…how about half an elevator?

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.

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“Europa Report”

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.

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Ignition!

The National Ignition Facility – a humongoid stack of lasers all aimed at a tiny target to try and compress it until it fuses – announced today that they had “positive fuel gains,” meaning that fusion happened and that more energy came out than went in.

Clearly, this is big news for power generation on Earth.

But, with this breakthrough, I want to do something slightly different.

The ignition rocket!

The ignition rocket!

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Space fleets

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.

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Jove’s Moon Shot

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.

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Despite tactical errors, Bill Nye is right

Tuesday night, Bill Nye (the Science Guy) had a webcast debate with Ken Ham, founder of the Creation Museum. In many respects, this was a silly idea. Nye wasn’t going to change any minds, and I think he fell into the traps creationists try to set: distracting him into side issues, for example, or redefining the terms of the debate. Moreover, the Creation Museum benefited monetarily from the event.

I admire Nye for being willing to make the attempt, but in the end, I think the event was a wasted opportunity. The whole reason for the debate was not to contest the relative merits of creationism versus science. Rather, the spark for the event was Nye’s contention that teaching creationism in schools is dangerous. And I agree with him – for two fundamental reasons that Ham illustrated beautifully throughout the debate, but I don’t think Nye ever articulated. Continue reading

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Maps page

I’ve decided that, since I’ve been more serious about the map-drawing lately, that I would take my generic photography/art web page and focus it specifically on my maps as a little online showcase. This qualifies as an update to my web presence, so here I go, writing about it on the blog.

It’s here, on my main site: http://www.josephshoer.com/personal/images.html

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