Space Shuttle Atlantis has landed safely

Launch of STS-132
Launch of STS-132

Space Shuttle Atlantis touched down at 8:48.11 Eastern time at Kennedy Space Center. This makes Atlantis our first Space Shuttle to retire. (I think that also makes it the second reusable space vehicle to retire, after SpaceShipOne decommissioned in 2004.)

This is a sad day in space exploration…but it is long overdue. In what other modern industry or field of endeavor other than space exploration do we continue to use 30-year-old vehicles and devices, and in what other field do we consider those vehicles to be “cutting-edge?” This is the beginning of a period of transition, and I can’t wait to see us get started on what’s next. That day, also, is long overdue.

Congratulations to Atlantis and its many crews on the successful completion of all its missions.

Go Falcon 9!

First: Go Atlantis!!!

Now, on to the purported topic of this post: The SpaceX Falcon 9 is slated to launch in less than a week!

Beautiful photo of Falcon 9 on the pad (SpaceX)

Ever since the FY11 NASA budget came out, I’ve been anxious to see the success of the Falcon 9, SpaceX’s heavy-lift vehicle, and the Dragon capsule. A good Falcon launch and successful Dragon flight demo would be like jumping NASA’s Constellation program straight to an Ares I/Orion system prototype. This is the rocket and capsule that the new budget banks on for ISS resupply and astronaut transport. Of course, SpaceX had already won the ISS resupply contract before the new NASA budget came out, so this really isn’t that big a change from the status-quo solution to the space access gap – except that a successful man-rated Dragon would close that gap entirely!

For the bajillionth time, Mike Griffin’s Constellation Program was on track to do what we did 40 years ago, with what we used 30 years ago, 20 years from now. I know the program says “by 2020,” but it ain’t gonna happen, even with billions of extra dollars.

The new budget focuses NASA on in-space vehicles. Vehicles for carrying people throughout the Solar System. Vehicles for building colonies in space. Vehicles for taking people to planets. Vehicles for exploring planets. The kinds of vehicles that cannot be built on Earth and launched, whole, on a Saturn or Ares rocket. The kinds of vehicles that nobody but NASA would try to build. The kinds of vehicles that would move the human spaceflight program forward!

But, in exchange, NASA is not going to develop boosters. The space agency is going to send its astronauts – still NASA astronauts, dammit! – up to LEO on board  vehicles bought from commercial providers. The outcry against this concept is based primarily on the objection that the commercial space access providers are “unproven.”

Well, phenomenal success of the Delta and Atlas lines aside, this is the proving ground. There’s a lot riding on the Falcon 9 flight test; the space community consensus could go dramatically one way or the other depending on the outcome. If SpaceX makes it, we can almost consider NASA fast-forwarded to what Constellation would have done in 2015, or later. (And we’ll be much closer to buying tickets to space!) They just have to buy their launchers from SpaceX, instead of….contracting to ATK to build them.

Good luck to the SpaceX launch crews! Hope the launch is spectacular!

Sol LeWitt

I spent last weekend in Williamstown, MA, with my family for my sister’s Williams Dance Company performance and the super-swanky Mother’s Day brunch at the Williams Inn. (I’m allergic to chicken and turkey, so I passed over the roast duck; but I made sure to grab some brunch swordfish!)

We also went to the Sol LeWitt retrospective exhibition at Mass MoCA. LeWitt is really interesting; first, because he drew his artwork directly on gallery walls, and second, because the artwork consists mainly of a detailed set of instructions describing how to create the drawing. If one museum sells a Sol LeWitt wall drawing to another museum, then they erase the wall, give the new museum the instructions, and that museum carefully follows the plan to reconstruct the wall drawing in a new space. I found this whole process to be quite interesting. (All the images here are from the Mass MoCA web site; click to see them on the original pages.)

Wall Drawing 289 (Mass MoCA)
Wall Drawing 289, Fourth wall: twenty-four lines from the center, twelve lines from the midpoint of each of the sides, twelve lines from each corner. (Mass MoCA)

The precision and care that went into each wall drawing (some on walls that were, maybe, thirty feet wide by eight feet tall) are amazing. Each drawing is the product of work by a number of drafters, some of whom are interns and some of whom are dedicated to Sol LeWitt wall drawing. They develop methods for interpreting LeWitt’s instructions. Some of those instructions even leave parts of the implementation wholly up to the drafters.

