Category Archives: Space

How to Get to Mars

26 March 2015 josephshoer Leave a comment

NASA wants to go to Mars. Great!

The approach, as the agency has been publicizing with fancy graphics like the one below, seems to consist of the following:

Send astronaut Scott Kelly to the International Space Station for one year, to learn about the effects of zero gravity.
Perform the Asteroid Redirect Mission, moving a near-Earth asteroid into lunar orbit, to prove that solar electric propulsion works in space.
Assemble a Mars transfer spacecraft in distant Earth orbit out of components launched on the Space Launch System.
Pack everything astronauts need for a round trip to Mars on the new spacecraft and send them on their way!
Keep the spacecraft in space for future trips to Mars. Bring the astronauts and supplies back and forth separately.

Not that these aren’t good brainstorming ideas, but they are not how I would get to Mars. I am too confident and impatient for this plan.

For one thing, we can probably skip this one-year mission. In fact, NASA, I can help you out by zipping straight to the conclusions: Being in zero gravity for a year results in bone loss, muscle atrophy, a compromised immune system, radiation exposure, and changes to the shape of the astronauts’ eyes. We know all that already. Similarly, we already know that solar electric propulsion works – quite effectively, robustly, and scalably – in space. Commercial satellites are flying solar electric propulsion right now, with more on the way. Heck, NASA itself has been flying solar electric propulsion, on missions like Dawn, since the turn of the millennium! Nothing needs proving here. We can take the known technology and use it.

Now, assembling a Mars transfer spacecraft, sending it onward, and reusing it for further exploration – that I like. Here is how I would do it.

First, get one of the companies developing solar-electric propulsion satellites to build a number of spacecraft buses. They will probably run a few tens of millions of dollars each, and they can ride up to space on Falcons, Arianes, or Atlases. (That’s bargain basement stuff for NASA!) Then, tie them together. All I really want are the propulsion systems. Each spacecraft has a propulsion system with something around 10 kW power, and NASA wants to get up to around 100 kW to go to Mars. So, by my rocket science calculations, we need…ten satellites. Or maybe, if we strip out all the telecommunications payloads that these satellites usually carry but I don’t care about for this application, maybe we can get the number down to five-ish.

Four of 'em stuck together — Four of ’em stuck together (with obligatory blue ion engine exhaust)

Somebody would probably have to do some thinking about the best way to support all these stuck-together satellites. Maybe a truss of some kind. But I’m not too worried about that, because NASA has two decades of experience building modular things and sticking them to trusses in space. They can just do what they do best, using their own well-proven techniques.

Now we need a place to put our astronauts. Preferably a place that has some accommodations for solving the problems that Scott Kelly will be confirming. Many of the major physiological issues with space travel have to do with being in zero gravity. Too bad our Mars transit vehicle can’t bring gravity along with it.

Oh, wait! Science fiction knows the answer. It’s known the answer for decades! Spin the spacecraft. The astronauts get to live with a force akin to gravity, pulling them outward along the spin axis.

But building a giant ring-ship takes a lot of time, effort, energy, and resources. I have something different in mind. Something simpler:

On the right, that’s supposed to be an inflatable, cylindrical habitat. (Inflatable things would be terrific for space construction, because they only need a small launcher. Since everything on my vehicle is made of small components, we can launch them once a month instead of once every two years, if they needed a super-heavy launcher like SLS.) This inflatable habitat is tied to the central propulsion core by tethers, or maybe trusses of some type. The astronauts would feel “gravity” pulling them toward the right-hand side of this image (and a little bit downward, because of the thrust). On the left is a dumb counterweight: I’ve drawn it to evoke the empty upper stage of a rocket. It could maybe be long-term storage, but its main purpose is simply to be dead weight to make the spinning easier. The whole vehicle would rotate about the thrust axis, rapidly enough to give the crew at least lunar or martian gravity levels. (The illustration isn’t to scale!)

I’d do one last thing before I send this to Mars with a crew. I’d pack the transit vehicle with enough food, water, and air to get the astronauts to Mars, and for their surface stay.

Not enough to get back, though.

Instead, I would bring seeds. When the astronauts land on Mars, the first thing they will do is become high-tech space farmers. They are going to grow all the food for their return trip on Mars’ surface.

