After rubbing elbows with Space Shuttle mission commanders (sorry, still squeeing) at last Thursday’s NASA press conference for the 25th anniversary of the launch of the Hubble Space Telescope (HST), the attendees at the NASA Social were taken out to NASA’s Goddard Space Flight Center where we learned about the James Webb Space Telescope (JWST) and saw where it was being assembled.
First of all, I want to apologize to all of the wonderful researchers and engineers at Goddard whose names I did not get. They all deserve all of the credit in the world for the amazing work they’re doing, and have been doing for decades. If anyone from Goddard or any fellow NASA Social attendees can fill in any names that I missed, I would greatly appreciate a note in the comments with the information.
This is a 1:5 scale model of HST. The see-through panel at the back end is there to show where the instruments are. HST was visited five times by Space Shuttle crews who replaced and upgraded control systems, instruments, cameras, and optics. Any one of those visits could have ended disastrously. One loose screw, one bolt that wouldn’t come loose, and HST could have been permanently crippled.
The fact that the five servicing missions were 100% successful despite glitches and problems is one of the reasons I like crewed missions. Things never go the way they’re planned and humans are highly adaptable. Check out the PBS’s Nova program, “Hubble’s Amazing Rescue” for a great description of what was at stake, how nearly impossible to get it right was, and how spectacularly triumphant the results were.
Ben Reed runs the Satellite Servicing Capabilities Office (SSCO) at Goddard, where they design and build tools and robots to work in space. Here he’s holding a Pistol Grip Tool (PGT) which is used to screw and unscrew nuts, bolts, and screws in microgravity. This particular one is actually from the Neutral Buoyancy Laboratory (NBL) where astronauts train for their space walks.
One of the projects being worked on at the SSCO is the Robotic Refueling Mission (RRM). I remember seeing these experiments being run on the International Space Station (ISS) a while back. This test panel is identical to one flown to Low Earth Orbit (LEO), as is the next one shown below.
Thousands of satellites have been sent to orbit and then become useless as they aged. Sometimes a critical piece fails, maybe a power relay or the onboard computer. Sometimes satellites get hit by meteorites or other orbital debris. More often than not though, the satellite fails when it runs out of maneuvering fuel.
Due to various factors such as atmospheric drag and gravitational pull from the Sun, Moon, and other planets, satellites tend to not stay where you put them. They’ll all use some sort of small thrusters to “station keep.” When that fuel runs out, they drift, lose attitude control , and become useless. Oh, and 99.9999% of these satellites were never intended to be serviced or refueled, so when they’re dead, they’re dead.
Let’s say you built a robot. A very clever robot with a bunch of nifty tools. Maybe the robot is autonomous, or remote controlled from the ground, or a little of both. (Yeah, I would send a crewed mission since humans are incredibly dexterous and clever monkeys, but that’s just me.) Maybe these nifty tools and clever programming would allow securing wires to be snipped, locked on bolts to be unlocked, thermal blankets to be peeled back, and sealed access ports to be unsealed on dead satellites.
Now you need to test your robot. It’s expensive (and a whole different engineering problem) to accurately locate the broken satellite, rendezvous, and attach your refueling robot to it. Especially when you don’t know yet if you’ll actually be able to do the undoable when you get there. So you want to test the breaking and entering and refueling before you spend all of that other money on finding and rendezvousing and capturing. This is where the RRM and ISS come in.
These panels have fueling ports and connections that are the same as those used on numerous commercial satellites. The test is to see if controllers on the ground can remotely use the tools built into the robot to do the job.
The RRM mission on ISS uses the Canadian-built Dextre two-armed robot along with tools built for this task. Dextre can be held at the end of Canadarm2 or it can be docked at one of the Mobile Base Stations on ISS. Seen here is a heavy-duty version of a remotely controlled robot similar to Dextre. (Dextre’s tough, but lightweight and designed to work in microgravity. This one has to be bigger and heavier to work at 1G.)
So far the RRM tests on ISS have gone very well. There have been no “show stoppers” in proving that a remotely controlled robot can break into a satellite with empty fuel tanks, refill the tank, reclose the port, and release the satellite.
The issue, as it always is, is money. A robotic refueling mission like this might cost $500M or more, plus the initial development costs. (Please note, all of these numbers are Wild Ass Guesses (WAGs) and yes, I am trying to see how many Three Letter Acronyms (TLAs) that I can put into this article.) Would it make economic sense? That was one of my questions for Ben Reed.
The answer is, not surprisingly, “It depends.” It’s not a single calculation but a spectrum. On the low end, if you have a cubesat that only cost $50K to build & launch, spending hundreds of millions of dollars to refuel it would be stupid. On the high end, if you spend $7.998B to build and launch JWST, perhaps a couple hundred million dollars to double or triple its lifetime might make sense.
