Once the fuel
runs out, there is no more mission.
You have to decommission.
So the fuel is very important for the spacecraft.
It can only last as long as the fuel.
Title: Moving Roman - Propulsion
Telescopes like NASA's Nancy Grace Roman Space
Telescope move and point using two methods.
There are reaction wheels to turn the spacecraft with precision
and then hold it steady.
And then there are thrusters that use propellant for large motions
to push the spacecraft into its correct orbit and maintain that orbit.
All which require fuel.
Before entering the large clean room,
the propulsion tanks were assembled in a smaller lab.
So right now we're looking at the propulsion system for the Roman
Space Telescope.
Today
we put our last tank on the propulsion support frame.
The propulsion support frame is the frame that's supporting everything.
The four tanks seen here
were each carefully lifted individually.
The deck that supports them gets positioned below that tank.
These four tanks fuel a series of 24 thrusters
with two different sizes.
On the sides.
We have all of the engines, so we have four sets up top.
Those are our upper ACS’s.
We have four sets at the bottom.
Those are our lower ACS engines.
And then at the bottom over here, those big triangle pods,
those are all of our Delta V engines.
So those will do our big maneuvers.
With the tanks in position.
They're ready for integration into the telescope spacecraft bus,
which happens in NASA's largest clean room.
Now, thrusters use conservation of momentum, ignited
fuel creates expanding gas, which exits the engines in one direction.
And the observatory moves in the opposite direction.
The thrusters are so efficient in the vacuum of space
that they can be surprisingly small to move
the 18 thousand pound spacecraft.
This is all it needs.
With the thrusters on the outside of Roman,
the propellant tanks will sit within the observatory central cylinder
close to their teammates, the reaction wheels.
When the reaction wheels get to their maximum speed,
they have to be slowed down again.
The thrusters fire to balance the angular momentum change
so that the spacecraft doesn't turn as the wheels slow.
Since fuel is limited,
it usually determines the lifespan of distant
spacecraft.
Luckily, the telescope can also point
only using electricity.
But how reaction wheels work.
That's another story.