Why would I want to do that? Well, for one thing, seeds are smaller and less massive than full-grown food products. They are probably less expensive – in an energy sense – to get to Mars than those food products would be. Then, on Mars, we can get water and carbon dioxide from the atmosphere, to fuel plant growth. So, over the whole mission, I’m actually saving time and money. There’s also a second reason, one I find more compelling. What’s the point of this whole endeavor if we don’t come out of it knowing how to colonize and explore other planets, and keep colonizing and exploring them? Learning to use the resources on other worlds is fundamental to the future of space exploration. We know Mars has water, we know it has oxygen, and we even know that we might be able to grow crops in its soil. We should focus on that idea and advance it. In other words, I think that – both pragmatically and philosophically – it would be shortsighted and silly to attempt Mars exploration using only what supplies we can bring from the Earth.

We need a space program that focuses on developing the technology to use the resources on Mars to support further Mars exploration. We need to do this in a modular, reusable, scalable manner. We need to make sure our astronauts – no, our pioneers – have the tools, the materials, the infrastructure, and the autonomy to solve their own problems. In other words, we need to stop thinking about how to put a few guys in spacesuits on Mars, and stop thinking about how to have astronauts do science on Mars, and instead think about how to colonize Mars. That requires a lot of little things to come together, with more than a few big things in the mix as well. But, for the most part, we have the technology. We’ve had it for my entire lifetime. We need a space program with the right stuff to use it.

That’s how to take a journey to Mars.

NASA, Space

Space to get excited about

6 January 2015 josephshoer Leave a comment

Last month, NASA repeated an accomplishment they first checked off in 1964 – with some few improvements hardly worthy of the intervening half-century. But tomorrow morning, assuming the weather is a “go,” we will get to see a space travel event that has me far more excited. SpaceX is going to launch a rocket…and they’re going to turn the first stage around from high altitude and hypersonic speed to land on this:

in the Atlantic Ocean.

I love this.

I love this because of the technical meaning of the capability: being able to reuse a rocket would be seriously cool. It has the potential to alter forever the economics of spaceflight. And it’s not as crazy an idea as you might think at first – SpaceX has actually pretty much done it already, albeit without the barge underneath the landing rocket.

But I also love this because of what the event represents! Elon Musk estimates a 50/50 chance of success. SpaceX is trying this because nobody has tried it before. They are trying it because there’s no way to convince people it’s possible except by doing it. They are being incredibly ambitious, and they are willing to accept failure in order to learn from it.

In an industry increasingly defined by incrementalism and risk aversion, SpaceX recognizes that sometimes reward comes from risk. They are truly innovating; trying things that are new. It seems that while NASA’s human spaceflight programs once had the “right stuff,” they lost it in bureaucratization – but the “right stuff” didn’t vanish. It just moved – to the robotic explorers like Curiosity or New Horizons and to the “new space” companies like SpaceX.

Best of luck to the SpaceX team tomorrow. I know that even if you don’t succeed, you’ll be proud of your achievements and you will try again. But I’d bet you’ll see that first stage again!

Concepts, NASA, Skepticism, Space

Back to the Future

7 December 2014 josephshoer 1 Comment

This week, NASA launched the Orion spacecraft on a test flight. I have a conflicted viewpoint about this event. To me, Orion is both exciting and deeply disappointing.

On the one hand, Orion is NASA’s first entirely new spacecraft for human crews in over twenty years. There have been only seven in American history: Mercury (first successful flight in 1959), Gemini (1964), Apollo (1966), Skylab (1973), Space Shuttle (1981), Space Station (1992), and Orion (2014). Those dates have been getting unacceptably distant from one another, and it is wonderful to see NASA getting its game back on. Test flights are NASA’s business. The agency is supposed to operate in the proving ground of technology. I want to see it doing new things, and the Orion flight was a reasonable first step towards NASA getting back to its roots. Those roots, after all, were triumphant!

