SpaceX Starship : First Flight : Starbase, TX : 20 April 2023 - DISCUSSION

[meekGee]

It doesn't need all 33 engines to climb from the pad. 2 or 3 less I  remember seeing somewhere.

If my math is right, Super Heavy could lose up to 8 engines at liftoff and still make it off the pad, i.e., TWR is >1

However, that would look a lot like that Astra launch that went sideways. It wouldn't get very far and there'd likely be considerable damage to the OLM and surrounding ground equipment.

It can lose 2 or 3 engines at liftoff and still make it to orbit. Losing engines later in the flight is less of an issue.

That said, I think that SpaceX will not release the hold-down clamps without all 33 engines running and healthy.

Every launch attempt is a risk.  This has to be factored in when deciding whether to commit or abort if n<33.

IMO, you get the most bang for the buck if you allow flight with n>=32.

The impact is the least possible, and the odds of it occurring are the highest.

If you're allowing flight with n=31, you have to think what if the failures are correlated, and also you can have more asymmetrical thrust, and we know B7 is less tolerant of that.

So maybe ok to go with n=31 only if the failed engines are on opposite sides or some similar criteria.

[AU1.52]

It doesn't need all 33 engines to climb from the pad. 2 or 3 less I  remember seeing somewhere.

If my math is right, Super Heavy could lose up to 8 engines at liftoff and still make it off the pad, i.e., TWR is >1

However, that would look a lot like that Astra launch that went sideways. It wouldn't get very far and there'd likely be considerable damage to the OLM and surrounding ground equipment.

It can lose 2 or 3 engines at liftoff and still make it to orbit. Losing engines later in the flight is less of an issue.

That said, I think that SpaceX will not release the hold-down clamps without all 33 engines running and healthy.

Every launch attempt is a risk.  This has to be factored in when deciding whether to commit or abort if n<33.

IMO, you get the most bang for the buck if you allow flight with n>=32.

The impact is the least possible, and the odds of it occurring are the highest.

If you're allowing flight with n=31, you have to think what if the failures are correlated, and also you can have more asymmetrical thrust, and we know B7 is less tolerant of that.

So maybe ok to go with n=31 only if the failed engines are on opposite sides or some similar criteria.

What if you were not carrying 150 tons to orbit? How many engines would you need then? What if any payload / mass simulation would S24 contain if any?

[meekGee]

It doesn't need all 33 engines to climb from the pad. 2 or 3 less I  remember seeing somewhere.

If my math is right, Super Heavy could lose up to 8 engines at liftoff and still make it off the pad, i.e., TWR is &gt;1

However, that would look a lot like that Astra launch that went sideways. It wouldn't get very far and there'd likely be considerable damage to the OLM and surrounding ground equipment.

It can lose 2 or 3 engines at liftoff and still make it to orbit. Losing engines later in the flight is less of an issue.

That said, I think that SpaceX will not release the hold-down clamps without all 33 engines running and healthy.

Every launch attempt is a risk.  This has to be factored in when deciding whether to commit or abort if n&lt;33.

IMO, you get the most bang for the buck if you allow flight with n&gt;=32.

The impact is the least possible, and the odds of it occurring are the highest.

If you're allowing flight with n=31, you have to think what if the failures are correlated, and also you can have more asymmetrical thrust, and we know B7 is less tolerant of that.

So maybe ok to go with n=31 only if the failed engines are on opposite sides or some similar criteria.

What if you were not carrying 150 tons to orbit? How many engines would you need then? What if any payload / mass simulation would S24 contain if any?

I was talking about this specific flight, where the risk of every ignition is high, and priority is to risk the OLM as little as possible, and when a partial flight is also pretty much considered a success.

Later on the considerations change.

[VLN]

By happy coincidence, I am going to be in Hawaii on starting April 17th visiting the islands Oahu and Kauai. If I go to the north shore when the water landing is attempted, is there a chance that I may be able to catch a glimpse of the water landing off in the distance, or it is still going to be too far away?

{snip}
... at best you will be able to see the ship while it is 3km+ above sea level. Just the fact that it will be 200km a way though means you likely could not see it with the naked eye at all.

If the landing burn begins above 3km, you could see that part. (It also would be visible all the way down if you're in an aircraft at 10,000 ft or more.)
From the eastern suburbs of Los Angeles we can see a Falcon 9 entry burn with the naked eye from more than 240 km.
The main impediment is clouds and haze near the horizon.
So I'd recommend that you at least set up a chair in a dark spot, keep the livestream audio in your ear so you know when it's coming, and see what you see. Bring enough beverages.

