collectively suggest strongly that this was a single-engine landing. Also someone posting elsewhere said that.
Since the three engine landing by simple physics is more fuel-efficient, this means they had a little bit of spare gusto on this mission. But the fullest commitment to checking the toughest cases would seem to call for another 3-engine landing. I wonder if they biased their choices toward improving the chances of visible success. Another picture of a rocket blowing up was not just what their PR needs valued at this moment.
Agreed. I only clearly see one engine and usually with throttle down there is residual flame for a bit, so that implies any others were shut down a good, say, 10 seconds earlier ( if they were operating ) ? For that matter if you look at the initial re-entry burn ( on board camera ) it has far more flame than the landing burn. So would that suggest a three engine burn up high and a single for landing ? However, bear in mind that sea level pressure is somewhat greater than up high where the exhaust plume expansion will be more.
As for gusto it seemed to me to that the launch pad was cleared rather more promptly than typical too. But it's an LEO insertion plus downrange recovery so that's the most favorable scenario for having excess fuel to play with ( assuming that you keep the first stage to reuse at all ). And yes, naturally they would keep any experimental/developmental ideas unprobed for this one, and probably for a while is a good strategy .....
Each Iridium Next satellite will weigh 860 kilograms at launch, for a total satellite payload mass of 8,600 kilograms, plus the 1,000-kilogram dispenser, which will make it one of heavier missions for SpaceX.
( edit ) SpaceX quotes max payload to LEO as 22.8 tonnes, so 9.6 is about half of that. But in turn there are degrees of LEO requirements, basically what speed at what height do you particularly want ?
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
Try this zoom where I have labelled six non-operating bells not obscured by the central flame :
That leaves two not accounted from this view, on the other side of the centre. So if there were three operating at this moment it would be quite asymmetric ie. nett off-axis thrust.
If, say, you might propose that '3' is operating then carefully contrast the lower edge of that bell with the flame pattern behind it. Keep in mind that the centre engine is gimballed and don't worry about the underside of the far leg.
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
Now there's a rear end that's done a lot in a short time.
NB There are six more Iridium missions just like this one. I've read reports that during this calendar year the aim is to completely swap out all seventy original satellites. They plan to bring each new one alongside the corresponding older version in some given orbital slot, try to seamlessly ( without loss of customer service ) transfer duties to the new one, and then retire the old one via de-orbit. This is why the window for launch is zero. They have to rise up along/within the exact same plane that the older ones are already circulating, and then later sneak up on them to swap out. I believe they are presently in lower orbit getting checked out after launch and will be singly managed in the following weeks. That sounds very challenging ! ;_0
I suppose that implies that there are already seven such planes, each currently holding ten satellites each. Presumably per plane those ten are transiting with equal delays b/w ie. spread over an entire orbital period for that height. Being polar the seven planes would be rotated with respect to each other about a common north-south axis, the mutual angles b/w each plane being equal I guess.
FWIW : the orbital period at the final height of 780 km above Earth is close to 100 minutes ie. around 14.4 full orbits per ( sidereal ) day. That means that from a given spot on Earth the whole 70 satellite constellation will appear to rotate in the sky at about 10 degrees per day.
{ Derivation : if I have a specific satellite transiting directly above me at datum_time, then one sidereal day later it will be 0.4 of an orbit ahead of where it was at datum_time. Hence if I had moved 0.4 * 100 = 40 minutes to the east I would see it directly above me again at datum_time + sidereal_day - 40 minutes ( use UTC, ignore local civil times ). It is to the east because the Earth rotates that way and I want to meet that satellite's plane earlier, in order to have it over my head, and not further along in orbit. This physical shift of the observer is ( 40 / 60 ) * ( 360 / sidereal_day_in_hours ) ~ 10 degrees of longitude to the east. Presumably this precession has some use. }
In theory : if you sat at precisely the South Pole, say, and kept looking up you would each of the satellites in the constellation pass above you in some never ending & repeating sequence. Well, probably. I have ignored many important aspects here & it might be relevant that seven is a prime number ..... interleaving the transits from different planes seems the go. Whatever. Seventy satellites per every hundred minutes would be a cool show if you could always see them. Actually the entirety of all polar orbiting satellites seen from either pole would be an amazing show. A very busy volume of sky indeed .... :-)
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
I suppose that implies that there are already seven such planes, each currently holding ten satellites each. Cheers, Mike.