On the other hand, though, Orion falls far short of what NASA could, and should, do. The spacecraft is an improvement over the last capsule NASA designed – the Apollo Command Module – but it is an incremental improvement rather than a revolutionary one. As an example, one of the technological advancements NASA has been touting about Orion is its glass cockpit. But this is the era of the iPad: in such a mass- and volume-constrained environment as a space capsule, the glass cockpit is simply not innovative – it is obvious. (For examples of innovation in space vehicles, try inflatable habitats, rockets that fly back to their landing pads or crew shuttles that could land at any normal-sized airport runway.) To make matters worse, not only is Orion an incremental step in capability from the early ’70s, but its development is horrendously stretched. For reasons that are political, programmatic, and cultural, rather than technical, the next flight of Orion will be in 2018. A human crew will not use the capsule until after 2021, at which point it will be almost a decade old itself.

I think the most bitter disappointment is the concept of what Orion will do when it finally does have astronauts on board. The current plan is to build the world’s biggest rocket, the Space Launch System, and use it to send an Orion crew to asteroids and Mars. I’m all for visiting those places, but the “giant rocket with space capsule” architecture – the architecture of Apollo – is a recipe for one-shot visits to other worlds. After the first astronauts return from such “flags and footprints” missions, there is a very strong risk of program cancellation. I don’t want to see our space program cancelled.

An Orion capsule riding a Space Launch System rocket is not even close to how I would design a sustainable, long-term space program. A much better approach is to use many different spacecraft, and specialize them for individual purposes. Think of the Apollo Lunar Module: it was a flimsy, silly-looking vehicle that was exactly suited for the prospect of landing and taking off from the Moon’s surface. Instead of building on Apollo and Space Shuttle heritage to make an “all-purpose” space capsule, I would like to see NASA lean on its Space Station experience to design a set of interplanetary transport spacecraft. These vehicles would stay in space for their whole lives: we would assemble them in space, launch them out of Earth orbit rather than from Earth’s surface, and we’d never use them to carry astronauts up from and down to the ground. Whenever they need more fuel, we’d send only the fuel up to them – not a whole new vehicle. When we need to rotate astronaut crews, we could always hire SpaceX.

That sort of multi-vehicle concept offers some big advantages. First of all, it’s much more flexible than giant, infrequent, one-shot missions. Second, it’s far more efficient and cost-effective. Think about this: 20% of Orion’s mass is its heat shield, a component only needed for the last ten minutes of its mission. If Orion is returning from Mars, then that means our Mars return rocket needs to be huge in order to push that heavy heat shield on its half-year-long journey back to Earth. And if the heat shield and Mars return rocket need to be huge, then the Earth departure rocket needs to be enormous. Instead, though, we could forget sending the heat shield to Mars in the first place. Forget having the vehicle that goes to Mars also be responsible for landing on Earth. When the astronauts come back from Mars, you just send a little rocket with a little capsule into Earth orbit – just enough to bring the astronauts to the ground. The lightweight interplanetary spacecraft stays in space.

In 2011, when Congress ordered NASA to begin work on the Space Launch System, internal NASA studies came out that agree with my assessment. Multi-vehicle approaches that we can re-fuel and re-use in space are more efficient and cheaper than SLS. They will also get astronauts to other worlds much sooner. Most importantly, such approaches won’t be reliant on one-and-done missions. They will be much more likely to keep our explorers in space.

That is why, while I applaud NASA’s successful demonstration of the ability to launch new vehicles, I hope the agency moves on quickly from Orion, and begins work on a new fleet of exploration vehicles to stay in space.

Concepts, Space

…how about half an elevator?

20 March 2014 josephshoer Leave a comment

If you’ve paid any attention to science fiction in any form, you’ve probably seen the concept of the space elevator. A super-strong tether or tower extends upward from the surface of the Earth, past geostationary orbit, and beyond; to get into orbit you just need to ride a car up the elevator to the geostationary point and…step off.

The space elevator solves a fundamental problem with access to space: speed. Getting height up from the Earth is fairly easy – just point a rocket up. But to get a spacecraft to stay in orbit, you also need to accelerate your vehicle to orbital velocity, which is at least 7 km/s. That’s where all the big booster rockets come from. The elevator, though, lets you get this speed without even trying. Since the whole structure remains oriented radially out from the Earth at all times, as your car climbs up the tether you automatically gain rotational kinetic energy. At the geostationary point, you will have enough energy to simply push out of the airlock and remain in orbit. Easy!

