Quote from: OneSpeed on 04/10/2018 12:09 pmQuote from: woods170 on 04/10/2018 11:38 amPlease note the rather significant difference in orbital altitude between GRACE-FO and the Iridium sats and than remember that neither GRACE-FO, nor the Iridium sats have circularisation capabilities.I see what Ultrafamicom is getting at, but if you deploy the Iridium satellites first, you then require the same plane change (admittedly of less mass), combined with the additional ∆V of a reduction in perigee, a circularisation at 490kms before deployment of the GRACE-FO satellites, and ultimately a de-orbit burn. So, four S2 burns, and probably a higher ∆V requirement.Indeed. And although an F9 S2 is quite capable it does make sense to do things as efficiently as possible. Which precludes dropping off the Iridium sats first.
Quote from: woods170 on 04/10/2018 11:38 amPlease note the rather significant difference in orbital altitude between GRACE-FO and the Iridium sats and than remember that neither GRACE-FO, nor the Iridium sats have circularisation capabilities.I see what Ultrafamicom is getting at, but if you deploy the Iridium satellites first, you then require the same plane change (admittedly of less mass), combined with the additional ∆V of a reduction in perigee, a circularisation at 490kms before deployment of the GRACE-FO satellites, and ultimately a de-orbit burn. So, four S2 burns, and probably a higher ∆V requirement.
Please note the rather significant difference in orbital altitude between GRACE-FO and the Iridium sats and than remember that neither GRACE-FO, nor the Iridium sats have circularisation capabilities.
I'm predicting that the second stage will directly insert itself into the GRACE-FO orbit (490 km, inclined 89 degrees) before the second burn increases the apogee and lowers the inclination while the third burn circularizes the Iridium-NEXT orbit (625 km, inclined 86.66 degrees).
Quote from: woods170 on 04/10/2018 01:22 pmQuote from: OneSpeed on 04/10/2018 12:09 pmQuote from: woods170 on 04/10/2018 11:38 amPlease note the rather significant difference in orbital altitude between GRACE-FO and the Iridium sats and than remember that neither GRACE-FO, nor the Iridium sats have circularisation capabilities.I see what Ultrafamicom is getting at, but if you deploy the Iridium satellites first, you then require the same plane change (admittedly of less mass), combined with the additional ∆V of a reduction in perigee, a circularisation at 490kms before deployment of the GRACE-FO satellites, and ultimately a de-orbit burn. So, four S2 burns, and probably a higher ∆V requirement.Indeed. And although an F9 S2 is quite capable it does make sense to do things as efficiently as possible. Which precludes dropping off the Iridium sats first.Also, for structural reasons, it makes sense to put the heavier sats below the light sats. Otherwise the payload would be quite top heavy in comparison..
Also, for structural reasons, it makes sense to put the heavier sats below the light sats. Otherwise the payload would be quite top heavy in comparison..
Quote from: Semmel on 04/10/2018 01:53 pmAlso, for structural reasons, it makes sense to put the heavier sats below the light sats. Otherwise the payload would be quite top heavy in comparison.. Huh? From a rocket control perspective, the farther forward you move the rocket's center of mass (Top Heavy), the easier the control problem becomes. That's why the LOX tank is usually above the kero tank in most rocket first stage designs. The only real exception is some LH upper-stages where it is reversed due to it being more mass efficient to run LH piping around and through the much smaller LOX tank.
GRACE-FO on the top dispenser, Iridium on the bottom dispenser.Quote"Following next month’s launch, our cadence with SpaceX should move more rapidly as launch frequency is planned to increase to approximately one launch every five to six weeks or so. In fact, our sixth launch is currently scheduled for a quick turnaround at the end of April, that will be a rideshare with the JPL German Grace satellites in which we’ll utilize half of the payload to launch five Iridium NEXT satellites alongside the two Grace satellites which will be mounted on the dispenser above ours."
"Following next month’s launch, our cadence with SpaceX should move more rapidly as launch frequency is planned to increase to approximately one launch every five to six weeks or so. In fact, our sixth launch is currently scheduled for a quick turnaround at the end of April, that will be a rideshare with the JPL German Grace satellites in which we’ll utilize half of the payload to launch five Iridium NEXT satellites alongside the two Grace satellites which will be mounted on the dispenser above ours."
Brian Webb (Vandy's Launch Alert dude) may have just suggested that Iridium-6 and Iridium-7 have swapped spots. I'm checking to see if it was a mistake, but it seems unlikely given that he uses the correct satellite numbers for 6-8.
QuoteMay 19 2018 on a new Falcon 9 Do we not have confirmation from Matt Desch that this will be flight-proven?
May 19 2018 on a new Falcon 9
The first few satellites went through full vacuum and thermal (and acoustic etc) tests to validate the design (and assembly processes). Subsequent vehicles only go through thermal cycling to validate assembly workmanship.
Some pre-launch information on GRACE-FO.I don't think there is anything that has not been well covered before.
Remind me if this question was answered already:Does GRACE-FO use the same dispenser as the one for Iridium-NEXT? If not, then the top dispenser should be lighter than 500 kilograms.
From the update thread we apparently have two 'second stage' entry areas active 11 minutes apart. Have we seen this before? Are we about to see some more aggressive/active S2 entry testing?
Just read over the newly-released press kit; how is the second stage going to reach a circular orbit of 625 kilometers, using one restart, from the initial orbit of 490 kilometers?I thought three burns would be necessary.
