SpaceX Starship - IFT-3 - Starbase TX - Launch Thread and Post Launch Discussion

Launch Date: March 14
Launch Window: 7:00 am CDT (9:00 am EST, 13:00 UTC)
Launch site: LC-1 - Starbase, Boca Chica Beach, Texas
Core Booster Recovery: Expended in Gulf with a landing burn
Starship Recovery: A controlled reentry through the atmosphere to a terminal velocity splashdown in the Indian Ocean
Booster: Super Heavy Booster 10
Starship: Starship 28
Mass: No mass simulator mentioned
Orbit: LEO-ish
Yearly Launch Number: 26

A SpaceX Super Heavy and Starship launch vehicle will launch on its third not quite orbital integrated flight test designated IFT-3. The mission will attempt to place Starship into a nearly orbital trajectory that will attempt a controlled reentry through the atmosphere to a terminal velocity splashdown in the Indian Ocean . The Super Heavy booster will attempt a landing burn in the the Gulf of Mexico where it will likely be destroyed. This is a further test of Stage 0, the booster, full power ascent, Max-Q, stage separation using the new hot staging, a booster stage test of a hard turn and boostback, full burn boost of Starship to space and sub LEO, Starship will do one partial orbit, simulate a de-orbit burn, test tiles and heating from atmospheric reentry, until it has a splashdown in the Indian Ocean.

It has also been determined that for this test flight there will be a fuel transfer test done on Starship for NASA's Tipping Part contract. The Starship will also test its payload bay door in zero-G for a test of future Starlink 2.0 deployments.

 

[scaesare]

Also, an interesting thought: the Starship rolling/instability may have started with the prop transfer test, as significant mass within the ship changed locations at that point...

 

[JB47394]

Interesting... is this where the exhaust plume is going from super- to sub-sonic and in essence a sonic boom?

That sounds like a good explanation to me. I wonder if staggering the engines up the side of the booster would soften that effect. That's only an academic question. I can't see SpaceX making the back of the booster look like a cathedral pipe organ.

Looks like 8 he could see... feels like less than previous flights...

Much less. Here's a still of IFT-2 from the WB-57 footage. IFT-3 was a huge advance for the tiles.

 

[scaesare]

That sounds like a good explanation to me. I wonder if staggering the engines up the side of the booster would soften that effect. That's only an academic question. I can't see SpaceX making the back of the booster look like a cathedral pipe organ.


Much less. Here's a still of IFT-2 from the WB-57 footage. IFT-3 was a huge advance for the tiles.

If the engines were staggered, they'd still all be producing shockwaves thought, right? Are you just thinking that they wouldn't be additive and therefore less impactful to the surroundings?

Couple shots of tiles recovered after the flight (presumably from IFT-3):

Still at a loss for how those wins could pull out and the mounting slots not be deformed. I'd like to see a closeup of the pins and if the heads are barb-shaped as opposed to semi-spherical. If the latter, I wonder if they'll go to the former.

 

[mongo]

How did the OLM infrastructure fare ? Any damage?

Experts like me have pointed out many times, having an exhaust tunnel is the only way to go. Please tell me that I am correct and SpaceX is wrong.

The OLM is 6 exhaust tunnels, one every 60 degrees with a hydraulic flame diverter in the middle. The tower might prefer only 5 tunnels though...

 

[mongo]

If the engines were staggered, they'd still all be producing shockwaves thought, right? Are you just thinking that they wouldn't be additive and therefore less impactful to the surroundings?

Couple shots of tiles recovered after the flight (presumably from IFT-3):

View attachment 1029233

View attachment 1029234

Still at a loss for how those wins could pull out and the mounting slots not be deformed. I'd like to see a closeup of the pins and if the heads are barb-shaped as opposed to semi-spherical. If the latter, I wonder if they'll go to the former.

Could be as simple as a vibration based version of wave rake/ bump lockpicking. Keep a load on the tile and wiggle back and forth with each oscillation shifting the pins a little more toward unengaged.

Or the lock tabs on the pin failed. Or there was some insulation trapped between pins and tile.

 

[JB47394]

Are you just thinking that they wouldn't be additive and therefore less impactful to the surroundings?

Yep. Destructive interference vs constructive interference. Imagine if the engines just created a constant pressure wave without any peaks. The GSE would certainly fare much better.

 

[scaesare]

Could be as simple as a vibration based version of wave rake/ bump lockpicking. Keep a load on the tile and wiggle back and forth with each oscillation shifting the pins a little more toward unengaged.

Or the lock tabs on the pin failed. Or there was some insulation trapped between pins and tile.

