Helios: Impulse Space Unveils New Space Tug

Impulse Space recently announced their plans for a high-performance kick stage: Helios. Designed to enable existing launch vehicles to efficiently send payloads toward Geostationary Orbit, this stage would be the latest addition to a growing environment of orbital services.

Business Case

While launches to Low Earth Orbit have been getting cheaper and cheaper, sending payloads beyond is still rather expensive. Directly reaching very requested orbits such as Geostationary requires an expensive high-energy launcher. Another option is to equip the satellite with ion thrusters and spend months increasing the orbital altitude. This isn’t cheap either and also adds radiation exposure while slowly crossing the Van Allen belts.

*A rendering of Helios hauling a satellite high above Earth. Credits: Impulse Space*

Impulse Space aims to offer a new option. They plan to build a kick stage that can be launched together with the payload on existing LEO-optimized rockets. This way, the stage can then bring the satellite directly to Geostationary Orbit or beyond. Effectively, this would add a high-energy third stage to rockets such as the Falcon 9 or Terran R.

Design

Helios is a cryogenic kick stage. It is capable of carrying up to 14 tons of methane and oxygen, an ever more popular propellant choice. These will be burned by a new engine, called Deneb, capable of developing 67 kN of thrust. This means it’s slightly smaller than the venerable RL-10, used in similar roles. Deneb will use a staged combustion cycle and will be capable of multiple starts to support a wide range of missions. Depending on the launch vehicle, these specifications would allow the stage to send 4 to 5 tons of payload to GEO in less than 24 hours.

*A rendering of Helios inside a fairing and its main technical specifications. Credits: Impulse Space*

The company

Impulse Space was founded in 2021 by Tom Mueller, a SpaceX veteran who led the design of the Merlin engine. The goal was to provide efficient in-space transportation. Their first venture was Mira, an Orbital Transfer Vehicle that can deliver payloads to their final destinations. It is capable of hosting 300 kg of payloads, providing power, communications, and 600 m/s of delta-v. The first one was launched on SpaceX’s Transporter 9 in November 2023 and is still operating.

With the addition of Helios to its portfolio, Impulse Space aims to provide a full range of orbital transport services. With Mira, the company proved it can move fast. Testing of the Deneb engine is slated to start in mid-2024, and Helios should fly in 2026. Then it will have to prove itself against possible competitors, such as Blue Origin’s Blue Ring. Integrating a cryogenic stage on top of a rocket will also require dedicated ground infrastructure. Nonetheless, the in-orbit services market is attracting increasing interest, and Impulse Space has already proven it can deliver.