To be quite clear — NO ONE at Goddard said ANYTHING about possibly refueling JWST. In fact, whenever the concept got brought up, it was politely but firmly squashed. JWST has been designed from the get-go to be a “fire & forget” spacecraft with no possibility of being repaired or refueled. I’m just speculating wildly here.
But that being said, remember, it’s an economic spectrum. Even if you can’t refuel JWST, what about if you’ve got a $1B+ weather satellite or communication satellite. If your choice is to build & launch another $1B+ satellite or try spending $250M to refuel the old one (again, WAGs!), which do you choose?
More to the point, if you build your robot with lots of different capabilities and a big tank of fuel, maybe you can refuel ten satellites. Or fifteen. Or thirty. Now your cost per satellite is maybe $20M each. So if you have a perfectly good, functioning $1B+ satellite that’s out of fuel, do you build another, or risk $20M or so to double its lifespan? If the technology’s there, the answer seems obvious.
The SSCO isn’t developing this technology just because NASA necessarily has any plans to use it. The key word in SSCO is “Capability.” Yes, NASA would like to be capable of doing this if they need to, but it could be another NASA spinoff that saves billions of dollars.
That’s not all the SSCO is working on. Here you can see “test rocks” of different sizes, weight, and composition. Some are hard as a rock, some are more like clumps of sand barely holding together. Some are metallic, some not.
These test rocks are being used to see how current robots and their manipulators (“hands,” if you will) can deal with different objects they might encounter on the surface of a comet or asteroid. (Remember OSIRIS-REx from yesterday?) We don’t know what we’ll find on the surface of any given object (that’s the reason we’re going, to find out – right?) so the robot spacecraft we design and build have to be prepared for a range of options.
Also on the left in this picture you can see a grey-white object. I believe this is a model of a device currently on ISS in the Japanese Experiment Module (JEM, better known as Kibo) and used to launch cubesats from ISS. What I want you to see however is that this has been made by “additive printing,” otherwise known as “3D printing.”
3D printing is going to be HUGE! For example, in a case like this, you can prototype an object for hundreds or thousands of dollars instead of spending hundreds of thousand dollars or more. Then you can test it, tweak it, break it, refine it, and print another. You work out the bugs using the cheaper 3D printing route, then you build the final product the old fashioned way.
I’m sure I’ll be ranting at length about 3D printing here at some point.
In the other corner of SSCO they’re working on the other part of the robot refueling problem – rendezvous and capture of a satellite that might not be under control. If the fuel’s gone (or there’s some other problem) it could be spinning, rolling, tumbling — or doing all three at once. The more it’s moving, the harder it’s going to be to latch onto.
This mockup of a satellite panel is mounted on a rig that can move it through a wide range of motion. The (again, heavy duty, designed for 1G, not microgravity) robot arm on the right is being used to develop software and techniques to learn how to approach and grapple a tumbling satellite, or to figure out when it can’t be done and back off.
These three tools were on display in SSCO, demonstrating how much smaller, more capable, and more elegant our tools for working on orbit have become.
The big blue on on the left was used in the rescue & repair of the Solar Max satellite in 1984. The center tool is that PGT used by shuttle astronauts and now by ISS astronauts on their space walks. The far right tool is one of the tools that was used by Dextre during one of the RRM experiments.
Again, I apologize for not getting the name of this woman who did such a great job of walking us through many of the discovery highlights from HST. From planets, to planetary nebula, to galaxies, to black holes, Hubble has spent the last twenty-five years revolutionizing the way we look at the universe around us.
Getting observing time on Hubble is non-trivial. There are, of course, far, far more requests for observing time than the telescope can perform. Observing time is allocated by a committee that picks the most worthy proposals.
In addition, there is a certain amount of time that is set aside as “director’s discretionary” time. One thing that this time is used for is Hubble observing time when something transitory or unexpected happens. Maybe there’s a supernova, or a comet’s going to slam into Jupiter. With discretionary time, these objects and events can be observed without kicking anyone else off the schedule.
In fact, the landmark “Deep Field” image by HST was done using director’s discretionary time. After all, it was quite literally a blank, empty piece of the sky, without any known stars or other objects in it. Why would the committee give anyone ten continuous days of observing time to look at “nothing”? Yet this image, covering the area the size of a dime as seen from seventy-five feet (let that sink in) contains over 1,500 galaxies.
1,500 galaxies, each with billions of stars, many of them with planets, almost certainly some of the planets containing life, almost certainly some of that life reaching a level of intelligence equal to or better than ours. All that from an “empty” area that small.
The universe is a big place!
Next, we see how HST is operated every day, how it points so stinkin’ accurately, and how it got fixed and upgraded on the servicing missions.