(This energy is easy to get, but it doesn’t come for free. Every time you go up the space elevator, you slow down the rotation of the Earth.)

Space elevators have some problems of their own, though. For one thing, we need materials and technologies sufficient to support the tether against the forces of gravity and rotation. For another, the Earth’s troposphere has some pesky disturbances that we call weather, and the space elevator has to be near the equator – where tropical storms happen. And then there’s…politics.

Great concept art from DVICE's article about the partial elevator. (Tony Holmsten) — Great tangentially related concept art from DVICE’s article about the partial elevator. (Tony Holmsten)

There was an article the other day about a paper examining a “partial” space elevator. The idea is to place a station at geosynchronous orbit, and run a tether only partway down to the Earth. The tether doesn’t have to deal with cyclones or touch the surface. Rockets bring payloads just to the bottom of the elevator, where they can ride the rest of the way up.

The idea reminds me of Robert Forward’s “rotovator,” which involves placing a long tether in orbit and making it rotate in the same sense and at the same rate as its orbital motion. Each tip of the tether traces a cycloid around the Earth: a trajectory that momentarily stops (relative to Earth’s surface) at the low point where it can pick up a payload, and swings back up to a high point where it flings the payloads forward much faster than the orbit velocity. It also has some similarities with cyclers, which are hypothetical objects in orbits that visit two (or more) celestial bodies at regular intervals without propulsive maneuvers. (Buzz Aldrin is a fan of these; he has an Earth-Mars cycler orbit named after him. That vehicle would alternately visit the Earth and Mars, with a 146-day transit time.)

Fundamentally, what all these concepts are trying to do is establish infrastructure in space – infrastructure that lets us offload some of the delta-v requirements from individual spacecraft, at the expense of an initial investment.

A more near-term such architecture would be an orbital propellant depot: a place where space vehicles could pause, after launch, and “top off” before they proceed onward to destinations beyond Earth orbit. Lots of technologists and policymakers have given thought to these depots, with many concepts nowadays revolving around the Falcon 9 and Falcon 9 Heavy launchers.

I’m a fan of these ideas. Any infrastructure that lets us explore space freely, without our launches being tied to landing requirements or our excursions on other worlds being limited by how we take off from the Earth, will only help our efforts to discover our place in the universe and establish humanity on other worlds. I think it’s high time our space program got back to thinking about the nuts and bolts of working in space and building the space-based vehicles that will take us to other planets and moons.

Movies, Space

“Europa Report”

16 March 2014 josephshoer Leave a comment

I just watched “Europa Report.” Finally; I’d been holding off because it gets categorized as horror and I didn’t want random slasher aliens invading my sci-fi suspense thrillers. Also I don’t like horror movies in general.

But I have to say that, first, the movie was a terrific portrayal of near-future space exploration; the filmmakers were clearly watching a lot of NASA TV and boning up on their science and engineering before they started. Many of the things that seemed hokey to me did so more because I have a lot of really specific knowledge than because they were blatantly wrong. (Ahahaha, Conamara Chaos isn’t going to have thin crackling ice ready to break through at any moment! Clearly, it must have re-frozen to a thickness sufficient to push the ice rafts up to a higher level than the surrounding terrain, which must be at least…oh, right, I’m watching a movie.) In fact, on the engineering side of things, a lot of the movie was very well-done.

Second, I was refreshed to see that the tension in the movie comes largely from the technical challenges of space exploration. About halfway through is a particularly intense scene revolving around oxygen depletion and the toxicity of hydrazine, which – while somewhat contrived in its specifics – ended up giving the plot a novel way to introduce one of those psychological horror situations that is really unique to the space environment. No aliens, pop-up scares, or spurting blood needed. In this way, the movie harkens back to a lot of Clarke-era hard sci-fi.

(Sadly, that sequence did illustrate one of “Europa Report’s” shortcomings, which was its relatively shallow focus on the characters themselves. We see allusions to the interpersonal issues, and allusions to the emotional impact of the scene I’m talking about on the rest of the characters, but it’s not really explored in detail. In some ways, the form of the movie as a series of documentary recordings may have forced that lack of depth. Fortunately, I found myself filling in some of the pieces on my own.)

