Starship SN10 High-Altitude Flight Test - Page 1
Forum section: electronics / general

author: wraper
author_rank: Unknown
timestamp: March 03, 2021, 11:23:22 pm
content: Yay!

author: wraper
author_rank: Unknown
timestamp: March 03, 2021, 11:29:58 pm
content: Delayed RUD, LOL.

author: Gyro
author_rank: Super Contributor
timestamp: March 03, 2021, 11:37:48 pm
content: That's the first one that I've seen take off twice and land twice!

author: wraper
author_rank: Unknown
timestamp: March 04, 2021, 02:09:32 am
content: Quote from: Gyro on March 03, 2021, 11:37:48 pmShortest turnaround time ever.

author: Refrigerator
author_rank: Super Contributor
timestamp: March 04, 2021, 07:52:26 pm
content: I wonder could that have been a self-destruct due to it leaning pretty hard? Was it too dangerous to recover or maybe there was nothing more to be gained from saving SN10?Starship does have explosive charges mounted for self destruct purposes.

author: Neilm
author_rank: Super Contributor
timestamp: March 04, 2021, 08:23:10 pm
content: Quote from: Refrigerator on March 04, 2021, 07:52:26 pmI thought the explosives were further up the vehicle. Certainly there is something associated with them halfway up. The explosion seemed to happen at the base. Scot Manley did a video where he showed the explosion from all the available angles.

author: raptor1956
author_rank: Frequent Contributor
timestamp: March 05, 2021, 12:42:07 am
content: Scott Manley's analysis appears pretty spot on -- it landed hard and bounced quite noticeably and that can't be good. It also looks like only half the landing legs deployed properly and that can't be good either. If you watch the Lab Padre feed and single frame the video just before the second launch you can see a puff of gas AND the beginning of the vertical movement several frames before you see any flame. The explosion, BTW, appears more of a deflagration and it probably had a minor effect on the second launch. My guess is that the hard landing caused a tank support to damage a tank and after about 10 minutes it failed. The second launch was almost entirely the result of pressurized gas/liquid venting. However, as Scott pointed out there appears to be a notable difference in engine performance as it was descending AND just before the landing a substantial amount of burning gas appears which might indicate a plumbing problem before the hard landing.So, great that they actually landed this time but they still have a lot of work to do. I'm not comfortable with where the Raptor engines are at this point.Brian

author: Brumby
author_rank: Unknown
timestamp: March 05, 2021, 03:51:06 am
content: I'm getting fairly comfortable with the Raptor engines themselves ... it's the other things like plumbing and landing leg deployment that have my reservations.

author: floobydust
author_rank: Super Contributor
timestamp: March 05, 2021, 09:12:24 pm
content: Look at how much plumbing there is, it looks an order of magnitude more complicated. I would say good luck getting this reliable at those temperatures, pressures, forces and the occasional bath in flames. If there was some way to increase integration and reduce the number of tubes and fittings. I thought SN9 had a leak as part of its demise?

author: rdl
author_rank: Super Contributor
timestamp: March 05, 2021, 11:56:24 pm
content: It looks complicated but a lot of it is wiring and connections for sensors and such. Take what's visible there and divide by three, then compare to what's under the hood of a modern automobile. Not that much different really. But yeah, the temperatures and pressures are insane.

author: Brumby
author_rank: Unknown
timestamp: March 06, 2021, 03:06:32 am
content: .... and all of those engines are gimballed - so moving bits on top of the insane vibration ... and pressures ... and temperatures.

author: rdl
author_rank: Super Contributor
timestamp: March 06, 2021, 03:18:19 am
content: They're using three engines, so most of the time during these tests the thrust is not along the centerline. Pretty impressive how well they deal with that. I'm amazed they landed one.

author: Brumby
author_rank: Unknown
timestamp: March 06, 2021, 03:53:28 am
content: The gimballed engines that enable vectored thrust make the control an easy concept.Making it work in this arena is quite the challenge ... and they're getting there!

