Starship

[Phil1111 911]

Well I was hoping for more success. The length of time it stood on the pad post ignition must have done some pad damage. The six engines that didn't ignite made the t/o look a little less sporty than the Falcon.

and OK I can now overlook Elon's twit/F**k up. He is back in my good books.

Edited April 20, 2023 by Phil1111

[billvon 2,400]

I was just happy it cleared the pad.  Then when it passed max-Q I thought it might make it to staging.

But then they showed the rear view with a lot of asymmetrical thrust, and that problem just gets worse and worse as the levels in the tanks drop.  And you could see engines going rich even after that, so I suspect they just kept losing engines until they couldn't gimbal the remaining ones enough to maintain control.

So I'm really glad they got good data and didn't destroy the launch pad - but I wished they had at least made it to staging, if for no other reason that to get data on the upper stage engine performance at altitude.

[SethInMI 145]

1 hour ago, billvon said:

and didn't destroy the launch pad

barely. I saw NSF has video of one of their remotes with a car parked by the camera. A big chunk of concrete smashes into the car, maybe totaling it depending on if there is frame damage. As Phil said, those seconds on the pad with the engines running was not good for it. Maybe knocked out a few engines or caused some other damage to the rocket itself...

[Erroll 49]

I enjoyed their technical term for the eventual explosion : "rapid unscheduled disassembly".

[David Wang 48]

SpaceX does things differently. They prefer rapid design & testing and learn from their many failures. NASA does the opposite, probably because it's a government agency. Each has its own merits. I have no doubt that we will see significant improvement in the next Starship test flight. We have some important dates - Artemis II is scheduled in November 2024, and Artemis III is some time in 2025. It's an exciting era. To the Moon and Mars!

[SethInMI 145]

a pic from twitter showing the pad damage (with the original forms for the concrete pour on left).

Elon says they were planning a flame diverter / water deluge but it wasn't ready in time so they rolled the dice and went anyway. I wonder if his desire to launch on 4/20 overrode some people who wanted to wait, but OTOH they have another rocket soon ready to go so just saying "lets get this one gone and we can keep iterating" has a point.  

Elon claims next launch in 2 months, the armchair QBs on NSF say 4-6 months.

[Phil1111 911]

On 4/20/2023 at 10:05 AM, billvon said:

I was just happy it cleared the pad.  Then when it passed max-Q I thought it might make it to staging.

But then they showed the rear view with a lot of asymmetrical thrust, and that problem just gets worse and worse as the levels in the tanks drop.  And you could see engines going rich even after that, so I suspect they just kept losing engines until they couldn't gimbal the remaining ones enough to maintain control.

So I'm really glad they got good data and didn't destroy the launch pad - but I wished they had at least made it to staging, if for no other reason that to get data on the upper stage engine performance at altitude.

A commentator for the launch stated that the rocket is supposed to conduct a planned yawing maneuver(flip) prior to second stage separation.  Which makes no sense whatsoever: CNN video at 4:53 he states that the Starship is "beginning the flip for stage separation."

Does the first and second stage not separate. The first stage then make its 180 for a back burn to the landing? With the second continuing a new burn to orbit along a straight line of flight to orbit?

[SethInMI 145]

2 hours ago, Phil1111 said:

Which makes no sense whatsoever

I wondered a bit about that too, so I looked it up, here is one explanation:

"Sidestepping decades of precedent, Musk says that Starship will have no separation mechanism at all. Instead, at some point during the design or testing process, Musk decided that a separation mechanism was entirely superfluous and that the same effect could be more or less replicated by using existing systems on Super Heavy. By using the booster’s gimballing Raptor engines to impart a small but significant rotation on the rocket moments before separation, Super Heavy could effectively flick Starship away from it – a bit like how SpaceX currently deploys Starlink satellites from Falcon by spinning the upper stage end over end and letting the spacecraft just float away thanks to centripetal forces.

