may become Exomars 2022.
I do not believe buying seats was the problem…. only the price.. if commercial crew could sell seats lower Russia would be forced to drop prices or not sell any to NASA any longer
Agreed, excellent that people and organisations can have different opinions on technical matters and respect these differences, and still talk to common ground.
Does anyone else think that Bridenstine looks like a Walmart/BestBuy greeter ?
Sunlight is an AWESOME disinfectant.
It shouldn’t have happened in the first place.