author: TerraHertz
author_rank: Super Contributor
timestamp: March 06, 2021, 10:17:08 am
content: SN8 watch?v=egHxiX40eJY BOOM!SN9 watch?v=zwZl6YV3xYA BOOM!SN10 watch?v=CF9mdMI1qxM Yay! uh.... BOOM!SpaceX and Elon's rapid prototyping method are certainly entertaining.Also very effective. An amazing rate of progress.

author: Refrigerator
author_rank: Super Contributor
timestamp: March 06, 2021, 02:29:15 pm
content: Quote from: TerraHertz on March 06, 2021, 10:17:08 amCan't wait for NASA to pick up speed with artemis.

author: raptor1956
author_rank: Frequent Contributor
timestamp: March 09, 2021, 11:55:12 am
content: Quote from: rdl on March 06, 2021, 03:18:19 amNormally, when you use three engines, they are arranged in a row so that you can have balanced thrust with 3 engines, 2 engines or 1 engine -- not sure why that wasn't used. In an operational rocket requiring more than one engine you would prefer three in a row, five arranged with one in the center and four arranged 90 degrees around the center, or seven with one in the center and the others spaced at 60 degrees. Again, not sure what SpaceX is trying to prove with the arrangement they're using.Brian

author: wraper
author_rank: Unknown
timestamp: March 09, 2021, 12:10:19 pm
content: Quote from: raptor1956 on March 09, 2021, 11:55:12 amMaybe think a little bit and realize you cannot make a round rocket with such arrangement. Then think a bit again and realize you will have thrust vectoring issues in certain directions. Not to say starship will have 6 engines in total (3 of which vacuum engines with large bells). Then think for a third time, and realize you cannot switch between 2 engines and 1 or 3 in a way that thrust remains in center. You either need to fire additional engine during switchover or shut down them all. Or deal with even more off center thrust compared with current arrangement. Just because you have no understanding, does not mean somebody tries to prove anything.QuoteNormally where? Delta IV Heavy which uses 3 separate boosters and does not even have an option to shut them down separately?QuoteThese are inefficient in regards to space usage, especially 5 engine variant. A lot of space wasted for nothing.

author: rdl
author_rank: Super Contributor
timestamp: March 09, 2021, 01:14:44 pm
content: QuoteThe Saturn V used the first arrangement. The Falcon 9 uses the second, though with eight engines in the outer ring. The first version of Falcon 9, at least one of them, had the nine engines in 3x3 pattern which seems really weird. The Shuttle Orbiter's three main engines were in a triangle. It seems the designers use whatever they think is best.

author: iMo
author_rank: Super Contributor
timestamp: March 09, 2021, 01:42:26 pm
content: They land with help of 1 raptor only - so the arrangement is not so important, imho.After failing with SN8 and SN9 (due to issues with raptors) a guy in a discussion (or was it a tweet??) asked something like ..why not to reignite all three during the landing, then to decide which one of the raptors works best, then switch the other off...So it seems Elon has been following the hintPS: below the tweets after SN9 landing..

author: Medved
author_rank: Contributor
timestamp: March 09, 2021, 09:50:28 pm
content: My guess was there was an attempt to keep two engines running at landing, but one of them flamed out just after they shut down the one.To me the SN10 flight was surprisingly soon after the SN9 failure to have the whole landing sequence redone (first ignite 3, then if successful, shut one down).To me it looked more like there were two groups of engineers, each group preferring one way (light two vs light 3 and shut down one), arguing about how important the advantages/disadvantages of each approach are, so they designed in actually both scenarios (having no redundancy in case of SN9 vs handling the 4 liquid hammer surges in the fuel piping in the SN10 would be my guesses for the disadvantages). They decided to try first the "light 2" and then later the "light 3, shut down 1".Well, both have failed so far, so they have some homework to do...