[TrueBlueWitt]

It doesn't need all 33 engines to climb from the pad. 2 or 3 less I  remember seeing somewhere.

If my math is right, Super Heavy could lose up to 8 engines at liftoff and still make it off the pad, i.e., TWR is >1

However, that would look a lot like that Astra launch that went sideways. It wouldn't get very far and there'd likely be considerable damage to the OLM and surrounding ground equipment.

It can lose 2 or 3 engines at liftoff and still make it to orbit. Losing engines later in the flight is less of an issue.

That said, I think that SpaceX will not release the hold-down clamps without all 33 engines running and healthy.

Every launch attempt is a risk.  This has to be factored in when deciding whether to commit or abort if n<33.

IMO, you get the most bang for the buck if you allow flight with n>=32.

The impact is the least possible, and the odds of it occurring are the highest.

If you're allowing flight with n=31, you have to think what if the failures are correlated, and also you can have more asymmetrical thrust, and we know B7 is less tolerant of that.

So maybe ok to go with n=31 only if the failed engines are on opposite sides or some similar criteria.

What if you were not carrying 150 tons to orbit? How many engines would you need then? What if any payload / mass simulation would S24 contain if any?

Another question here. Raptors at 90% at liftoff. If they lose engines, will they allow the other engines to throttle higher to makeup the difference?

[joek]

What if you were not carrying 150 tons to orbit? How many engines would you need then? What if any payload / mass simulation would S24 contain if any?

Based on first order BOTE calc. Given: Raptor 2 thrust = 230t (100%); TWR = 1.5 ...
= SS payload 150t requires 33 Raptors @100% thrust.
= SS payload 0t requires 32 Raptors @100% thrust.
= SS payload 0t requires 31.9 Raptors @90% thrust.
... so not much room to maneuver based on those simple pro-forma calcs. You effectively need 32 Raptors regardless of scenario.

That said, for this test, the TWR might be relaxed as they don't plan on recovering the booster, so they might make it up with a longer booster burn with fewer engines or lower thrust (and thus the booster travels farther down range).

[Chinakpradhan]

just thinking its not just a piece of metal but even if stage 0 (mecazilla) is ok, launch tale need to e rebuilt (if the plan is to e at boca chica as 39a launch tale is still under construction. isnt it?? https://twitter.com/whateverfithere/status/1644994630755426304
https://twitter.com/thePrimalSpace/status/1644973813325524992?s=20

[FutureSpaceTourist]

https://twitter.com/vickicocks15/status/1645028120087461888

Overnight this happened. Pic 1 shows a metal plate, apparently securing objects to the chopstick stabilisation pin socket on Booster 7, before being removed (pic 2) presumably after adhesive had dried. @elonmusk Are you going to attempt a catch maybe?
@LabPadre #Rover2Cam

We know no catch attempt this flight; other ideas?

[saturnsky]

Any suggestions for viewing and photography for the interested civilian?

[baking]

Any suggestions for viewing and photography for the interested civilian?

Everyday Astronaut just put up a video on the subject:

[Kaputnik]

Any chance of seeing this from the Caribbean?

[kevinof]

Any chance of seeing this from the Caribbean?

Northern Caribbean maybe. I am going from Antiqua to Bahamas and hope to catch it on the way.

[RedLineTrain]

The NOTAM red-shaded area tracks just South of Shell's Perdido oil platform (Lat 26.1289, Long -94.8979), although the platform is within the orange-shaded area.  This appears to be the only in-use oil platform nearby the ground track.

New NGA notices. Note that these do not cancel the existing notices. (NAVAREA XII 189/23 being canceled by NAVAREA XII 191/23 was a new notice that came out shortly before, so I'm not posting 189/23.)

For completeness, added maps of the research buoys, and a global ground track.

[OTV Booster]

It doesn't need all 33 engines to climb from the pad. 2 or 3 less I  remember seeing somewhere.

If my math is right, Super Heavy could lose up to 8 engines at liftoff and still make it off the pad, i.e., TWR is >1

However, that would look a lot like that Astra launch that went sideways. It wouldn't get very far and there'd likely be considerable damage to the OLM and surrounding ground equipment.

It can lose 2 or 3 engines at liftoff and still make it to orbit. Losing engines later in the flight is less of an issue.

That said, I think that SpaceX will not release the hold-down clamps without all 33 engines running and healthy.

Every launch attempt is a risk.  This has to be factored in when deciding whether to commit or abort if n<33.

IMO, you get the most bang for the buck if you allow flight with n>=32.

