Starship is Go...

Oldfart1939 · 2021-04-06 08:58:53

I fully agree about fixing the damn leaks and making sure that fires don't occur in the engine bay. But I'm a "belts and braces" kinda guy when something this critical is involved. Use teflon insulation inside armored wiring harness, after the leaks have been fixed.

Oldfart1939 · 2021-04-06 10:17:30

Starship SN-15 is scheduled for rollout to the launch pad either today or tomorrow. Musk claims that the leaks have been worked on "six ways to Sunday." "hundreds of new upgrades included..."

louis · 2021-04-06 10:55:02

I'd trust Musk and Co over anyone else to fix this - on this sort of timescale.

Oldfart1939 wrote:

Starship SN-15 is scheduled for rollout to the launch pad either today or tomorrow. Musk claims that the leaks have been worked on "six ways to Sunday." "hundreds of new upgrades included..."

GW Johnson · 2021-04-06 12:33:20

So, did I not nail the causality train in post 1042 above, several days ago?

I stand by the two recommendations I made in that post.

GW

RobertDyck · 2021-04-06 13:13:25

I wish we had a "thumbs up" button for posts #1051, #1053, #1054.

SpaceNut · 2021-04-06 17:12:32

Video in post 1041 shows where this leak is.

it matches the color of an engine running coming down in between them

simular video showing the flames in the engine area about 20 seconds after launch

https://youtu.be/4zVyznBrHNI

This one is a closer view of the engines
https://youtu.be/3Et-dwX6s5c

GW Johnson · 2021-04-07 12:35:52

I saw the videos that Spacex posted on their website. The one camera view that showed the fire on the side of the engine powerhead was quite informative. You could see the sparks from the wires shorting out as their insulation burned away.

Of more interest, and still unaddressed, is the reason for the explosion that blew the vehicle apart. Musk tweeted about a "hard start". One has to wonder whether the extreme force transient of that "hard start" cracked the thrust puck open, and in the process cracked open a fitting in the oxygen piping from the oxygen tank ahead of the fuel tank.

Put oxygen into an ongoing fuel-air fire and you get a fast-deflagration explosion nearly every single time. I'm talking about the kind of event that "disassembled" shuttle Challenger. The loose booster poked a hole in the LOX tank, that dumped LOX onto the chronic hydrogen-air base fire at the base of the tank. In less than the blink of an eye, the explosion ripped the center tank to shreds. The shuttle turned broadside to the slipstream, and was ripped to pieces. In the cabin section, the crew was still alive, until they hit the sea.

It's not too hard to put together a similar (and very credible) scenario to explain what happened to SN-11. I just did.

GW

louis · 2021-04-07 12:47:32

It was bigger than your average Space X explosion I believe - didn't a large part land something like 5 kms away?

GW Johnson wrote:

I saw the videos that Spacex posted on their website. The one camera view that showed the fire on the side of the engine powerhead was quite informative. You could see the sparks from the wires shorting out as their insulation burned away.
Of more interest, and still unaddressed, is the reason for the explosion that blew the vehicle apart. Musk tweeted about a "hard start". One has to wonder whether the extreme force transient of that "hard start" cracked the thrust puck open, and in the process cracked open a fitting in the oxygen piping from the oxygen tank ahead of the fuel tank.
Put oxygen into an ongoing fuel-air fire and you get a fast-deflagration explosion nearly every single time. I'm talking about the kind of event that "disassembled" shuttle Challenger. The loose booster poked a hole in the LOX tank, that dumped LOX onto the chronic hydrogen-air base fire at the base of the tank. In less than the blink of an eye, the explosion ripped the center tank to shreds. The shuttle turned broadside to the slipstream, and was ripped to pieces. In the cabin section, the crew was still alive, until they hit the sea.
It's not too hard to put together a similar (and very credible) scenario to explain what happened to SN-11. I just did.
GW

Last edited by louis (2021-04-07 12:48:02)

SpaceNut · 2021-04-07 18:24:12

It never got to burn up the fuel so yah its going to give a big bang.....

Wiring harness built with different materials can and do some time shift the frequency response as well as power that they can provide so its going to need testing, so we will see more explosions....

GW Johnson · 2021-04-07 20:41:37

I suggest you look up the test film of a particular von Braun V-2 at Peenemunde in 1943. The rocket failed to throttle up adequately, then lost thrust and fell back, then it toppled over. When it smacked the ground, the forward alcohol tank split wide open, releasing a pool of liquid alcohol fuel onto the ground, with a fire into the air. A split second later, the LOX spilled from its breached tank into that fire, and created an explosion. A very violent explosion. Not a full shock detonation, but it fools a lot of people into thinking that there was a detonation.

