In the SES-9 mission press kit, SpaceX mentions:

"Given this mission’s unique GTO profile, a successful landing is not expected."

What is considered "unique" about this transfer orbit's profile?

At the end of this spaceflightnow article, it states:

"The SES 9 satellite separates from the Falcon 9 rocket in an orbit with a predicted high point of about 39,300 kilometers (24,400 miles), a low point of 290 kilometers (180 miles) and an inclination of 28 degrees."

In that case, the satellite carries enough propulsion to move to a geostationary orbit (zero eccentricity, zero inclination) from there ? Where (at what point in the orbit) will the satellite separate from the second stage?

  • $\begingroup$ I've posted a follow-up question. $\endgroup$
    – uhoh
    Commented Feb 24, 2016 at 16:25

2 Answers 2


SpaceX has stated a goal that every launch going forward will attempt to land. The expectation initially is not 100% success, but an attempt at the very least.

Large GTO payloads do not leave enough fuel reserve for a Return to Launch Site (RTLS) at Landing Zone 1. Instead they will use the ASDS (Autonomous Spaceport Drone Ship) as far downrange as needed to land upon. This cuts down on the required fuel used in the first reentry burn since you only have to cancel most of the stages forward motion, not also boost it back towards the launch site.

In the case of SES-9, the launch was delayed numerous times and thus entry into revenue service is delayed costing the owner money every day it is not orbited. In order to keep the customer happy SpaceX has agreed to cut the margins they reserve for recovery to the bare minimum and likely risk not recovering the stage. The fuel not reserved for recovery can then be used for additional performance in the first stage.

The goal is to put the payload into the more energetic orbit, so that transitioning to full GEO is faster and simpler. This means it gets there faster (less distance to go/energy to impart by the built in thrusters) and uses less onboard fuel getting there, which means a longer life span in orbit.

Time is money, since SpaceX cost them time/money on launch dates, they are trying to give some back with performance.

The actual orbit they will be delivering the payload into is basically a standard GTO (Geosync Transfer Orbit) where the payload itself must finish the job of getting to GEO. There are several accepted versions GTO-1500, GTO-1800 where additional m/s of delta V are required to finish the job. They had contracted for GTO-1800 I think, and SpaceX is offering a better orbit.

  • $\begingroup$ So it's not really a "unique GTO profile" as far as rocketry goes, but it will hopefully be unique from a SpaceX perspective going forwards, in that they won't want a repeat of having to use their landing reserves in this fashion? $\endgroup$ Commented Feb 24, 2016 at 13:05
  • $\begingroup$ It is more unique in that a vendor (SpaceX) is willing to take risks (lower prob of recovery) to make a customer (SES) happy. This is quite unique. $\endgroup$
    – geoffc
    Commented Feb 24, 2016 at 13:15
  • $\begingroup$ Can you help me understand with one or two sentences - is there something unique about the geostationary transfer orbit, and if so, what is it. I don't think the use of the phrase is a typo. The transfer orbit itself - not interested in info about 1st stage after separation. $\endgroup$
    – uhoh
    Commented Feb 24, 2016 at 13:49
  • 1
    $\begingroup$ Ask the question, what is GTO vs GEO vs GSO. Better to answer there. $\endgroup$
    – geoffc
    Commented Feb 24, 2016 at 13:58
  • 1
    $\begingroup$ I think I am trying to say that the unique part is they were contracted for X and they are giving up their value (recovered vehicle risk) for the customers value, after a mission was contracted for no apparent cost change. $\endgroup$
    – geoffc
    Commented Feb 24, 2016 at 14:56

Since @geoffc is satisfied with, and handsomely rewarded for unsourced answers from time to time, I'll finish the job by quoting the sources I provided there in comments 1, 2 since comments are considered temporary.

Spaceflight Now's Falcon 9 rocket to give SES 9 telecom satellite an extra boost:

But Martin Halliwell, chief technology officer of SES, sang SpaceX’s praises in a preflight press briefing at Cape Canaveral on Tuesday.

“I know we’re a little bit late, but we can live with that,” he said. “We’ll move on. What’s most important is that we get the perfect mission.”

SES is the world’s largest operator of geostationary communications satellites, and the Luxembourg-based company approached SpaceX for some relief after the launch delay.

“We sat with SpaceX and said, ‘Guys, how can you improve our mission profile? How can you get us to orbit a little bit quicker?’ We have agreed with SpaceX that we will change the mission from a guidance controlled shutdown of the second stage to what we call a minimum residual shutdown of the upper stage,” Halliwell said.

In plain speak, the adjustment is a change in the Falcon 9 rocket’s control logic.

Instead of programming a target orbit into the rocket’s guidance system, the Falcon 9’s second stage will burn its single Merlin engine until the launcher’s supply of kerosene and liquid oxygen propellants are nearly gone.

“We’re going to burn the motor on the second stage for a few more seconds,” Halliwell said. “That’s all it really means.”

[...] “Initially, it was going to take about 93 days to get to orbit, but those few more seconds of burn will bring us down to about 45 days, so we should be in operational service towards the end of May or right at the very beginning of June,” Halliwell said. “That is a big deal for us.

This reddit thread contains the following. Unfortunately their links to sources are now broken:

Apparently SES-8 was delivered to a supersynchronous orbit as well and I found a reason for that here

SES-8 is being inserted into a Super-Synchronous orbit to reduce the total velocity change required by the satellite to reach Geostationary Orbit. A conventional insertion into GEO from an elliptical transfer orbit would require a delta-v of 1,800m/s while the SSTO design reduces the total dV requirement to 1,500m/s.

edit: Just wanted to clarify that SSTO stands for Super-Synchronous Transfer Orbit in this case, not Single Stage to Orbit like it often does.

and also

The supersynchronous orbit saved SES-8 300 m/s of ∆v, or about 6 extra years of station-keeping in GEO.

  • 2
    $\begingroup$ -1 for tone of opening paragraph $\endgroup$
    – user20636
    Commented Dec 26, 2018 at 9:24
  • $\begingroup$ @JCRM I'm pretty sure geoffc and most others understand the humor. He and I are on the opposite tails of the bell curve when it comes to supporting linkage. The bonus is that you have yet another opportunity to ding me ;-) So it's a win-win-win. $\endgroup$
    – uhoh
    Commented Dec 26, 2018 at 9:36
  • $\begingroup$ @JCRM data: # links for the last ten answers (excluding music videos) geoffc: sum([0, 0, 1, 0, 2, 0, 0, 1, 1, 0]) = 5, uhoh: sum([5, 6, 2, 0, 7, 4, 2, 9, 5, 7]) = 47 a factor of 10 difference in style, and yet he gets all the up votes too! What a scoundrel, no wonder the big grin. $\endgroup$
    – uhoh
    Commented Dec 26, 2018 at 9:51
  • $\begingroup$ Ha! now i just got the Peacekeeper hat, so it's win-win-win-win! Making Stack Exchange Win Again! $\endgroup$
    – uhoh
    Commented Dec 26, 2018 at 10:20
  • 2
    $\begingroup$ @JCRM I have no objection to Uhoh's tone. He and I have been discussing this via chat/answers for quite a while now, and I find it pretty funny. His answer is actually pretty good. (Not like the quality of my linkless answers, which scintillate in their brilliance that makes lesser posters wither in shame). But still pretty good. $\endgroup$
    – geoffc
    Commented Dec 26, 2018 at 12:15

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