Safe Instantaneous Impact Point Tracks for Starship Launch and Recovery

[InterestedEngineer]

I found this neat population explorer

https://google.earthengine.app/view/population-explorer

[InterestedEngineer]

So how are they going to land in Florida?

Attached is a Shuttle trajectory that avoids populated areas.  the only way to get into a landing at KSC is from the NNW direction, which is the same direction as the shuttle landing runway faces.

I don't see how they are going to get "as east as possible" launches to work from KSC.


Also give the turns the shuttle made are the same ones made in Flight 11, I'm starting to think they were practicing KSC returns, not just BC.

[TheRadicalModerate]

FWIW here are the descending leg approaches for 53º and 43º (the most likely Starlink deployment inclinations) and 30.2º, which is as good as I could do for a common depot orbit that allowed launches out of both Boca Chica and the Cape.  It has a very small dogleg, but it's fairly far downrange, which may not be necessary; I didn't model where downrange debris would fall if the dogleg were earlier in the launch.  That launch trajectory is shown as well.

Update:  The BC approach says 32º; it's a typo.  Should say 30.2º.

Second Update:  I decided to put in the doglegs to get to the common refueling orbit between BC and KSC (now it's 30.3º inclination), as well as those for the 43º and 53º
Starlink inclinations.  43º doesn't look too bad, once you figure where the pre-dogleg debris would impact, but 53º is unlikely to work.

The 30.3º approach into KSC is very bad from an overflight perspective:  Austin, Houston (actually the Woodlands, so... maybe no big loss?), and New Orleans are all on the hit list.

The problem is that going to a lower inclination requires overflying Cuba and Hispaniola, and going to a higher inclination requires going south of Jamaica and the Caymans, which will be a considerably higher inclination (34.7º), which also happens to overfly Caracas, albeit 3000km downrange.  It's gonna be tricky.  Maybe you jog south on EDL with as much cross range as you can get, then aggressively north after you leave New Orleans behind?

Yet Another Update:

The KML file is here.

[Twark_Main]

FWIW here are the descending leg approaches for 53º and 43º (the most likely Starlink deployment inclinations) and 30.2º, which is as good as I could do for a common depot orbit that allowed launches out of both Boca Chica and the Cape.  It has a very small dogleg, but it's fairly far downrange, which may not be necessary; I didn't model where downrange debris would fall if the dogleg were earlier in the launch.  That launch trajectory is shown as well.

Update:  The BC approach says 32º; it's a typo.  Should say 30.2º.

Second Update:  I decided to put in the doglegs to get to the common refueling orbit between BC and KSC (now it's 30.3º inclination), as well as those for the 43º and 53º
Starlink inclinations.  43º doesn't look too bad, once you figure where the pre-dogleg debris would impact, but 53º is unlikely to work.

The 30.3º approach into KSC is very bad from an overflight perspective:  Austin, Houston (actually the Woodlands, so... maybe no big loss?), and New Orleans are all on the hit list.

The problem is that going to a lower inclination requires overflying Cuba and Hispaniola, and going to a higher inclination requires going south of Jamaica and the Caymans, which will be a considerably higher inclination (34.7º), which also happens to overfly Caracas, albeit 3000km downrange.  It's gonna be tricky.  Maybe you jog south on EDL with as much cross range as you can get, then aggressively north after you leave New Orleans behind?

Yet Another Update:

The KML file is here.

Incredible analysis.

How many orbits are you assuming for the landing? It seems like the exact number of orbits (and thus the longitudinal phasing) might be one of the parameters you can tweak to avoid hazardous overflights.

Eg if you have to go to 5 orbits instead of 3 (numbers made up), that may be worth it because it opens up a feasible aerodynamic corridor.

[rsdavis9]

FWIW here are the descending leg approaches for 53º and 43º (the most likely Starlink deployment inclinations) and 30.2º, which is as good as I could do for a common depot orbit that allowed launches out of both Boca Chica and the Cape.  It has a very small dogleg, but it's fairly far downrange, which may not be necessary; I didn't model where downrange debris would fall if the dogleg were earlier in the launch.  That launch trajectory is shown as well.

Update:  The BC approach says 32º; it's a typo.  Should say 30.2º.

