Flight 9 (Booster 14, Starship 35) pre-flight preparations

[FutureSpaceTourist]

Updates and discussion thread for Starship flight 9.

Separate threads will be created nearer launch.


https://twitter.com/nasaspaceflight/status/1893019265550496158

FCC document notes that Starship Flight 9 (after the upcoming launch) has the option of Ship returning to the launch site for a catch.

Although unconfirmed by SpaceX, Flight 9 has the potential of reflying Booster 14, with Ship 35, and both returning to the launch site, with Booster returning to Pad A and Ship to Pad B.

https://apps.fcc.gov/oetcf/els/reports/STA_Print.cfm?mode=current&application_seq=140596&RequestTimeout=1000

[TomH]

I suppose the Operation Start and End Dates of 3/14-6/30 are based on the outcome of Flight 8. Would I be assuming correctly that a completely nominal Flight 8 might enable Flight 9 as early as 3/14?  That would be an outstanding increase in cadence.

[litton4]

Wouldn't the critical path to that being Pad B in a good enough state to support a catch as well as safeing and removal of the vehicle.

At the moment, it doesn't look remotely close:
Flame trench is a lot of open earth.
No piping to support offloadnig of propellants
No launch mount

[CaptainFilter]

Wouldn't the critical path to that being Pad B in a good enough state to support a catch as well as safeing and removal of the vehicle.

At the moment, it doesn't look remotely close:
Flame trench is a lot of open earth.
No piping to support offloadnig of propellants
No launch mount

Recall how things were done in the suborbital hop tests where detanking and safing were done without connected plumbing after landing. If anything, they probably want to do the catch attempt as soon as possible to minimize impact to the GSE they are currently installing - less things to break when things go wrong

[DanClemmensen]

Wouldn't the critical path to that being Pad B in a good enough state to support a catch as well as safeing and removal of the vehicle.

At the moment, it doesn't look remotely close:
Flame trench is a lot of open earth.
No piping to support offloadnig of propellants
No launch mount

There is no reason to try to land Ship after a single 90-minute orbit, and in fact it would be challenging. They can wait 24 hours (16 orbits), which provides for plenty of time to safe Booster after the catch and move it off the pad. If the Booster catch attempt disables the tower and it cannot be repaired in 24 hours, then either wait another day or ditch Ship into the Gulf near BC to verify the "aborted catch" scenario.

[eriblo]

Wouldn't the critical path to that being Pad B in a good enough state to support a catch as well as safeing and removal of the vehicle.

At the moment, it doesn't look remotely close:
Flame trench is a lot of open earth.
No piping to support offloadnig of propellants
No launch mount

There is no reason to try to land Ship after a single 90-minute orbit, and in fact it would be challenging. They can wait 24 hours (16 orbits), which provides for plenty of time to safe Booster after the catch and move it off the pad. If the Booster catch attempt disables the tower and it cannot be repaired in 24 hours, then either wait another day or ditch Ship into the Gulf near BC to verify the "aborted catch" scenario.

We do not know the on orbit endurance of the current prototypes - it could be that a day or more is beyond what they are comfortable with. A single orbit is a minimum extension of the duration demonstrated on previous flights and full EDL with a new version + catch might be enough risk for this flight if they can do it.

[DanClemmensen]

Wouldn't the critical path to that being Pad B in a good enough state to support a catch as well as safeing and removal of the vehicle.

At the moment, it doesn't look remotely close:
Flame trench is a lot of open earth.
No piping to support offloadnig of propellants
No launch mount

There is no reason to try to land Ship after a single 90-minute orbit, and in fact it would be challenging. They can wait 24 hours (16 orbits), which provides for plenty of time to safe Booster after the catch and move it off the pad. If the Booster catch attempt disables the tower and it cannot be repaired in 24 hours, then either wait another day or ditch Ship into the Gulf near BC to verify the "aborted catch" scenario.

