Rocket general questions 1

[rb1957]

From today's launch (nice launch, not so nice flight) of SpaceX ...
1) what gas are they venting ? can't think they've venting methane
2) how do they control pressure in the tanks ? do they have a bladder/balloon where they can add/remove gas/liquid (N2 ?)
3) they made a point of filling the header tanks (which would not be used) ... so they intended to dump a tank (small though it may be) full of methane into the Pacific ??
4) when they chill the plumbing and such before loading fuel, I assume they're only passing N2 through the system, and it doesn't hang around long (as it did when they did the cryo testing)

"Hoffen wir mal, dass alles gut geht !"
General Paulus, Nov 1942, outside Stalingrad after the launch of Operation Uranus.

 

[IRstuff]

If you are referring to the jets coming out the sides of the rocket, I think those were maneuvering thrusters, trying desperately to regain control of the wobble from not all of the engines firing

TTFN (ta ta for now)
I can do absolutely anything. I'm an expert!

https://www.youtube.com/watch?v=BKorP55Aqvg

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[WKTaylor]

RB... I replied in the SLS thread... earlier.

However here are some of my thoughts on what was visible...

The 1st stage had multiple [5 or 6???] engine failures probably leading to loss of control [cork-screwing] and disintegration before staging could occur, ~3:57 into launch. It appears that SpaceX MAY have allowed the fight to proceed to vehicle 'break-up' and did not initiate self-destruct sequence.

I suspect that with one or more engine failures, there were multiple plumes of uncontroled hot gases venting from the base of the 1st stage. These plumes possibly contributed to instability that could not be controlled by engine gimbling.

On launch, it appears that 3-engines were in-op from lift-off... then 1 other went in-op soon after.

At ~+40 seconds 1-more engine went in-op.

At ~+1:25 another engine went in-op. At this time there were no tramp 'plumes'.
Oddly the figure in the lower left corner of the picture showed 5-engine down... but the image of the base showed 6-engines in-op... most in the outer row and very asymmetric.

At ~+1:45 the nominal plume expansion began to show asymmetry irregularities and instability.

At about +1:50 a noticeable roll develops... and soon after the entire vehicle begins to slowly pitch and roll... corkscrew-wise. At this point failure was inevitable.

At 4:14 the camera in the launch control room pans... and Musk is sitting quietly/stoically. A little later he appears annoyed at the clapping.

This 'commentary' just popped-up on You-Tube...

https://www.youtube.com/watch?v=vta1rueCMW0

I wonder how many launch failures will come... and how many will be tolerated by the FAA and Texas?

Regards, Wil Taylor
o Trust - But Verify!
o For those who believe, no proof is required; for those who cannot believe, no proof is possible. [variation, Stuart Chase]
o Unfortunately, in science what You 'believe' is irrelevant. ["Orion", HBA forum]
o Only fools and charlatans know everything and understand everything." -Anton Chekhov

 

[rb1957]

shame on you Will ... linking SLS and SpaceX !

yeah, you could see it unfolding. Nice launch, shame about the flight ?

I still don't get Starship as a lunar lander; what do you mean the door is all the way up there ??
Much prefer the "Space 1999" Eagle ... landing on 4 legs, close to the ground.

"Hoffen wir mal, dass alles gut geht !"
General Paulus, Nov 1942, outside Stalingrad after the launch of Operation Uranus.

 

[btrueblood]

Thinking about 30-some odd engines starting simultaneously, at north of 1.7 million pounds of thrust, and where does the exhaust flow go? The shock reflection off the flat concrete launch pad some 10 feet or so below the nozzle bells has GOT to cause problems for ignition and flame development across the swath of engines trying to light off. Would be an interesting plume calculation, though likely futile - was the base structure and fairings near the base designed to prevent full throttle rocket plume from travelling back up along the tanks and engine plumbing? Stupid not to use a flame diverter/bucket on the launch pad, as all rocket launches since the Mercury program have used. And yeah, I'd have been annoyed at all the clapping and cheering going on, it would be like cheering a crash at the Indy 500.