Hard to completely make out, but it does look like there's a notch on the heads, but they are a bit spherical shaped on the bottom also:

 

[scaesare]

Yep. Destructive interference vs constructive interference. Imagine if the engines just created a constant pressure wave without any peaks. The GSE would certainly fare much better.

I guess we could calculate what 1/2λ would be and figure out the degree of engine stagger would need to be.. but yeah, they aren't gonna do that.

 

[Electroman]

The OLM is 6 exhaust tunnels, one every 60 degrees with a hydraulic flame diverter in the middle. The tower might prefer only 5 tunnels though...

?? What tunnels? Flame diverter? You mean in Starbase, TX? I presume you are kidding

 

[JB47394]

?? What tunnels? Flame diverter? You mean in Starbase, TX? I presume you are kidding

The gaps between the legs represent the tunnels, and the water deluge system provides the diversion. It is a 360 degree solution instead of a unidirectional one. If SpaceX had been first, people would be wondering why NASA was overloading a single flame trench with all the thrust. And why they built a physical trench instead of a virtual one.

 

[ecarfan]

Looks like 8 he could see... feels like less than previous flights...

That is a huge improvement over IFT-2. Let me try to find an image from that flight…

EDIT: I see @JB47394 beat me to it. Here’s what I found.

 

[ecarfan]

How did the OLM infrastructure fare ? Any damage?

Experts like me have pointed out many times, having an exhaust tunnel is the only way to go. Please tell me that I am correct and SpaceX is wrong.

Based on post-launch photos I’ve seen the OLM and surrounding infrastructure looks undamaged. Of course we only have long distance photos to go on. But after the first two test flights SpaceX greatly improved things and I think they have got it figured out.

 

[scaesare]

Scott Manley and Marcus House appeared on a YouTube segment... they talk about the booster re-entry instability perhaps being due to loss of a grid fin being operational...

 

[JB47394]

I'm sure others will get this data out with a thorough analysis, but here's the speed and altitude telemetry data for the booster plotted in 2 second increments. the first chart plots speed and altitude over time. The second chart plots acceleration over time in g units, computed from a change in speed. It can be a little difficult to interpret, and I'm sure there's a way to chart the acceleration experienced onboard.

Staging is at 02:44
Apogee is at 04:14
Atmosphere interface is around 06:14

I mostly wanted to see the accelerations that they were throwing at the booster.

Note that during staging, there is a brief negative acceleration (-0.4g) induced by the Starship engines, then a brief positive acceleration (0.4g) while the engines are running but the booster hasn't turned around yet, then an extended negative acceleration (3g) as the booster cancels out its downrange speed.

 

[scaesare]

So that drop in acceleration I assume would start with MECO... interesting we don't see sperate points as the engines were cut off in groups. Lack of resolution? The slope I would have thought would get steeper each step as well...

Is that couple of seconds of positive acceleration the ship dragging the booster with it before it detaches? If so, I wouldn't have expected the side-vented exhaust to impart much thrust....

 

[scaesare]

And here is the rest of SpaceX’s first public analysis:


“Initiated” the prop transfer, no indication it was successful.

Interesting about the “vehicle roll rates” stopping the engine relight test. So the roll was not intentional.

So this NASA article says prop xfer was "completed":

The propellant transfer demonstration operations were completed, and the NASA-SpaceX team is currently reviewing the flight data that was received.

It also talks about the effect on ship dynamics during the mass shift as something they want to study and understand... it makes me again wonder if that affected the ship's stability we saw issues with...

 

[JB47394]

Here you go; a closeup of staging with frame-by-frame data. Staging is at 5710 km/h, and the booster's stable speed after slowing is 5658 km/h.

 

[scaesare]

Ah cool... that "engines lit" graph really demonstrates what's going on.

It appears that the final 3 engines that remain lit bring acceleration to 0 and the stack actually slows down for a couple of secs before the stack lights it's engines....

 

[JB47394]

It appears that the final 3 engines that remain lit bring acceleration to 0 and the stack actually slows down for a couple of secs before the stack lights it's engines....

That dip before lighting the engines is interesting. I was going to say that it's the Starship's thrust pushing on the body of the booster, but it's probably just the change in orientation compromising its absolute speed. Once the engines fire, it briefly accelerates while it's facing downrange, then quickly decelerates as it completes its turn back to the west.

Here's the view from Starship at the beginning of that dip (02:52). A second later (02:53), the view is pretty much the same, but 11 booster engines are lit. At 02:55, the graphic of the booster orientation flips, suggesting that it has crossed an axis. I assume it's the point where it has just started to turn west. It jibes with the blue peak at the bottom right of the first chart - that local maximum when it is just about to start canceling that downrange velocity.

 

[JB47394]

Real Engineering's video on IFT-3. It's a fluff piece, but it's always fun to watch Starship footage.