Then look again at the video of the Challenger explosion. It is precisely the same process: spilling LOX onto an existing fuel-air fire. Precisely the same process. Just slightly-different circumstances. Also incredibly violent.

Put some confinement on it, and you don't even need the LOX. The center tank explosion that destroyed TWA-800 had no LOX. Just a fuel-air fire inside a closed jet fuel tank. Same as ever since the WW1 aerial gunfights. Not WW2, WW1.

They use natural gas or propane for fireballs, explosions, and simulated fires in the movies and TV. You can tell, because natural gas and propane don't smoke very much. The real things do.

Fuel, air, fire, and explosions are things I know very, very, very well. I got to do that stuff both in aerospace weapons work, and also in civil engineering in the fire protection sector of business.

GW

louis · 2021-04-08 14:08:43

SN15 being rolled out.

https://www.youtube.com/watch?v=b0tpApLtukc

Last edited by louis (2021-04-08 14:09:15)

GW Johnson · 2021-04-09 12:46:20

Answer to Quaoar's question, coming from the ballistic delivery topic, per TH's instructions:

From the simulations that I have seen at various times on Spacex's website, both the Earth entry from LEO and the Mars entry from interplanetary trajectories, look about the same to the end-of-hypersonics at about local Mach 3. Both show Starship at 60 degrees angle-of-attack from the relative wind vector, generating a very small amount of lift and a whopping amount of drag.

In both cases, the pitch plane is initially rolled about the wind axis to be inverted (lift directed downward). Later in the entry, this pitch plane is rolled upright so that the lift is oriented upward. The speed where this roll-upright takes place is less than orbit speed. I do not know the exact numbers.

From interplanetary at Mars, entry starts at a speed (at least 5.4 km/s and up to 7.5 km/s) much greater than escape (5 km/s). It the craft were to bounce off the atmosphere, it would escape and be permanently lost in space. Entry remains inverted between escape and circular orbit speed (71% of escape), so as to prevent bouncing off the atmosphere. While the craft would not escape, it would skip far downrange, skipping like a stone on water, and miss its landing location by hundreds to thousands of km. So you stay inverted, downlifting, until well below orbit speed (3.5 km/s), and thus much deeper in the atmosphere, where you cannot skip off. Then you roll upright and lift upwards, so as not to bend the trajectory too far downward.

I have never seen a simulation for the return to Earth from Mars, but it is an above-escape entry very much like Mars, only the numbers are larger. Entry interface nearer 12 km/s (worst case could be as high as 17 km/s). Earth escape is 11 km/s, and orbit speed just under 8 km/s.

The simulation I have seen for Earth entry is from low Earth orbit. You hit the atmosphere just below orbit speed, inverted, so you cannot skip downrange. Then you roll upright, so as not to bend the trajectory too far downward.

The two simulations differ when the hypersonics end. At Mars, this is well under 10 km (rather near 5 km) altitude at local Mach 3, about 0.7 km/s velocity. Supposedly the craft executes an aerodynamic pull-up nearly into a tail-slide maneuver, at nearer 10 km altitude and about Mach 1.5-ish speeds, and fires up its engines to pitch tail-first and land vertically.

At Earth, end of hypersonics occurs at local Mach 3 about 40+ km up, and nearer 0.9 km/s velocity. They just pitch up to 90-degree angle-of-attack (meaning dead broadside to the wind), and do the belly-flop maneuver, falling straight down. As altitude decreases, air density increases, and the equilibrium falling velocity decreases. By near sea level, it is very subsonic (0.06 to 0.07 km/s), like what we have already seen in the flight tests. There, it flips tail first, and lands propulsively.

GW

Last edited by GW Johnson (2021-04-09 12:47:48)

tahanson43206 · 2021-04-09 14:08:22

For GW Johnson re #1062

SearchTerm:Landing sequence for Starship preview see post #1062 above

For Quaoar ... thanks for asking this excellent question!

(th)

Quaoar · 2021-04-09 16:05:32

Thanks

louis · 2021-04-10 05:51:22

https://www.reddit.com/r/spacex/comment … uperheavy/

Whatever you might think about the quality of some aspects of the Starship - legs, fire control, whatever - the pace of development is truly amazing. They are already working on SN20 and BN3!

GW Johnson · 2021-04-10 08:28:29

Re post 1062 entry descriptions: the lift vector down/lift vector up approach applies to every US capsule since Gemini in the mid 1960's. It also applied to Space Shuttle, and it applies to X-37b, and will apply to Dreamchaser if that one ever flies. It did not apply to Mercury because we hadn't yet learned how to do it then. It does not apply to Soyuz (or its copy Shenzou) because those entry modules are round and cannot lift.