author: raptor1956
author_rank: Frequent Contributor
timestamp: March 10, 2021, 01:17:04 am
content: Quote from: wraper on March 09, 2021, 12:10:19 pmJesus, where to begin...Yes, you can make a round rocket using three engines in a row -- it's been done so it follows its possible.It's not uncommon to alter the thrust by shutting down one or more engines -- the Falcon 9 tends to shutdown one or more near the end of the first stage burn to limit acceleration to about 4g's. They then use three engines for the entry burn and one for the landing.If the max thrust of a rocket stage is equal to it's weight then it will accelerate at one g initially (in space outside of a gravity field) BUT, since propellent often equals 90% or more of the entire mass the acceleration at the end of the burn could be 10g's and that's not good with people onboard and it's not wise to design and build a rocket stressed to handle 10g's as the extra mass needed would not be helpful -- so, being able to reduce thrust is important! Operating a rocket engine at partial thrust comes at the penalty of lowered ISP so it's better, where possible, to shutdown one or more engines so you can run the remaining engines closer to rated thrust.The Apollo second stage used 5 J2 engines arranged with one in the center and four around it at 90 degrees. The Falcon 9 uses 9 Merlin engines arranged with one in the center and eight around it at 45 degrees.Brian

author: raptor1956
author_rank: Frequent Contributor
timestamp: March 10, 2021, 01:24:11 am
content: Quote from: rdl on March 09, 2021, 01:14:44 pmThe Shuttle was a weird beast that differs from traditional rockets based on the cylinder and the trust of the three main engines was not directed directly aft do to the off center mass of external fuel tank. The angle of the offset was pretty significant so the net thrust was less than the thrust produced do to cosine error.Brian

author: wraper
author_rank: Unknown
timestamp: March 10, 2021, 01:41:20 am
content: Quote from: raptor1956 on March 10, 2021, 01:17:04 amIt does not. It uses part of its engines only during descent. During ascent it always uses all of its engines. And I don't know any other rocket which can use part of its engines.

author: Brumby
author_rank: Unknown
timestamp: March 10, 2021, 02:15:57 am
content: Starship Raptor engines are run in 3 stages: All 3 for lift off, 2 part way up and 1 near the top of these 10km trials - for good engineering reasons, I might add.All the old rules were necessary from having zero experience in order to get things up in space.Now that we know alotmore and have much more advanced technology, those old rules can be revisited. Gimballed engines providing thrust vectoring being one brilliant example. One engine off to the side of a central axis can control a craft for propulsive landing. We've seen it done.

author: raptor1956
author_rank: Frequent Contributor
timestamp: March 10, 2021, 03:48:24 am
content: Quote from: wraper on March 10, 2021, 01:41:20 amHere ya go...https://spaceflightnow.com/2015/01/05/falcon-9-spacex-5-launch-timeline/"Moments after two of the Falcon 9’s first stage engines shut down, the remaining seven Merlin engines cut off at an altitude of 80 kilometers, or about 50 miles, and a velocity of Mach 10."But even in your reply you admit that they use less than all 9 engines for entry and landing -- not sure what your particular problem is!Brian

author: wraper
author_rank: Unknown
timestamp: March 10, 2021, 10:50:34 am
content: Quote from: raptor1956 on March 10, 2021, 03:48:24 amIf 2 engines were shut down before the rest, it happened only fractions of second earlier. I could not see it happening in the video and cannot find any mentions of it besides your link. Dunno if it even happened since that article is pre-launch flight description.There is no 2 engine shutdown in the flight plan provided by nasa.https://www.nasa.gov/sites/default/files/files/SpaceX_NASA_CRS-5_PressKit-105.pdfQuoteQuoteMy problem is your claim that "It's not uncommon to alter the thrustby shutting down one or more engines" is not true in context of doing so during ascent:QuoteAnd even during descent, they are not shutting down the engines. They fire part of them. A big difference.Looks like instant shutdown of all engines. 18:40

author: David Hess
author_rank: Super Contributor
timestamp: March 10, 2021, 12:37:17 pm
content: Quote from: floobydust on March 05, 2021, 09:12:24 pmThe Raptor engines use thefull-flow staged combustion cycleso are more complex, and this is the first time that a full-flow stage combustion cycle engine has flown.