Well it's good to see them getting on with it. I guess there is commercial pressure to up the tempo with the backlog after July, plus they had quite a packed order book before then anyway. The Jason-3 is only about 500kg so that implies plenty spare fuel to return etc. Should be good, though the range safety officer is going to be a tad on edge I reckon.
Cheers, Mike.
Not sure of the state of the "return pad". It is done? I have not seen anything mentioned about a return to pad attempt. I am thinking that until they can successfully demonstrate multiple returns at one location and a positive turnaround with a return to flight that they will attempt "land recovery" only at one site. No need to build multiple refurbish facilities until you have a proven track record at one location.
Of course. Ah, but I am a cheeky one indeed ( and obviously not an investor either ) ....
.... why not take off at Vandenberg and then after separation land on the East coast ? Maybe not this time but perhaps sometime ? :-)))
Cheers, Mike.
I have made this letter longer than usual because I lack the time to make it shorter ...
... and my other CPU is a Ryzen 5950X :-) Blaise Pascal
.... why not take off at Vandenberg and then after separation land on the East coast ? Maybe not this time but perhaps sometime ? :-)))
Cheers, Mike.
Had not considered that. Why not indeed!!!!!!!
Well it's a longer jump for sure, but still much like the land-on-the-barge scenario. The kinetics are so favourable because you don't have to come back, remembering Elon's quote of a ~ 200 GJ KE dividend b/w barge vs shore.
Cheers, Mike.
I have made this letter longer than usual because I lack the time to make it shorter ...
... and my other CPU is a Ryzen 5950X :-) Blaise Pascal
Another option besides the land pad is the West Coast drone ship. Given how tightly the Vandenberg landing pad is close to important stuff, at this stage I'd personally think it wise for them to try a ship landing again.
Regarding refurbishment: while that is a crucial topic for the eventual success, I think at this stage the important thing is to do enough inspection/tear down of any returned vehicles to support preparation for eventual refurbishment (and design changes to improve the prospects).
I've seen seemingly authoritative claims that they do not plan to fly the first returnee again, though they do plan to use it to "burn in" a static test facility or some such.
In looking for information on the west coast drone ship, about all I find is that it is a rebuild of Marmac 303, and transited the Panama canal outbound from the rebuild site in Lousiana in June 2015. I did not find a name, as the two announced names apparently belong to two other ships (Just Read the Instructions, and Of Course I Still Love You), although in January 2015 Elon tweeted that OCISLY would be the West Coast drone ship.
Folks posting there who seem somewhat informed assert that before things went kablooey it had been the plan to attempt a land recovery on the Jason-3 launch. If true the pad has been pretty ready for months. However these folks are currently of the opinion that Jason-3 is more likely an ASDS than a land recovery attempt, and point out that the booster is an older one without recent upgrades to the recovery provisions (which I think might point in the direction of no attempt on this one). Apparently there was a tent in the middle of the Vandenberg landing pad as of very recently--they are watching that, as unless it is removed a Return to Launch Site is not feasible.
Meaning they don't have permission to point inland then ? Oh well.
In looking for the Vandenberg launch azimuth limits I happened on this handy summary of most of the world's satellite launch facilities. As it is written for the use of amateur satellite observers, it more reliably gives the orbital inclinations than the actual launch azimuth limits, but for many it gives the azimuth allowed range.
For Vandenberg it lists the allowable range for orbital launches as 147 to 201 (ICBM tests aimed at Kwajalein atoll are something close to due West, but are sub-orbital). Other sources list 158 to 201. Possibly the limits have changed over time, or maybe differ by specific launch complex.
Yes, with enough delta-V you can change the orbital plane at will, but it is very expensive to change it very much.
Certainly some sites launch over land (all the Soviet sites, and the Chinese as well), but the sites blessed with a coast seem generally to restrict themselves to over-water for the early ascent.
What a terrific little summary. Thanks for that ! :-)
The Vandenberg range is from slightly east of south to slightly west of south, so if it matters one can choose slightly pro-grade or slightly retrograde. Thinking of polar orbits - and pretending to be a fly-in-a-spacesuit over either pole - I wonder how many polar or peri-polar satellites there are ? I believe there is one altitude which is much preferred as it is Sun synchronous*. In any case there would seem to be a volume above either pole that would be very busy indeed. No traffic lights evidently ....
Cheers, Mike.
* Meaning a satellite could be overhead a given spot on Earth at very close to the same local time each day.
( edit ) Yup. For say about 90 minute orbit thus 16 per day ( -ish ) then ~ 660km is an altitude for sun-synchrony. But that's a sidereal estimate. So now the pro/retro grade matters ( the angle to the Sun for both satellite and earth is slowly changing ), giving a slightly higher or lower orbit respectively ..... short answer is that if you want that type of polar orbit then the azimuth choice at launch also implies an altitude selection when the burn is done.
