Author Topic: Discussion of trajectories out of Texas launch site  (Read 34577 times)

Offline LouScheffer

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Re: Discussion of trajectories out of Texas launch site
« Reply #40 on: 01/16/2018 02:47 pm »
Would the Texas launch site have better or worse performance than Florida?

There is a performance gain since the site is further south.  The boost from the Earth's rotation is 416 m/s at the 26o of Brownsville, compared to the 409 m/s of Cape Canaveral at 28.5o.  So a gain of 9 m/s

There is a performance loss since a dogleg, or an non-direct-East launch azimuth is needed.   For simplicity, assume the booster heads straight east, then the second stage heads off at different angle.  Since the F9 stages at about 2500 m/s, we can find the angle that loses 9 m/s as cos-1((2500-9)/2500) = 4.86o.  Looking at the maps above, 5o is a pretty sharp turn, plus more optimized trajectories are possible.  So likely the losses from the dogleg are less than 9 m/s, and Texas will be slightly better.

Finally, most of the satellites from Texas will be heading to GTO.  To go from a 300 x 300 parking orbit to GTO, with no inclination change at injection, takes about 2430 m/s.   From Texas, this leaves the satellite with a GEO apogee and 26o inclination, with about 1770 m/s to GEO.   To get this from Florida, you need to either remove some inclination with the injection burn, or go a super-synchronous orbit.  Either case requires at least 20 m/s more from the booster.  Not a big difference, but the advantage goes to Texas.

So overall, despite the dogleg, Texas should be slightly better to GTO than the Cape.


Offline deruch

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Re: Discussion of trajectories out of Texas launch site
« Reply #41 on: 01/16/2018 04:07 pm »
Would the Texas launch site have better or worse performance than Florida?

There is a performance gain since the site is further south.  The boost from the Earth's rotation is 416 m/s at the 26o of Brownsville, compared to the 409 m/s of Cape Canaveral at 28.5o.  So a gain of 9 m/s

There is a performance loss since a dogleg, or an non-direct-East launch azimuth is needed.   For simplicity, assume the booster heads straight east, then the second stage heads off at different angle.  Since the F9 stages at about 2500 m/s, we can find the angle that loses 9 m/s as cos-1((2500-9)/2500) = 4.86o.  Looking at the maps above, 5o is a pretty sharp turn, plus more optimized trajectories are possible.  So likely the losses from the dogleg are less than 9 m/s, and Texas will be slightly better.

Finally, most of the satellites from Texas will be heading to GTO.  To go from a 300 x 300 parking orbit to GTO, with no inclination change at injection, takes about 2430 m/s.   From Texas, this leaves the satellite with a GEO apogee and 26o inclination, with about 1770 m/s to GEO.   To get this from Florida, you need to either remove some inclination with the injection burn, or go a super-synchronous orbit.  Either case requires at least 20 m/s more from the booster.  Not a big difference, but the advantage goes to Texas.

So overall, despite the dogleg, Texas should be slightly better to GTO than the Cape.

Assuming the 5.5mT to GTO that SpaceX lists on their capabilities page is the limit for ASDS recovery of GTO launches.  How much of a mass increase does launching out of Boca Chica (vs. KSC/CCAFS) gain them, for launches to equivalent orbits?  I can't imagine it's very much given the small delta-v differences you've calculated.  Probably not within the significant digits.
Shouldn't reality posts be in "Advanced concepts"?  --Nomadd

Offline RedLineTrain

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Re: Discussion of trajectories out of Texas launch site
« Reply #42 on: 01/16/2018 04:28 pm »
In September 2014, subsequent to the bulk of this thread, Dan Adamo released a paper and was interviewed on The Space Show (link) where he expressed a great deal of skepticism about safe trajectories from Brownsville.

It is interesting to see the Air Force's recent calculations and receptiveness to Cuban overflight that is supported by the 2017 introduction of AFTS by SpaceX.  See Florida Today article.
« Last Edit: 01/16/2018 04:31 pm by RedLineTrain »

Online gongora

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Re: Discussion of trajectories out of Texas launch site
« Reply #43 on: 01/16/2018 04:57 pm »
In September 2014, subsequent to the bulk of this thread, Dan Adamo released a paper and was interviewed on The Space Show (link) where he expressed a great deal of skepticism about safe trajectories from Brownsville.

It is interesting to see the Air Force's recent calculations and receptiveness to Cuban overflight that is supported by the 2017 introduction of AFTS by SpaceX.  See Florida Today article.

