Spaceflight’s chemically powered space tug heads for launch

Spaceflight shipped its Sherpa-LTC2 orbital transfer vehicle (OTV) Aug. 10 to Cape Canaveral in Florida, where it will make a second attempt to debut the chemically powered space tug on a SpaceX launch. The Seattle-based company’s first Sherpa-LTC, which has more powerful thrusters for dropping satellites off in specific orbits post-launch faster than the other tugs it has deployed, leaked propellant in December after integrating with SpaceX equipment at Cape Canaveral. That led to SpaceX dropping the OTV from a Falcon 9 rideshare mission in January, forcing Spaceflight to find alternative launches for 10 cubesats set to hitch a ride on it. Benchmark Space Systems provided the non-toxic propulsion subsystems for both OTVs. The upcoming SpaceX launch will be the first time Benchmark’s Halcyon Avant bi-propellant thrusters have flown in space. Spaceflight CEO Curt Blake said Sherpa-LTC2 has “gone through all kinds of checks to get things right” ahead of its launch in September. Ahead of its four-to-five-day journey via truck from Seattle to Cape Canaveral, the OTV was integrated with a payload for Boeing’s Varuna Technology Demonstration Mission (Varuna-TDM). The demonstrator aims to test V-band communications for a proposed constellation of 147 non-geostationary broadband satellites.

“Potential customers and industry partners will have the opportunity to participate in preliminary evaluations of this service, which is intended to provide unprecedented levels of connectivity across the globe to government and commercial customers,” a Boeing spokesperson said.

California-based Astro Digital designed and built the payload, and booked the launch from Spaceflight on behalf of Boeing for what will be a dedicated mission. Astro Digital also provided the command and control system for Spaceflight’s Sherpa-LTC2.

SpaceX is slated to launch the OTV as part of a mission to deploy a batch of Starlink broadband satellites that Spaceflight expects will launch to low Earth orbit this fall.

If the mission goes according to plan, the Sherpa-LTC2 will deploy from Falcon 9 around 310 kilometers above the Earth, from where the OTV will ignite and transport its customer payload to a 1,000-kilometer low Earth orbit.

Frayed SpaceX relationship

Spaceflight has relied on SpaceX launches to deploy its expanding line of next-generation space tugs.

The first of these was a Sherpa-FX, which has no propulsion, that made its debut as part of SpaceX’s Transporter-1’s rideshare mission in January 2021

SpaceX’s Transporter-2 mission then deployed a Sherpa-FX2 and a Sherpa-LTE — Spaceflight’s first OTV with electric propulsion — later that year in June.

After the Sherpa-LTC was removed from SpaceX’s Transporter 3 flight in January 2022, Spaceflight had planned to launch a Sherpa-FX on its next rideshare flight in April.

However, SpaceX decided to remove the tug from its Transporter 4 mission following concerns about environmental factors affecting the satellites installed on the OTV.

About a week later, SpaceX said it would no longer work with Spaceflight after currently manifested missions.

Blake declined to discuss Spaceflight’s relationship with SpaceX, or what would be its last OTV to fly with the company.

To broaden its options, Spaceflight announced Aug. 8 an agreement to launch future space tugs on Arianespace’s Vega launch vehicles, including its next-generation Vega C rocket.
Spaceflight said it signed a deal to access Vega with Italy’s SAB Launch Services — which also provides launch services on other European launchers — to cover launches starting as soon as next year.

Blake said Spaceflight is “very close to identifying specifics” for the customers and Vega missions that would use Sherpa, with the first launch likely around the end of 2023 or early 2024.

Spaceflight and SAB are also partnering to offer customers access to shared integration and storage facilities across Europe and the United States.

Blake said Spaceflight is talking to “a number of” other launch providers, and “getting close to finalizing deals to launch OTVs on various launch vehicles.”

Growing space tug family

Meanwhile, Spaceflight has been working through its remaining manifest with SpaceX to develop its space tug product line.

In May 2022, the company debuted Sherpa-AC (attitude control), a version for hosting payloads, on SpaceX’s Transporter 5 mission.

SpaceX is slated to launch a Spaceflight space tug in mid-2023 when it is set to deploy a Sherpa EScape (Sherpa-ES), which is designed to swing around the moon to deliver payloads in geostationary orbit.

According to Blake, its next OTV to fly could be the initial Sherpa-LTC that is under refurbishment.

“It’s a possibility,” he said, “we’ve got some customers that want to go, and we’re trying to find the capacity right now.”

A large portion of those are new vehicles, he added.