We do not know the on orbit endurance of the current prototypes - it could be that a day or more is beyond what they are comfortable with. A single orbit is a minimum extension of the duration demonstrated on previous flights and full EDL with a new version + catch might be enough risk for this flight if they can do it.

Does Ship have enough cross-range to do a single-orbit return? The earth rotates 22.5 degrees in 90 minutes, so the landing site moves about  2240 Km eastward before Ship completes one orbit. Ship will come in from the NW, i.e., over the US.

[meekGee]

Does Ship have enough cross-range to do a single-orbit return? The earth rotates 22.5 degrees in 90 minutes, so the landing site moves about  2240 Km eastward before Ship completes one orbit. Ship will come in from the NW, i.e., over the US.

Cross-range is about shifting the landing point once EDL started.  It became a talking point with Shuttle and odd reentry Scenarios like abort to launch site.

If ship comes back after a single orbit it will be by making a burn in orbit - just a question of delta V.

I think you don't need a full-blown inclination change if you're only interested in passing over a certain point on the ground once.

[DanClemmensen]

Does Ship have enough cross-range to do a single-orbit return? The earth rotates 22.5 degrees in 90 minutes, so the landing site moves about  2240 Km eastward before Ship completes one orbit. Ship will come in from the NW, i.e., over the US.

Cross-range is about shifting the landing point once EDL started.  It became a talking point with Shuttle and odd reentry Scenarios like abort to launch site.

If ship comes back after a single orbit it will be by making a burn in orbit - just a question of delta V.

I think you don't need a full-blown inclination change if you're only interested in passing over a certain point on the ground once.

I'm sorry I used the wrong terminology. Let me ask the right question: Does Ship have the capability to do whatever it takes, either propulsively or aerodynamically or both,  to land at BC after one orbit? What about later orbits? What about landing from the SW instead of the NW?

[eriblo]

Does Ship have enough cross-range to do a single-orbit return? The earth rotates 22.5 degrees in 90 minutes, so the landing site moves about  2240 Km eastward before Ship completes one orbit. Ship will come in from the NW, i.e., over the US.

Cross-range is about shifting the landing point once EDL started.  It became a talking point with Shuttle and odd reentry Scenarios like abort to launch site.

If ship comes back after a single orbit it will be by making a burn in orbit - just a question of delta V.

I think you don't need a full-blown inclination change if you're only interested in passing over a certain point on the ground once.

I'm sorry I used the wrong terminology. Let me ask the right question: Does Ship have the capability to do whatever it takes, either propulsively or aerodynamically or both,  to land at BC after one orbit? What about later orbits? What about landing from the SW instead of the NW?

Most likely. Remember that you don't really care how far away the launch site is when you return to that exact point in the orbit - you will then pass it with a much smaller perpendicular distance (a few hundred km). We don't know what Starships cross range capabilities are but even if they are smaller than expected you can launch to a slightly higher inclination or do a plane change during de-orbit to pass closer to or even directly over Starbase.

[crandles57]

If ship comes back after a single orbit it will be by making a burn in orbit - just a question of delta V.

I think you don't need a full-blown inclination change if you're only interested in passing over a certain point on the ground once.

Just wondering if it can be done on ascent burn rather than by deorbit burn:

You cannot orbit for long away from an Earth Great Circle. However if you are just planning one loop back to same spot, is it possible to do a suborbital trajectory that is nowhere near an Earth great circle? If possible, this might avoid issue of  a deorbit burn that is supposed to change inclination but fails? But perhaps inaccuracy in the path aimed for is a worse problem?

Even if possible, I wouldn't be surprised if it was crazy for delta v requirements.

[meekGee]

Does Ship have enough cross-range to do a single-orbit return? The earth rotates 22.5 degrees in 90 minutes, so the landing site moves about  2240 Km eastward before Ship completes one orbit. Ship will come in from the NW, i.e., over the US.

