Quote from: DanseMacabre on 02/08/2016 09:22 pmJames has confirmed ASDS landing: https://twitter.com/flatoday_jdean/status/696816102010200065Looks like the rocket/bottle bank's still open for deposit Wait, a super-synchronous insertion with a 5,300kg payload AND a stage 1 return? O_oThis means more than 30% better GTO performance for the FT over v1.1 . It's a beast! (or some part of the information we have about the mission is incorrect).
James has confirmed ASDS landing: https://twitter.com/flatoday_jdean/status/696816102010200065Looks like the rocket/bottle bank's still open for deposit
If there was no incl change doesn't super sync still mean less delta-v to circularize?
Quote from: rsdavis9 on 02/08/2016 09:33 pmIf there was no incl change doesn't super sync still mean less delta-v to circularize?No, if you had a craft in an 0° inclination equatorial LEO then putting it into an elliptical orbit with an apogee equal to the perigee and apogee of the target circular GEO orbit it would require less impulse to in a single impulse at apogee to circularize the orbit than the sum of the two impulses needed to raise the perigee then lower the apogee. Though each of those impulses individually would be lower than the single impulse needed to circularize the orbit in the direct case.
Quote from: nadreck on 02/08/2016 09:52 pmQuote from: rsdavis9 on 02/08/2016 09:33 pmIf there was no incl change doesn't super sync still mean less delta-v to circularize?No, if you had a craft in an 0° inclination equatorial LEO then putting it into an elliptical orbit with an apogee equal to the perigee and apogee of the target circular GEO orbit it would require less impulse to in a single impulse at apogee to circularize the orbit than the sum of the two impulses needed to raise the perigee then lower the apogee. Though each of those impulses individually would be lower than the single impulse needed to circularize the orbit in the direct case.So the only advantage of super sync is to do the plane change at the lowest possible velocity.
Did anyone actually confirm that this was not subsyncronous on FT? Otherwise it might still be, just less so...
In order to minimise the impact of moving the launch from late last year, SpaceX is supporting a mission modification. The changed mission will reduce the time needed for SES-9 to reach its orbital slot, keeping the Operational Service Date (OSD) in the third quarter of 2016, as previously foreseen.
So would a "synchronous transfer orbit" (not sub, not super) still have an apogee beyond the GEO altitude? Put another way, the "simple Hohmann transfer" strategy where the apogee matches GEO altitude and all you need to do is raise perigee, that's subsynchronous, right?
Quote from: sewebster on 02/08/2016 10:16 pmSo would a "synchronous transfer orbit" (not sub, not super) still have an apogee beyond the GEO altitude? Put another way, the "simple Hohmann transfer" strategy where the apogee matches GEO altitude and all you need to do is raise perigee, that's subsynchronous, right?No, the simple Hohmann transfer orbit which is initiated at the point where the initial orbit crosses the equator and has an apogee equal to the altitude of a geosynchronous orbit is neither sub nor super synchronous.
Quote from: nadreck on 02/08/2016 10:22 pmQuote from: sewebster on 02/08/2016 10:16 pmSo would a "synchronous transfer orbit" (not sub, not super) still have an apogee beyond the GEO altitude? Put another way, the "simple Hohmann transfer" strategy where the apogee matches GEO altitude and all you need to do is raise perigee, that's subsynchronous, right?No, the simple Hohmann transfer orbit which is initiated at the point where the initial orbit crosses the equator and has an apogee equal to the altitude of a geosynchronous orbit is neither sub nor super synchronous.Ok, maybe I'm misunderstanding some simple orbit stuff (realize this is probably getting off topic pretty fast). But isn't period proportional to semi-major-axis^(3/2)? Semi-major axis of GEO is the radius. An elliptical orbit with the same apogee but lower perigee would have a smaller semi-major axis and therefore a shorter period?
However, my point was that the change of inclination is done from apogee of a super synch orbit before you bring that apogee down.
EDIT: Lou also when I was suggesting that if they were expending S1 that they should use some of the extra impulse available in the 2nd stage to eliminate some of the inclination, it was rather than throwing that extra impulse away, or raising the Apogee beyond 100,000km
Quote from: ugordan on 02/08/2016 09:05 amQuote from: guckyfan on 02/08/2016 08:04 amTo make up for the delay the satellite will be delivered to a better orbit for faster arrival at GEO. Which probably means no landing attempt.The cynic in me is wondering whether the F9FT performance is less than expected, precluding the original nominal mission *and* barge landing so SpaceX just went ahead and committed all of the recovery reserve to SES-9.Less than expected by whom? The original nominal mission was a sub-synchronous expendable insertion with v1.1. One month after that, it changed to a sub-synchronous DPL insertion with FT. FT has never been advertised to send a 5,300kg sat to GTO-1800 and then do a DPL. They actually list far less on their website (assuming the max they do list is for a DPL profile). My take on this is that SES and SpaceX decided to go for a super-synchronous expendable mission profile so as to have the satellite come online sooner than expected, thus offsetting the delays that have plagued this campaign. It's a good decision for business imo, although less exciting for SpaceX fans (that want to see the company nail its first FT barge landing sooner rather than later).
Quote from: guckyfan on 02/08/2016 08:04 amTo make up for the delay the satellite will be delivered to a better orbit for faster arrival at GEO. Which probably means no landing attempt.The cynic in me is wondering whether the F9FT performance is less than expected, precluding the original nominal mission *and* barge landing so SpaceX just went ahead and committed all of the recovery reserve to SES-9.
To make up for the delay the satellite will be delivered to a better orbit for faster arrival at GEO. Which probably means no landing attempt.
Do you mean the SES9 launch uses a previously flown first stage? (no), or that the first stage if landed, will be re-flown? Inquiring minds etc.
Yes I meant if the stage is recovered (which I think has a pretty good chance) it will likely be the first to be reused. This will open the whole reused rocket market, which will be very interesting.
The big part of this launch is that a successful returned first stage will be reused. This will hopefully let us know the economics of reusing rockets something both the ESA and Russians have said would not work. How quickly can the first stage be turned around and at what price? How much new business will be created with these new prices? What will the reaction be from other launch providers? Very exciting stuff.