HOUSTON — Spaceflight Inc. is looking to late 2015 for the debut launch of its Sherpa commercial small satellite dispensing space tug, with a nearly sold-out manifest that includes a 300-kg (660-lb.) U.S. government Earth-observing spacecraft, a pair of 50-kg commercial Earth-observing  microsats that will take advantage of the Sun-synchronous primary payload orbit, and 60 Cubesats.
In 2016, the Seattle startup expects to be launching twice annually – one low Earth orbit, solar-powered, monopropellant-fueled Sherpa 400 and a bi-propellant, fuel-rich Sherpa 2200 for the delivery of small payloads to geostationary transfer orbit (GTO) as well as the lunar environs, says Spaceflight Inc. President Curt Blake.
“Once you get to GTO, there is tons of stuff you can do,” he said during a May 2 phone interview. Spaceflight has discussed the potential of the Sherpa 2200 to deliver small, fully fueled payloads to low lunar orbit with Google Lunar X Prize participants and envisions future small spacecraft missions even deeper into space.
The Spaceflight tug, with its independent attitude determination control system, is designed to launch as a secondary payload with up to 1,500 kg of small satellite types. Riding atop the launcher’s second stage, Sherpa’s release follows deployment of the primary mission payload for the dispensing of minisatellites, microsatellites, nanosatellites and Cubesats.
During Sherpa’s inaugural flight, a battery powered, non-propulsion, low-orbit version will deploy its payloads within hours of separation, then fly on for a day-long checkout of communications, avionics and attitude control systems, Blake said. The checkout will emphasize the dispensing mechanism’s collision-avoidance strategies.
“In a large way it’s a risk-reduction mission, but also revenue sharing since we are deploying payloads,” Blake noted. Spaceflight was founded in 2010 by Jason Andrews, also founder of Andrews Space Inc., to provide space access to small and secondary payloads.
As Spaceflight transitions to GTO missions, it will introduce capabilities to raise and lower Sherpa’s altitude for custom deployments.
After departing GTO, the solar-powered Sherpa 2200 will be capable of reaching lunar orbit with fully fueled payloads, opening the lunar environs to a range of new small spacecraft missions. The low Earth orbit version of Sherpa will be capable of accompanying an Earth observing primary payload to 800 km, for instance, then descending several hundred kilometers to a more favorable altitude to drop off secondaries.
“We’re thinking of a UPS that delivers to space,” Blake said. “We figure out which plane or truck your package needs to go on. Then we try to make sure it’s packed in the most efficient way possible.”
For its inaugural flight, the Sherpa 400 will be restricted to 1,200 kg of its 1,500-kg capacity. All but 100 kg of that capacity has been reserved. A mid-June deadline for reserving the remaining mass and volume is anticipated.
Spaceflight is not disclosing its first launch provider, or the names of its payload customers, because of contractual agreements, Blake said. But the company has current agreements with Orbital Sciences Corp., SpaceX and Rosmosmos to manifest secondary payloads when there is excess capability, which it has put to use recently.
Spaceflight is working primarily with U.S. launch providers for Sherpa activities, Blake acknowledged. So far, Spaceflight counts the launches of 36 small satellites.
Without the tug, Spaceflight delivered Cubesats to the International Space Station aboard Orbital’s first contracted resupply mission to the six-person orbiting laboratory in January. Customers including PlanetLabs, University Peruvian Wings and Southern Stars watched as their spacecraft were jettisoned from the station’s Japanese Experiment Module. More will fly aboard Orbital’s June cargo mission to the station.
The company arranged the launch of Planet Labs’ Dove 3 spacecraft aboard a Russian Dnepr rocket in late November and Dove 2 on a Soyuz that launched on April 13, 2013. Orbital Sciences’ inaugural flight of the Antares carried Dove 1 and NASA Ames Research Center’s PhoneSat spacecraft into orbit on that same day, in secondary missions also arranged by Spaceflight.