SpaceX SN9 Flight Scheduled for 25-27th

[glend]

Following on from another successful static fire, SpaceX has confirmed that the SN9 test ship will conduct a high altitude test flight sometime on the 25-27th of January (CST), depending on range weather forecast. Obviously they will aim for clear skies. Today the FTS ( Flight Termination System), a fancy name for the self destruct package, was installed, to be used if necessary due to loss of control, failure, or danger of straying outside exclusion zone.

[Startrek]

Good news it’s finally ready
There have been some delays on this Starship, swapping raptor engines etc...
Cant wait to watch the test flight
Thanks for the update

[astronobob]

yup, hopefully tonight early morning, Aus Time.
tfr's for only the 27th now.

Edit: Scrubbed for today, Elon tweeted 5 hrs ago - "We’re hoping for FAA approval of a test flight tomorrow afternoon" ?

[glend]

Yep, scrubbed for today, although they were proceeding with the new tank version pressure test, which is setup on a stand at the pad. They have a new tank design using 3mm stainless, with internal load spreading bracing, which is hoped to achieve NASA crewed space flight pressure targets, while also reducing the overall weight to boost payload capacity of the vehicle. They pump liquid nitrogen into the tank first to "cure" the structure, apparently these stainless tanks become stronger when treated cryogenically, then after a couple of cold soaks, they push up the pressure, to the point of failure.

Update: Elon has Tweeted that the Pressure Test was successful.

[astronobob]

Yes indeed - SN7.2 Dome-Tank passed the initial test although Musk did not give any pressure data ?

Currently 2am Fri 29th Aus time -
SpaceX teams are working on removing the straps from Starship SN9's flaps – a good sign that launch is still go for today. 10am Thurs 28th - US Time

[Startrek]

Just checked NASA space flight , WAI Felix and a few other sites
No go this morning
FAA have advised Space X no clearance
Flight is on hold
More delays ......

[glend]

Yeah, there is some dispute going on. The FAA pulled the already existing TFR they had issued. Elon is not pleased according to the NASA Spaceflight guys, he had a SpaceX live feed all set up. There seems to be some underlying issue with the old way the FAA works and the new reality of SpaceX rapid development.
The FAA system is fine for NASA which has just a few launches, into existing military managed corridors, but it is not going to work for commercial space flight ops. Imagine the problems with numerous sub-orbital flights on a daily basis, multiple launches in quick succession for Mars cargo delivery missions, etc. The system needs to be more responsive to the new reality of commercial space operations. Imho.

[glend]

SN9 scrubbed again today (30th Jan) our time, 29th there. Not sure why at this point, may still be awaiting FAA.
On the positive side SN10 is being rolled out on the transport rig, and the big crane us waiting for it at Pad A.

[astronobob]

Complications with FAA & SpaceX, bit of disorder, randomness of the system setting flight restrictions ?

[glend]

SpaceX finally launched SN9 Starship this morning our time, successfully reaching its 10km target altitude. The descent attitude looked ok but once again they had an engine restart problem on landing burn, with the second engine failing to ignite. The ship did not actually achieve a vertical landing position this time, and was carrying too much speed, resulting in destruction on impact. It is hard to know, at this point, if SpaceX triggered the auto destruct explosives or whether it was ground impact. In any case, it is another failure at the same point in the flight. I will not speculate on cause, perhaps Elon will say something. We do know that the SN8 failure on landing restart was due to low pressure in the header tank.
The launch was livestreaned by SpaceX and the usual Utube channels, so the replay video is available online now if your interested.
Note that SN10 is sitting on Pad A and it may need to be inspected for damage as a result of debris from SN9 RUD.

[astronobob]

Another one bites the Crust !
Watched it live, good fun.. Interesting virtually same issue as SN8, 2nd Raptor failed to re-ignite, hmmm, why does one engine start and not the other ?
Maybe not a pressure issue, more like Plumbing design & fuel delivery system me thinks.
Doubt the Raptor engine failing directly, if raptor gets fuel it should fire up, unless automation program issue/callibration and so- on ?

Reckon SN10 would be to traumatized to launch next week or two, hehe..

[glend]

Yes, Raptors are pretty solid performers, and they are obviously not cheap to produce. The people building them must be pretty disappointed to see another three destroyed. I think we can agree it is fuel delivery related, and fundamental. You are right in that SN10, if it has the same fuel system, is not a great bet to succeed. What puzzled me about today's test was why they left it so late to try to flip, it was basically horizonal when it hit the ground, and traveling much faster than SN8 as it neared the ground.

[Startrek]

Yes definitely a problem getting that 2nd Raptor fired up and operating at full thrust on the lower part of the descent ( less than a kilometer from ground level )


Out of the two it looked like SN9's Raptor failed later than SN8's ( ie closer to impact )


I'm sure SN10 will fly sooner than later once they sort out the descent thrust issue on the Raptors


Also FAA approval is becoming an obstacle for Space X , they need to sit down and sort it out so ongoing testing can continue in a timely manner ( staggering pace )

[Gary47]

Another Oops. Starting to look like the American space program from the 1960's, lots of colorful explosions being hailed as a step forward.