The impact is the least possible, and the odds of it occurring are the highest.

If you're allowing flight with n=31, you have to think what if the failures are correlated, and also you can have more asymmetrical thrust, and we know B7 is less tolerant of that.

So maybe ok to go with n=31 only if the failed engines are on opposite sides or some similar criteria.

What if you were not carrying 150 tons to orbit? How many engines would you need then? What if any payload / mass simulation would S24 contain if any?

Or, what if they decide to reduce propellant because there's no payload? All of a sudden there's a stack even more tolerant of engine loss on the booster.


They get some points for form but most of the points are for performance. I can hear it now. The booster launches on 31 engine and goes on for a flawless seperation and faux landing. The ship goes on to successful EDL and a faux landing. And all the SX haters will make noise about is the engine out problem.


Yeah, they'll loose a few point here. So what.


PS. That's not a prediction, just a what if...

[Alberto-Girardi]

It doesn't need all 33 engines to climb from the pad. 2 or 3 less I  remember seeing somewhere.

If my math is right, Super Heavy could lose up to 8 engines at liftoff and still make it off the pad, i.e., TWR is >1

However, that would look a lot like that Astra launch that went sideways. It wouldn't get very far and there'd likely be considerable damage to the OLM and surrounding ground equipment.

It can lose 2 or 3 engines at liftoff and still make it to orbit. Losing engines later in the flight is less of an issue.

That said, I think that SpaceX will not release the hold-down clamps without all 33 engines running and healthy.

Every launch attempt is a risk.  This has to be factored in when deciding whether to commit or abort if n<33.

IMO, you get the most bang for the buck if you allow flight with n>=32.

The impact is the least possible, and the odds of it occurring are the highest.

If you're allowing flight with n=31, you have to think what if the failures are correlated, and also you can have more asymmetrical thrust, and we know B7 is less tolerant of that.

So maybe ok to go with n=31 only if the failed engines are on opposite sides or some similar criteria.

What if you were not carrying 150 tons to orbit? How many engines would you need then? What if any payload / mass simulation would S24 contain if any?

Or, what if they decide to reduce propellant because there's no payload? All of a sudden there's a stack even more tolerant of engine loss on the booster.


They get some points for form but most of the points are for performance. I can hear it now. The booster launches on 31 engine and goes on for a flawless seperation and faux landing. The ship goes on to successful EDL and a faux landing. And all the SX haters will make noise about is the engine out problem.


Yeah, they'll loose a few point here. So what.


PS. That's not a prediction, just a what if...

I have heard many times in the NSF streams and I agree with the opinion that loading less propellant is not a good idea. You want a test flight that accurately rappresents a "normal" flight. Having non full tanks at the start changes a variable. I remember, but i am not sure ( i hope someone can confirm or disprove me), that on Falcon 9 flights they do NOT  change the amount of loaded propellant even if the payload is lighter, they simply stop the burn before ( i assume the 2nd stage burn given that the first can't have too much propellant before landing, because the drag wouldn't slow it down enough). They do this beacuse the vehicle has been caracterazed to a high precision on THAT fuel load, and you don't want to mess with that.

Again I can't quote any source, but I think I heard that on a NSF stream.

[Kaputnik]

It doesn't need all 33 engines to climb from the pad. 2 or 3 less I  remember seeing somewhere.

If my math is right, Super Heavy could lose up to 8 engines at liftoff and still make it off the pad, i.e., TWR is >1

However, that would look a lot like that Astra launch that went sideways. It wouldn't get very far and there'd likely be considerable damage to the OLM and surrounding ground equipment.

It can lose 2 or 3 engines at liftoff and still make it to orbit. Losing engines later in the flight is less of an issue.

That said, I think that SpaceX will not release the hold-down clamps without all 33 engines running and healthy.

Every launch attempt is a risk.  This has to be factored in when deciding whether to commit or abort if n<33.

IMO, you get the most bang for the buck if you allow flight with n>=32.

The impact is the least possible, and the odds of it occurring are the highest.

If you're allowing flight with n=31, you have to think what if the failures are correlated, and also you can have more asymmetrical thrust, and we know B7 is less tolerant of that.

So maybe ok to go with n=31 only if the failed engines are on opposite sides or some similar criteria.

What if you were not carrying 150 tons to orbit? How many engines would you need then? What if any payload / mass simulation would S24 contain if any?

Or, what if they decide to reduce propellant because there's no payload? All of a sudden there's a stack even more tolerant of engine loss on the booster.


