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Re: Re: Arcjet Motor



>From: "i8cvs" <domenico.i8cvs@tin.it>
>Ed and all:
>
>The ArcJect thruster is about 100 mN,giving an acceleration of order
> 0,0002 m/s^2 provided the ammonia is heated by electric arc, then
>the heated gas is expanded via a nozzle and thermal energy is converted
>into kinetic energy.
>Is AO40 there is ammonia for about 500 hours of operation offering a total
>delta-V
>of up to 470 m/s
>
>On the other side, 400 Newton is the nominal thrust of the rocket liquid
>propellant motor.
>Since spacecraft launch mass is 632 Kg,the motor,if no problems occurred,was
>able to  impart an initial acceleration of typ,400/632 = 0,6m/s^2 or about
>0,06 g.
>Total delta-V available is about 1100 m/s
>
>The 100 mN thrust of ArcJect motor is 1/4000 of the main motor,but can fire
>for long periods,giving significant velocity changes.
>
> The kick motor used on AMSAT Phase III-A was a solid propellant Thiokol TEM
>345-12 containing approximately 35 kg of a mixture of powdered aluminum and
>organic chemicals in a spherical shell with a single exit nozzle.
>The unit was capable of producing a velocity change of about 1600 m/s
>during its single 20 second burn but unfortunately this AMSAT Phase III-A
>satellite was lost in the Atlantic with ARIANE-4
>
>OSCAR-10 and 13  used a liquid-fuel roket produced by the German company
>Messerschmitt .
>This unit produces a thrust of 400 Newton  with the advantage to be ignited
>several time and is similar to that used on AO40
>
>All tree satellites OSCAR-10,13 and AO40 had problems with the 400 N liquid
>propellant motor and no one of it was able to reach the final orbit
>inclination.
>
>I hope this information is usefull for the ArcJect Motor forum.
>
>73 de i8CVS Domenico

Domenico,

Thanks.  I had not read anything specific on the engines for AO-40, so was
talking in generalities.  Its very interesting that the arc-jet can achieve
roughly one third of the velocity change of that of the chemical engine.  I
would not have expected this, though I understand about low-thrust being
additive over time.  Apparently there is substantial fuel for the arc-jet.

Regarding the liquid fuel history, that too is interesting, and sheds some
light on previous comments.

Ed




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