Marc Millis, former head of NASA’s Breakthrough Propulsion Physics Project, has designed ion thrusters, electronics for rocket monitoring, cryogenic propellant equipment, and even a cockpit display to guide free-fall aircraft flights. His recent retirement after nearly 30 years with NASA has freed him to devote full time to his Tau Zero Foundation, “using the dream of reaching other worlds as both a long-range goal and a catalyst for near-term progress.”
Millis and h+ Editor-in-Chief RU Sirius met during separate TEDxBrussels 2009 presentations — Millis’ talk dealt with finding and reaching habitable worlds while RU, naturally, talked about transhumanism. Here’s a video of Millis’ TEDx presentation:
Millis’ book, Frontiers of Propulsion Science, is a compendium on where things are with the science of space drives, warp drives, gravity control, and faster-than-light travel. It’s really a graduate-level text for someone with a substantial math and physics background. He says that one of his hopes now that he’s retired from NASA is to make the time to write a public companion version of the book with more artwork and simpler language to help convey the concepts.
Known for his level-headed, peer-reviewed thinking on such complex topics as hyperspace, quantum tunneling, and space colonization, Millis took time out to speak with h+ on a variety of topics including Alpha Centari, space and time travel paradoxes, space sails, the future of NASA’s space programs, Mars, space elevators, scramjets, and orbiting hotels.
h+: During your TEDx presentation, you mentioned that “we’re 2-4 centuries away from having the technology to launch a mission to Alpha Centari” using conventional physics.
MM: That estimate is based not so much on technology prowess, but on available energy. When you look at the pace of human energy production and consumption and how much of that energy is devoted to spaceflight — and you compare it to what it would take to undertake an interstellar mission — the calculations suggest that it will take 2-4 centuries until we can pull off a mission like that.
Those estimates could go one way or the other if any assumptions are varied. For example, the way I did the comparison of the energy devoted to spaceflight is that I took the space shuttle program and compared how much energy was used by the rocketry compared to the amount of energy being used by the entire Earth. However, if people decide that it’s important to put 10 times that amount of energy into the space program, then the estimate would show a decrease in the time until we’re able to launch a mission to Alpha Centari. My calculations were a way of putting bounds on the problem and defining where those bounds came from.
Relative to the technology, as a culture we’re so used to thinking how we can get “there” the quickest, or what’s the best single approach. When it comes to interstellar flight and learning to live beyond Earth, this thinking sidetracks us because we’re so far from fruition in our understanding of interstellar space options, that there’s no way for us to pick “the” one way. Instead, there are many different options and unknowns. We stand to gain a lot more from the attempt to understand them – chipping away at them rather than not doing anything at all. By researching the spectrum of possibilities, we’re likely to be better off in the near term.
I really want to change the paradigm of how we look at interstellar flight. It’s not just a matter of trying to get there quickly or to find “the best approach,” rather it’s finding the smartest things we can do today that set the stage for a more productive future. At the Tau Zero Foundation, we cover simple solar sails to the seemingly impossible faster-than-light. Rather than trying to identify the best approach, we’re trying to identify the next steps that students can work on to chip away at where their own personal interests lie.
h+: Doesn’t the possibility of faster-than-light interstellar space travel involve time travel?
MM: Whenever you broach the faster-than-light topic, it inherently includes the time travel issues. I would love to figure out how to do faster-than-light without the time-travel paradoxes. For me, the hardest chapter in my book is the one that deals with quantum entanglement and faster-than-light implications such as time travel. It finally occurred to me what the real problem is — in our normal language, the idea of things that happen simultaneously is difficult to convey. If something happens over at point A, it normally takes a while before the surrounding points even know about it. To have a language of time that also includes both distance and clear distinctions between before and after… I mean the language doesn’t exist to get into those details. So when you’re looking at an experiment where light is split and goes through more than one path, it seems paradoxical that things somehow appear to be connected instantaneously. How can we turn that into sending signals across time? It’s really confusing, but the confusion is largely due to our language in addressing these situations. The discipline is still so young and unfamiliar that it’s hard to even explain what’s going on.