Third and finally, when there are aliens on the scene causing the movie to become more suspense-thriller-like, the movie never devolves into straight-up horror. Instead, it focuses on the characters’ choices when faced with that awful situation. The movie makes very clear that the characters are motivated by a love of exploration, a desire to complete their mission, and a strong awareness of the significance their discoveries will have on the rest of humanity. Self-sacrifice becomes the theme of the film: the crew may have all met their ends on Europa (don’t worry, not a spoiler – this aspect of the plot is established in the first few minutes of the movie), but they know the service they are performing. And, in the universe of this movie, they are going to live forever. I found the overall message to be quite positive toward exploration.

I liked it.

Oh, by the way, there are totally space lobsters under the ice on Europa.

NASA, Space

Space fleets

12 February 2014 josephshoer Leave a comment

A couple days ago, an article on NASASpaceFlight described an architecture of vehicles Bigelow Aerospace allegedly presented to NASA. Bigelow is a company developing inflatable space habitats – they’ve launched a few technology demonstrators already, and an inflatable module is set to go up to the International Space Station in the near future. Apparently, they presented a series of modular, inflatable habitats along with a set of space-based utility “tug” vehicles designed to carry out various support functions.

I like this general idea – it fits in with my own vision for a successful space exploration architecture. Specifically, rather than a multipurpose vehicle that must shuttle up and down from Earth’s surface, I want to see a set of many vehicles highly specialized for space exploration purposes. Those vehicles should be native to the space environment – designed never to enter the Earth’s atmosphere. They might even be built in space in the first place.

It would be really terrific to see a company ready to provide that space exploration fleet.

Concepts, Space

Jove’s Moon Shot

9 February 2014 josephshoer Leave a comment

Here’s a bit of wild speculation for the weekend:

Suppose there is intelligent life in the globe-spanning ocean on Europa. Given how small our space exploration budget is, and our generally declining investments in R&D, how likely is it that the Europan life would discover us before we discover it?

An artist’s concept of Europa’s structure. (Britney Schmidt/DEAD Pixel VFX/University of Texas at Austin)

Any life or societies that evolve on Europa would do so underneath a shell of water ice. A human would no doubt find the environment claustrophobic, whether near the bottom of the ice shell or at extreme depths. Native Europans, though, would live comfortably with the perpetual presence of hydrostatic pressure. The creatures’ science would be familiar with the concepts of temperature and pressure. Some intrepid Europan theorists may even have extrapolated their equations to pressure = 0, but it’s likely that none of the creatures would have any firsthand experience with vacuum. The surface environment of the moon would therefore be totally alien and inhospitable; possibly, many of the creatures would have died in attempting to breach the ice before any succeed.

Would they even think to go up to the surface? I think so, as there is a strategic rationale. Without viscosity to slow them, and with about the same gravity as Earth’s moon pulling them down, a Europan army could move much more quickly over the surface of the moon than through the ocean. Europan kingdoms could launch surprise attacks if they were able to access the surface. Of course, the notion of doing this requires that the creatures realize that the ice over their heads has a surface. There may be ways to determine this from below, perhaps by watching for minute changes in lighting conditions, or even by direct observation of one of Europa’s surface cracks during its process of formation. Or maybe the Europans will just have to rely on explorers analogous to Earth’s Ferdinand Magellan.

Still, even with that strategic rationale, I think penetrating to the ice surface would be the Europan equivalent of the United States’ moon shot in the 1960s. That is, there would have to be a certain high level of technology, as well as a sufficiently well-organized political organization to support a successful attempt. The creatures of Europa would need to figure out how to support their high-pressure life requirements in the vacuum of space, not to mention figuring out how to tunnel or otherwise travel through anywhere from one to one hundred kilometers of ice. If the creatures aim for one of the cracks which may provide surface access from the ocean, then they would have only about a quarter of a Europan day (7/8 of an Earth day) to make the traversal before Jupiter’s tides close the crack again. Any way I look at it, I think that the creatures getting to the surface represents a tremendous achievement of technological prowess.