Second Update:  I decided to put in the doglegs to get to the common refueling orbit between BC and KSC (now it's 30.3º inclination), as well as those for the 43º and 53º
Starlink inclinations.  43º doesn't look too bad, once you figure where the pre-dogleg debris would impact, but 53º is unlikely to work.

The 30.3º approach into KSC is very bad from an overflight perspective:  Austin, Houston (actually the Woodlands, so... maybe no big loss?), and New Orleans are all on the hit list.

The problem is that going to a lower inclination requires overflying Cuba and Hispaniola, and going to a higher inclination requires going south of Jamaica and the Caymans, which will be a considerably higher inclination (34.7º), which also happens to overfly Caracas, albeit 3000km downrange.  It's gonna be tricky.  Maybe you jog south on EDL with as much cross range as you can get, then aggressively north after you leave New Orleans behind?

Yet Another Update:

The KML file is here.

Is there a reason we aren't considering ascending node landings? They appear to be much less populated. Something to do with overflying foreign countries? Mexico, Costa Rica

[spacenut]

Why not land a Vandenburg in California?  Then ship the Starship back to either Starbase or the Cape for relaunch.  Sure time at sea, but lots of Starship launches and landings.  Maybe even a landing site in the eastern Caribbean off the Virgin Islands, or off some other islands with a sea platform in shallow water, then ship back for launchings?  Maybe build a landing tower in shallow water off the west coast of Florida. 

For now, from what I have read on here, they are going to ship Starships and boosters from Starbase to Florida anyway.   

[TheRadicalModerate]

Is there a reason we aren't considering ascending node landings? They appear to be much less populated. Something to do with overflying foreign countries? Mexico, Costa Rica

I just hadn't added them to the KML file yet.  They're in now.¹  Note that things get really busy if all the arcs are enabled at once.  I've placed them into separate folders so it's easy to turn them on and off. (If you hover over the folder names in Google Earth, a little eye-like icon pops up.  Click it, and everything contained in the folder and any subfolders will go away.)

KML file is here.  Note that I didn't bother doing the departures from KSC--they're easy.

Once we get through with the IFT launches, we're interested in three things:

1) What's the best inclination for depots that need to be reached from both BC and KSC?  Two options shown: 
a) 30.3º, which is the lowest inclination that works without overflying Cuba, but requires a slight dogleg.  It's also pretty terrible for overflying pretty much every city on the Gulf Coast on approach to KSC.
b) 33.4º, which is a straight shot (no dogleg), but slightly higher inclination.  I'd vote for this one.  Note:  It overflies Phoenix, albeit far uprange.

2) How do we fly from BC for 43º?  It requires a dogleg, which has to be far enough downrange that debris stays in the Yucatan channel.  Only then can the Ship turn right.  Note that this lines are trajectories, not IIP tracks.  Going over the Yucatan is OK, as long as the IIP track stays out to sea, which it should.

Note that the descending approach from 43º into BC overflies Marin.  Descending approach to KSC is pretty good..

3) How do we fly from BC for 53º?  I think the short answer is, we don't.  The IIP track may or may not stay out to sea and avoid Guatemala and Nicaragua, but it's going straight over Panama City.  The dogleg is also hefty, with a hefty performance hit to go with it.

Fortunately, things are clear from KSC, and the descending leg into KSC looks pretty clean.

I'm unimpressed with any of the ascending approaches.  They all go over heavily populated parts of Mexico and Central America, and none of them appear to be much better than the corresponding descending approaches.


___________
¹Some things to remember:

1) I'm not accounting for the rotation of the Earth along the trajectory.  This would make all the trajectories curve slightly westward.  It's not really an issue on ascent, but it might be on descent.

2) If you dig into the azimuths, they're all inertial.  These would therefore not be the departure azimuths from the pad, which have to assume the vector sum of the inertial azimuth and Earth's rotational velocity.  But I'm pretty sure that the inertial azimuth is good from just a few seconds after the vehicle lifts off the pad.

3) We now know that we have at least a little bit of cross-range in the approaches.  The unknown question is whether it's enough to dodge urban areas far up-range, where we do need some dodging.

4) I had trouble using the local version of Google Earth to read the KML file.  Things seem to work fine with the web-based version.