I would love to figure out how to do faster-than-light without the time-travel paradoxes.
With that said, I will try to explain it. And I’ll try to keep it in terms of the actual physical effects because I know I get frustrated when I hear theorists talk about what the implications of these things are and say, “Where did he get those ideas from? Where’s it anchored in the physical measurements?” Well, the physical measurements derive from taking light and splitting it so that it’s going across more than one path. The original beam is going across more than one path, and you’re going to recombine them and compare them later on. And in each of those separate paths, you do funky things. You either change their length, you send it through a mirror so that one path gets a lot longer, or you modify something. And the odd part is that somehow apparently the change you made in one path affects the other path before they recombine. And you can tell the difference when they recombine. So, what’s going on there? Are each of those fragments of light somehow still connected even after they’re separated? Or is there some way that maybe there are other relations going on that have to make a full-closed loop before the one single way that reality will precipitate itself?
When you do the mathematics for a particle or light moving from one place to another, and you do it in the quantum way (waves rather than particles), you create a situation where you notice the math says there’s a part moving forward in time, and there’s a part moving backward in time. When the mathematics of both of these coalesce — in other words, they’re both saying the same thing — well, that’s what happens in nature. Are phenomena connected in some way where the only things that are allowed to happen are the ones where there is a balance in the flow of time, and other things are just not allowed? So the light might not necessarily be connected from one beam to the other in a direct sense, but in how each of them is related though a flow of time and events in that there are a multitude of things that could happen, but the only things that balance out are the ones that give the appearance that they are connected in time. What this confusing stuff boils down to is that we do not know yet whether quantum entanglement is definitely showing instantaneous connections or if there’s something else going on. The faster-than-light implications of that for quantum tunneling are still uncertain. [Editor’s note: quantum tunneling is the weird quantum process by which a quantum particle passes through a potential barrier that a classical particle can’t traverse.] We’re barely beginning to figure out how to ask the right questions to decide what the most revealing and least confusing experiments are.
h+: Now that the Constellation program has been cancelled, will we ever get to interstellar missions?
MM: It comes as no surprise to me that the Constellation program was cancelled because there just was never any budget for it. It seemed like NASA was being asked to do more than they were paid to do, and like the Black Knight in Monty Python’s Holy Grail not having the right amount of arms and legs to do the job, they were still diligently trying. What’s going on here? Perhaps it’s just the normal progression of a maturing organization. Do you remember all the Collier magazine images of man conquering space that von Braun put together? [Editor’s note: this was a series of six articles on rocketry and space travel illustrated by Chesley Bonestell and published in Collier’s magazine in 1952-1954.] It’s almost like the articles cast this image of what space flight is supposed to be into our collective social psyche. Since then, we’ve never really had a newer vision to supplant it.
Eventually we’re going reach a point where we’ve got to rethink this image of space travel. Ever since the cuts to Apollo back during the Nixon administration, the budgets for NASA have remained at about the same level. There have been fluctuations, but it appears that our nation’s legislators and administrators have decided that this is what the space program is worth — and it’s remained relatively the same. It seems like the budget has been stuck in the mode of “we’ve got to finish those von Braun images and maybe next year we’ll get the budget we need.” Even when President Bush said we’re going to go back to space, and yes, I’m going to give you a budget… well, he never did.
h+: Do you see NASA becoming more like DARPA?
MM: The talk I’ve heard is that NASA is trying to get back to more of a research mode. How will they handle it? I don’t know. DARPA has a ton of money. And even the small amount devoted to space is substantial. I don’t have the numbers in front of me, but it’s by no means a trivial amount. To avoid getting stuck in the same mindset, the people who manage the budget serve (I think) six year terms. But many of the advances that will eventually make it possible to explore and take advantage of things in the solar system and beyond are not short-term prospects.
h+: President Bush did set a goal to go to Mars at one point. What’s the most realistic way to get to Mars?