I stopped listening to the Adamo interview when he started going on about the risk to Hawaii from Brownsville launches.  Give me a break.

Offline Nomadd

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Re: Discussion of trajectories out of Texas launch site
« Reply #44 on: 01/16/2018 05:09 pm »
I was talking about Mexican Penisula, which is only 500 miles down range, and is just a few degrees offline from the SE path to the Caribbean. They need to sneak between the Yucatan and Cuba, right ?

And it should be WEST Africa, for the directionally challenged. I doubt debris crossed the entire continent of Africa from an east coast launch.

Mexico is close to 600 miles if you go to Veracruz, and you'd be flying over  less land.
 I wouldn't mind if some enterprising mod wanted to move a load of posts from the Texas thread to here.
« Last Edit: 01/16/2018 05:13 pm by Nomadd »
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Online gongora

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Re: Discussion of trajectories out of Texas launch site
« Reply #45 on: 01/16/2018 05:16 pm »
I wouldn't mind if some enterprising mod wanted to move a load of posts from the Texas thread to here.

That would be more likely to happen if an enterprising forum member gave the mods links (or at least the reply #'s of the posts) that should be moved.

Offline LouScheffer

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Re: Discussion of trajectories out of Texas launch site
« Reply #46 on: 01/16/2018 06:55 pm »
Would the Texas launch site have better or worse performance than Florida?

There is a performance gain since the site is further south.  The boost from the Earth's rotation is 416 m/s at the 26o of Brownsville, compared to the 409 m/s of Cape Canaveral at 28.5o.  So a gain of 9 m/s

There is a performance loss since a dogleg, or an non-direct-East launch azimuth is needed.   For simplicity, assume the booster heads straight east, then the second stage heads off at different angle.  Since the F9 stages at about 2500 m/s, we can find the angle that loses 9 m/s as cos-1((2500-9)/2500) = 4.86o.  Looking at the maps above, 5o is a pretty sharp turn, plus more optimized trajectories are possible.  So likely the losses from the dogleg are less than 9 m/s, and Texas will be slightly better.

Finally, most of the satellites from Texas will be heading to GTO.  To go from a 300 x 300 parking orbit to GTO, with no inclination change at injection, takes about 2430 m/s.   From Texas, this leaves the satellite with a GEO apogee and 26o inclination, with about 1770 m/s to GEO.   To get this from Florida, you need to either remove some inclination with the injection burn, or go a super-synchronous orbit.  Either case requires at least 20 m/s more from the booster.  Not a big difference, but the advantage goes to Texas.

So overall, despite the dogleg, Texas should be slightly better to GTO than the Cape.

Assuming the 5.5mT to GTO that SpaceX lists on their capabilities page is the limit for ASDS recovery of GTO launches.  How much of a mass increase does launching out of Boca Chica (vs. KSC/CCAFS) gain them, for launches to equivalent orbits?  I can't imagine it's very much given the small delta-v differences you've calculated.  Probably not within the significant digits.
Yes, it's not much.  Making generic assumptions, 4.5t second stage + 5.5t payload, and 120t starting mass, the delta-V of the second stage is 348*9.8*ln(120/10) = 8475 m/s.   Incrementing the mass by 70 kg loses about 22 m/s, in the range of what the difference might be.  So no significant difference, as you speculated.

Offline dglow

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Re: Discussion of trajectories out of Texas launch site
« Reply #47 on: 01/16/2018 08:18 pm »
Maybe Envy887 or somebody else smarter than me could say how far downrange an expended 1st stage or a second stage that fails to fire might come down. That's probably a big factor in how far downrange a populated area has to be.

Well I'll reply even though I'm dumber than both you and envy887. According to the FCC filings and Raul's nice map, recoverable GTO first stages can hit about 420 miles downrange. Fairings can go 560 miles downrange.

550 miles to Yucatan  Over 800 miles to Cuba
With the certified FTS why can't BC get the same OK they just got in Florida for high inclination launches?

Depends on probability of failure while the IIP is over land and the population density of that land. A longer IIP dwell over high population areas means less likelihood of meeting the casualty requirements. Out of FL, the IIP only crosses ~80 miles of Cuba and later ~50 miles of Panama, which only takes seconds. Crossing Mexico and/or South America takes much longer and potentially crosses more population. They would have to run the numbers - it's possible this could be done, but it's a very different situation than launching south out of the Cape.

[reposting this Q from the Texas Launch Site thread  (you're welcome, Nomadd)]


Regarding 550 to Yucatan and 560 for fairings, specifically, but asking more generally: does SpaceX's work with fairing recovery have the opportunity to open up routes previously unavailable for overflight?

