# ADN-Based LMP-103S Green Propellant Implementation on SkySat

June 2, 2020

SkySat-3, launched in June 2016 on PSLV, was the first commercial spacecraft to load and fly ECAPS' ADN based green monopropellant known as LMP-103S. Previously the technology had flown on the Swedish Space Corporations PRISMA mission, which launched in June 2010.

## Evolution of SkySat

In November 2013 Skybox Imaging launched SkySat-1 from Yasny, Russia. Eight months later SkySat-2 was launched from Baikonur, Kazakhstan. Shortly afterward Skybox Imaging was aquired by Google and rebranded to Terra Bella. To enhance mission flexibility and increase on-orbit life, the next design iteration of the SkySat platform incorporated a chemical propulsion subsystem.

## Need for Propulsion

A critical requirement identified in the evolution from SkySat-1 and SkySat-2 towards a full constellation (SkySat-3 thru SkySat-21) was the inclusion of a highly performant propulsion system capable of maximizing available $\Delta V$ within a tight volume and low power restrictions. The chief capabilities enabled by inclusion of such a propulsion system are:

• Constellation Phase Management
• Launching multiple spacecraft on a single rocket requires the use of propulsion to phase the spacecraft within each orbit plane and then overcome orbit perturbations to maintain their relative spacing
• Mission Flexibility
• A high thrust to spacecraft mass propulsion system enables the constellation to take advantage of a wide range of primary or secondary launch opportunities with established providers and emerging new entrants. The ability to correct for large orbit injection errors or accept injection into a wide range of altitudes and quickly absorb those individual launch differences without significant delay to incorporation of spacecraft into the constellation’s product is a tremendous value

## ECAPS System Used on SkySat-3 to SkySat-21

The resulting system was designed and manufactured by ECAPS AB in Solna, Sweden. It is a fully integrated, modular drop-in to the existing SkySat bus design, which was extended in height to include the propulsion system.

The system provides a total impulse of approximately 21 kN-s at a satellite internal volume fraction of about 11% and a mass fraction of approximately 10% dry and 19% wet. Four 1N HPGP thrusters are blowdown pressure fed LMP-103S from 3 tanks holding 10.5 kg of propellent total. The schematic and physical layout is shown in Figure 1.

## Cumulative Time in Space

At the time of posting, SkySat-3 to SkySat-15 are operating in-space and SkySat-16 to SkySat-21 are scheduled to be launched in summer of 2020 on SpaceX Falcon 9 vehicles (SkySat-1 and 2 are excluded because they do not have propulsion systems). The total on-orbit years for the ECAPS propulsion systems are tabulated below:

SatellitesVehicleSiteDateSat Years In Space
SkySat-3PSLVSriharikota, IndiaJune 20163.9
SkySat-4, 5, 6, 7VegaKourou, French GuianaSept 201614.9
SkySat-8, 9, 10, 11, 12, 13MinotaurVandenberg, USAOct 201715.5