MM: There’s any number of ways of doing it depending upon what you want to do when you get there — perhaps set up some sort of permanent habitat. I see this as the long-term goal: living somewhere else other than Earth to help assure humanity’s survival.
The idea of practicing by first living on the Moon sounds like a smart way to go. The Moon’s a lot closer — 3 days away, roughly — and there’s an existing infrastructure of launch vehicles to move things from here to there. You can experiment with humans living away from Earth without it being quite as dangerous as Mars. We could spend a few years doing that before taking the big step to Mars. So in that case, the Moon makes sense.
But if you’re on like an Apollo-like push — the cliché NASA uses is “flags and footprints” — then you don’t need the Moon. The propulsion options are numerous depending upon how much you want to take with you. This is a completely different direction than using the Moon as a stepping stone. You can go to Mars with standard chemical propulsion, but the catch is that you need enormous amounts of propellant and it will take you a fairly long time to get there. You could do it with nuclear-electric propulsion, where you need a nuclear power source that provides electricity to drive ion thrusters. That requires a lot less propellant. In that case, when you get there, you still have a substantial power source that you can use for things that you need to do there. And then there’s either nuclear-thermal propulsion or variations where the nuclear reactor is part of the actual rocket engine. Based on very crude estimates — and the details in the studies vary — this might be the fastest, although you still need a power supply to be able to do anything when you get there.
h+: What about a space elevator on either Mars or the Earth as a means of getting to low orbit?
MM: When it comes to space elevators, I have no idea whether it would be feasible on Mars — I’ve never seen the numbers worked out. A space elevator from Earth could work in principle, but the make-or-break issue is having the tether (the actual line) strong enough and not too heavy. I think this is beyond materials that can be foreseen today, but that are still possible. Space elevators to me are on the edge of the unknown, and chipping away at them will provide some good learning experiences.
h+: “Scramjets” are another technology mentioned as a possible transport.
MM: Sometimes they’re called RBCC or Rocket-Based Combined Cycle where you use jets or scramjets or combinations of vehicles to get to higher altitudes. These are good options to consider in the suite of possibilities of getting up there. I’m not sure which of them would be the best approach, but they certainly should be considered as a way to get into orbit. It’s a matter of engineering optimization rather than feasibility. In principle, they are fairly straightforward and you can carry quite a bit if you only have to go as far as lower Earth orbit. And now you have space entrepreneurs — the ones that are going to giving joy rides — who are not quite getting into Earth orbit just yet. This is much more difficult than just getting into space and coming back down. It’s interesting that the technologies they’re using are different than the ones that have been used for NASA programs. For what they’re doing, the market they’re going after, what they’re doing makes sense. The more players trying to make progress, the more likely that one of them is going to succeed.
h+: What sort of breakthroughs will it take for the average person to be able to take a multi-day holiday in space for about the same price as going to Europe?
MM: Well, the way the dollars-to-euros conversion is going (laughs)… you currently have SpaceShipTwo and there is experimentation with orbiting platforms to provide the technologies for creating orbiting hotels. $200K is the current price for a SpaceShipTwo ride, but that will come down over time. But safety is a major concern. With Apollo, we were lucky for so long and had so many engineering successes, that it’s become a hard act to follow. I almost wonder sociologically and historically that it might have been better to have more accidents along the way to show that danger is a part of it. Part of the allure in trying to live beyond Earth — which I think we’ll have to do to assure humanity’s survival — is that it’s worth trying to take some of those risks.
Conceivably within our lifetimes, orbiting hotels are a possibility. Ah, but here’s the rub. You’ve heard of space sickness, right? If you’re planning an overnighter or a weekend in space for that zero-G sex experience with your significant other, you might want to stay a little bit longer. During your first two days up there, you’re going to have bad headaches, back pains, swelling, and nausea. You’ll want to be able to at least adapt and then enjoy yourself. Book more than two days! It’s definitely harder than jet lag, but adaptable.