Wiki Super Heavy/Starship - General Development Discussion

[mongo]

This is also evidenced from looking at the 2nd graph in that page. If you look at that you can see the horizontal velocity does NOT dip but goes flat for a few seconds after MECO.

That small flat section tells us there is no reduction in horizontal velocity between MECO and Merlin ignition - Ergo no atmospheric effect

Yeah, an F9 at staging has a high mass to area ratio.
From the plot, drag at staging is equivilent to drag at 200 m/s at 4km. That's 13,000 ft (60% sea level density) at 450 MPH maybe 3kN. But... mass is huge. Second stage is 96k kg sans payload, so 3kN gives an acceleration of 1/32m/s^2 or 0.3% of a G...
As in G I was off

Sattelites are a lot lighter (and moving faster).

 

[mongo]

Ship 25 static fire, 6 engines
They also concreted the OLP today

https://twitter.com/x/status/1673509777819967488

 

[ecarfan]

Watching Scott Manley’s latest Deep Space Update video he says that the new stage sep technique will have the 3 sea level Starship Raptors ignite while the vehicles are still attached and a few (maybe only 1?) R boost engines will be running (most will have been shut down), the R Vacs will then ignite sometime after separation.

That was a detail I had not seen before. Interesting.

 

[mongo]

Watching Scott Manley’s latest Deep Space Update video he says that the new stage sep technique will have the 3 sea level Starship Raptors ignite while the vehicles are still attached and a few (maybe only 1?) R boost engines will be running (most will have been shut down), the R Vacs will then ignite sometime after separation.

That was a detail I had not seen before. Interesting.

Yeah, 50% thrust on the three sea level engines.

https://twitter.com/x/status/1673684418974609410

 

[Electroman]

There were concerns raised on the interstage section of the booster, but the real question is, is there a danger of SS engine damage due to exhaust blow back ?

 

[JB47394]

the real question is, is there a danger of SS engine damage due to exhaust blow back ?

There should be no blowback because the exhaust is going to be vented away. It's depicted in that first image of the tweet. I think they've got the vent direction backwards because the exhaust will push the booster forward. If they vent forward, it will push the booster backward. I will be intrigued if my intuition is backwards.

the interstate section of the booster

So tempting.

 

[ecarfan]

There were concerns raised on the interstage section of the booster, but the real question is, is there a danger of SS engine damage due to exhaust blow back ?

I don’t think so due to the assumed new interstage section with side vent holes.

The Starship sea level Raptor exhaust will impact the top of the booster tank dome. Obviously SpaceX has put a lot of thought into that issue. They could use slightly thicker steel in the dome, but B10 is already built and ready to go. Perhaps some TPS tiles could be added now? They don’t weigh much. But it’s a different curvature than any surface currently covered by tiles on the ships, so they would have to be special tiles.

Or, will the new interstage include a bottom piece that completely covers the booster tank dome surface?

However, for test flight #2 the booster won’t be reused so if they leave it like it is and there is some damage on the top tank dome it doesn’t matter as long as the tank doesn’t rupture.

 

[mongo]

I don’t think so due to the assumed new interstage section with side vent holes.

The Starship sea level Raptor exhaust will impact the top of the booster tank dome. Obviously SpaceX has put a lot of thought into that issue. They could use slightly thicker steel in the dome, but B10 is already built and ready to go. Perhaps some TPS tiles could be added now? They don’t weigh much. But it’s a different curvature than any surface currently covered by tiles on the ships, so they would have to be special tiles.

Or, will the new interstage include a bottom piece that completely covers the booster tank dome surface?

However, for test flight #2 the booster won’t be reused so if they leave it like it is and there is some damage on the top tank dome it doesn’t matter as long as the tank doesn’t rupture.

The latter, they need to protect the grid fin systems and clamps.
Threre is the ring with side ports that could have a secondary dome installed.

 

[Electroman]

The interstage is what around 10 feet tall or less? The vents seems quite small. Vents will help greatly getting the exhaust out of the system, but I guess there will be still significant blowback.. I think.


Also why the need to run one Booster engine during hot staging?

 

[mongo]

The interstage is what around 10 feet tall or less? The vents seems quite small. Vents will help greatly getting the exhaust out of the system, but I guess there will be still significant blowback.. I think.


Also why the need to run one Booster engine during hot staging?

There may be both the high vent section and the port section. If two full rings, that would be 3.6m or so, just under 12 feet.

As to blow back, the engine bells are built to withstand full thrust and the rest of the structure is inherently strong as it directly interfaces to the vehicle mass.
Also, how much pressure can be developed before the sections part and there is a widening escape path?
Ship only equivalent thrust. Really, separation depends on accelerating Starship faster than booster.
3 V2 Raptors * 250 tons of thrust * 50% throttle = 375 tons of thrust = 3.7 MN
Ship diameter = 9m, area = 63.5m2
3.7MN/63.5= 5.9k kg / m2 = 58 kPA = 0.58 bar = 8.3 psi.
Or:
375metric ton= 825000 pounds
9 m= 354 inches
Area = 98423 sqin
825000/354 =8.4 psi

Turbopumps alone might do it?