The original system design contemplated seven planes, but that was changed to six before the original launch. A fully-populated constellation has 66 active birds in six planes, and a healthy constellation has some orbiting spares.
You are right that it uses a good bit of (otherwise) station-keeping fuel to change a bird to an adjacent plane, but it is both possible and in the plan. Also, as the standard parking orbit is lower altitude than the operational orbit, the non-spherical components of the Earth's mass distribution actually twist the inclination of parked vs. operation birds over time, so with patience the plane-change fuel cost can be greatly reduced.
Thanks for that information. A few spares and some patience, by using gradients within the higher order spherical harmonic components of the field. That's a neat way of turning an annoyance into a virtue.
As for Gene : I remember well when all those guys were gods. In reality, of course, they were well placed men. Vale.
As for going back to the Moon, there is probably some depressing statistic like the cost would be less than we spend on maintaining parking meters or some such. I think Elon said something along those lines about lipstick.
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
In upcoming SpaceX events, there are pretty strong indications that the first launch of a reused booster is on the schedule. The mission is SES-10, with a current target launch date of February 22, 2017. The first stage is indicated to be the one that flew and landed successfully on CRS-8. The usual temporary RF license indication suggests that they plan a barge landing for this one.
The remarkably ambitious launch cadence in the plans actually has that the third flight into the future, after Echostar 32 on January 26, with a barge landing, and a Dragon flying as CRS-10 on February 8, all launching from LC39A, which has not yet launched a SpaceX booster (LC40 is still in recovery from the Amos explosion). The current hoped-for first Heavy flight shows in the very helpful NSF Spacex Flight manifest as August 2017.
Most of these dates are best considered to be "not before", dates, and slips should be expected.
archae86 wrote:Mike Hewson
)
Agreed. I only clearly see one engine and usually with throttle down there is residual flame for a bit, so that implies any others were shut down a good, say, 10 seconds earlier ( if they were operating ) ? For that matter if you look at the initial re-entry burn ( on board camera ) it has far more flame than the landing burn. So would that suggest a three engine burn up high and a single for landing ? However, bear in mind that sea level pressure is somewhat greater than up high where the exhaust plume expansion will be more.
As for gusto it seemed to me to that the launch pad was cleared rather more promptly than typical too. But it's an LEO insertion plus downrange recovery so that's the most favorable scenario for having excess fuel to play with ( assuming that you keep the first stage to reuse at all ). And yes, naturally they would keep any experimental/developmental ideas unprobed for this one, and probably for a while is a good strategy .....
Cheers, Mike.
( edit ) As of this article :
( edit ) SpaceX quotes max payload to LEO as 22.8 tonnes, so 9.6 is about half of that. But in turn there are degrees of LEO requirements, basically what speed at what height do you particularly want ?
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
Try this zoom where I have
)
Try this zoom where I have labelled six non-operating bells not obscured by the central flame :
That leaves two not accounted from this view, on the other side of the centre. So if there were three operating at this moment it would be quite asymmetric ie. nett off-axis thrust.
If, say, you might propose that '3' is operating then carefully contrast the lower edge of that bell with the flame pattern behind it. Keep in mind that the centre engine is gimballed and don't worry about the underside of the far leg.
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
Smokin' hot :Now there's
)
Smokin' hot :
Now there's a rear end that's done a lot in a short time.
NB There are six more Iridium missions just like this one. I've read reports that during this calendar year the aim is to completely swap out all seventy original satellites. They plan to bring each new one alongside the corresponding older version in some given orbital slot, try to seamlessly ( without loss of customer service ) transfer duties to the new one, and then retire the old one via de-orbit. This is why the window for launch is zero. They have to rise up along/within the exact same plane that the older ones are already circulating, and then later sneak up on them to swap out. I believe they are presently in lower orbit getting checked out after launch and will be singly managed in the following weeks. That sounds very challenging ! ;_0
I suppose that implies that there are already seven such planes, each currently holding ten satellites each. Presumably per plane those ten are transiting with equal delays b/w ie. spread over an entire orbital period for that height. Being polar the seven planes would be rotated with respect to each other about a common north-south axis, the mutual angles b/w each plane being equal I guess.