Detail from Wall Drawing 305 (Mass MoCA)
Detail from Wall Drawing 305, the location of one hundred random specific points (Mass MoCA)

LeWitt’s method seems to revolve around abstraction – taking something observable and representing it in a symbolic way. The descriptions at Mass MoCA describe how LeWitt was interested in removing the artist from the artwork. This concept resonates for me: here I am, trained as a physicist and engineer, with my livelihood based on constructing, manipulating, and extracting results from mathematical models. Those models are based on the theories that govern physical phenomena; but they never are a full, complete description. Still, we use them to great effect in making predictions or developing new theories. The philosophy of science question here is, are the models conceptually different from the theories they describe? Or are they just a different representation of the same thing? In the same vein, is Sol LeWitt’s art the wall drawing, or the instructions? His opinion seemed to be the latter.

The other thing I ended up thinking about while strolling through the wall drawings was how the implementation of the drawings corresponded to realizations of models in the science and engineering world. We can come up with incredibly complex models for how the universe works, but when constructing a simulation or making a prediction, we often choose to use only a small part of the model. For instance, Einstein’s theory of General Relativity describes how objects move under the influence of gravity (or, equivalently, how they move through curved spacetime). But for a great many applications, Newton’s single equation for gravitational attraction between two bodies is enough: The force is attractive, proportional to the product of the masses of the bodies, and inversely proportional to the square of their separation. Then for yet another large subset of applications, the simple high-school physics expression F = -mg is quite sufficient. In a sense, both of these simplifications are realizations of General Relativity, in the presence of certain simplifications that let us “zoom in” on part of the model. When the drafters have a LeWitt wall drawing instruction sheet, they must match the instructions up to the wall space they have to work with. The instructions seems to be written in reference to relative measurements on the wall (the midpoint of the left side, the corner, the center of the wall, etc), which means that the same instructions – the same idea, the same “theory” can produce very different realizations on different walls. (And, speaking of relativity, I wonder if LeWitt ever took a look at the math behind Einstein’s theories. It would have been neat to see something like this wall drawing as viewed by an observer traveling at 0.5c!)

Not only do the spaces shape the wall drawings, but the drafters themselves may be left with choices in how to interpret and then implement LeWitt’s instructions. Take this wall drawing:

Wall Drawing 386 (Mass MoCA)
Wall Drawing 386, stars with three, four, five, six, seven, eight, and nine points, drawn with a light tone India ink wash inside, an India ink wash outside, separated by a 6-inch (15 cm) white band. (Mass MoCA)

I spent a little while thinking about that three-pointed star. Without that, it’s obvious how the progression works: the nth star is centered in the middle of each square, its points are evenly spaced about a circle, they all extend to the same radius, and the border of the star comes in between each point so that the shape is concave. But that three-pointed star breaks all those rules! It need not have – it could have been just like the four-pointed star, only with three points. Instead, it is a triangle with one concave side. Here, I do not know: was this in LeWitt’s instructions, or did a drafter determine how to construct this three-pointed star?

Some of the wall drawings definitely did have ambiguity built in. My favorite of MoCA’s drawings was 146A:

Wall Drawing 146A (Mass MoCA)
Wall Drawing 146A, all two-part combinations of arcs from corners and sides, and straight, not straight, and broken lines within a 36-inch (90 cm) grid. (Mass MoCA)

The instructions for this drawing specify that the drafters make “not straight” lines. Okay…so we define the line by what it isn’t, and leave a still-infinite space of possible lines that meet this description. The drafter can make “not straight” lines as un-straight as they like. They can make lines that wander as much as they want. They can choose to tie their “not straight” lines in to the “not straight” lines in the rest of the drawing or not. If you take a look at the timelapse video of this wall drawing being drafted, you can see how each drafter does each “not straight” line differently.

Were I Sol LeWitt, I think it would have been interesting to create a set of wall drawing instructions that contained intentional contradictions. Some drawings might have tiny contradictions, some might seem like egregious errors. What would the drafters do? Would they prioritize the instructions, and satisfy the most important ones first? Would they try to satisfy both constraints equally? Would they push back at all the instructions for the wall drawing, going for the most “average” level of meeting the instructions? That would sure be an interesting way to comment on our artistic, geometric, scientific, or philosophical methodologies. In an exhibition with many drafters and many walls, giving them all the same set of contradictory instructions would likely turn up some very interesting results!

Wall Drawing 692 (Mass MoCA)
Wall Drawing 692, continuous forms with color ink washes superimposed. (Mass MoCA)

Some of LeWitt’s later wall drawings were just plain fun. Drawing 692, above, was also one of my favorites – I liked how it gave the impression of different planes, and how the vibrant colors made the painting stand out as if with its own light. It was like looking through a windowpane onto another stained-glass window. Remember – this image doesn’t convey it, but I stood only a little taller than the second black line from the floor!