Keeping the booster lit eliminates the need for ullage and flip thursters. No slosh effects either. It reduces restart gas requirements. Cross bleed starts would be interesting, if they could spin up from the hot side...

 

[mongo]

There may be both the high vent section and the port section. If two full rings, that would be 3.6m or so, just under 12 feet.

As to blow back, the engine bells are built to withstand full thrust and the rest of the structure is inherently strong as it directly interfaces to the vehicle mass.
Also, how much pressure can be developed before the sections part and there is a widening escape path?
Ship only equivalent thrust. Really, separation depends on accelerating Starship faster than booster.
3 V2 Raptors * 250 tons of thrust * 50% throttle = 375 tons of thrust = 3.7 MN
Ship diameter = 9m, area = 63.5m2
3.7MN/63.5= 5.9k kg / m2 = 58 kPA = 0.58 bar = 8.3 psi.
Or:
375metric ton= 825000 pounds
9 m= 354 inches
Area = 98423 sqin
825000/354 =8.4 psi

Turbopumps alone might do it?

Keeping the booster lit eliminates the need for ullage and flip thursters. No slosh effects either. It reduces restart gas requirements. Cross bleed starts would be interesting, if they could spin up from the hot side...

Correction, per Elon's tweet, the booster will have 3 engines at 50%, not the ship.

 

[ecarfan]

Correction, per Elon's tweet, the booster will have 3 engines at 50%, not the ship.

Thanks! Can’t believe I misread Elon’s tweet, it was crystal clear.

So we don’t yet know which Starship engines will first ignite for stage sep.

 

[ecarfan]

There may be both the high vent section and the port section. If two full rings, that would be 3.6m or so, just under 12 feet.

I assume this new interstage section will be permanently attached to the booster and not discarded like on the Saturn V.

Which means it will raise the height of the entire vehicle, including the Starship QD ports. Is the QD arm on the tower height adjustable? It must be, to some extent.

 

[mongo]

I assume this new interstage section will be permanently attached to the booster and not discarded like on the Saturn V.

Which means it will raise the height of the entire vehicle, including the Starship QD ports. Is the QD arm on the tower height adjustable? It must be, to some extent.

Yeah, permaship.

QD is only slightly adjustable, they were using the crane on it today to reposition the assembly.

Thanks! Can’t believe I misread Elon’s tweet, it was crystal clear.

So we don’t yet know which Starship engines will first ignite for stage sep.

I misread it also and posted with my incorrect interpretation previously, feel free to put that one on me.

 

[ecarfan]

Deluge Plate Moved to Launch Site

 

[Cosmacelf]

Deluge Plate Moved to Launch Site

The amount of scrutiny that SpaceX and Tesla get is simply mind blowing. Also mind blowing that SpaceX allows this level of scrutiny. I am reminded by a presentation Elon did many many years ago to the European space agency, and he was asked how ESA could become as efficient as SpaceX. He told them, in detail. Their reaction was “we can’t do that…”. Secrecy is for wimps

 

[ecarfan]

The amount of scrutiny that SpaceX and Tesla get is simply mind blowing.

Yes but I think it simply reflects that the fact that the two companies are doing some of the most interesting work anywhere as part of their attempt to create a better future for humanity.

And in the case of SpaceX, of the fact that they do their work right next to a public road and move huge stuff on that road.

 

[JB47394]

Yes but I think it simply reflects that the fact that the two companies are doing some of the most interesting work anywhere as part of their attempt to create a better future for humanity.

Add in the fact that the two companies are incredibly disruptive to their respective industries. Tesla has pulled the rug out from under legacy auto, has obvious impact on oil and gas companies, is eliminating dealerships, and I'm sure folks can come up with more. SpaceX is pretty much rewriting the book on rocket operations, making existing rocketry companies look like plodding oafs.

All of this produces visible drama, and media thrives on drama.

Also, each company provides lots of interesting stuff about what they're doing. Compare this with other companies that just aren't interested in the public. They're businessmen and they want to make money. SpaceX and Tesla have an entire ecosystem surrounding what they do.

 

[Nikxice]

I'd be amazed if an August launch comes to fruition. Forget about Musk vs. Zuck. This David and Goliath battle is the real deal.

Here's an excerpt from an article published this evening by CNN, "Musk has repeatedly said he’d like to try to launch Starship again as soon as this summer, but the FAA said in a statement to CNN that SpaceX has yet to take public safety actions or submit a mishap report with corrective actions for FAA review and approval."
For better context, full story below.

https://www.cnn.com/2023/07/07/world/spacex-starship-explosion-south-texas-fallout-scn/index.html

 

[spacerfc]

There is no David and Goliath battle, it's the same few people stirring up trouble. If you have been following Boca Chica for a few years, you'd recognize their names since they appear in pretty much every hit piece.

The lawsuit is irrelevant, the NIMBYists are irrelevant. The only one who can stop SpaceX is SpaceX themselves, they need to finish the report, fix the pad, fix the FTS, that's the only thing matters.