PARIS — Satellite fleet operator SES said it is likely to trade its midyear launch aboard a SpaceX Falcon 9 rocket for a slot later in the year rather than be the first to fly a Falcon 9 with Merlin 1D engines adjusted for improved thrust.

The company’s decision is unrelated to Hawthorne, California-based SpaceX’s ongoing effort to win U.S. Air Force certification to bid against United Launch Alliance of Denver on military launches. But SES’s internal debate – the company said no formal decision had been made – shows the often complicated trade-offs each organization, government or commercial, must make before signing up with a launch service provider.

NASA, which is working through its own Falcon 9 certification, has already delayed a planned Falcon 9 launch this spring until later this year in part to wait for the certification process to complete.

While NASA relies on SpaceX to deliver cargo to the International Space Station, NASA has not certified the Falcon 9 rocket to launch science satellites, which is why the Jason-3 ocean-topography satellite, a U.S.-European mission, will not launch until mid-year despite the fact that its predecessor, Jason-2, is well past its scheduled retirement date.

Luxembourg-based SES in December 2013 flew its SES-8 satellite on the Falcon 9’s first mission to geostationary transfer orbit – an extraordinary step the conservative company took to show how much it believed in the Falcon 9’s importance to the commercial launch sector. SES-8 was successfully placed into orbit.

Second Thoughts about Being First

SpaceX has been working since then to coax more thrust out of the Merlin 1D engine, which the company said before the SES-8 launch was operating at only 85 percent of its potential.

In a briefing with reporters here Jan. 22, SES officials said they retain full confidence in SpaceX and have seen the data showing the Merlin 1D engine’s improved performance on the ground.

But the SES-9 satellite scheduled for launch this year is not SES-8, and the cost-benefit trade-offs on whether to be the first to trust your satellite to an upgraded rocket engine are not the same, either, said Martin Halliwell, SES’s chief technical officer.

“The situation we have now with SpaceX is that we are awaiting manifest updates,” Halliwell said. “You know SpaceX is introducing into their manifest a new engine, or a modification of the current engine, with about a 20 percent increase in thrust. We’re making a decision internally as to whether we want to be the first to fly it.”

SES-9, a Boeing Space and Intelligence Systems 702-HP spacecraft expected to weigh 5,300 kilograms at launch, is near the limit of what the current Falcon 9 v1.1 vehicle can carry and was to be placed into a subsynchronous orbit.SES-9 then would use its on-board propulsion to climb to final geostationary orbit.

SES-9 carries 81 transponder, 53 of which are designed to capture new business in the Indian Ocean region, including maritime customers, from is operating slot at 108.2 degrees east.

SES-8, by comparison, weighed just 3,200 kilograms at launch. It carries a payload of up to 33 transponders, including 21 for new business.

Halliwell said completion of SES-9 is on track for April or May.

One of the trade-offs that SES will look at is whether, having allowed one SpaceX launch slot to pass, it will have another in short order. SpaceX has stopped publishing its launch schedule but at last count it had well over a dozen missions planned this year from both the Cape Canaveral Air Force Station in Florida and Vandenberg Air Force Base in California.

“If we decide we are not going to be the first to fly this, then we will be launching later in the manifest, Halliwell said. “It’ll be probably later in the year, in the August-September time frame.”

One of the benefits of the Merlin 1D performance upgrade is that it will permit SpaceX to launch payloads with the same maximum weight as it does currently while at the same time preserving capacity so that the first stage can power itself to an unmanned oceangoing barge to be recovered and reused.

As he has been for several years, Halliwell said he is rooting for SpaceX to succeed with a first-stage recovery as the company advances toward its goal of reusing the stage to cut launch costs.

“We know the rocket has done a lot of testing and has run many, many hours,” Halliwell said. “It looks like a good solution. However, we’ll be making a decision soon. From a power-to-weight point of view this is already a powerful engine and now we’re stretching it another 20 percent. So we’ll have to take a very close look at this.”