I have made this letter longer than usual because I lack the time to make it shorter ...
... and my other CPU is a Ryzen 5950X :-) Blaise Pascal
I wonder how many polar or peri-polar satellites there are ?
Lots.
As a generalization, there are a goodly many communications satellites in geosynchronous orbit, but lots of other satellites either need to be much closer to Earth to get adequate resolution, or need to scan a much higher fraction of the earth's surface at respectable angles than that orbit offers.
So a good many observing satellites, whether military optical, military radar, or weather, operate in rather high inclination orbits. The Sun synchronous type you mentioned is a particular case, but others vary. Any system which means to cover most of the earth's surface pretty well needs at least some of the constellation at somewhat high inclination, and most of the ones I'm familiar with tend to use a standard inclination for the whole group.
For one example, the original Motorola Iridium constellation chose a rather low altitude, thus enabling smallish handsets without an insanely large antenna nor enormous power on the satellite. That came to 780 Kilometer altitude at 86.4 degree inclination--not quite polar, but rather close. I believe all Iridium (past) and Iridium-NEXT (coming real soon now) launches have been from Vandenberg.
DigitalGlobe's Worldview-4 has quite high resolution--so needs a low altitude, but means to cover most of the earth, and they chose the consistency of the sun-synchronous orbit at 617 Km. I did not find the inclination, but as Mike pointed out, it is locked to the altitude, and has to be quite high.
The GPS system uses a much higher altitude of 20,200 km, so the needed inclination is less, and they chose 55 degrees. Those, I think, have launched from the Cape.
US Keyhole optical reconnaissance satellites need low altitude to get high resolution, so use non-circular orbits with altitudes in the 300 to 800 km range, and high inclinations of the order of 95 to 98 degrees. I think for years these have all launched from Vandenberg, and the perceived need to launch them probably drove the (never used) Vandenberg Shuttle launch site requirement.
Excellent points. For the merit of other readers :
- azimuth refers to degrees from due North. In this case the interesting one is True North ( toward where the axis of Earth's actual rotation is ) and not magnetic ( which can't stand still on a good day anyway ). This is easterly/clockwise looking down from above or towards your right hand if you face North while standing on your feet with the planet below ie. the usual compass understanding. You may find some negative azimuths mentioned which goes the other way eg. NNW is minus 22.5 degrees azimuth.
- inclination is with respect to the equator and usually quoted as Eastward being zero but beware the sense of the discussion. Did you launch with a southerly or northerly component ? But note that if it is transiting the equator South-to-North it will transit North-to-South one half orbit later. Etc.
- I should add that many other orbits satisfy Sun synchrony. It doesn't have to be 90 minutes but ought to at least recur on about a 24 hour basis. This yields correspondingly higher orbits for longer periods.
- the calculation of period to orbital radius is actually good old Kepler's Third Law ie. the radius cubed goes like the period squared ( gravity is to an excellent approximation causing that variation ). Beware that the height above the surface is that radius minus the Earth's radius.
Quote:
To an extremely rough approx, if time is in minutes then
orbital height above surface = (330 * t^[2/3]) - 6370
in kilometres. The factor of 330 is calibrated against geostationary orbits. For various reasons 350 will work better for LEO. The mean radius is used but the Earth is non-spherical to about 30km variation. It's fatter at the equator, just like me .....
... and if you are really fussy then an elliptical orbit has that as well-ish, provided that you interpret 'radius' as the length of the semi-major axis ( one half the long axis of the egg ). But don't forget to NOT crash into the planet* !
Cheers, Mike.
* Which is why we just don't fire these things out of a ruddy great gun with a one-shot ballistic trajectory. It will try to do a full orbit and attempt to return to your launch site from below by burrowing along an underground arc. Remember it's acting as if all the planet's mass is at the centre. For satellites you want some non-trivial angular velocity around Earth's centre so that you get, well, an orbit. The first and more so the second stage boosting is what largely does that : which way do you point the burning end ? Of course if you DO want to hit the planet other than your launch site, then that's different. :-)
( edit ) So that is why the 'B' in ICBM is Ballistic. You DO want to hit the planet before a full orbit.
( edit ) I will use this opportunity to plug a very good & readable book by one of our fearless leaders at AEI : Bernard Schutz. It is called Gravity From The Ground Up. It explains all this stuff in a comfortable tone for the interested layman. At most you may need some late high school maths ( slight bit of That Ugly Trigonometry Monster ). You can still learn heaps by just holding your breath when running through the mathematical thickets though. There is some straight forward Java code ( Triana Project ) that you can download to replicate his calculations, if that is your pleasure. Reasonably priced at a good bookstore near you ( or maybe Cambridge University Press sells online ) .... :-)))))
{ the Triana Download link has moved since 2003, try here.}
I have made this letter longer than usual because I lack the time to make it shorter ...
