On 8/28/2019 10:58 AM, Henry Vanderbilt wrote:
On 8/28/2019 10:01 AM, Uwe Klein wrote:There are systems that electrostatically accelerate small charged liquid droplets; the terms you want to search for are colloid thruster or electrospray thruster. Acceleration distance doesn't have to be very long because they all exploit the very high field gradients you get near the tip of a needle-shaped anode or cathode to simultaneously extract, charge and accelerate the droplets. Also, the geometric size and throughput constraints on electrostatic thrusters are mostly set by space charge density rather than mass density, so putting e.g. half a dozen surplus charges (positive or negative) on a 10,000 AMU blob of some liquid salt solution is pretty appealing.
Am 28.08.2019 um 17:43 schrieb Henry Vanderbilt:A 20 km/s sandblaster? Drives that emit discrete particles rather than self-dispersing individual molecules would be a hazard to navigation at some large distance, I would think. Perhaps not good if the object is vastly increased space traffic.
Knowledgeable reduction of my ignorance RE electric propulsion much
appreciated - thanks!
So, all other electric-propulsion things being equal, in terms of
overall efficiency of converting electrical energy in to thrust energy
out, the ionization energy requirement favors heavier atomic-weight
propellants and higher isp's.
What do I get from putting a charge on fine dust?
You obviously have to increase acceleration time/length
due to less applyable force per mass.
Beyond that, I might guess that you could reduce the charge energy required if not every molecule must be charged, but as you imply at cost of heavier/longer acceleration machinery for a given exhaust velocity. Whether that's a good trade depends on the circumstances, of course.