Then, of course, there were wall drawings like Splat, the intentionally impossible-to-look-at Loopy Doopy, Whirls and Twirls, and some cool experimentation with glossy and matte paints.

Wall Drawing 824 (Mass MoCA)
Wall Drawing 824, a black square divided in two parts by a wavy line. One part flat; one glossy. (Mass MoCA)

But of course, being a Williams guy, I had to like Wall Drawing 852 best of all.

Wall Drawing 852 (Mass MoCA)
Wall Drawing 852, a wall divided from the upper left to the lower right by a curvy line; left: glossy yellow; right: glossy purple. (Mass MoCA)

The Sol LeWitt Retrospective is a very cool exhibit. I didn’t always like the art at Mass MoCA, but I’ll happily recommend a trip to see this!

A Case for Asteroid Missions

Asteroid bases in our future?
Asteroid bases in our future?

We’ve discussed President Obama’s plans for NASA in my research group. Things look good for us: as a team working on spacecraft technology research, looking for things that will make construction, maneuvering, and other activities in space easier, cheaper, and better, we are very happy to see the technology research arm of NASA finally getting the funding it deserves. (It’s amazingly ironic that “space age” technology means thirty-year-old tech.) However, one grad student in my group questioned the value of targeting asteroids, specifically, for exploration. Is it worth it to send people to asteroids? Do we gain anything by doing so?

I think we do, and I’m going to explain why here. But first, I want to make clear two things I am not going to do. I am not going to make a scientific case for going to asteroids. The reason why I’m not going to use science to justify asteroid missions is that we can gain scientific knowledge wherever we go. We can learn new things anywhere. I’m not going to try to prioritize that knowledge, because in the end, it’s all valuable and it’s likely that there will be breakthrough theories germinated from any field of endeavor. In addition, I am not going to make a case against returning to the Moon or going directly to the Martian surface. I am not going to list reasons opposing either of those destinations simply because I don’t think there are any. Rather, I am going to focus on the reasons why I think asteroids are exciting destinations.

Reason one: Operations on and around asteroids are extremely challenging.

On the one hand, anything in space is challenging. But asteroids may be especially tricky, mostly because we don’t yet understand what being around an asteroid would be like. We have only a few close-up pictures of asteroid surfaces, and have only touched the surface of asteroids with two robot spacecraft that I can think of. As far as we can tell, their surfaces are covered with fine regolith, perhaps like the Moon, but their odd shapes give them very strange (micro)gravity fields. Imagine you’re standing on the “side” of a tiny, potato-shaped world like Ida. Which way is down? Harder question than you might think!

243 Ida and Dactyl
243 Ida and Dactyl

NASA can simulate operations on planets and moons by visiting “analog” sites on Earth, trying out procedures in mock space suits and pretend capsules. NASA also has a wealth of free-fall experience from its operations in low Earth orbit with the Space Shuttle and Space Station. But no space agency has any experience with or ways to simulate environments like asteroids. So, not only are asteroids tricky places to be, but the only way to learn about being around asteroids is to go to an asteroid. We’ve never done or thought about this stuff before, at least not in detail. I think that’s exciting!

In particular, I think the challenge of operations around asteroids demands that we send people there. There has been a lot of talk about how the new NASA plans will leave our astronauts without jobs and focus entirely on robotic missions. Whether you think that is a good thing or not, I think it is untrue. While robotic precursor explorers will give us some inkling about what to expect, figuring out how to actually do things on asteroids (science, construction, etc) may be better achieved through an in-situ human learning process. The closest analog we have to asteroid operations is work around the outside of ISS, which we do not yet trust to robots and have tremendous experience with. Astronauts around asteroids could rapidly tell NASA Mission Operations analysts what the major differences are between an ISS spacewalk and asteroid spacewalk. At the same time, a human’s ability to learn on-site, manipulate four limbs in a coordinated manner, and perceive situations clearly and directly would be desirable qualities.

Why do we care about learning how to operate crewed missions around asteroids? Well, Reason Two is that these asteroid operations skills are transferable.

Buzz Aldrin likes to talk about Phobos. Well, if we want to go to Mars, then the first question we must answer is exactly what sort of mission profile we want to use. Options include a Moon-landing-like sortie mission, in which we put boots on the planet, bounce around picking up rocks for a couple weeks, plant a flag, and then take off for home. We could also send a mission that lasts a year or two and involves building a temporary (or permanent) base, establishing laboratories, and zipping around in rovers; this probably involves multiple launches to and from the Red Planet. Or we could go for the interesting option of picking 50 or so people and sending them to Mars, in one launch, with everything they need to be self-sufficient. The point of all this is that, depending on the mission, it might be valuable to use Phobos as a way station. And if we want to be around Phobos, we have to learn how to be around Phobos. More than that, we have to learn how to be around Phobos and be very, very far from and out of reach from Earth.