Cross-range is about shifting the landing point once EDL started.  It became a talking point with Shuttle and odd reentry Scenarios like abort to launch site.

If ship comes back after a single orbit it will be by making a burn in orbit - just a question of delta V.

I think you don't need a full-blown inclination change if you're only interested in passing over a certain point on the ground once.

I'm sorry I used the wrong terminology. Let me ask the right question: Does Ship have the capability to do whatever it takes, either propulsively or aerodynamically or both,  to land at BC after one orbit? What about later orbits? What about landing from the SW instead of the NW?

To my very untrained eye:

The earth shifts 40000/16 km every 90 minutes, at the equator. Let's say 2000 km at the launch site.

Aerodynamic glide from some 20 km won't make a dent in that.

Once orbital injection is done, you're on a great circle by definition, but as noted above, since orbital injection (10 minutes) is a substantial portion of an orbit, that great circle can be made to already not overfly the launch site and eat into the 2000 km. I don't know by how much.

From basic principles, once thrust stops, at any point in orbit, your velocity vector and the center of the earth define a plane, in which your orbit lies. So if you change your vector (impulse burn) you'll still come back to the same point (inertially speaking) and also the other side of your orbit will remain over the same point.

So if you want to move your landing point, you best burn 1/4 orbit before EDL, so you have 1350 seconds to benefit from it.

(Did I get this right? I'm kinda spitballing)

From this I'm estimating the ship needs about 1-1.5 km/sec, maybe a bit more, to modify its orbit enough to RTLS after one orbit.

Safe Harbor: I don't know that this is right..

[Twark_Main]

So if you want to move your landing point, you best burn 1/4 orbit before EDL, so you have 1350 seconds to benefit from it.

(Did I get this right? I'm kinda spitballing)

Correct AFAIK. See the "orange slice" diagram: https://hopsblog-hop.blogspot.com/2013/01/deboning-porkchop-plot.html

[Yggdrasill]

Am I correct in thinking that you could make an orbit in a plane defined by three points where you would pass over the launch site after one orbit with no on-orbit adjustment needed?

1. The coordinates of the launch site.
2. The coordinates of where the launch site will be after one orbit.
3. The center of the earth

If so, this actually give a lot of different options for orbits, as orbital period can be adjusted with altitude, meaning the second point is a variable.

But if I'm thinking correctly, all the options would overfly the US. You would be launching in a northernly direction.

[DanClemmensen]

Am I correct in thinking that you could make an orbit in a plane defined by three points where you would pass over the launch site after one orbit with no on-orbit adjustment needed?

1. The coordinates of the launch site.
2. The coordinates of where the launch site will be after one orbit.
3. The center of the earth

If so, this actually give a lot of different options for orbits, as orbital period can be adjusted with altitude, meaning the second point is a variable.

But if I'm thinking correctly, all the options would overfly the US. You would be launching in a northernly direction.

Sorry, I need to add an additional constraint: Launch must be on one of the two corridors over the Gulf of Mexico from Boca Chica, and for this particular flight (IFT-9) it must be the one between Florida and Cuba.

[meekGee]

Am I correct in thinking that you could make an orbit in a plane defined by three points where you would pass over the launch site after one orbit with no on-orbit adjustment needed?

1. The coordinates of the launch site.
2. The coordinates of where the launch site will be after one orbit.
3. The center of the earth

If so, this actually give a lot of different options for orbits, as orbital period can be adjusted with altitude, meaning the second point is a variable.

But if I'm thinking correctly, all the options would overfly the US. You would be launching in a northernly direction.

My guess is that since ascent/injection takes 10 minutes, you need the first point to be the point where you stop thrusting.  And by that time, you're already going in a certain direction, which is not what yoi want according to your formula.

And since you take off in a known direction more or less, that velocity vector has a strong preference, and we've just constrained the rub.

