Miles Space now offers low cost primary or secondary thrusters to satisfy the pending FCC regulations on maneuverability.
The ConstantQ™ family of thrusters use a pulsed electrostatic cycle to enable a variety of Earth-orbiting and deep space missions using water propellant. Test results show water’s vapor pressure and its plasma speciation are especially useful to this operating cycle.
A ConstantQ™ thruster has:
Vapor enters the plasma formation region, expanding and changing pressure on its path towards the exhaust ports. Paschen’s law ensures a spark occurs within the vapor at the point where the supply voltage meets the pressure on the Paschen curve.
Each exhaust port is ringed with high voltage electrodes. One exhaust port’s voltages act to focus and extract positive ions from the plasma. The other affects electrons.
Electrons, being far less massive than ions, leave the plasma before ions, generating thrust from their interaction with the acceleration electrodes. Once outside the thruster, the electrons form a virtual cathode that pulls upon the ions remaining within the thruster.
As the ions leave, thrust is obtained from acceleration electrodes. However, the ions also derive kinetic energy from the virtual cathode, slowing the exhaust electrons and even causing electrons to flow back toward the thruster. This gives an increased acceleration voltage upon the ions, expanding the classic Child-Langmuir limits for space-charge flow rate and thrust density.
As the ions exit the thruster, they meet the returning electrons, neutralizing the plasma. With water vapor, the interface between exiting ions and returning electrons appears as a white-hot sphere 5-8mm outside the ion’s exhaust port. This phenomenon is believed to be due to the presence of multiple ion species with different velocity profiles. In the image below, the two exhaust ports are shown, with the electron port on the left and the ion port on the right. Note the distinctly different exhaust appearances of the two.
A resonance occurs between the incoming gas pressure, spark push back, and plasma drain rate through the exhaust ports (as driven by the supply’s high voltage which can be varied to align with mission Isp). The ConstantQ™ uses a very specific geometry to drive this resonance, minimize wear, reduce power supply complexity, and reduce flight computing demands.
ConstantQ™ thrusters have produced thrust using water vapor, Xenon, Argon, Krypton, Iodine, and air.
First flight scheduled Q1, 2021
Yes. For deorbit, the Delta-v for 3U or 6U spacecraft is sufficient to reduce orbit and accelerate decay through drag. Delta-v is sufficient for several orbit maneuvers.
The M1.4 device uses ConstantQ™ propulsion technology, converting electricity and water
vapor into thrust. Thrust is derived from electrostatic acceleration of separated ions and
electrons using a combination of classic collisionless flow and electrohydrodynamic (EHD)
regimes, all working in a cycle determined by propellant temperature, input power, and device
geometry. The operating cycle is self stabilizing and does not require real time active control
once initiated, though altering temperature and/or power will alter delivered thrust. The process
is self neutralizing and does not require a neutralizer device. Pressures throughout the system
generate water vapor through sublimation, avoiding the need for water to boil and tolerating
frozen ice as the propellant.
Temperature management is achieved with a high-density flat heater on the tank, a valve
self-heating feature, and routing of electronics waste heat to minimize freezing of water vapor.
Thrust is attained with a wide range of temperatures, including a tank full of frozen water ice.
Water vapor is generated through sublimation that occurs when the system is run below the
vapor pressure – a process that does not require water to boil into steam. Water vapor, not liquid
water, reaches the thrust heads and is converted into plasma and thrust. Should liquid water get
near the thrust heads, it would rapidly sublimate into vapor due to vacuum exposure
11.5W is drawn by the heater when energized with 12V. The heater’s resistance is 12.5 Ohms, so it draws 0.96 Amps at 12 Volts. Thermal modeling of a 3U spacecraft shows this is 10%+ more power than required to compensate for a typical 10C change when a LEO satellite is eclipsed.
5V digital logic and valves are expected to draw 65mA, 0.33W, peak. At idle, 20mA, 0.1W, is expected.
12V heater power draws 11.5W.
At room temperature, 12V thruster operation draws 150mA, 1.8W, per thrust head. All four thrust heads running concurrently draw 600mA, 7.2W total.
The heater and thrust heads should not be run simultaneously.
No. The M1.4 naturally operates in pulses with a slight breathing mode around an unstable operating point. Internal capacitors essential to starting the process also prevent instant shutdown as their stored energy continues to feed pulses. As such, impulse bit timing, duration, and thrust are likely not regulated tightly enough for precision pointing of small craft.