Spaceflight Inc’s Sherpa hosted Payload and in-space transportation system. Photo: Spaceflight Inc.

[Via Satellite 05-08-2014] Spaceflight Inc., a company dedicated to launching small satellites, has nearly filled all the slots for the maiden flight of its Sherpa hosted payload and in-space transportation system. Sherpa is a free-flying platform that uses an oversized Evolved Expendable Launch Vehicle (EELV) Secondary Payload Adapter (ESPA) ring exclusively for small satellites ranging from a few to several hundred kilograms. The first flight, planned with an undisclosed launch provider, will carry a myriad of satellites into a sun-synchronous Low Earth Orbit (LEO).

“The Sherpa itself can carry up to 1,500 kg. In this case we only contracted for 1,200 from the launch vehicle provider,” Curt Blake, president of Spaceflight Inc., told Via Satellite. “Of the 1,200 we have booked roughly 1,000.”

Small satellites, though cost effective to manufacture, can be difficult to send into orbit because they are not particularly lucrative to launch providers. Most can only launch when an opportunity comes along to piggyback with a larger payload.

“It is a waiting game where small satellites owners have to wait for other payloads to get a ride and thus get the best launch vehicle, or they have to be ready to pay a very high price [in dollars per kilogram],” said Stéphane Gounari, senior analyst at NSR. “Finding the right launch provider to work with can be the daunting first step —  some small satellite owners have had to talk with nearly every launch provider to find a match for their satellite.”

Alone, CubeSats, NanoSats and other small satellites do not present much of a revenue opportunity for launch companies. Some of these satellites have found chances to deploy from the International Space Station (ISS) through NanoRacks when paired with resupply missions. Dedicated small-sat launchers are under development by companies like XCOR, Virgin Galactic, Firefly Space Systems and others as the market grows. Orbital Sciences’ Minotaur C and Arianespace’s Vega rockets also target this market, and Lockheed Martin has resurrected its Athena program to gain a piece of the pie. Still, small satellites have a much better chance of getting to orbit when they can launch in groups.

“In that sense, part of the value-proposition of a service such as Spaceflight Inc.’s Sherpa is to provide this ‘pooling’ service and hopefully accelerate the process,” said Gounari. “But being a secondary payload on a ride-share mission also offers small-sat customers less control, particularly if the primary payload is delayed.”

Spaceflight Inc.’s Sherpa has five ports and a series of adapters to attach various payloads. It can remain positioned on the launch vehicle, or separated and controlled propulsively on its own as it sequences off distributions of the payloads. This gives small satellite operators much more freedom, as their spacecraft often end up near the destination of the primary payload. Using Sherpa, spacecraft can access new orbits that otherwise would have been unreachable.

“Say we were deploying 10 CubeSats, just to pick a number, and the primary [payload] was going to 800 kilometers, and that’s where the Sherpa was deployed,” said Blake. “If we had 10 3U CubeSats, and we tried to deploy at 800 km, there’s a pretty good chance that they wouldn’t be able to adhere to the 25-year [orbital debris] rule. In that case we could bring the altitude down so that those CubeSats could adhere to that rule.”

After the LEO mission, Spaceflight Inc. is preparing a Geostationary Transfer Orbit (GTO) flight for 2016. Following this, the company is planning for two launches a year, alternating between LEO and GTO missions. Blake said both flights are filling up, but that the LEO mission remains the most popular. He is confident that the second mission will gain traction in the market as well.

“I think there is a lot more focus to build small satellites that want to go to LEO. On the other hand, there aren’t very many GTO missions that secondary payloads can avail themselves of, and we only recently started marketing the GTO mission,” he explained. “There is scarcity of supply on the GTO mission to a much greater extent than there is on the LEO mission. The demand will get there.”

The company is planning more steps with each mission. After delivering customers’ satellites to their orbits, Spaceflight Inc. plans to test Sherpa’s avionics, attitude determination and control system, along with communications and other key systems. The 2015 flight will not include a propulsion system, but according to the company, future flights will offer more orbits, including low lunar and beyond.

“They can [use propulsion, but] that’s not the way we are doing things right now. We’re trying to walk then run,” said Blake. “We are trying to do a simple version of the Sherpa this time. Next time it will be propulsive, and we are moving in that progression. After the propulsive model, we’ll hook two together and separate them off [after launch] and send them in different directions.”