Because Starship is something like five times heavier than Super Heavy at stage separation, the ship would effectively float away from the booster in a straight and stable line, use cold gas thrusters to settle its propellant, and ignite its six Raptor engines to head to orbit. In return for the slightly unorthodox deployment profile, if this new approach works, SpaceX can entirely preclude the development of a pusher/spring system capable of pushing a ~1300 ton Starship away from Super Heavy. That approach is possible on Starship in large part because the ship’s six Raptor engines are completely tucked away inside a skirt, meaning that there is zero chance of nozzles being damaged by impacting the booster interstage."

[billvon 2,400]

On 4/20/2023 at 10:40 AM, SethInMI said:

barely. I saw NSF has video of one of their remotes with a car parked by the camera. A big chunk of concrete smashes into the car, maybe totaling it depending on if there is frame damage. As Phil said, those seconds on the pad with the engines running was not good for it. Maybe knocked out a few engines or caused some other damage to the rocket itself...

One speculation I saw was that one of the hydraulic power units (near the lower skirt) was damaged by debris, and thus both engine gimbaling failed and the latches could not separate for staging.

 

[Phil1111 911]

6 hours ago, billvon said:

One speculation I saw was that one of the hydraulic power units (near the lower skirt) was damaged by debris, and thus both engine gimbaling failed and the latches could not separate for staging.

 

Something with the latching mechanism makes sense. Because Starship yaw was well developed before the termination of flight decision was made.

This was tweeted "The damage in Boca Chica at the Starbase launch site looks pretty serious, but a former senior SpaceXer from there says he believes the pad can be repaired; and a (water-cooled?) flame diverter installed in 4 to 6 months. Just passing on what I was told." To which Elon respoinded:

"3 months ago, we started building a massive water-cooled, steel plate to go under the launch mount. Wasn’t ready in time & we wrongly thought, based on static fire data, that Fondag would make it through 1 launch. Looks like we can be ready to launch again in 1 to 2 months...

Aware that this schedule is hyper ambitious, Musk then explained, on Apr. 22, that the engines may have caused unexpected damage.

"Still early in analysis, but the force of the engines when they throttled up may have shattered the concrete, rather than simply eroding it," he argued. "The engines were only at half thrust for the static fire test."

Flying another in two months seems overly ambitious. IMO Elon has a history of using the whip on employees and exaggerating. So maybe?

A video has emerged of pad damage actual damage starts at 1:22.

Edited April 23, 2023 by Phil1111

[billvon 2,400]

On 4/22/2023 at 5:53 PM, Phil1111 said:

Flying another in two months seems overly ambitious. IMO Elon has a history of using the whip on employees and exaggerating. So maybe?

Well, it's very hard to push engine develoment faster.  But concrete and ground steel work?  You can throw money at that problem and have 200 people there the next day working on it.

[SethInMI 145]

if Elon says 1-2 months, it's probably 3-4. Either way, the next launch will be here before we know it, and be far likelier to get to splashdown.  Fun times if you are a space nerd.

[Stumpy 256]

Can't say I am overly optimistic about his planned 2029 mission to mars

[billvon 2,400]

Updates on the flight - 

All engines were started, but three engines showed enough out-of-limits indications that they were shut down.  That meant they were at 30 engines which is the minimum for takeoff.

There is no evidence of debris damage to the vehicle so far.  (from all the debris kicked up due to the disintegration of the concrete pad.)

27 seconds into flight, engine 19 lost communications due to an "energetic event" that also blew the heat shields off four other engines.  From that point on there was a fire in that area, but the other engines kept running.

At 85 seconds they lost hydraulic control of the engines and thus lost the ability to steer.  They sent the FTS command (self-destruct) and the FTS fired but did not destroy the vehicle.  It kept running for another 40 seconds before it finally blew up.  

The loss of hydraulic control was likely due to damage caused by engine 19 blowing up.

[kleggo 138]

interesting, thanks BVN