 

[dik]

You've heard about the Model A and the Model T... What about the Model B through to Model S?

-----*****-----
So strange to see the singularity approaching while the entire planet is rapidly turning into a hellscape. -John Coates

-Dik

 

[btrueblood]

Dik -

In SpaceX's case, they have taken a page from failures (Energiya) rather than proven designs (Apollo, Shuttle, SLS) for heavy booster designs. So it's going from an F150 or whatever back to the Edsel...

And I agree with Wil, so far SpaceX has gotten lucky and not killed anybody (that I know of?). Drop a million pounds of esplody booster on a small African country and watch what happens to Tesla stock prices.

 

[dik]

Agree... my attempt at humour was not so good...

-----*****-----
So strange to see the singularity approaching while the entire planet is rapidly turning into a hellscape. -John Coates

-Dik

 

[rb1957]

I think that's a bit harsh on SpaceX. Sure they have a bunch of experiments before they figure things out. How many experiments did NASA have in the 60s ?

Ok, so they've taken a different design approach to achieve different goals. Are solid fuel rockets better than liquid fuel ? IMHO, no, each design has pros, and cons. SpaceX is trying to make a highly reusable design ... is that "wrong" ? is staying with expendable rockets the way of the future ? SpaceX has shown a much higher launch cadence than anyone has done before, and much cheaper. is that "bad" ?

To claim that a SpaceX design is several generations behind SLS is, IMHO, ludicrous.

"Drop a million pounds of esplody booster on a small African country and watch what happens to Tesla stock prices." What happened when NASA did this over Texas ?
Range safety is designed expressly so this doesn't happen. By the time StarShip was over Africa the Booster had already been staged, so it was much lighter and higher ... and would probably burn up on descent.

"Hoffen wir mal, dass alles gut geht !"
General Paulus, Nov 1942, outside Stalingrad after the launch of Operation Uranus.

 

[btrueblood]

Sorry to poke fun at your hero, Rb. I don't dispute most of what you wrote (my 2nd post was mostly in jest), except the following rebuttals

- why did they not replicate the launch pad designs that NASA developed and proved to work over decades? The damage done to their pad, and the likelihood that the launch pad destruction may have (via debris collisions) contributed to their launch failure (pardon me, "unplanned disassembly") speak to a level of hubris that is common to the startup mentality (move fast and break things). Successful and cheap it may be...until somebody gets hurt.
- NASA has range safety officials that aren't on Musk's payroll, and will destroy a rocket safely over the Atlantic, long before it executes two (or three? I lost count) cartwheel rolls. NASA didn't drop a fuel-heavy booster on Texas, get your facts straight.
- Having 30-plus engines spread across the base of the rocket is a novel, unproven (Energiya blew up on first test launch too, and then Russia gave up on it), and tricky configuration, and worth a lot more testing to verify startup characteristics long before doing a full stack launch. I think they did one brief hot fire of the booster? And had engine failures on that test, which would have made a more conservative outfit repeat the test to get the ignition sequence figured out.

"To claim that a SpaceX design is several generations behind SLS is, IMHO, ludicrous."

Ludicrous is exactly what SpaceX strives for, i.e. development speed at all costs. I've spoken to quite a few engineers who worked there, and all of them left because they were afraid of being sucked into a lawsuit deposition. Acceptance of risk ...ah screw it, it's beer 30 on Friday. Good luck to them.

 

[WKTaylor]

A few random thoughts crossed my mind.

I understand the concept of liquid methane + LOX for the crew stage... propellant of convenience on the Red planet for the return. HOWEVER, the first stage/booster will never leave the surely bonds of earth returning softly or 'splashing'. What bothers me is that the immensely successful Falcon 9 and Falcon-Heavy use conventional RP-1 + LOX for the first stages. Introducing a novel propellant into a novel booster design seems sketchy-at-best... especially 'early in development'... one more thing to count as 'experimental'.

