The M1.4 Thruster with ConstantQ™ Propulsion

Our thruster maneuvers satellites and spacecrafts with water, which proves to be a safe, energy efficient, and inexpensive propellant. ConstantQ™ provides strong and reliable thrust for any mission.

The Model M1 is a new form factor, now available for quick delivery from Miles Space. It has a 1U envelope and is designed for 3+U spacecraft needing:

  • Orbit raising
  • Orbit phasing
  • De-orbit
  • Drag makeup
  • Desaturation of reaction wheels
  • Attitude control

ConstantQ™ Water Propulsion offers: 

  • Efficient power use
  • Non-toxic (low safety risk)
  • Ease of transportation and ground support
  • Ease of fueling/refueling
  • Low handling costs
  • Low Manufacturing costs
  • Easily added to ride share 
  • Excellent fuel economy
  • Powerful thrust

Miles Space offers low cost primary or secondary thrusters to satisfy the pending FCC regulations on maneuverability.


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.

Thermal Draw: 11.5 Watts (Heater on, no thrusters active) 

System Power: 6 Watts (all thrusters active)

Power Interface: 12V (unregulated)

Command Interface: 5V (Regulated, UART)

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.

  • Thrust: 17.2 mN (all thrusters active, no vectoring)

The applied equations are based upon an assumption of collisionless particle acceleration which is not fully applicable to this thruster design. The thruster instead operates in a mixture of regimes, some of which include collisions. Within the electrostatic acceleration region, the mean free path is short compared to the exit distance, causing charged particles to have many collisions with neutrals before exiting. The short mean free path means ion velocity never reaches high values, power consumption is lowered (due to that u^2 term in the power equation though with power gains offset by the number of collisions). Collisions do work on neutral gas, compressing and heating, forming a shock wave of higher pressure neutrals with anisotropic pressure and temperature distributions, further lowering the mean free path. The higher pressure gas wave pushes against the exhaust nozzle, giving the majority of the thrust. This is known as electrohydrodynamic (EHD) operation where charged particles are used to drag and compress neutrals.

In the flow rate regime used, there is more thrust per watt and higher Isp compressing neutrals (which are counted in the Isp) with a few charged particles rather than converting and accelerating most of the neutrals. Efficiency drops at higher flow rates where no initial long mean free path region exists after ionization, so the required compression shock wave never forms. At lower rates, the mean free path isn’t long enough to cause compression and indeed power consumption rises.

We have observed the pressure increases and have created a model that well captures the energy coupled into the gas and charged particle acceleration. The model shows the thruster is actually only moderately efficient, though clearly doing well enough to fit the size factor and thrust levels needed by the market. We are currently preparing for very high quality 3rd party thrust measurements to test the model, then will release details of this mixed-regime model under non-disclosure.