[TheRadicalModerate]

Incredible analysis.

How many orbits are you assuming for the landing? It seems like the exact number of orbits (and thus the longitudinal phasing) might be one of the parameters you can tweak to avoid hazardous overflights.

Eg if you have to go to 5 orbits instead of 3 (numbers made up), that may be worth it because it opens up a feasible aerodynamic corridor.

I didn't plot how the trajectory arcs would curve westward due to Earth's rotation during the actual flight.  I doubt that's more than a few tens of km for launch, but might be more substantial for EDL.

I also assumed that all the approaches were lined up with their landing sites, irrespective of how many orbits that took.  It's hard to figure things beyond that, unless your commit to particular orbital altitude, and you have a good handle on cross-range.

I'm cautiously optimistic that there's enough cross-range to get things clear--at least until you get to approaching Florida.  Central Florida is basically a giant urban wasteland, punctuated with the occasional uninhabitable swamp.  It'll be interesting to see what they can get approved, not only for the hazard to the public computation, but also for sonic booms.

[Twark_Main]

I also assumed that all the approaches were lined up with their landing sites, irrespective of how many orbits that took.  It's hard to figure things beyond that, unless your commit to particular orbital altitude, and you have a good handle on cross-range.

I'm suggesting that we can treat the longitude offset as the "free parameter," one which we can adjust to avoid risky overflights.

This isn't committing to an orbital altitude any more than before. If you can plan a reentry which exactly intersects the launch site, you can also plan a trajectory that is offset by (say) 10 miles to the west. Either way you still need to to aim for a single point, you're just changing the exact target location.

Basically this extra parameter can give a little extra "wiggle room" to plan your reentry.

[TheRadicalModerate]

I also assumed that all the approaches were lined up with their landing sites, irrespective of how many orbits that took.  It's hard to figure things beyond that, unless your commit to particular orbital altitude, and you have a good handle on cross-range.

I'm suggesting that we can treat the longitude offset as the "free parameter," one which we can adjust to avoid risky overflights.

This isn't committing to an orbital altitude any more than before. If you can plan a reentry which exactly intersects the launch site, you can also plan a trajectory that is offset by (say) 10 miles to the west. Either way you still need to to aim for a single point, you're just changing the exact target location.

Basically this extra parameter can give a little extra "wiggle room" to plan your reentry.

I don't see the difference.  If you're sliding stuff east or west (and I'd pick east, since it's a lot easier to bleed extra energy than it is to stretch the energy for more distance), then the amount you can slide is closely related to the cross-range, or at least to some total amount of turning that you're pulling from the Ship's potential energy.

Beside that, I can't plot what you're proposing without much, much more work than I'm willing to put into it.  And it's an infinite amount of work without knowing what the total cross-range budget is--and what's available at what speeds and distances uprange.

[Twark_Main]

I also assumed that all the approaches were lined up with their landing sites, irrespective of how many orbits that took.  It's hard to figure things beyond that, unless your commit to particular orbital altitude, and you have a good handle on cross-range.

I'm suggesting that we can treat the longitude offset as the "free parameter," one which we can adjust to avoid risky overflights.

This isn't committing to an orbital altitude any more than before. If you can plan a reentry which exactly intersects the launch site, you can also plan a trajectory that is offset by (say) 10 miles to the west. Either way you still need to to aim for a single point, you're just changing the exact target location.

Basically this extra parameter can give a little extra "wiggle room" to plan your reentry.

I don't see the difference.  If you're sliding stuff east or west (and I'd pick east, since it's a lot easier to bleed extra energy than it is to stretch the energy for more distance), then the amount you can slide is closely related to the cross-range, or at least to some total amount of turning that you're pulling from the Ship's potential energy.

Beside that, I can't plot what you're proposing without much, much more work than I'm willing to put into it.  And it's an infinite amount of work without knowing what the total cross-range budget is--and what's available at what speeds and distances uprange.

I get it. Yes, there's no sense searching for reentry RAANs beyond your vehicle's maximum crossrange ability, I agree with that.

It's not really something extra to plot on the map. Really this is just something to keep in mind when designing a trajectory.

[rsdavis9]

This launch ascent goes over the narrow part of mexico where it connects to the yucatan. Looks like very low population. Gives a 74 deg inclination. Maybe with a dogleg we could down to 60deg?