Shuttle used a 20-40 degree angle of attack (not Starship's 60 degrees) because of some aerodynamic peculiarities that Spacex may have to face with Starship. We'll see, I dunno yet. Shuttle's pilot cabin windscreen could not survive the direct hypersonic windblast below 20 degrees. Above 40 degrees, the interaction of the separated flow over the nose with the lateral vortices along the sides caused a hypersonic windblast jet to reattach and strike the windscreen again. Neither was survivable. **** see PS below.

Starship crew/passenger versions have windows planned for the lee-side dorsal surface near the nose. These are at risk for the same phenomena that limited angle of attack to a very narrow range on Shuttle. I dunno; we'll see.

X-37b does not suffer from this risk: there is no windscreen to be vulnerable. Dreamchaser would be vulnerable; it has a windscreen.

As for Starship's aerodynamic pull-up near the Martian surface, I am very skeptical it can really do that. I tend to disbelieve there can be sufficient lift available to bend the trajectory that sharply. I think they will have to add thrust-at-high-angle-of-attack to that (stalled) body lift to get sufficient cross-trajectory force to bend the trajectory upward. Mars's "air" is just too thin. Obviously Spacex doesn't think so, but they may end up changing their minds. It is a very real risk that will have to be addressed.

GW

PS (update 4-11-21): decades ago when I was a graduate student, I worked on a wind tunnel test program that identified this problem in the UT Austin Mach 5 wind tunnel, and confirmed it at AEDC in Tennessee, among many other things. The supervising professor had a contract with NASA to do this, to support the design of its space shuttle vehicle, which by this time had gelled into the tank/boosters/orbiter configuration that finally flew.

The problem was pretty much independent of all the shuttle nose shape candidates that we investigated. Which suggests that other, more divergent shapes are also vulnerable. That would include Spacex's Starship. Quartz windscreens could not survive outside the narrow AOA interval, because quartz has little emissitivity by which to cool re-radiatively, and not enough thermal conductivity to cool by conduction to adjacent structures (which would then be at risk of overheating themselves). It overheats and fails, quite quickly, unless in a wake zone. The conditions otherwise are just too extreme.

Last edited by GW Johnson (2021-04-11 10:31:59)

Quaoar · 2021-04-13 09:58:08

GW Johnson wrote:

Starship crew/passenger versions have windows planned for the lee-side dorsal surface near the nose. These are at risk for the same phenomena that limited angle of attack to a very narrow range on Shuttle. I dunno; we'll see.
X-37b does not suffer from this risk: there is no windscreen to be vulnerable. Dreamchaser would be vulnerable; it has a windscreen.
.

Just a question about windscreens: are they really necessary? Why not to put some little cameras connected to monitors?

P.S.
I remember my travel to Milan with the Covid Team with a military plane: the fuselage had not windscreens. Initially it seemed to me quite claustrophobic, but when the plain went up and down I didn't notice any discomfort to my ears, unlike the civil planes which have plenty of windscreens. I deduced that windscreens are not perfectly sealed and there is always some air leakage.

Last edited by Quaoar (2021-04-13 16:32:19)

GW Johnson · 2021-04-13 16:10:08

Quaoar:

I suppose the answer to your "windscreen necessity" question is "it depends".

It depends on what kind of craft and how you expect to fly it. If it is a manned spaceplane like space shuttle or Dreamchaser, the pilot really needs a way to see outside to land the thing like an airplane.

Automated landings are possible (see X-37B), but you'll notice the airlines do NOT choose to use that technology. Most of their passengers would not fly, if they ever thought the pilot couldn't see to fly the plane, or wasn't flying the plane because some idiot computer was flying it.

In the case of Spacex's passenger-carrying Starship, the landing is automated. The windows are for the entertainment and sanity of the passengers. Sightseeing out the windows really is psychologically important for passengers. Quite different from trained crew.

GW

Last edited by GW Johnson (2021-04-13 16:12:32)

Quaoar · 2021-04-13 16:37:39

GW Johnson wrote:

Quaoar:
I suppose the answer to your "windscreen necessity" question is "it depends".
It depends on what kind of craft and how you expect to fly it. If it is a manned spaceplane like space shuttle or Dreamchaser, the pilot really needs a way to see outside to land the thing like an airplane.
Automated landings are possible (see X-37B), but you'll notice the airlines do NOT choose to use that technology. Most of their passengers would not fly, if they ever thought the pilot couldn't see to fly the plane, or wasn't flying the plane because some idiot computer was flying it.
In the case of Spacex's passenger-carrying Starship, the landing is automated. The windows are for the entertainment and sanity of the passengers. Sightseeing out the windows really is psychologically important for passengers. Quite different from trained crew.
GW

But it would be possible to study some kind of solution like false windscreens that are plasma monitors connected to external cameras, or glass windscreen that are covered by PICA-X protected panels during the atmospheric entry, or a glass panoramic module for observation that is jettisoned before the entry.

