NASA/GSFC Satellite Servicing Projects Division

Phase 3 of the Robotic Refueling Mission


Phases 1 and 2 of RRM (RRM1 and RRM2) were extremely successful.  These two missions focused on refueling technologies with "room temperature" commodities such as Nitrogen Tetroxide and Monomethylhydrazine.  This success caused NASA to fund us to perform an investigation of technologies for cryogenic refueling. This uses super-cold commodities such as liquid Hydrogen and Oxygen.  In RRM1, we used Ethanol (alcohol) to simulate these substances.  This time, we would use Methane.  Although dangerous and explosive on the ground, in space (due to lack of oxygen), it is just a cold liquid substance.

Under Construction
More to come for the intro write-up.

Hardware Development

PDU EDU in test
The first Engineering Development Unit to be tested was the Power Distribution Unit, which generates our low voltage power and has the switching MOSFETs to the many loads.
Here it is in our "Flatsat" lab being tested with EMI test equipment.  
It is the Aluminum box to the far right.
(December 2016).

As part of the planning for our mission, we had a meeting with
SpaceX at the Hawthorne, CA factory.  May 2017

Picture from the web with a view from the cafeteria into the factory.
In the foreground is the first returned Dragon capsule.

In June 2017, we had a TIM with SpaceX at the KSC
launch site.  This is inside the vertical processing

In June 2017, we had our first thermal vacuum test of RRM3, and it was a test to
see how the two cryogenic coolers would work in the RRM3 thermal environment.

View of the two coolers inside the vacuum chamber (June 2017).  In RRM3, there is one
cooler for the Dewar that holds the Methane, and another for the Dewar that will
receive the Methane.  With the latter, we can demonstrate a transfer and fill
without loss of cryogen.

The wiring harness of RRM3 is extremely complicated compared to the previous ones
we built, so we built a mockup of the structure to use as a template to build the flight
harnessing (July 2017).

The wiring mockup gives a sense for the size of RRM3.  It is a little
larger than RRM1, larger than a clothes washing machine.

As part of this project, we travelled many times to Los Angeles to meet at Motiv
Space Systems
, where one assembly was being built.  This electronics assembly
powers the twin cryocoolers and the various motors. (August 2017).

This image shot during a visit to MSS where we were able to show a successful run
with the cryocooler.  This was a very important milestone in our development.
You can see the resonator on the left vibrating (August 2017).  Snow
would form on the right end as it cooled down.

Around the same time back home, my colleagues were building the various
avionics units needed for RRM3. This is the Power Distribution Unit
on the test bench.

Here are other avionics units such as the SpaceCube being vibration tested
(November 2017).

We spent the month of December and January integrating half a dozen avionics units,
50 or so harnesses and numerous other smaller items together.  Due to the complexity
and number of new technologies integrated there were many problems and
I would have a hard time sleeping. So sometimes I would nap in between

RRM3 does not consist only of the main Fluid Transfer Module, but also includes three
new robotic tools such as this one, the Cryo Servicing Tool (CST).  This is it
undergoing EMI testing (December 2017).

To best ensure that the tools were compatible to the Space Station avionics system,
we would test with this facility at the Johnson Space Center (near the
Sonny Carter Training Facility).  This is known as the SDIL.  We would test
by connecting our hardware to this and flowing video and data (Jan 2018).

Something new for us is the Power Quality testing at the Power Lab at SDIL.  In this facility, they subject our hardware to all kinds of power line anomalies to
verify we can handle the transients on the power bus on ISS (Jan 2018).

At one of these visits to the Johnson Space Center, I had the
good fortune of seeing the James Webb Space Telescope being
prepared for shipment to California after it had completed
its thermal vacuum testing (Jan 2018).

A photo of RRM3 almost complete and ready to start its environmental testing (Jan 2018).

Closeup of one part of RRM3.  This is a cool new color pan-tilt-zoom-focus camera that
we are going to be testing out on this flight.

Team picture at the meeting where we were told we were GO for launch on SpaceX-16 (CRS-16).  Feb 2018.

In March 2018 we did our final vibration test.  This video is of the RRM3 being
craned into the vibe cell.

under construction
Current launch is SpaceX-16.  November 2018 estimated launch date.


  • Wikipedia page on CRS-16.  As of March 2018, it still showed that the International Docking Adapter would be the main payload, but that has been changed to RRM3 and JEDI.  The IDA is an important addition to the ISS as it allows commercial crew vehicles to dock with Station.  The fact that they rescheduled it to accomodate us is a big confidence booster for us.
  • SSPD Home Page.

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