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Education Module
Background
Dawn Dictionary
Dawn Journal
Dawn's
Early Light
Fact Sheet (PDF 525 Kb)
FAQs
Ion Propulsion Interactive
Mission Status
Objectives
Overview
Partners
Spacecraft
Timeline
Trajectory
Where is Dawn?
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| Ion
Propulsion
System
Hot
Fire
Test
for
Deep
Space
1 |
Credit:
NASA/JPL |
The Dawn
spacecraft
uses ion
propulsion
to get
the additional
velocity
needed
to reach
Vesta once
it leaves
the Delta
rocket.
It also
uses ion
propulsion
to spiral
to lower
altitudes
on Vesta,
to leave
Vesta and
cruise
to Ceres
and to
spiral
to a low
altitude
orbit at
Ceres.
Ion propulsion
makes efficient
use of
the onboard
fuel by
accelerating
it to a
velocity
ten times
that of
chemical
rockets.
This efficiency
is measured
in terms
of the
specific
impulse
of the
fuel (Isp).
Dawn's
engines
have a
specific
impulse
of 3100
s and a
thrust
of 90mN.
While a
chemical
rocket
on a spacecraft
might have
a thrust
of up to
500 Newtons,
Dawn's
much smaller
engine
achieves
an equivalent
trajectory
change
by firing
over a
much longer
period
of time.
The figure
below shows
the specific
impulse
and thrust
of different
thruster
types.
The ion
thruster
is powered
by large
solar panels.
The power
ionizes
the fuel
(Xenon)
and then
accelerates
it with
an electric
field between
two grids.
Electrons
are injected
into the
beam after
acceleration
to maintain
a neutral
plasma.
Further
information
on
Ion Propulsion |
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accountability report