[Vultur]

It'll be interesting to see what they can get approved, not only for the hazard to the public computation, but also for sonic booms.

I wonder if some of this ends up being more a political question than an engineering one. Especially sonic booms.

[TheRadicalModerate]

This launch ascent goes over the narrow part of mexico where it connects to the yucatan. Looks like very low population. Gives a 74 deg inclination. Maybe with a dogleg we could down to 60deg?

What payloads need to be deployed in the 60-74º inclinations?  All of the scheduled v3 Starlinks go to either 43º or 53º.

For the foreseeable future, Starships are either going to carry Starlinks, propellant, HLS Starships, or depots.  Eventually, they'll need to be able to access a wide range of orbits, but that's going to happen way, way after LC-39A is up and running.  I don't expect BC to handle high-inclination traffic, ever.

[DanClemmensen]

This launch ascent goes over the narrow part of mexico where it connects to the yucatan. Looks like very low population. Gives a 74 deg inclination. Maybe with a dogleg we could down to 60deg?

What payloads need to be deployed in the 60-74º inclinations?  All of the scheduled v3 Starlinks go to either 43º or 53º.

For the foreseeable future, Starships are either going to carry Starlinks, propellant, HLS Starships, or depots.  Eventually, they'll need to be able to access a wide range of orbits, but that's going to happen way, way after LC-39A is up and running.  I don't expect BC to handle high-inclination traffic, ever.

They will need to hit the high-inclination orbits when it's time to de-orbit and replace the earlier Starlinks in those orbits, which will start happening in two years or less. Those orbital planes have inclinations of 97.6 degrees and 70 degrees. Not a lot of satellites, and they could probably just do a few last F9/V2 mini missions to keep providing good polar coverage until they can use Starship.

[TheRadicalModerate]

They will need to hit the high-inclination orbits when it's time to de-orbit and replace the earlier Starlinks in those orbits, which will start happening in two years or less. Those orbital planes have inclinations of 97.6 degrees and 70 degrees. Not a lot of satellites, and they could probably just do a few last F9/V2 mini missions to keep providing good polar coverage until they can use Starship.

In two years, LC-39A will likely be up and running for Starship.  Meanwhile, the v2 mini isn't going away instantly, because Starship launch cadence isn't sufficient to provide the supply of new satellites needed to keep growing the subscribers.  Until v2 mini is gone completely, SpaceX can use them to launch replacements to high-inclination orbits from Vandy or Canaveral, using F9's.

[DanClemmensen]

They will need to hit the high-inclination orbits when it's time to de-orbit and replace the earlier Starlinks in those orbits, which will start happening in two years or less. Those orbital planes have inclinations of 97.6 degrees and 70 degrees. Not a lot of satellites, and they could probably just do a few last F9/V2 mini missions to keep providing good polar coverage until they can use Starship.

In two years, LC-39A will likely be up and running for Starship.  Meanwhile, the v2 mini isn't going away instantly, because Starship launch cadence isn't sufficient to provide the supply of new satellites needed to keep growing the subscribers.  Until v2 mini is gone completely, SpaceX can use them to launch replacements to high-inclination orbits from Vandy or Canaveral, using F9's.

"Prediction is hard, especially the future." (miss-attributed to Neils Bohr). As soon as possible, they will replace V2/F9 with V3/Pez. A Pez launch can carry twice as many V3 as F9 carries V2, and Pez is cheaper to launch. Therefore, you need to try to predict when this will happen. My guess: the transition will be sudden. It depends on when they achieve rapid reuse. Those near-polar orbits are potentially a special case. If they achieve rapid reuse before LC-39A comes online, They may continue to use V2/F9 for those near-polar orbits. I can't even begin to assign probabilities to any of this.

[TheRadicalModerate]

As soon as possible, they will replace V2/F9 with V3/Pez. A Pez launch can carry twice as many V3 as F9 carries V2, and Pez is cheaper to launch.

I agree with that, but "as soon as possible" will be when Starship can handle the needed range of inclinations.  70+º from BC simply isn't happening.  But the Cuban dogleg should be available from KSC after not too long.  (Depends on how Starship launch reliability evolves.)