FWIW : the orbital period at the final height of 780 km above Earth is close to 100 minutes ie. around 14.4 full orbits per ( sidereal ) day. That means that from a given spot on Earth the whole 70 satellite constellation will appear to rotate in the sky at about 10 degrees per day.
{ Derivation : if I have a specific satellite transiting directly above me at datum_time, then one sidereal day later it will be 0.4 of an orbit ahead of where it was at datum_time. Hence if I had moved 0.4 * 100 = 40 minutes to the east I would see it directly above me again at datum_time + sidereal_day - 40 minutes ( use UTC, ignore local civil times ). It is to the east because the Earth rotates that way and I want to meet that satellite's plane earlier, in order to have it over my head, and not further along in orbit. This physical shift of the observer is ( 40 / 60 ) * ( 360 / sidereal_day_in_hours ) ~ 10 degrees of longitude to the east. Presumably this precession has some use. }
In theory : if you sat at precisely the South Pole, say, and kept looking up you would each of the satellites in the constellation pass above you in some never ending & repeating sequence. Well, probably. I have ignored many important aspects here & it might be relevant that seven is a prime number ..... interleaving the transits from different planes seems the go. Whatever. Seventy satellites per every hundred minutes would be a cool show if you could always see them. Actually the entirety of all polar orbiting satellites seen from either pole would be an amazing show. A very busy volume of sky indeed .... :-)
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
http://www.space.com/35341-ex
)
http://www.space.com/35341-experimental-japanese-rocket-launch-fails.html
David
Miserable old git
Patiently waiting for the asteroid with my name on it.
http://abc7chicago.com/news/g
)
http://abc7chicago.com/news/gene-cernan-last-astronaut-to-walk-on-the-moon-dies-at-82/1705215/
David
Miserable old git
Patiently waiting for the asteroid with my name on it.
Mike Hewson wrote: I suppose
)
The original system design contemplated seven planes, but that was changed to six before the original launch. A fully-populated constellation has 66 active birds in six planes, and a healthy constellation has some orbiting spares.
You are right that it uses a good bit of (otherwise) station-keeping fuel to change a bird to an adjacent plane, but it is both possible and in the plan. Also, as the standard parking orbit is lower altitude than the operational orbit, the non-spherical components of the Earth's mass distribution actually twist the inclination of parked vs. operation birds over time, so with patience the plane-change fuel cost can be greatly reduced.
Thanks for that information.
)
Thanks for that information. A few spares and some patience, by using gradients within the higher order spherical harmonic components of the field. That's a neat way of turning an annoyance into a virtue.
As for Gene : I remember well when all those guys were gods. In reality, of course, they were well placed men. Vale.
As for going back to the Moon, there is probably some depressing statistic like the cost would be less than we spend on maintaining parking meters or some such. I think Elon said something along those lines about lipstick.
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
United Launch Alliance just
)
United Launch Alliance just had a successful Atlas V Launch from the cape. Night launches seem magical.
In upcoming SpaceX events,
)
In upcoming SpaceX events, there are pretty strong indications that the first launch of a reused booster is on the schedule. The mission is SES-10, with a current target launch date of February 22, 2017. The first stage is indicated to be the one that flew and landed successfully on CRS-8. The usual temporary RF license indication suggests that they plan a barge landing for this one.
The remarkably ambitious launch cadence in the plans actually has that the third flight into the future, after Echostar 32 on January 26, with a barge landing, and a Dragon flying as CRS-10 on February 8, all launching from LC39A, which has not yet launched a SpaceX booster (LC40 is still in recovery from the Amos explosion). The current hoped-for first Heavy flight shows in the very helpful NSF Spacex Flight manifest as August 2017.
Most of these dates are best considered to be "not before", dates, and slips should be expected.
http://xkcd.com/1788/
)
http://xkcd.com/1788/
Richard