Building on our research into green propulsion technologies for launch vehicles, ARES Institute has started an initiative to investigate the applicability of our work to in-space propulsion. The GreenSat project is an experimental mission to demonstrate the applicability of our new propellant blend to cubesat propulsion requirements.
There is great interest within the satellite industry to develop propulsion technologies that could replace hydrazine, nitrogen tetroxide and other toxic propellants for on-board propulsion. One monopropellant is AF-M315E, an ionic liquid derived of hydroxylammonium nitrate (HAN), water, and a hygroscopic fuel. AF-M315E offers comparable performance to traditional storable bipropellants for low delta-V missions while employing roughly half the number of components, thereby retaining the well-established increased reliability and reduced cost of traditional monopropellants.
NASA’s Green Propulsion Infusion Mission (GPIM) is a demonstration of AF-M315E in an actual space mission environment.
Other research has focused on the use of catalyzed hydrogen peroxide, water and other novel liquids. Our approach is somewhat different. The objective of our research is to develop a propulsion system using our tri-element propellant blend in a miniature hypergolic bi-propellant propulsion module. We have already demonstrated the safety of our propulsion and so the goal with GreenSat is to miniaturize it for use on smallsats.
One aspect of our present work is the minimization or elimination of the alcohol component in the ethanolamine-based fuel. Instead, the ethanolamine is stored in a gel-like consistency with the ionic salt catalyst suspended within. Adequate suspension and even dispersion is the challenge here. However, by maximizing the mass loading of ethanolamine consequently results in a lower catalyst mass requirement while still maintaining hypergolicity.
Another focus area of our research is the safe and stable long-term storage of ultra-high strength hydrogen peroxide at 95% concentration. This requires both novel materials and design. Loading and offloading of the oxidizer before flight is also more challenging due to the corrosive and reactive nature of the peroxide. However, ground handling is still much safer and cost-effective than the contemporary propellants in use today.
NASA’s 2019 SBIR/STTR solicitation specifies a focus area for proposals addressing the agency’s goal of developing new in-space propulsion systems for cubesats and smallsats. We are leveraging our prior and ongoing work for a proposal addressing this solicitation. Proposals are due by March 29, 2019 and could result in a Phase I contract with NASA to support continued work on our system. Below is the text from the SBIR solicitation:
NASA is interested in utilizing SmallSats/CubeSats (6U-12U, < 50kg CubeSats targeted) for cislunar, interplanetary and/or deep space missions, including lunar exploration precursor missions and missions identified in recent Planetary Science Deep Space SmallSat Studies (PSDS3). To accomplish this, advances in chemical propulsion systems for these class of spacecraft are sought, to complete maneuvers such as attitude control, trans-orbit injection, orbit changes, and planetary intercept, with a minimum of transit time.
Chemical propulsion systems considered here can include cold-gas, warm-gas, monopropellants and/or bi-propellant systems. These propulsion systems are preferentially envisioned as modular, add-on sub-systems to the larger SmallSat/CubeSat payloads, and would be comprised of the sum components of tank(s), valve(s), pressurant, feed system, thrusters and/or controls. Proposers should place emphasis on full propulsion systems offering long life, reliability, and minimalistic use of spacecraft resources (power, energy, volume, and mass).
The use of existing component technologies to build a propulsion system is encouraged to minimize overall development, however proposers are also cautioned that experience to date has shown component technologies for larger systems do not necessarily and easily scale down to CubeSat platforms.
Since the focus is on complete propulsion systems, proposals will not be considered that focus purely on individual component development (e.g., new thruster designs or propellant formulations) without addressing how the innovative component solution supports improved mission outcomes and clearly identifies how the product will be incorporated into an overall propulsion system solution. Component solutions must clearly demonstrate a willing system infusion customer and/or mission for consideration.
Proposals are sought that can deliver a propulsion system hardware prototype at or greater than Technology Readiness Level (TRL) 4 (breadboard validations within a laboratory environment) within Phase II resources.
Propulsion system solutions are sought that provide as many of the following features as possible within a single propulsion system module:
- Volumetric efficient designs (> 50-60% propellant mass fraction), with tank expulsion efficiency of 95-99%. Propellant mass fraction here is defined as the usable mass of propellant divided by the total wet mass of the propulsion system.
- Maximized Delta-V capability, with target capabilities of 200-500 m/s desired. Proposers must clearly delineate how Delta-V capability is defined including anticipated payload mass/volume.
- Thrust levels from 0.2 to 1.0 N to provide rapid orbit insertions (hours vs. days/months of maneuver time)
- Operation on spacecraft bus voltage
- Systems with low/zero pre-launch pressurization needs (< 1.5 atm at launch)
- Thermal regulation of propellant (e.g., Low temp (< 0° C) storage to reduce system power requirements)
- Ability to conduct both translation and attitude control maneuvers
- Restart and pulsed operation capable, with pulse mode and impulse-bit control to meet station keeping and pointing requirements
- Systems presenting reduced ground processing hazards, or reduced risks to primary payloads (i.e., secondary payload safe)
- Ability to tolerate > 12 mo. of loaded storage without degradation or need for servicing
- Ability to drain & flush system of propellant and/or pressurant during ground processing
- System lifetime & reliability > 2 years under flight
- Dual fault tolerance
- Optimized for the rigors of interplanetary/deep space missions (i.e., radiation tolerant > 20 krad, thermal management to minimize heat soak to remainder of spacecraft, etc.)
A Citizen Space Mission
GreenSat is a a “citizen space mission” and relies on the contributions and participation of the public. A substantial amount of our budget is being fulfilled via contributions from private citizens and supporters of commercial space exploration. Through crowdfunding, people are able to donate not only financially but also through labor, software programming and ideas, thereby becoming participants and co-owners of the mission – stakeholders in its success.
An Open Source Architecture
GeenSat is an “open-source” project. Except for restricted or third-party proprietary hardware, hardware designs and source code will be publicly available on the project website and feedback, ideas and improvements will be sought from the wider community.