e-FTW
New electron smell
Finally, views of Snoopy! He was actually quire useful as you can see him bounce around because of the thruster firings.
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e-FTW
New electron smell
So the IFA mission that was planned for today has been pushed out 24 hours due to poor weather in the capsule recovery area (rough seas, high winds). Understandable, but it led me to wonder this: why did SpaceX elect to land their capsule in the ocean and Boeing elect to land their capsule on land?
It would seem that returning a capsule to solid ground has several advantages; no pitching seas, easier for the recovery support team to get to, less costly because no ship needed, etc. Obviously the Russians have done it on land for the entire history of their manned space program, but then they have a huge suitable land area (the Central Asian steppes) and no easy access to a suitable ocean area.
Also obviously, the US moon program in the 60’s always landed manned capsules in the ocean, as far as I know. Boeing decided not to do it that way. Why?
It would seem that returning a capsule to solid ground has several advantages; no pitching seas, easier for the recovery support team to get to, less costly because no ship needed, etc. Obviously the Russians have done it on land for the entire history of their manned space program, but then they have a huge suitable land area (the Central Asian steppes) and no easy access to a suitable ocean area.
Also obviously, the US moon program in the 60’s always landed manned capsules in the ocean, as far as I know. Boeing decided not to do it that way. Why?
This is speculation on my part but the original intention was SpaceX's powered landing with a water landing as the backup. It was a year or two into the process that SpaceX dropped the concept of powered landing for the capsule. Once that was gone, SpaceX either had to redesign the capsule from scratch or go with their backup water landing. Boeing chose a land landing from scratch and had to make that very complex design work. Capsules landing in water is a tried and true system with vast amounts of history and data to back up how safe and successful the system is. So SpaceX, in this case, went with the simpler choice.
e-FTW
New electron smell
I tend to agree.
Also, those oceans are pretty big targets. I would imagine the landing areas in the ocean can be pretty large, potentially providing more flexible re-entry windows? But yeah, weather...
Elon says the best part is no part. Thus, the best landing cushion is no landing cushion.
Personally I think they have to redo the flight test.
Devils advocate... the crew on the space station is still at significant risk in a botched docking, even if the spacecraft has no crew. Potentially a live crew could abort docking. So it’s not entirely clear what the safest course of action is.
Yes I remember that but I thought it was NASA who told SpaceX that a retropropulsive landing was not acceptable to them.
Excellent point.
Actually no. NASA just said that, if SpaceX was going to do powered landings then a significant amount of testing would have needed to be done to prove the safety. That testing would have come with a significant price tag that SpaceX would have had to cover. So SpaceX, not NASA, dropped propulsive landings for Crew Dragon. The even more significant reason was that SpaceX and Elon decided that they weren't going to use Crew Dragon for Mars. The earliest stages of Raptor and BFS (Starship) were already being considered which was much closer to Elon's vision for Mars colonization. So Crew Dragon and powered landings became obsolete and unnecessary for cost and lack of need.
It's still an idea that SpaceX could revive but spending the money and effort to prove it out when you will soon(ish) have a fully reusable Starship and Super Heavy at your disposal...
Thanks for the correction. Must have been a hard decision for Elon to make, as we know how attached he is to retropropulsive landings. Ironically, after so many successful F9 booster landings It seems the concept has been demonstrated to be safe, but I take the point that to prove that concept with Crew Dragon would have added a lot of time and cost to the capsule development. Too bad though, given that right now we are seeing repeated postponements in the IFA mission due to poor weather and heavy seas at the capsule recovery area.
That is overly harsh. Complex systems always have bugs. That's why you do testing.
The Space Shuttle has its first ever launched scrubbed because the computers wouldn't synchronize. Turned out there was a minor design flaw and therefore a small chance (something like one in a hundred) that when you turned the computers on they wouldn't sync up. The solution turned out to be the old "turn it off and back on again".
The Shuttle program was incredibly careful about software bugs, and the possible impact of fixing a bug causing new ones. As a result they would usually implement workarounds for known bugs instead of fixing them. They had a phonebook sized document full of bug workarounds on board.