Moreover, microgravity operations around small bodies are exactly the kinds of operations that would be relevant in the asteroid belt. Or around the Jupiter Trojans. Or in Jupiter’s moon system. Or Saturn’s moon system. Or near comets. Or by near-Earth asteroids. You get the picture: small-body operations will be important for the manned exploration of the Solar System beyond the Moon and Mars, and the more capabilities we develop, the easier it will be to get to and function in exotic places.

Next, reason three: not only is there science to be done, but around asteroids, we could learn techniques that may be necessary for Earth defense.

Yeah, I’m talking about defending the planet from rogue asteroids. We certainly won’t be doing this by launching a team of misfit miners and Bruce Willis. Now, the asteroid deflection techniques we develop may or may not involve manned missions, but when we’re talking about the survival of a city – or the entire human race as we know it – why remove any tool from our kit?

The fourth reason is one that ought to appeal to space technologists out there: asteroids could provide resources for construction which are much easier to get into orbit than the resources on Earth.

Asteroids are made of useful things. Nickel-iron asteroids are composed of metals, both common and rare. Carbonaceous asteroids contain other materials. Some even have organic compounds. There is even recent evidence that many asteroids have water! These potential resources may be easy to get to, if the asteroids are rubble-piles, or the useful materials are in the asteroid regolith, or if the asteroid is entirely made of metals that can be melted or dissolved for processing.

Budding space industrialists may be disappointed, but mining asteroids for rare metals to sell on Earth isn’t likely to be economically viable. (It’s too hard to safely get those metals from the asteroids down to Earth’s surface – for instance, we would have to spend more money to launch a Space Shuttle than we would get for the mass of materials that Shuttle could bring down from orbit – a launch costs roughly $450 million, and at current prices, the Shuttle could bring down $15 million in pure silver if filled to the brim. We’d have to find asteroids made of pure gold and platinum and cram the Shuttle to make that come out positive.) However, what could be viable is mining and processing the resources on asteroids into spacecraft bodies, components, consumables, and fuels, which could be jettisoned from their parent asteroids with very little effort. This is simply because asteroids have very small escape velocities compared to planets and moons. If we could get ISRU going, it could be the great moneysaver of the space industry!

ISRU, or in-situ resource utilization, is already a hot topic of research; applications include processing lunar regolith into bricks or reacting chemicals with Martian soil to produce rocket fuels. This would be the next level of complexity: imagine landing a facility on an asteroid that grapples to the rock, bores its way down, processes the metals in the asteroid, and extrudes spacecraft pieces that are ready to assemble. Or perhaps a spacecraft that can land on an asteroid and scoop up material to refill its fuel and consumables. These abilities would let humans build whole new classes of spacecraft, capable of going further than any before. And, given the complexity of building the International Space Station, many of these activities will probably require the involvement of astronauts.

The last reason I can think of – at least, right now – why asteroids make very cool targets is that the asteroids themselves could be used as spacecraft.

The science-fiction way to do this is to find an asteroid and hollow it out with tunnels, crew compartments, fuel tanks, or big, cylindrical chambers. The excess rock and metal from the digging can be fed to mass drivers (or combined with antimatter) to propel the asteroid.

As big a fan as I would be of asteroid colonies or arkships to the outer Solar System and beyond, that’s a pretty farfetched idea at this point. However, an interesting possibility if we want to get to far-flung destinations is to locate an asteroid in an orbit that starts somewhere easy to get to and goes somewhere we want to go, and then hitch a ride. There’s an interesting class of resonant orbits called “cyclers,” which have the property that they rendezvous with two bodies of interest at least once per synodic period. For example, the so-called Aldrin cycler is an orbit trajectory that matches up with the Earth and Mars, with a travel time of 146 days between planets. All we’d have to do is get there and grab on!

We’re not likely to find an asteroid that is naturally on such an orbit, but we may locate asteroids that are on other potentially useful orbits. If we learn enough about asteroid deflection from our planetary defense studies, we might even be able to nudge asteroids onto such orbits, on purpose!

The Moon is a cool place to go. Mars is a cool place to go. Jupiter is a cool place to go. But, you know what? Asteroids are cool places to go, too. We will learn and benefit from any exploration destination. Small bodies, which come in all sorts of shapes, sizes, and compositions, may be very, very different from planets and moons. If we can learn how to use them as platforms for exploration, then perhaps we can jump off them to explore all the far reaches of the Solar System.