Once they get to the surface, the creatures would make a stunning array of discoveries. They may already know that their own world is spherical, but suddenly and immediately they would become aware – for the first time in their history – of Jupiter, the Sun, and the stars. In short order, they would discover the other large moons of Io, Ganymede, and Callisto. After spending some time making astronomical observations, they would see other Jovian moons, followed quickly by objects that orbit the Sun rather than Jupiter: Saturn, Mars, Earth, Venus, Uranus, comets. It would be an astonishing and groundbreaking time to be a Europan, as their worldview would experience revolution after revolution.

However, the downside of all this rapid discovery is that the Europan creatures’ science may lag behind the science of Earth. They would not have the long history of looking at the stars that we do. They might not have very good models for gravitational force. Until they get very good telescopes trained at the Sun, the very idea of fire or explosions might be foreign to them.

This is important for my main question, because without the concept of a gaseous explosion, the creatures would find it difficult to conceive and build rockets to begin a true space exploration program.

There is a way the creatures could start to explore their local system without developing rocket propulsion, though: it is conceivable to build large-scale catapults capable of accelerating objects to Europan escape velocity, which is only 2 km/s compared to the Earth’s 11 km/s. (“Only,” though that’s still very fast…Wolfram Alpha tells me that a reasonable comparison to the speed of 2 km/s is the X-15 rocket plane, though, which suggests to me that 1960s-equivalent Europans might have some hope to reach that speed technologically.) Surface-based accelerators would give the creatures the ability to explore the Jovian system.

Maybe a surface catapult plus a gravitational slingshot around Jupiter would allow the creatures to explore the wider Solar System. But I think that they need to develop some kind of rocket propulsion to have control over their efforts – or to return again. They also need to develop the sciences of orbital mechanics and Newtonian motion. These are disciplines that humans have been studying since the dawn of civilization. Our quantitative study of orbits and classical physics goes back to the 1500s.

I think the bottom line is this: if the Europan civilization has the same 7000 years of recorded history that human civilization does, and they reached the surface of their moon around the 1950s-1970s, even if they are more inherently curious and more willing to put forth exploration efforts than we are…they aren’t going to discover us first.

Unless we sit on our hands for a few hundred more years.

Science, Space

Let’s go to Europa already!

12 December 2013 josephshoer 1 Comment

I’ve been thinking I should write something about the recent discovery of geysers from Europa’s subsurface ocean, but Casey Dreier at the Planetary Society blog basically said everything I want to already.

Europa appears to have all the ingredients for life as we know it: liquid water, energy sources, organic molecules. Scientists have known these things since the Galileo mission to Jupiter. But we haven’t gone back to look for life under the ice – because designing and mounting a mission to do so would be a multi-year, expensive effort. It’s much simpler, and less expensive, to think about smaller missions to Mars, which could launch at a cadence of once every couple years. However, the scientific, societal, psychological, educational, inspirational, and public reward of discovering extraterrestrial life certainly would make a multibilliondollar Europa mission worthwhile.

What the new discovery gives us is easy access to Europa’s subsurface material. Perhaps we can sail a probe through these geyser plumes, testing for biological components. Perhaps we can trawl a few space squid while we’re at it. The easy access, while not up to the same level as Mars, certainly makes a Europa mission easier to think about than one that has to drill through a hundred kilometers of ice!

Science Fiction, Space, Wow

“Gravity”

14 October 2013 josephshoer 6 Comments

I’ve been a delinquent spacecraft engineer, and didn’t see “Gravity” until today.

In short: it was awesome. It’s a tremendous story about courage, fear, perseverance, the human spirit, our ability to solve the most insurmountable problems, and triumph in the face of adversity. It’s also visually, sonically, musically, and generally aesthetically breathtaking. The integration of the stunning visuals, physically accurate sound, camera movement through space and spacecraft, and music was extraordinarily well integrated into a complete artistic whole.

And, although the events depicted in the movie would not (or could not) play out exactly as shown, they are all plausible from a physics standpoint.

Everyone should go see it. And, yes, see it in 3D – because this is the first movie I have ever seen in which the 3D adds to the visuals and the drama.

Before I read any other physicists’ reviews, I’m going to go through some of the concepts and sequences in the movie, make a few points about the physics involved, and then explain why I am totally fine about it all.

Spoilers ho!

Continue reading “Gravity” →

Joseph Shoer