How are the IIPs for each element calculated? Per the numbers cited above, it appears a SSE GTO trajectory would clear Mexico of any first stage impact risk. If the fairings could (reliably) be steered in a manner that reduced impact risks, would the the second stage then clear the peninsula (for some probability of 'clear')?

Asking to better understand and learn here. Thanks.

Offline envy887

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Re: Discussion of trajectories out of Texas launch site
« Reply #48 on: 01/16/2018 08:41 pm »
Maybe Envy887 or somebody else smarter than me could say how far downrange an expended 1st stage or a second stage that fails to fire might come down. That's probably a big factor in how far downrange a populated area has to be.

Well I'll reply even though I'm dumber than both you and envy887. According to the FCC filings and Raul's nice map, recoverable GTO first stages can hit about 420 miles downrange. Fairings can go 560 miles downrange.

550 miles to Yucatan  Over 800 miles to Cuba
With the certified FTS why can't BC get the same OK they just got in Florida for high inclination launches?

Depends on probability of failure while the IIP is over land and the population density of that land. A longer IIP dwell over high population areas means less likelihood of meeting the casualty requirements. Out of FL, the IIP only crosses ~80 miles of Cuba and later ~50 miles of Panama, which only takes seconds. Crossing Mexico and/or South America takes much longer and potentially crosses more population. They would have to run the numbers - it's possible this could be done, but it's a very different situation than launching south out of the Cape.

[reposting this Q from the Texas Launch Site thread  (you're welcome, Nomadd)]


Regarding 550 to Yucatan and 560 for fairings, specifically, but asking more generally: does SpaceX's work with fairing recovery have the opportunity to open up routes previously unavailable for overflight?

How are the IIPs for each element calculated? Per the numbers cited above, it appears a SSE GTO trajectory would clear Mexico of any first stage impact risk. If the fairings could (reliably) be steered in a manner that reduced impact risks, would the the second stage then clear the peninsula (for some probability of 'clear')?

Asking to better understand and learn here. Thanks.

I am not an expert, but presumably the IIP is calculated from the ballistic trajectory plus dispersions for uncertainty in flight path and aerodynamic effects during reentry. If the plan for controlling the dispersion in fairing landing sites includes active control systems, they would need to show the probability that those control systems will actually work as intended, and also include the probability that loss of control of a fairing might cause a casualty.

IOW, controlling the fairings definitely helps, but without all the numbers it's hard to say exactly how much it helps. You still have the (IMO more critical) issue of the second stage IIP going over a large populated land mass.

The booster would always land in the water on F9 flights, so that's not really an issue. But a Heavy launch might result in the booster going further downrange, which could also be a problem.

Offline stcks

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Re: Discussion of trajectories out of Texas launch site
« Reply #49 on: 01/16/2018 08:49 pm »
This Embry-Riddle paper has been mentioned on NSF before but it deserves to be linked here as well.

Offline RedLineTrain

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Re: Discussion of trajectories out of Texas launch site
« Reply #50 on: 06/15/2021 02:52 pm »
To necro this worthy thread, Musk was asked about Starship revenue service with Starlink satellites.  His reply...

Quote from: Elon Musk on Twitter
After several successful launches, land overflight earlier in trajectory passes E-sub-c safety threshold. That said, Starship will also launch from Cape long-term.

https://twitter.com/elonmusk/status/1404336029776027651

To recap, without dogleg, the 53 degree track would hit the Yucatan at about 600 miles or the Louisiana shore at about 350 miles.

Online rsdavis9

Re: Discussion of trajectories out of Texas launch site
« Reply #51 on: 06/15/2021 03:02 pm »
Dogleg allows launches from BC to access the all important ~50 deg incl.(ISS, starlink).
The other usefull inclinations will be:
1. 23.5 for ecliptic plane launches. (moon, mars, etc)
2. as close to 0 as possible. (geostationary)

so when phobos is deployed what is the best compromise position to launch from to get to these inclinations with minimal dogleg?
 
With ELV best efficiency was the paradigm. The new paradigm is reusable, good enough, and commonality of design.
Same engines. Design once. Same vehicle. Design once. Reusable. Build once.

Offline RedLineTrain

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Re: Discussion of trajectories out of Texas launch site
« Reply #52 on: 06/15/2021 03:40 pm »
This Embry-Riddle paper has been mentioned on NSF before but it deserves to be linked here as well.

It's interesting all of the changes that have occurred since this paper was written.  A few of note.