[Brigantine]

To my very untrained eye:

The earth shifts 40000/16 km every 90 minutes, at the equator. Let's say 2000 km at the launch site.

Aerodynamic glide from some 20 km won't make a dent in that.
[...]
From this I'm estimating the ship needs about 1-1.5 km/sec, maybe a bit more, to modify its orbit enough to RTLS after one orbit.

Safe Harbor: I don't know that this is right..

Yes, the launch site moves 2000km. To the east. (I get 2380km by the time you catch up to it)
After finishing one complete orbit, you're traveling east, within a few degrees. You can make up most of that 2000km just by timing your de-orbit burn later. What's left is on the order of 2 degrees of latitude, 220km.

It's a shame that de-orbit burns typically want to be ½ an orbit away, right where inclination change doesn't move your landing location - and also potential dog-legs ~2000km down-range of launch won't help you much either for the same reason.

2 degrees of latitude corresponds to a 2⁰ plane change ¼ of an orbit earlier, so (on the order of) 270m/s? Or 245m/s if you also use 20km of aerodynamic cross-range.
[very rough approximation, +/- 50%]

[EDIT]
I should be clearer:
It launches to the east (nearly)
After 1 orbit (sidereal frame, ignoring precession) you're back at the same point in the orbit, momentarily going the same direction as you launched - east (nearly)

Over the next 2000+ km, as you follow a great circle path your bearing keeps increasing, and then you overtake the launch site far to the south.
At maximum latitude you're going exactly east, at the descending node your ground track will be 118⁰ or so

[TomH]

I don't know that this is right..

From everything I know, it is.

There is no reason to try to land Ship after a single 90-minute orbit, and in fact it would be challenging. They can wait 24 hours (16 orbits), which provides for plenty of time to safe Booster after the catch and move it off the pad.

7.5 or 8.5 orbits later the ship should pass close to overhead of LS. Earth has made a half rotation. This would likely be a nighttime landing, though. They'd likely prefer daylight. I agree with you on 24 hr. being optimal.

[DanClemmensen]

I don't know that this is right..

From everything I know, it is.

There is no reason to try to land Ship after a single 90-minute orbit, and in fact it would be challenging. They can wait 24 hours (16 orbits), which provides for plenty of time to safe Booster after the catch and move it off the pad.

7.5 or 8.5 orbits later the ship should pass close to overhead of LS. Earth has made a half rotation. This would likely be a nighttime landing, though. They'd likely prefer daylight. I agree with you on 24 hr. being optimal.

As I (mis)understand it, the ascending pass is 12 hours later only when the orbit is polar. The ascending and descending passes are progressively closer together as the inclination decreases, and merge into a single pass (once a day from due West) when the inclination equals the latitude of the Boca Chica (i.e., a launch due East). You cannot launch into lower inclinations as they do not pass over BC. Qualitatively, I think this means that the relatively lower-inclination launch thru the Florida-Cuba gap will result in an ascending pass nearer 24 hours than a launch into the Yucatan gap, but I don't know how to do the math. Shifting these passes requires a plane change.

Separately from all this, we of course still need to worry about phasing, I have implicitly assumed that for this flight we are free to use an orbital apogee and perigee that bring us over the landing site at the correct time. For an actual mission (e.g. an RPOD to a station) you need to factor in phasing separately.

Is any of this correct? Is there a calculator app somewhere for all this?

[litton4]

I think someone did the calculations a while back  about the single orbit and came up with a figure of about 200 miles.

There are a few other considerations as well, they have to cater for a failure (partial)  of the deorbit burn.

This makes me think that since they'll have only had 2 demonstrations of this, at most, and not for the full deorbit duration, they'll go for a single orbit.
This would eliminate the concerns about being able to survive for 12/24 hours and THEN relight successfully.

My thought would be for them to target a passive re-entry in the Atlantic or Gulf of Mexico.
Deorbit would them bring them closer to BC, with final adjustments on the way down.
Is this possible?