SpaceX took four attempts to reach orbit...
I could go on but you get the point.
Issues with their system:
How did the clock get into the wrong state?
Why does the system only rely on the clock? Why didn't the software check other parameters like altitude before autonomously making important decisions? Why isn't the software written with defensive principles where you never rely on a single, or even double parameter? This is the same problem Boeing had with the 737 Max - making an important control decision based on ONE sensor. That problem killed hundreds of people.
Why doesn't their system report on the state of the software via telemetry?
Why did they lose telemetry (SpaceX never manages to)?
I could go on but you get the point.
Boeing’s aircraft people are a completely different group from their space people.
Totally agree that Boeing should not have based the MAX software on one sensor. In fact the aircraft never should have been certified as it didn’t comply with safety regulations. (I can say this with some authority since in a previous job I did a flight safety review of another aircraft’s software-controlled stick pusher system. Basically the exact same type of system, though simpler. What Boeing did was stupid, unconscionable, and ultimately self-defeating.).
That doesn’t necessarily mean the Starliner people were just as sloppy as the MAX engineers. And making a system more complex doesn’t tend to make it more reliable; it tends to do the opposite in fact.
Telemetry outages are normal; both companies have to rely on the same government satellites and ground stations for that.
All that said, I do agree that the software should have recognized that there was something anomalous going on and put the craft into a safe mode.
Totally agree that Boeing should not have based the MAX software on one sensor. In fact the aircraft never should have been certified as it didn’t comply with safety regulations. (I can say this with some authority since in a previous job I did a flight safety review of another aircraft’s software-controlled stick pusher system. Basically the exact same type of system, though simpler. What Boeing did was stupid, unconscionable, and ultimately self-defeating.).
That doesn’t necessarily mean the Starliner people were just as sloppy as the MAX engineers. And making a system more complex doesn’t tend to make it more reliable; it tends to do the opposite in fact.
Telemetry outages are normal; both companies have to rely on the same government satellites and ground stations for that.
All that said, I do agree that the software should have recognized that there was something anomalous going on and put the craft into a safe mode.
Boeing, of course, fired and replaced their CEO in December, so I got around to looking at the new CEO they put in place. Boeing has real engineering challenges in both their aircraft and spacecraft areas, so I thought it interesting that their new CEO has a background in ... accounting.
OMG. When you make an accountant the CEO that is usually the beginning of the end for a technology company.
Eric Berger has a source inside NASA stating that “engineers are looking closely at the performance of the Starliner propulsion system...eight or more thrusters on the service module failed at one point and that one thruster never fired at all.” Boeing’s explanation is that (as phrased by Eric) “service module thrusters were stressed due to their unconventional use in raising Starliner's orbit instead of performing one big burn”. Hmm...
Starliner’s thruster performance receiving close scrutiny from NASA
Since that Starliner mission, no official statement from NASA or Boeing as to when it will fly crew...
Starliner’s thruster performance receiving close scrutiny from NASA
Since that Starliner mission, no official statement from NASA or Boeing as to when it will fly crew...
Nikxice
Active Member
Quote from Eric, "The NASA source said eight or more thrusters on the service module failed at one point and that one thruster never fired at all." Ouch.
Here is a suited up volunteer for the next Starliner mission, although I think he might be a little undecided!
Hmm... that is concerning.
I suppose if the root cause was also the timer anomaly, resulting in the thrusters being used outside their design envelope, then it may not be a big problem. But Boeing will have to prove that, and demonstrate an adequate safety margin for crewed operations. Clearly if the thrusters are not working to spec it could represent a significant threat to the crew and the ISS.
I suppose if the root cause was also the timer anomaly, resulting in the thrusters being used outside their design envelope, then it may not be a big problem. But Boeing will have to prove that, and demonstrate an adequate safety margin for crewed operations. Clearly if the thrusters are not working to spec it could represent a significant threat to the crew and the ISS.
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