If you’ve read enough space blogs, forums, and usenet groups, you’ve probably heard of the one-way-to-stay Mars mission, but what most people don’t realize is that in 1961 and ’62 such an approach was also seriously suggested and investigatedfor early lunar missions as well. While this may sound like a historical curiosity, I think the idea may have more merit today than it did when it was originally proposed.
One of the big challenges in lunar exploration, settlement, and economic development is our profound ignorance about our closest celestial neighbor. We have no idea if economically interesting concentrations of important metals or elements exist, or if so, where. We have ideas for dust mitigation and ISRU techniques, but really have no idea for sure if they will work. More importantly, we have no idea how many iterations it’s going to take to make it work. We have no idea if lunar gravity is high enough to avoid the effects of microgravity on the human body. There have been lots of lunar manufacturing ideas floated, from fusing regolith with microwaves based on nanophase iron embedded in the regolith to bulldozers, pneumatic excavators etc. The problem is that it’s impossible to simulate enough of the lunar environment here on earth to really know that there aren’t subtle but important effects we’re ignoring. Really for most of this stuff, the only way to find out is to go there and try it. And fail. And figure out why you failed, and try again. The whole idea that we can make complex aerospace hardware work the first time in an environment we do not fully understand and can’t adequately replicate here on earth is hubris. We might get lucky, but more likely than not, it’s going to take work to sort a lot of this out.
There is a reason why the Technology Readiness Level scale exists. It doesn’t matter how pretty your calculations are, because in reality you’ve made at least one or two incorrect assumptions. It doesn’t matter how good your bench test went, because when you test it in the right environment in a flight-weight integrated system there are environmental effects and subsystem interactions you couldn’t adequately test on the ground. That doesn’t mean you can’t eventually make the system work–it’s just that the only way to know a technology is ready for primetime is if it has been adequately tested in the actual environment. It’s only then that you’ll have figured out all the weird and quirky second-order effects that can’t be ignored. It’s only then that you can know that a system is actually dependable. That may sound harsh and unfair, but it’s probably sugar-coating the case.
What would really be useful is to find a way to break out of this knowledge-poor environment we’re in, and lower the cost drastically of getting lunar technology through the try-fail-fix cycle. The earlier in the design process you can get correct information, the better the decisions you can make. One-way lunar missions are an interesting way of achieving that goal of early information.
When you think about it, you actually only need a single piece of new transportation hardware for a one-way lunar mission–the lander itself. You don’t need a crew capsule return capsule capable of reentry from lunar trajectories or capable of autonomous operations in lunar orbit for months at a time. You don’t need an ascent stage that has to be hyper-weight-optimized because it drives the mass of the whole system. You don’t even need an HLV or an Earth Departure Stage–a stock Atlas V 551 or Delta-IVH would be more than able to softland two people on the moon in a single launch. You don’t even need depots, long-duration cryo storage (though it would help), tugs, RLVs or anything else. In fact, you probably don’t even need a “man-rated” booster, a crew capsule, or a launch escape system unless they’re already available (the odds of dieing on a mission like this are substantially higher than the odds of an EELV failing during the 80% or so of the mission that the lander couldn’t do an abort-to-orbit).
You’d probably want to prelaunch some supplies and extra living quarters, and be ready to launch regular supply missions. Call it three flights to get setup, and the fourth carries the crew. You might be talking about $1-2B total to develop the lander and get the crew and their supplies there, and another $500m-2B per year to support them (assuming current EELV prices–it’d be cheaper if Falcon 9 pans out, or if you can use foreign boosters). I’m probably being overoptimistic here, but we’re in all likelihood talking a very tiny fraction of the cost of any of the typical lunar architectures, and you could have the project going within only a few years. More importantly, the project is cheap enough that you could start getting your initial information from the lunar surface while simultaneously preparing the systems needed for a more robust round-trip transportation system (depots, transfer vehicles, crew return vehicles, reusable landers, etc). In comparison, the Constellation PoR would cost about $200B to get to the first boots on the ground, and cost about another $1-2B per set of boots thereafter. For the first few years, you’d probably be talking about mostly short sorties, so the $/boot-day factor would probably be ridiculously high for a long time.
The risk is a lot higher of course, since you can’t easily get back to earth in a hurry, but the situation isn’t anywhere near as bad as a one-way Mars mission. First off, even without any of the other systems developed beyond the lander, you can actually get the crew back from the Moon. It would be a complex, inefficient, sub-optimal, and more risky approach, but you could do it. You could just send enough cargo landers with propellant to refuel a lander to take them back to lunar orbit, and from there do a TEI burn. Instead of direct reentry, you could do an aerobraking maneuver designed to minimize the number of passes through the van Allen belts. You would need access to some sort of crew return vehicle like Soyuz to get you down from orbit, but you could do all the hard work of coming back. So the crew isn’t really stranded with no hope of return until a bunch of other stuff gets developed. Also, if something critical breaks down, it’s realistic that you could launch a resupply mission fast enough that the crew could just sit-tight in their spacesuits for a few days.
Is something like this still beyond the pale politically? I’m not sure. You’d definitely be accepting risks much higher than CxP (probably in the 25% range), but many of the worst risks from the Mars one-way option would be gone, and a lot of them are front-loaded. If you can make it through the first month or so, it’s likely you can keep them resupplied with stuff frequently enough to prevent catastrophe. It would definitely be a more nitty-gritty and therefore interesting mission.
Anyhow, I know I’m leaving out a lot of details and thoughts, but I wanted to throw the idea out there for discussion. I’m not suggesting that this should be done in lieu of getting a real lunar transportation system done right (ie one with RLVs, depots in LEO and L1 or L2, private crew transportation to orbit, reusable transfer stages and landers, etc) I’m just suggesting that this is a way to get information quickly, and quickly figure out what ISRU options are really viable, and therefore how difficult it would really be to start doing medium-scale settlement of the Moon.