totm nov 2023 SpaceX Discussion Thread

[JoeSchmuckatelli]

On 1/25/2021 at 11:37 AM, RealKerbal3x said:

Approximately 30 minutes until pad clear according to a launch pad announcement:

 

On my phone - what is the white structure currently off gassing? 

 

I can't read the text on the screen 

[RealKerbal3x]

Just now, JoeSchmuckatelli said:

On my phone - what is the white structure currently off gassing? 

That's SN7.2, the new test tank using 3mm thick steel. It's white because they've loaded liquid nitrogen to test the integrity of the tank.

[JoeSchmuckatelli]

11 minutes ago, RealKerbal3x said:

That's SN7.2, the new test tank using 3mm thick steel. It's white because they've loaded liquid nitrogen to test the integrity of the tank.

Thanks.  I just watched the 7.1 fast replay.  Are they planning to pop this one as well? 

[RealKerbal3x]

Just now, JoeSchmuckatelli said:

Thanks.  I just watched the 7.1 fast replay.  Are they planning to pop this one as well? 

Probably, but it's likely they're just proof-testing it today. They'll most likely test to destruction at some point.

[RealKerbal3x]

SN7.2's vents have shut off, they may be going for a pop today!

Edit: No pop, but the valves released quite suddenly and violently. Could have been a valve failure.

Edited January 26, 2021 by RealKerbal3x

[sevenperforce]

49 minutes ago, RealKerbal3x said:

SN7.2's vents have shut off, they may be going for a pop today!

Edit: No pop, but the valves released quite suddenly and violently. Could have been a valve failure.

The vents are off again.

[RealKerbal3x]

1 minute ago, sevenperforce said:

The vents are off again.

Yeah, it's been holding pressure without venting for close to 40 mins now.

[JcoolTheShipbuilder]

Did it explode yet?

[RealKerbal3x]

Just now, JcoolTheShipbuilder said:

Did it explode yet?

No, it seems to be defrosting.

[JcoolTheShipbuilder]

Oh ok

[RCgothic]

5 hours ago, sevenperforce said:

Is this official?

As much as it feels like you really, really want an engine in the middle, putting them in a ring farther apart like this gives much better roll authority.

1 fixed engine in the middle wouldn't interfere with the gimbaling at all. If it were a 310t version that's another ~3.5% Gross Launch Weight. 

[sevenperforce]

What happened?

[tater]

 

[.50calBMG]

Any word on if they got TFRs for another hop attempt today?

[RCgothic]

1 hour ago, .50calBMG said:

Any word on if they got TFRs for another hop attempt today?

No attempt today.

[tater]

 

Regarding BN1, there's a pic on NSF of a thrust structure with 2 pairs of holes around the outside for plumbing I think.

[tater]

https://www.spacex.com/vehicles/starship/

Quote

As early as Thursday, January 28, the SpaceX team will attempt a high-altitude flight test of Starship serial number 9 (SN9) – the second high-altitude suborbital flight test of a Starship prototype from our site in Cameron County, Texas. Similar to the high-altitude flight test of Starship serial number 8 (SN8), SN9 will be powered through ascent by three Raptor engines, each shutting down in sequence prior to the vehicle reaching apogee – approximately 10 km in altitude. SN9 will perform a propellant transition to the internal header tanks, which hold landing propellant, before reorienting itself for reentry and a controlled aerodynamic descent.

The Starship prototype will descend under active aerodynamic control, accomplished by independent movement of two forward and two aft flaps on the vehicle. All four flaps are actuated by an onboard flight computer to control Starship’s attitude during flight and enable precise landing at the intended location. SN9’s Raptor engines will then reignite as the vehicle attempts a landing flip maneuver immediately before touching down on the landing pad adjacent to the launch mount.

A controlled aerodynamic descent with body flaps and vertical landing capability, combined with in-space refilling, are critical to landing Starship at destinations across the solar system where prepared surfaces or runways do not exist, and returning to Earth. This capability will enable a fully reusable transportation system designed to carry both crew and cargo on long-duration, interplanetary flights and help humanity return to the Moon, and travel to Mars and beyond.

There will be a live feed of the flight test available here that will start a few minutes prior to liftoff. Given the dynamic schedule of development testing, stay tuned to our social media channels for updates as we move toward SpaceX’s second high-altitude flight test of Starship!

 

[mikegarrison]

It has only just occurred to me that because the aerodynamics and gravity on Mars are quite different than on Earth, I wonder how much of what they learn here is actually transferable?

(Not that I believe there is a chance in hell that the first-gen Starship will ever actually be landing on Mars. I imagine they will have to do at least one major redesign before they get that far along.)

[tater]

9 minutes ago, mikegarrison said:

It has only just occurred to me that because the aerodynamics and gravity on Mars are quite different than on Earth, I wonder how much of what they learn here is actually transferable?

At the current test altitudes? Nothing at all, aside from the basics of landing (which should be largely the same).

Where they will get some transferable data will probably be early stages of EDL from LEO in the atmospheric density regime where it approximates Mars (somewhere above 50km). I suppose they already have some of that from F9 booster entry (and passively for fairings)... heck, for all we know they have instrumented S2 for a while just for EDL data.

Another pic off their page:

Edited January 28, 2021 by tater

[JoeSchmuckatelli]

They've probably got all kinds of data from Nasa given the number of times we've landed stuff.  Duffer guess: shallow insert to give them more time to aerobrake and then a hard abrupt burn to touchdown.

[mikegarrison]

8 minutes ago, tater said:

At the current test altitudes? Nothing at all, aside from the basics of landing (which should be largely the same).

Will they, though? The suicide burn will probably have to be at least three times as extreme, assuming they don't find a way to reduce the minimum thrust levels.

Edited January 28, 2021 by mikegarrison

[JoeSchmuckatelli]

3 minutes ago, mikegarrison said:

Will they, though? The suicide burn will probably have to be at least three times extreme, assuming they don't find a way to reduce the minimum thrust levels.

What's terminal velocity on Mars?  They've only got to slow down from 120mph on Earth... lower gravity and albeit lower atmosphere - maybe its close to the same?

 

Edit: nvm - its a lot more: Point Break: Mars! | Skulls in the Stars (585mph)

 

Presuming this guy's math is close to correct

 

Edited January 28, 2021 by JoeSchmuckatelli

[MKI]

The air pressure at "sea level" on mars is minimal at best. There's a reason Perseverance isn't using chutes, and it the size of a car. 

This probably means an earlier flip, longer burn and thus more fuel to land on the red planet. 

I'm having a hard time wrapping my head around the lower gravity, less atmosphere effect on landing with Starship. Obviously you need more data on a bunch of stuff, but on paper its just physics right? 

[tater]

19 minutes ago, mikegarrison said:

Will they, though? The suicide burn will probably have to be at least three times as extreme, assuming they don't find a way to reduce the minimum thrust levels.

I think the terminal propulsive phase is probably well characterized, they've shown the same sort of simulation for Mars EDL as Earth (and the skydive and flip were remarkably close to the simulation they showed a year ahead of doing it).

I think getting to that terminal phase is the hard bit. This paper is pretty fascinating:

https://citeseerx.ist.psu.edu/viewdoc/download?doi=10.1.1.463.8773&rep=rep1&type=pdf

 

[RealKerbal3x]