Also... any one else notice that the [4] grid fins on the upper last few feet of the booster were deployed on lift-off... not folded/faired back like the Falcons? In every other stationary photo they were folded/faired-back. I wonder if this was deliberate... or was feature intended for extra control due to booster engine failures?

When it became obvious the booster was beginning to cork screw. Why NOT force the stage separation and light-up the crew stage engines... to see if abort was possible in this bizarre circumstance... or find-out what else might happen???

Also... concept of Starship landing tail first on the Moon or Mars... with extendable legs. The dust/debris kicked-up by even reduced-thrust engines might actually damage the engines/bell-expansion chambers, clog injector-plates, etc. These same engines, I presume, are intended for lift-off and return-maneuvering and ultimately soft landing on earth. Sketchy survival with potentially damaged engines... or insulation or aft thrust structure.

NOTE: The Apollo Grumman-LEMs had the ultimately simple/elegant answers to many problem, including, to a degree, CREW SAFETY. Ditch the landing stage with it's potentially damaged engine/bell/weight and have a compact self-contained, undamaged/fully-fueled upper stage return to orbit from the surface or during a wild-crazy landing abort. OH yeah, conveniently, the maneuvering thrusters were all clustered on/stayed-with the upper-stage [4-quadrants]. KISS.

btrueblood... the STARSHIP booster/upper-stage likely disintegrated-over/crashed-into international waters of the Gulf of Mexico... but it is still practically in Texas's backyard... and certainly well within the USA ADIZ. OR perhaps it will come to light that NASA did 'push-the-terminate-button'... but I sincerely doubt it for this private test-launch from private-land. This incident will likely have an exhaustive mishap investigation to come, BEFORE next flight.

Regards, Wil Taylor
o Trust - But Verify!
o For those who believe, no proof is required; for those who cannot believe, no proof is possible. [variation, Stuart Chase]
o Unfortunately, in science what You 'believe' is irrelevant. ["Orion", HBA forum]
o Only fools and charlatans know everything and understand everything." -Anton Chekhov

 

[rb1957]

"Also... any one else notice that the [4] grid fins on the upper last few feet of the booster were deployed on lift-off... not folded/faired back like the Falcons? In every other stationary photo they were folded/faired-back. I wonder if this was deliberate... or was feature intended for extra control due to booster engine failures?" ... yes, I noticed that. I think they talked about it some time back. I think the idea is less complexity and less weight and more reliability to have the fins permanently deployed. the fuel penalty is less than the mechanism and system required to make them deployable. I believe they are deployable on Falcon rockets.



"Hoffen wir mal, dass alles gut geht !"
General Paulus, Nov 1942, outside Stalingrad after the launch of Operation Uranus.

 

[WKTaylor]

RB... the extended grid fins so far forward have to affect flight characteristics; IE destabilizing.

This analysis by Scott Manely has a ton of 'good' info on the SpaceX Starship Launch...

SpaceX's Massive Rocket Explodes Due to Rapid Unscheduled Digging [launch pad destruction]

https://www.youtube.com/watch?v=w8q24QLXixo

Also... The South Texas locals are from 'overjoyed' about the 'variety and intensity of the debris'...
SpaceX celebrated Starship's 1st launch. Some locals called it 'truly terrifying'

https://www.space.com/spacex-starship-launch-debris-terrifying?

Regards, Wil Taylor
o Trust - But Verify!
o For those who believe, no proof is required; for those who cannot believe, no proof is possible. [variation, Stuart Chase]
o Unfortunately, in science what You 'believe' is irrelevant. ["Orion", HBA forum]
o Only fools and charlatans know everything and understand everything." -Anton Chekhov

 

[rb1957]

yes, I'm aware of Scott's YT channel.

Whether they are destabliing or not I was answering the question "why?" as best I can think of. I'm "sure" they've accounted for these aero effects. The fins are steerable.

But ... this was the first time these fins flew ... and look what happened ... it was reasonably stable when sub-sonic, but no so much when supersonic ?? I'm sure they guys with the data can figure this out ...
(yes, I like ellipses ...)

