Hydrazine and its derivatives have been the traditional propellants for spacecraft since the 1960s. It is a conventional rocket fuel. Hydrazine is a hypergolic propellant. As such, it can ignite on contact with an oxidizer and does not require an independent ignition source. This attribute makes hydrazine a particularly well suited monopropellant for spacecraft maneuvering systems that require frequent restarting capability.
The drawbacks of hydrazine that make hydrazine thrusters less appealing include:
– High toxicity: exposure to even small amounts of hydrazine can cause cancer and so Hazmat suits must be worn when handling the propellant. The required safety protocol can extend spacecraft loading and unloading times and increase the associated cost. In 2011, Europe’s Registration Evaluation Authorization and Restriction of Chemicals classified hydrazine as a “substance of very high concern”
– Temperature requirement: hydrazine must be kept warm and therefore, entails heating costs
– Low specific impulse: Specific impulse is the measure of pounds of thrust that can be obtained from the consumption of 1 pound of propellant in 1 second. Therefore, a low specific impulse indicates low propellant efficiency
By contrast, ADN (ammonium dinitramide) based propellants are environmentally friendly compared to hydrazine. They are cost effective and have a wide range of propulsion applications such as for rockets, warheads and CubeSat thrusters. ADN based propellants have several additional advantages relative to hydrazine:
– Their safety allows for easier handling and contributes to lower lifecycle cost
– Higher specific impulse and therefore, higher efficiency
– Higher volumetric specific impulse as a result of higher density enabling the use of smaller tanks and therefore, lower structural weight
– Non-corrosive
– Not sensitive to air or humidity exposure
– Approved for air transportation
To learn more about the features and specifications of CubeSat propulsion systems, please visit www.cubesat-propulsion.com/vacco-systems/