... and my other CPU is a Ryzen 5950X :-) Blaise Pascal
RE: RE: Well it's good to
)
Of course. Ah, but I am a cheeky one indeed ( and obviously not an investor either ) ....
.... why not take off at Vandenberg and then after separation land on the East coast ? Maybe not this time but perhaps sometime ? :-)))
Cheers, Mike.
I have made this letter longer than usual because I lack the time to make it shorter ...
... and my other CPU is a Ryzen 5950X :-) Blaise Pascal
RE: .... why not take off
)
Had not considered that. Why not indeed!!!!!!!
RE: RE: .... why not
)
Well it's a longer jump for sure, but still much like the land-on-the-barge scenario. The kinetics are so favourable because you don't have to come back, remembering Elon's quote of a ~ 200 GJ KE dividend b/w barge vs shore.
Cheers, Mike.
I have made this letter longer than usual because I lack the time to make it shorter ...
... and my other CPU is a Ryzen 5950X :-) Blaise Pascal
Another option besides the
)
Another option besides the land pad is the West Coast drone ship. Given how tightly the Vandenberg landing pad is close to important stuff, at this stage I'd personally think it wise for them to try a ship landing again.
Regarding refurbishment: while that is a crucial topic for the eventual success, I think at this stage the important thing is to do enough inspection/tear down of any returned vehicles to support preparation for eventual refurbishment (and design changes to improve the prospects).
I've seen seemingly authoritative claims that they do not plan to fly the first returnee again, though they do plan to use it to "burn in" a static test facility or some such.
In looking for information on the west coast drone ship, about all I find is that it is a rebuild of Marmac 303, and transited the Panama canal outbound from the rebuild site in Lousiana in June 2015. I did not find a name, as the two announced names apparently belong to two other ships (Just Read the Instructions, and Of Course I Still Love You), although in January 2015 Elon tweeted that OCISLY would be the West Coast drone ship.
I did stumble across a truly massive and detailed thread on SpaceX ASDS topics
Folks posting there who seem somewhat informed assert that before things went kablooey it had been the plan to attempt a land recovery on the Jason-3 launch. If true the pad has been pretty ready for months. However these folks are currently of the opinion that Jason-3 is more likely an ASDS than a land recovery attempt, and point out that the booster is an older one without recent upgrades to the recovery provisions (which I think might point in the direction of no attempt on this one). Apparently there was a tent in the middle of the Vandenberg landing pad as of very recently--they are watching that, as unless it is removed a Return to Launch Site is not feasible.
RE: RE: .... why not take
)
Delta-V.
Vandenberg is used for polar launches. Cape Canaveral is not even kinda sorta downrange.
RE: RE: RE: .... why
)
Meaning they don't have permission to point inland then ? Oh well. Darn. I'm obviously not under the flight path .... :-)))
Cheers, Mike.
I have made this letter longer than usual because I lack the time to make it shorter ...
... and my other CPU is a Ryzen 5950X :-) Blaise Pascal
RE: Meaning they don't have
)
In looking for the Vandenberg launch azimuth limits I happened on this handy summary of most of the world's satellite launch facilities. As it is written for the use of amateur satellite observers, it more reliably gives the orbital inclinations than the actual launch azimuth limits, but for many it gives the azimuth allowed range.
For Vandenberg it lists the allowable range for orbital launches as 147 to 201 (ICBM tests aimed at Kwajalein atoll are something close to due West, but are sub-orbital). Other sources list 158 to 201. Possibly the limits have changed over time, or maybe differ by specific launch complex.
Yes, with enough delta-V you can change the orbital plane at will, but it is very expensive to change it very much.
Certainly some sites launch over land (all the Soviet sites, and the Chinese as well), but the sites blessed with a coast seem generally to restrict themselves to over-water for the early ascent.
What a terrific little
)
What a terrific little summary. Thanks for that ! :-)
The Vandenberg range is from slightly east of south to slightly west of south, so if it matters one can choose slightly pro-grade or slightly retrograde. Thinking of polar orbits - and pretending to be a fly-in-a-spacesuit over either pole - I wonder how many polar or peri-polar satellites there are ? I believe there is one altitude which is much preferred as it is Sun synchronous*. In any case there would seem to be a volume above either pole that would be very busy indeed. No traffic lights evidently ....
Cheers, Mike.
* Meaning a satellite could be overhead a given spot on Earth at very close to the same local time each day.