[glend]

They are good at putting a positive spin on any disaster. The Russians had their share of them as well. This current problem may require a redesign of some of the system, as they have to have reliable restart for landing burn. Throwing SN10 onto the pile is not going to help find out much more. I doubt It is a Raptor problem, they are pretty well tested before shipping to Boca Chica, more likely is fuel starvation or flow issues to that second engine once engine one is running. I would like to see them flip way earlier, giving them more time to get vertical, and recycle start on #2, or go to #3. If the fueling issue is related to attitude, then going vertical first might work much better. Worth testing imho. It also seemed to be falling much faster this time, not taking advantage of the winglet drag potential.

[gaseous]

Yeah they seem to leave the last tilt to "verticality" very late. I wonder if dropping horizontally messes with the fuel system somehow - seems like too simple a problem not to have been addressed though.

[Startrek]

The US got to the moon and back 9 times with the Saturn 5 ( 1.6million pounds of thrust or 160 million horsepower) with all the complexity’s of multiple staging , cryogenic fuels and oxidisers travelling from sea level pressure, varying atmospheric pressures on lift off and through ascent , zero G , lunar gravity one sixth G , lunar descent and ascent , start and restarting engines etc..... and with primitive electronics and avionics control systems by today’s standards
Space X will resolve this in time , the Raptor is an extremely complex engine, hopefully SN10 will be a copybook test flight in a couple of weeks or so

[RyanJones]

I also feel they don’t seem to leave enough head room before flipping back to vertical. I’m no rocket scientist though so there could be a very good reason to leave it late.

I wonder if the velocity of the air rushing past the engines cone is causing some kind of Venturi effect inside contributing to reignition issues. They never seem to have the same issue with the falcon 9 when it descends vertically ? Again, I’m no rocket scientist so it’s just a guess ?

[Startrek]

Excellent point Ryan about the rushing air but ( I’m no rocket scientist either ) I think the problem is not at the nozzle or even the ejector plate inside , the problem most probably is in the fuel delivery system or stability of the fuel delivery system to the engine as these Raptors require enormous fuel pressures sustained at high velocities and are required to start at a moments notice
Very complex !!
Maybe Glen might be able to provide a more learn’d explanation or possible explanation about the causes and failure of Raptor 2 engine to start and run at nominal performance just before landing
Martin

[glend]

Well, SN8 and SN9 seemed to suffer the same engine restart issue, and let's ignore the orientation differences for now. After the SN8 hard landing there was talk about low header tank pressure being the reason it started with poor thrust output. Without correct fuel mix it had hardly any thrust, and boom. At the time I believe Elon mentioned the possibility of pressurising the nose tank with helium to push the fuel. The problem with using helium as a tank pressure medium is that it is not easily available on Mars. I have not heard if they change the fuel system for SN9. The issue with the rapid build of Starships is that any required design correction can take a long time to get to the pad, what with so many older designs in the queue. Maybe they did not change anything on SN9 except procedural, system commands, sequence stuff. We may never find out.

One thing I think we can eliminate is fuel/oxidizer starvation, at least there was plenty still in the tanks when it hit the ground. I watched one head on view video where you can see the fuel erupt at the rear as the ship hit the ground, in an orange billowing cloud, but the front section split open and LOX shot forward in a white cloud, not burning at all.There was obviously still a lot of pressure in the LOX tank.

Beyond that, without knowing what data they collect, it is hard to speculate further.

[Startrek]

Thanks Glen
Good summary of events, possible cause and outcome
Cheers
Martin

[Xeteth]

My best guess on this is that they're trying to find the 'sweet spot' with regards to performing the flip as late as possible. Since the surface area of Starship is greatest when horizontal they can actually use the aerodynamic pressure to slow Starship down as it hits the denser atmosphere the lower in altitude it gets. By waiting until the last seconds to perform the flip it minimises the amount of fuel required for the landing burn and thus reduces the overall payload of Starship.

I could be completely wrong on this - but it seems to be the case. I do agree however that the approach (particularly through the rapid development cycle) of waiting to the last seconds is perhaps biting off more than they can chew at this time. It would make sense to master the flip first at a higher altitude and then fine tune this as the development cycle continues.

Elon has stated that they will attempt to light all three Raptors for SN10 then turn one off if all three light successfully, thus adding a bit of redundancy. Looking forward to seeing the next flight!

[RyanJones]

I had never considered that but it makes total sense

[glend]

It might make more sense to find that sweet spot working from altitude down, instead of from the explosion up. Flip at 1500 ft not 50ft.

[Startrek]

The launch, ascent , apogee , flip and glide during descent work perfectly and no doubt further test flights will achieve this
Why don’t they just do 500m to 750m hops with an attitude adjustment at apogee to resolve the landing issue. Once they nail the landing a few times then go for the complete test ??
Elon did do previous hops to get this far !

Any thoughts ??

[glend]

I believe they need more altitude (than 500-750m) to achieve terminal velocity in the freefall, and to learn the wing configuration adjustments, how much aero drag they get, throttle setting and duration. But yeah, learning to land is pretty important too. Surely they have computer simulations of all this stuff, augmented by real flight data now.
I am puzzled by why they did not destroy the ship when it obviously lost control and was not going to recover. As it was there are pieces everywhere. I watched the RGV flyover video today, and Mary's debris video; there were big pieces everywhere. They had to get heavy machinery out on the mud flats at low tide to drag out the big pieces. They will be picking up pieces for a week.

RFV flyover video here:

https://youtu.be/DMtd-4D4Dlw

Mary's NSF video of the cleanup, start at about 15 minutes into this videro:

https://youtu.be/MJhHaLANaYk