SpaceNut · 2021-04-13 19:59:01

SpaceX’s Starship program has won $53 million from NASA to perform a full-scale test of orbital propellant transfer, taking the company and space agency’s relationship on the crucial technology to the next level.

SpaceX's plan for in-orbit Starship refueling: a second Starship

Musk described it, having the ability to refuel a Starship means it can carry a full 1200 ton propellant load when leaving Earth's orbit. Starship's design, with its 50m-long body covered in 301 stainless steel, with ceramic tiles in certain high heat areas.

lxwgmq8ke3s61.jpg?width=640&height=533&crop=smart&auto=webp&s=532a3421c0b14b430533e7ef381bd2211202659d

louis · 2021-04-14 18:31:10

Felix is back...

https://www.youtube.com/watch?v=gl_n3Ac1V-k

SpaceNut · 2021-04-14 18:55:58

looking at the tank volume required to bring LH2 to mars is of the 60,000kg to use will actually be greater that that since it must contend with boiloff. But the equation is 60 m^2 to hold the 60,000kg so lets make that 100 mt for lh2 so if the rockets diameter is 9 meters so if we insolate better that might make it 8 meters and the height of the tank needs to be about 13 meters tall. Which is a bit larger than a Delta 4 tank of the first stage 2x in size or 2 common cores tied together.
I think water would be better to transport to mars but thats quite a bit of mass to deliver.

louis · 2021-04-14 19:25:40

I think false windscreens and false windows in Starships, Mars Habs and Rovers will be v. useful in the early stages of colonisation.

Quaoar wrote:

GW Johnson wrote:
Quaoar:
I suppose the answer to your "windscreen necessity" question is "it depends".
It depends on what kind of craft and how you expect to fly it. If it is a manned spaceplane like space shuttle or Dreamchaser, the pilot really needs a way to see outside to land the thing like an airplane.
Automated landings are possible (see X-37B), but you'll notice the airlines do NOT choose to use that technology. Most of their passengers would not fly, if they ever thought the pilot couldn't see to fly the plane, or wasn't flying the plane because some idiot computer was flying it.
In the case of Spacex's passenger-carrying Starship, the landing is automated. The windows are for the entertainment and sanity of the passengers. Sightseeing out the windows really is psychologically important for passengers. Quite different from trained crew.
GW
But it would be possible to study some kind of solution like false windscreens that are plasma monitors connected to external cameras, or glass windscreen that are covered by PICA-X protected panels during the atmospheric entry, or a glass panoramic module for observation that is jettisoned before the entry.

kbd512 · 2021-04-14 22:34:16

louis wrote:

I think false windscreens and false windows in Starships, Mars Habs and Rovers will be v. useful in the early stages of colonisation.

Louis,

I second this. Windows are weak points. When they fail, people die. At the cost of a few hundred Watts of power for a very large display, flexible wrap-around LED displays can provide photo-realistic views of the outside world that are so clean and accurate that the human eye can't resolve the individual pixels from mere inches away. New chips like Apple silicon are so powerful and integrated that they only require a few Watts to drive car window sized monitors. The lighting of the display uses far more power than the camera chip and graphics / cpu chip combined. There won't be any piloting of the ship using anything but onboard sensors and cameras, so the requirement to see out the cockpit is a moot point.

louis · 2021-04-15 14:39:01

What do I know - but looks like SN15 passed its cryo test...

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

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#1051 2021-04-06 08:58:53

Re: Starship is Go...

#1052 2021-04-06 10:17:30

Re: Starship is Go...

#1053 2021-04-06 10:55:02

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#1054 2021-04-06 12:33:20

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#1055 2021-04-06 13:13:25

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#1056 2021-04-06 17:12:32

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#1057 2021-04-07 12:35:52

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#1058 2021-04-07 12:47:32

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#1059 2021-04-07 18:24:12

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#1060 2021-04-07 20:41:37

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#1061 2021-04-08 14:08:43

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#1062 2021-04-09 12:46:20

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#1063 2021-04-09 14:08:22

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#1064 2021-04-09 16:05:32

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#1065 2021-04-10 05:51:22

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#1066 2021-04-10 08:28:29

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#1067 2021-04-13 09:58:08

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#1068 2021-04-13 16:10:08

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#1069 2021-04-13 16:37:39

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#1070 2021-04-13 19:59:01

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#1071 2021-04-14 18:31:10

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#1072 2021-04-14 18:55:58

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#1073 2021-04-14 19:25:40

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#1074 2021-04-14 22:34:16

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#1075 2021-04-15 14:39:01

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