"Hoffen wir mal, dass alles gut geht !"
General Paulus, Nov 1942, outside Stalingrad after the launch of Operation Uranus.

 

[hydrae]

The grid fins do not fold down on super heavy, that is part of the design, they do twist though.
The grid fins are also support structure for the tower to catch, lift, set
and hold while at the launch stand. My guess adding a pivot weighs more than the performance loss
of having them in the slip stream, and that pivot would need to be strong enough for those other uses.

The use of methane allows the use of full flow staged combustion cycle, the only cycle more efficient is the expander cycle which has a hard limit on size and only works best on H2. RP1 will soot up any partial combustion in a cycle.

side benefit, Methane is significantly lower cost that H2 or RP1

Hydrae

 

[rb1957]

ok, nice discussion, but back to the original questions ...

what gas are they venting ? there was much "talk" about the liquids boiling off which would imply methane and O2 are being vented. But I can't believe they'd vent methane (or any other fuel) ... so ...

how do they pressurise the tanks ? Do they use a bladder, by which they can control the volume (and therefore pressure) ? Then they could be venting this inert (N2) gas.

"Hoffen wir mal, dass alles gut geht !"
General Paulus, Nov 1942, outside Stalingrad after the launch of Operation Uranus.

 

[WKTaylor]

https://www.popsci.com/technology/spacex-starship-damage/

... 'last words'...
Update 4/25/23: The Federal Aviation Administration (FAA) confirmed to CNBC on Monday afternoon that it has grounded the company’s Starship Super Heavy launch program pending results of the “mishap investigation” which was “triggered by debris entering adjacent properties.”

Regards, Wil Taylor
o Trust - But Verify!
o For those who believe, no proof is required; for those who cannot believe, no proof is possible. [variation, Stuart Chase]
o Unfortunately, in science what You 'believe' is irrelevant. ["Orion", HBA forum]
o Only fools and charlatans know everything and understand everything." -Anton Chekhov

 

[WKTaylor]

SpaceX Starship launch under FAA investigation after raining potentially hazardous debris on homes and beaches

https://www.space.com/spacex-starship-faa-mishap-investigation

"The FAA will oversee the mishap investigation of the Starship/Super Heavy test mission," FAA officials wrote.
SpaceX's Starship has been grounded by the U.S. government following claims that the rocket's explosive first launch spread plumes of potentially hazardous debris over homes and the habitats of endangered animals.
The Federal Aviation Administration (FAA) — the U.S. civil aviation regulator — has stopped SpaceX from conducting any further launches until it has concluded a "mishap investigation" into Starship's April 20 test launch. The massive rocket’s dramatic flight began by punching a crater into the concrete beneath the launchpad and ended when the giant rocket exploded in mid-air around 4 minutes later.
... ...
SpaceX...

Regards, Wil Taylor
o Trust - But Verify!
o For those who believe, no proof is required; for those who cannot believe, no proof is possible. [variation, Stuart Chase]
o Unfortunately, in science what You 'believe' is irrelevant. ["Orion", HBA forum]
o Only fools and charlatans know everything and understand everything." -Anton Chekhov

 

[rb1957]

surely this is all very standard procedures after such a "mishap" ?
and not something exceptional ...

"Hoffen wir mal, dass alles gut geht !"
General Paulus, Nov 1942, outside Stalingrad after the launch of Operation Uranus.

 

[WKTaylor]

Pretty sure Musk hadn't planned on a 'real mishap investigation'.

Suspect He simply wanted everyone to 'just leave SpaceX alone to do-its thing and everything will work-out just fine'... with the most massive launch vehicle ever made by man.

Regards, Wil Taylor
o Trust - But Verify!
o For those who believe, no proof is required; for those who cannot believe, no proof is possible. [variation, Stuart Chase]
o Unfortunately, in science what You 'believe' is irrelevant. ["Orion", HBA forum]
o Only fools and charlatans know everything and understand everything." -Anton Chekhov