  A charged tether or wire experiences Coulomb drag when inserted into flowing
plasma. In the solar wind the Coulomb drag can be utilised as efficient
propellantless interplanetary propulsion as the electric solar wind sail
(electric sail, E-sail). In low Earth orbit (LEO) the same plasma physical
effect can be utilised for efficient low-thrust deorbiting of space debris
objects (the plasma brake). The E-sail is rotationally stabilised while the
deorbiting Coulomb drag devices
  According to numerical estimates, Coulomb drag devices have very promising
performance figures, both for interplanetary propulsion and for deorbiting in
LEO. Much of the technology is common to both applications. E-sail technology
development was carried out in ESAIL FP7 project (2011-2013) which achieved TRL
4-5 for key hardware components that can enable 1 N class interplanetary E-sail
weighing less than 200 kg. The thrust of the E-sail scales as inverse solar
distance and its power consumption (nominally 700 W/N at 1 au) scales as the
inverse distance squared. As part of the ESAIL project, a continuous 1 km
sample of E-sail tether was produced by an automatic and scalable "tether
factory". The manufacturing method uses ultrasonic wire to wire bonding which
was developed from ordinary wire to plate bonding for the E-sail purpose. Also
a "Remote Unit" device which takes care of deployment and spin rate control was
prototyped and successfully environmentally tested. Our Remote Unit prototype
is operable in the solar distance range of 0.9-4 au.
  The 1-U CubeSat ESTCube-1 was launched in May 2013 and it will try to measure
the Coulomb drag acting on a 10 m long tether in LEO when charged to 500 V
positive or negative. A more advanced version of the experiment with 100 m
tether is under preparation and will be launched in 2015 with the Aalto-1 3-U
CubeSat to polar LEO.
