Wiki Super Heavy/Starship - General Development Discussion

[mongo]

That’s an interesting definition of harmless you’re using

Why? It will have cooled a bunch due to expansion and deluge water, the ship is metal, F9 flys through its own farts on every landing, and SH will too. The aero covers are designed for reverse flow along with engine protection.
That's assuming there is even any significant backwash, it may pull the surrounding air downward like the Saturn V.

 

[ecarfan]

That's assuming there is even any significant backwash, it may pull the surrounding air downward like the Saturn V.

The Saturn V engine exhaust got pulled down because it had a huge flame trench to be channeled into, which over time sustained damage and required repair. Photos below.

The SpaceX OLM has nothing like that and the booster will generate more thrust than a Saturn V.

I am expecting some damage to the concrete pad. Hopefully it will be minimal.

I could of course be all wrong about this and everything will be fine at the OLM!

 

[mongo]

The Saturn V engine exhaust got pulled down because it had a huge flame trench to be channeled into, which over time sustained damage and required repair. Photos below.

The SpaceX OLM has nothing like that and the booster will generate more thrust than a Saturn V.

I am expecting some damage to the concrete pad. Hopefully it will be minimal.

I could of course be all wrong about this and everything will be fine at the OLM!

Yah, but as far as exhaust vs side of rocket, it may still create a downdraft. Could make loops. At least it won't be there long with its projected thrust to weight ratio.

The Flame trench at 39A is 42 feet high, add some more for the launch structure. Starship mount is 85 feet or so.

No Martinite perhaps?

 

[ecarfan]

Starship mount is 85 feet or so.

Are you sure it’s that high? I did not realize that.

 

[Cosmacelf]

Why? It will have cooled a bunch due to expansion and deluge water, the ship is metal, F9 flys through its own farts on every landing, and SH will too. The aero covers are designed for reverse flow along with engine protection.
That's assuming there is even any significant backwash, it may pull the surrounding air downward like the Saturn V.

The smiley was a hint that it was a joke in that the exhaust isn’t very harmless for organic life.

 

[mongo]

Are you sure it’s that high? I did not realize that.

Much Googling said 85-100. I think 85 is the height with it recessed into the base?
The initial test stand was/ is much lower when they had the debris damage.

 

[Electroman]

An another thing: it will be impossible to take those closeup highspeed videos of the launch sequence, like the one @mongo posted above for Saturn 5 Apollo launch. The exhaust gases will overwhelm the whole pad well above the base of the rocket. And those videos I am guessing are vital to better understand and troubleshoot those first few seconds of launch.

Only see upsides and no downsides to having a flame trench, although there is some initial cost of construction. But then I am not a Space engineer. So there is that.

 

[ecarfan]

The Flame trench at 39A is 42 feet high, add some more for the launch structure

The 39A flame trench looks deeper than 42 ft, and the rocket engines were positioned well above the top of the trench walls. I cannot find a web reference to the SpaceX OLM height but agree that 85 ft seems possible. Maybe the fact that the OLM is open on all sides will mitigate damage to the concrete pad.

 

[mongo]

The 39A flame trench looks deeper than 42 ft, and the rocket engines were positioned well above the top of the trench walls. I cannot find a web reference to the SpaceX OLM height but agree that 85 ft seems possible. Maybe the fact that the OLM is open on all sides will mitigate damage to the concrete pad.

View attachment 840083

Trench is 42, and yeah (like I mentioned) rocket is above that by quite a bit.
Derived OLM by difference in launch hight vs rocket height. Reddit pixel counting puts it at 100 ft (to top, likely).

 

[mongo]

B7 is off the launch mount and 13 gimbaling Raptors are waiting in the Megabay...

https://twitter.com/x/status/1558072141236649985

 

[ecarfan]

Trench is 42, and yeah (like I mentioned) rocket is above that by quite a bit.
Derived OLM by difference in launch hight vs rocket height. Reddit pixel counting puts it at 100 ft (to top, likely).

View attachment 840086

I bow to your superior research ability! It looks so much deeper in photos.