( edit ) Yup. For say about 90 minute orbit thus 16 per day ( -ish ) then ~ 660km is an altitude for sun-synchrony. But that's a sidereal estimate. So now the pro/retro grade matters ( the angle to the Sun for both satellite and earth is slowly changing ), giving a slightly higher or lower orbit respectively ..... short answer is that if you want that type of polar orbit then the azimuth choice at launch also implies an altitude selection when the burn is done.
I have made this letter longer than usual because I lack the time to make it shorter ...
... and my other CPU is a Ryzen 5950X :-) Blaise Pascal
RE: I wonder how many
)
Lots.
As a generalization, there are a goodly many communications satellites in geosynchronous orbit, but lots of other satellites either need to be much closer to Earth to get adequate resolution, or need to scan a much higher fraction of the earth's surface at respectable angles than that orbit offers.
So a good many observing satellites, whether military optical, military radar, or weather, operate in rather high inclination orbits. The Sun synchronous type you mentioned is a particular case, but others vary. Any system which means to cover most of the earth's surface pretty well needs at least some of the constellation at somewhat high inclination, and most of the ones I'm familiar with tend to use a standard inclination for the whole group.
For one example, the original Motorola Iridium constellation chose a rather low altitude, thus enabling smallish handsets without an insanely large antenna nor enormous power on the satellite. That came to 780 Kilometer altitude at 86.4 degree inclination--not quite polar, but rather close. I believe all Iridium (past) and Iridium-NEXT (coming real soon now) launches have been from Vandenberg.
DigitalGlobe's Worldview-4 has quite high resolution--so needs a low altitude, but means to cover most of the earth, and they chose the consistency of the sun-synchronous orbit at 617 Km. I did not find the inclination, but as Mike pointed out, it is locked to the altitude, and has to be quite high.
The GPS system uses a much higher altitude of 20,200 km, so the needed inclination is less, and they chose 55 degrees. Those, I think, have launched from the Cape.
US Keyhole optical reconnaissance satellites need low altitude to get high resolution, so use non-circular orbits with altitudes in the 300 to 800 km range, and high inclinations of the order of 95 to 98 degrees. I think for years these have all launched from Vandenberg, and the perceived need to launch them probably drove the (never used) Vandenberg Shuttle launch site requirement.
Excellent points. For the
)
Excellent points. For the merit of other readers :
- azimuth refers to degrees from due North. In this case the interesting one is True North ( toward where the axis of Earth's actual rotation is ) and not magnetic ( which can't stand still on a good day anyway ). This is easterly/clockwise looking down from above or towards your right hand if you face North while standing on your feet with the planet below ie. the usual compass understanding. You may find some negative azimuths mentioned which goes the other way eg. NNW is minus 22.5 degrees azimuth.
- inclination is with respect to the equator and usually quoted as Eastward being zero but beware the sense of the discussion. Did you launch with a southerly or northerly component ? But note that if it is transiting the equator South-to-North it will transit North-to-South one half orbit later. Etc.
- I should add that many other orbits satisfy Sun synchrony. It doesn't have to be 90 minutes but ought to at least recur on about a 24 hour basis. This yields correspondingly higher orbits for longer periods.
- the calculation of period to orbital radius is actually good old Kepler's Third Law ie. the radius cubed goes like the period squared ( gravity is to an excellent approximation causing that variation ). Beware that the height above the surface is that radius minus the Earth's radius.
Cheers, Mike.
* Which is why we just don't fire these things out of a ruddy great gun with a one-shot ballistic trajectory. It will try to do a full orbit and attempt to return to your launch site from below by burrowing along an underground arc. Remember it's acting as if all the planet's mass is at the centre. For satellites you want some non-trivial angular velocity around Earth's centre so that you get, well, an orbit. The first and more so the second stage boosting is what largely does that : which way do you point the burning end ? Of course if you DO want to hit the planet other than your launch site, then that's different. :-)
( edit ) So that is why the 'B' in ICBM is Ballistic. You DO want to hit the planet before a full orbit.
( edit ) I will use this opportunity to plug a very good & readable book by one of our fearless leaders at AEI : Bernard Schutz. It is called Gravity From The Ground Up. It explains all this stuff in a comfortable tone for the interested layman. At most you may need some late high school maths ( slight bit of That Ugly Trigonometry Monster ). You can still learn heaps by just holding your breath when running through the mathematical thickets though. There is some straight forward Java code ( Triana Project ) that you can download to replicate his calculations, if that is your pleasure. Reasonably priced at a good bookstore near you ( or maybe Cambridge University Press sells online ) .... :-)))))
{ the Triana Download link has moved since 2003, try here.}
I have made this letter longer than usual because I lack the time to make it shorter ...
... and my other CPU is a Ryzen 5950X :-) Blaise Pascal