-
#60 by Phil Stooke on 02 May, 2017 12:45
-
'Single stage to orbit' anyone? Don't use acronyms if people can't agree on what they stand for. Spell it out - you are not limited to 140 characters.
-
#61 by schaban on 02 May, 2017 13:08
-
Will they attempt fairing recovery?
-
#62 by su27k on 02 May, 2017 13:21
-
At 6100 kg this is the heaviest Falcon 9 GTO launch so far, right?
Right, and apparently it's heading to SSTO, quite an accomplishment if they can pull this off, I wonder if this would be the first F9 block 4. -
#63 by king1999 on 02 May, 2017 14:24
-
'Single stage to orbit' anyone? Don't use acronyms if people can't agree on what they stand for. Spell it out - you are not limited to 140 characters.
Acronyms Seriously Suck! - Elon
-
#64 by Star One on 02 May, 2017 14:25
-
SSTO = super sync transfer orbit, aka similar to GTO but higher energy (likely as partial compensation for the delays).
Ahhh, I thought the acronym meant Sun Synchronous Transfer Orbit! :-)
These acronyms are uninformative when they can be interpreted more than one way.
A Super-synchronous Transfer Orbit (SSTO) has an apogee height considerably above the GEO belt, with the added implications that after the perigee height is raised to GEO altitude, and inclination lowered to near-Equatorial, additional braking burns must be performed to lower the apogee height back down to GEO altitude, circularizing the final orbit. Not to be confused with an sSTO, or sub-synchronous transfer orbit, where the apogee altitude is considerably lower than GEO....
I know what they are, the issue I have is the acronyms are the same other than one starts with a small s rather than a capital. Which people aren't always going to remember or forget to use. -
#65 by envy887 on 02 May, 2017 14:38
-
SSTO = super sync transfer orbit, aka similar to GTO but higher energy (likely as partial compensation for the delays).
Ahhh, I thought the acronym meant Sun Synchronous Transfer Orbit! :-)
These acronyms are uninformative when they can be interpreted more than one way.
A Super-synchronous Transfer Orbit (SSTO) has an apogee height considerably above the GEO belt, with the added implications that after the perigee height is raised to GEO altitude, and inclination lowered to near-Equatorial, additional braking burns must be performed to lower the apogee height back down to GEO altitude, circularizing the final orbit. Not to be confused with an sSTO, or sub-synchronous transfer orbit, where the apogee altitude is considerably lower than GEO....
Both are non-Hohmann subsets of GTO. For clarity it's probably best to refer to them as super-sync GTO and sub-sync GTO. -
#66 by gongora on 02 May, 2017 14:39
-
What is the source for the SSTO orbit? Is it current and reliable? If the information didn't originate from a SpaceX or Inmarsat source within the last 6 months or so I wouldn't really trust it.
-
#67 by Star One on 02 May, 2017 15:10
-
What is the source for the SSTO orbit? Is it current and reliable? If the information didn't originate from a SpaceX or Inmarsat source within the last 6 months or so I wouldn't really trust it.
The OP looked like they were assuming it because this launch is expendable and to make up for the delay. -
#68 by BabaORileyUSA on 02 May, 2017 18:09
-
What is the source for the SSTO orbit? Is it current and reliable? If the information didn't originate from a SpaceX or Inmarsat source within the last 6 months or so I wouldn't really trust it.
Nothing was assumed. SpaceX is the source, three days ago. -
#69 by Herb Schaltegger on 02 May, 2017 21:58
-
What is the source for the SSTO orbit? Is it current and reliable? If the information didn't originate from a SpaceX or Inmarsat source within the last 6 months or so I wouldn't really trust it.
Nothing was assumed. SpaceX is the source, three days ago.
I just did a quick scan through SpaceX.com's press releases and looked at the SpaceX twitter feed for the past couple days and didn't see anything about Inmarsat. Was there a post-launch presser yesterday that mentioned it? Do you have a link to indicate the launch is in fact super-synch GTO?
Thanks.
-
#70 by rockets4life97 on 02 May, 2017 22:24
-
Nothing was assumed. SpaceX is the source, three days ago.
I just did a quick scan through SpaceX.com's press releases and looked at the SpaceX twitter feed for the past couple days and didn't see anything about Inmarsat. Was there a post-launch presser yesterday that mentioned it? Do you have a link to indicate the launch is in fact super-synch GTO?
Thanks.