They get some points for form but most of the points are for performance. I can hear it now. The booster launches on 31 engine and goes on for a flawless seperation and faux landing. The ship goes on to successful EDL and a faux landing. And all the SX haters will make noise about is the engine out problem.


Yeah, they'll loose a few point here. So what.


PS. That's not a prediction, just a what if...

I have heard many times in the NSF streams and I agree with the opinion that loading less propellant is not a good idea. You want a test flight that accurately rappresents a "normal" flight. Having non full tanks at the start changes a variable. I remember, but i am not sure ( i hope someone can confirm or disprove me), that on Falcon 9 flights they do NOT  change the amount of loaded propellant even if the payload is lighter, they simply stop the burn before ( i assume the 2nd stage burn given that the first can't have too much propellant before landing, because the drag wouldn't slow it down enough). They do this beacuse the vehicle has been caracterazed to a high precision on THAT fuel load, and you don't want to mess with that.

Again I can't quote any source, but I think I heard that on a NSF stream.

AIUI it's generally not even possible to part fill because the vehicle's sensors are not configured that way. I think it was Jim who explained this and it wasn't Falcon specific.

[meekGee]

It doesn't need all 33 engines to climb from the pad. 2 or 3 less I  remember seeing somewhere.

If my math is right, Super Heavy could lose up to 8 engines at liftoff and still make it off the pad, i.e., TWR is &gt;1

However, that would look a lot like that Astra launch that went sideways. It wouldn't get very far and there'd likely be considerable damage to the OLM and surrounding ground equipment.

It can lose 2 or 3 engines at liftoff and still make it to orbit. Losing engines later in the flight is less of an issue.

That said, I think that SpaceX will not release the hold-down clamps without all 33 engines running and healthy.

Every launch attempt is a risk.  This has to be factored in when deciding whether to commit or abort if n&lt;33.

IMO, you get the most bang for the buck if you allow flight with n&gt;=32.

The impact is the least possible, and the odds of it occurring are the highest.

If you're allowing flight with n=31, you have to think what if the failures are correlated, and also you can have more asymmetrical thrust, and we know B7 is less tolerant of that.

So maybe ok to go with n=31 only if the failed engines are on opposite sides or some similar criteria.

What if you were not carrying 150 tons to orbit? How many engines would you need then? What if any payload / mass simulation would S24 contain if any?

Or, what if they decide to reduce propellant because there's no payload? All of a sudden there's a stack even more tolerant of engine loss on the booster.


They get some points for form but most of the points are for performance. I can hear it now. The booster launches on 31 engine and goes on for a flawless seperation and faux landing. The ship goes on to successful EDL and a faux landing. And all the SX haters will make noise about is the engine out problem.


Yeah, they'll loose a few point here. So what.


PS. That's not a prediction, just a what if...

I have heard many times in the NSF streams and I agree with the opinion that loading less propellant is not a good idea. You want a test flight that accurately rappresents a "normal" flight. Having non full tanks at the start changes a variable. I remember, but i am not sure ( i hope someone can confirm or disprove me), that on Falcon 9 flights they do NOT  change the amount of loaded propellant even if the payload is lighter, they simply stop the burn before ( i assume the 2nd stage burn given that the first can't have too much propellant before landing, because the drag wouldn't slow it down enough). They do this beacuse the vehicle has been caracterazed to a high precision on THAT fuel load, and you don't want to mess with that.

Again I can't quote any source, but I think I heard that on a NSF stream.

If the payload is light, you still fly full for exactly that reason, and you additionally get more fault tolerance.

Basically there is no advantage in ever underfilling the first stage, and it only adds complications.

[FutureSpaceTourist]

https://twitter.com/nasaspaceflight/status/1645113568952479747

There's something wonderful about a LOX Tanker decorated in Shuttle, supplying the Starbase Tank Farm for Starship!

nsf.live/starbase

[MdBee]

(shifting this from another discussion thread) Quick question about the 7/24 OFT scheduling. As a non-US person, can somebody confirm my timezone maths, that the current suggested launch windows (12Z-15Z) are roughly dawn-till-midmorning in TX, and it would be night-till-barely-dawn at the wet-LZ near HI? IIUC, 16Z is 06HI, about 20min before sunrise there - anything much earlier is still dark. This is noting of course the TX-HI flight time of ~60-90min...

It feels to me like having as much daylight as possible at both hopeful ends of this test flight might be helpful for diagnosis if anything is off-norminal... (let alone any cool soft-landing footage potentially!). Thoughts or corrections?

[sferrin]

75% believe that's just good design with an unfortunate appearance.  25% think it's part Elon prank.