strapline
20 JUNE \\ AEROSPACETESTINGINTERNATIONAL.COM
Propulsion Laboratory in Pasadena, California, will
propel the Lunar Gateway around the Moon for many
years, once operational by 2030. The very long durations
that electric propulsion must operate for present
different challenges compared to typical rocket work.
“We’ve been doing increasingly long lifetime tests to
learn what it’s going to take to keep the vacuum facility
operational for such a long period of time,” says NASA
Glenn Research Center research electrical engineer,
Jason Frieman.
His team started with a 1,500-hour, test then a
1000-hour one and this year completed a 3,500-hour
test. “We’ve been trying to poke and prod, to see where
the fault points are in the facility,” he says. Hermes
is being tested in vacuum facility number five at Glenn,
which is 4.6m in diameter and 18m long. “It is the largest
vacuum system in the world in terms of pumping speed.
It has a pumping speed of 700,000 liters per second,”
says Frieman.
With such a long duration of 10,000 hours planned,
the test cannot be staffed all the time. “24/7 for years at a
Ten thousand hours, more than a year
of almost continuous testing, is to be
carried out from late 2020 by NASA
for its Hermes electric rocket, which
will propel the proposed Lunar Gateway space station
around the Moon. Meanwhile, a private testing effort for
a Mars expedition class electric propulsion system has
just completed 100 hours of continuous thrust.
While conventional rockets fire for durations
measured in minutes, electric propulsion produces much
lower thrust but is operational for many hours (See box:
What is electric propulsion?). Chemical rockets can
demonstrate fuel efficiencies of up to 35%, but ion
thrusters, a form of electric propulsion, have achieved
more than 90% efficiency. NASA’s Deep Space 1 probe,
which was launched in 1998, used its ion thruster for
more than 16,000 hours over two years.
EXTENDED DURATIONS
The Hermes rocket, which is being developed at NASA’s
Glenn Research Center in Cleveland, Ohio and Jet
1 // A vacuum chamber at
the NASA Glenn Research
Center uses hall effect
thrusters for solar electric
propulsion research
2 // The Variable Specific
Impulse Magnetoplasma
Rocket rocket is rolled
into the Ad Astra Rocket
Company’s vacuum
chamber for testing
1
2
engine testing
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