1.  AFTS has been demonstrated and is routinely used by SpaceX for F9 and Starship.
2.  The Southern Route over Cuba from Cape Canaveral has now been opened up for F9 with a dogleg, presumably in coordination with effected countries (ex-Cuba).
3.  Starship is now the rocket to fly out of the Texas launch site.
4.  Starship has a few suborbital demonstration flights under its belt, presumably in coordination with Mexico.
5.  South Texas has been demonstrated to have much less impact on passenger airliner itineraries than Cape Canaveral (e.g., Falcon Heavy demonstration flight).

So have all of the challenges been addressed?
« Last Edit: 06/15/2021 03:53 pm by RedLineTrain »

Offline wannamoonbase

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Re: Discussion of trajectories out of Texas launch site
« Reply #53 on: 06/15/2021 03:52 pm »
Dogleg allows launches from BC to access the all important ~50 deg incl.(ISS, starlink).
The other usefull inclinations will be:
1. 23.5 for ecliptic plane launches. (moon, mars, etc)
2. as close to 0 as possible. (geostationary)

so when phobos is deployed what is the best compromise position to launch from to get to these inclinations with minimal dogleg?
 

Sure maybe they can do it, but what is the payload impact?

It's going to be really hard to beat launching from the Cape for inclined orbits. 

If and when they get to a higher flight cadence then perhaps the off shore flight platforms make sense.  Even off shore, the supply of launch staff and commodity delivery may dictate their launch location.
Wildly optimistic prediction, Superheavy recovery on IFT-4 or IFT-5

Offline RedLineTrain

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Re: Discussion of trajectories out of Texas launch site
« Reply #54 on: 06/15/2021 04:17 pm »
Will a dogleg even by required for the 53-degree flights?

Online rsdavis9

Re: Discussion of trajectories out of Texas launch site
« Reply #55 on: 06/15/2021 04:44 pm »
Will a dogleg even by required for the 53-degree flights?

Out of BC yes if you want to go just offshore of the yucatan.
But that trajectory looks to be about 111deg. For 53 deg inclination you need 90+53=143deg azimuth.
Which goes over the campeche at 988km. Is that allowed?

With ELV best efficiency was the paradigm. The new paradigm is reusable, good enough, and commonality of design.
Same engines. Design once. Same vehicle. Design once. Reusable. Build once.

Offline RedLineTrain

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Re: Discussion of trajectories out of Texas launch site
« Reply #56 on: 06/15/2021 05:20 pm »
Will a dogleg even by required for the 53-degree flights?

Out of BC yes if you want to go just offshore of the yucatan.
But that trajectory looks to be about 111deg. For 53 deg inclination you need 90+53=143deg azimuth.
Which goes over the campeche at 988km. Is that allowed?

Yes, it's more or less over Campeche and then overflies land through most of Central and South America.

Offline Dave G

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Re: Discussion of trajectories out of Texas launch site
« Reply #57 on: 06/15/2021 08:31 pm »
Note: Nearly all of the property that SpaceX purchased in Boca Chica was under the name "Dogleg Park LLC".
Example shown in the images below.

Maybe SpaceX is trying to tell us something...

Offline ClayJar

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Re: Discussion of trajectories out of Texas launch site
« Reply #58 on: 06/15/2021 09:57 pm »
Note: Nearly all of the property that SpaceX purchased in Boca Chica was under the name "Dogleg Park LLC".
Example shown in the images below.

Maybe SpaceX is trying to tell us something...
I wouldn't so much say SpaceX is trying to tell us something.  I'd would, of course, say that when they set up the LLC with which to purchase properties, the orbital destinations most likely to be most useful would require a dogleg, so why not be fun and name it "Dogleg Park".

Having seen many generations of plans come and go, of course I don't think we ought to use the name as gospel truth henceforth and forevermore.  Still, the reopening of the polar corridor from Florida has shown us two things.  First, it's shown us that overflying land isn't an absolute prohibition.  Second, it has shown us that overflying land is not an "easy" thing to get approved.

Will there be launches from Boca Chica or thereabouts that are not doglegs around Cuba?  If SpaceX is ever going to succeed on their point-to-point plan, eventually the statistics, et al, will have to be such that overflying land is nominal.  At the same time, if Vegas puts the over/under on direct polar flights from BC at "after the first Mars landing", I'm not sure I'd bet the under.

(Even in a hypothetical future where SpaceX is regularly launching direct trajectories over land, I wouldn't be surprised to still see "Dogleg Park, LLC" floating around, as that would just strike me as an indication of a completely reasonable dislike of needless paperwork.)

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