BTW, there is a discussion of how much water sound suppression ability the OLM has at

SpaceX Starship : Texas Prototype(s) Thread 23 : Discussion

SpaceX Starship : Texas Prototype(s) Thread 23 : Discussion

forum.nasaspaceflight.com

 

[ecarfan]

The debate about whether or not the OLM was a “water deluge” system to mitigate pad damage and suppress sound or simply a “fire suppression system is ongoing at NSF. I would think that a water deluge system would be very important but of course I don’t have any expertise in that area, or really in anything SpaceX is trying to accomplish.

 

[mongo]

Go inner 13!

https://twitter.com/x/status/1558303186326265857

 

[ecarfan]

Latest NSF video at 7:20 shows “catch hardware” being installed on the chopsticks. Some may speculate that on the first test flight SpaceX will try to land the booster back at the OLM using the chopsticks. I’m skeptical. Seems like an extremely risky thing to attempt for the first flight. Would make more sense to me to do a soft landing in the ocean.

 

[Electroman]

We all know that they have been landing with excellent precession of upto what may within 10 feet off the big X on the drone ship.

But the margin needed here on the chopsticks I am guessing is in the order 3 or 4 feet? With a much bigger booster, that might be quite a challenge. Even if the error exceeds one in 10 landings, a crash will severely damage the launch/landing apparatus.

 

[mongo]

We all know that they have been landing with excellent precession of upto what may within 10 feet off the big X on the drone ship.

But the margin needed here on the chopsticks I am guessing is in the order 3 or 4 feet? With a much bigger booster, that might be quite a challenge. Even if the error exceeds one in 10 landings, a crash will severely damage the launch/landing apparatus.

Chopsticks have much greater side to side range than 4 feet and the catch slides likely do also.
Plus, the booster has a better thrust to mass range so it can adjust position better than the hover slam F9 (which seems better than 10 ft lately, booster radius is ~6 feet).

In the event of a critical misalignment, the booster may have enough reserves to yeet itself into the water. Loss of thrust would be bad, even with the offset catch positioning (though if it were an out of fuel issue, should buff right out).

 

[dhanson865]

That’s an interesting definition of harmless you’re using

The only entry about Earth in the Guide used to be "Harmless", but Ford Prefect managed to change it a little before getting stuck on Earth. "Mostly Harmless" Those two words are not what Ford submitted as a result of his research—merely all that was left after his editors were done with it.

I'm not sure if SpaceX rocket engine exhaust being "pretty harmless" is less or more accurate than the Earth being "Mostly Harmless" but I feel it meets the style guidelines.

 

[Cosmacelf]

We all know that they have been landing with excellent precession of upto what may within 10 feet off the big X on the drone ship.

But the margin needed here on the chopsticks I am guessing is in the order 3 or 4 feet? With a much bigger booster, that might be quite a challenge. Even if the error exceeds one in 10 landings, a crash will severely damage the launch/landing apparatus.

The F9 does a hover slam, meaning it drops its speed to zero within inches of the deck. It has to do this because the F9 booster cannot be throttled down enough to hover. But the Starship booster can (that's another benefit, by the way, of using large numbers of rocket engines rather than the much smaller number than New Glenn will use). Since both Starship and Booster can hover, there is much greater time to align everything and for the chopstick arms to move into position.

 

[bxr140]

(that's another benefit, by the way, of using large numbers of rocket engines rather than the much smaller number than New Glenn will use).

BE-4 can throttle way back.
New Glenn can hover.

 

[HVM]

I'm pretty sure than first New Glenn needs to (1) exist. (2) Launch at least ones, before it can show it can hover. It was supposed to land on the ship while on move, but not any more.

So sea-level thrust of the BE-4 is 240t (Metric tonnes), BO tested it at 40% so 96t
Using F9 S1 numbers we get empty weight of New Glenn S1 ~64t
So it needs to be throttle way deeper than that tested 40%.

Raptor and RD180 can throttle to 40%
RS 25 can throttle to 67%
Merlin to 70%

And BE-4 needs to be at ~27% ?