Sounds like BabaORileyUSA has an inside source. We'll find out soon enough if the source is reliable. -
#71 by Lar on 03 May, 2017 01:58
-
L2 might be more well suited for this
-
#72 by deruch on 03 May, 2017 02:46
-
If this does end up going to a super-synchronous transfer orbit, then it will provide an interesting comparison with the Echostar 23 launch. Echostar 23 was ~5500kg and was sent to 179km x 35903km x 22.43o, which works out to about GTO-1711. Inmarsat is currently listed as 6100kg. If they have enough performance in the F9 to get it to super-synch, this may be the first definite upgraded performance launch (there seems to be a bit of debate whether NROL-76 used upgraded thrust or not).
-
#73 by baldusi on 03 May, 2017 02:52
-
If this does end up going to a super-synchronous transfer orbit, then it will provide an interesting comparison with the Echostar 23 launch. Echostar 23 was ~5500kg and was sent to 179km x 35903km x 22.43o, which works out to about GTO-1711. Inmarsat is currently listed as 6100kg. If they have enough performance in the F9 to get it to super-synch, this may be the first definite upgraded performance launch (there seems to be a bit of debate whether NROL-76 used upgraded thrust or not).
They could have used all caps but actually meant subsynchronous GTO. PR people are surprisingly light in their handling of acronyms, and sub/super distinction is very ambiguous. -
#74 by Ben the Space Brit on 03 May, 2017 10:36
-
Slips could still happen but would I be correct in saying that this indicates a high level in confidence that the launch can happen on 5/15, all going well with the pad flow?
-
#75 by LouScheffer on 03 May, 2017 11:09
-
If this does end up going to a super-synchronous transfer orbit, then it will provide an interesting comparison with the Echostar 23 launch. Echostar 23 was ~5500kg and was sent to 179km x 35903km x 22.43o, which works out to about GTO-1711. Inmarsat is currently listed as 6100kg. If they have enough performance in the F9 to get it to super-synch, this may be the first definite upgraded performance launch (there seems to be a bit of debate whether NROL-76 used upgraded thrust or not).
This might also depend on the desires of the customer. If you have more performance than you need to reach a minimal GTO (GTO - 1800 for the cape, 179 x 36000 x 28o) , you can use it in two different ways.
(a) Keep the apogee at GTO, but reduce the inclination. Here they reduced it from 28o to 22.43, saving the customer about 100 m/s to get to GEO.
(b) Increase the apogee, but keep the inclination. With the same delta-V, they could have generated an orbit that was about 179 x 48000 x 28o (super-sync). In the case of Echostar this would have been a very similar reduction in delta-V.
Option (b) involves more navigation (at least two burns and longer intermediate orbits) by the customer, and the satellite has to be capable of working when above GEO. But in some cases it can be significantly less delta-V required by the launcher. In general, (a) is better if you have only a little extra performance to use. As performance increases, the two techniques become roughly tied at about GEO-1700 from the cape. But for better orbits than that, the super-sync method (b) pulls ahead. For example, the same delta-V can give you 179 x 119,000 x 28 (for GTO-1500) or 179 x 36000 x 17.7 (for GTO-1625).
From the point of view of SpaceX, the only difference is the pointing of the second stage at the GTO injection burn. It's at the same place and lasts the same time in either case. So I suspect they offer the option to the customer, and the customer chooses based on the navigation required, the delta-V saved, and the capabilities of the satellite.
Here is a plot of the effectiveness of both approaches, starting from a 180x180x28o parking orbit.
EDIT: Point out that (a) is better for small changes, (b) better for large ones. EDIT again to add plot -
#76 by ChrisGebhardt on 03 May, 2017 14:47
-
Slips could still happen but would I be correct in saying that this [45th Space Wing updating their Twitter page to show Inmarsat on 15 May] indicates a high level in confidence that the launch can happen on 5/15, all going well with the pad flow?
All this means at this point is that 15 May is the Range approved date and Inmarsat is the next sat up for launch. It means nothing more than that. -
#77 by Roy_H on 03 May, 2017 18:10
-
Slips could still happen but would I be correct in saying that this indicates a high level in confidence that the launch can happen on 5/15, all going well with the pad flow?
This should have been posted in Discussion not Updates.
SpaceX has proven several times they are capable of 2 week turn-around. Barring some snafu, I think it is highly likely they will launch on the 15th. With their latest TE there is little pad damage from launch, payload encapsulation takes place in the SPIF building so should already be done. Cores delivered and time to mate first and second stage, so that is probably done too. Not much left to do. -
#78 by feynmanrules on 03 May, 2017 21:23
-
Slips could still happen but would I be correct in saying that this indicates a high level in confidence that the launch can happen on 5/15, all going well with the pad flow?
NSF posting protocol on UPDATE threads is always use NET launch dates.
NET = No Earlier Than (but could be later) -
#79 by Johnnyhinbos on 05 May, 2017 17:36
-
If SpaceX quietly rolled out Block 4 hardware on the NRO launch, is there any possibility of ASDS return for this mission?
