The Christopher Nolan movie Interstellar has been released on home video today. Some of you may remember my review back when it came out, and I am very energized to have a copy of my own in my hands.
Monthly Archives: March 2015
Demonstrating planetary defense techniques.
If something similar to ARM Option B is selected, NASA is interested in using it to demonstrate the “gravity tractor” method for deflecting the parent asteroid. Learning how to deflect potentially hazardous asteroids is probably one of the more worthwhile things NASA could be spending money on right now, and providing a way of getting real hands-on experience applying those techniques would be very useful.
This is a big one to me, as it is aligns with one of the major rationale for the existence of the Outbound project. Even as a kid, I generally understood that an asteroid or comet impacting the Earth could ruin your whole day. Or your civilization. Or species. Given that seems that having the whole of humanity living on just Earth was never a good long-term plan. I’ve read my share of science-fiction, and books like Rendezvous with Rama and Lucifer’s Hammer drove the point home in good literary fashion, but real-life events in 1994 made it very clear to me that we are living on borrowed time. Comet Shoemaker-Levy 9 collided with Jupiter that July, with some spectacular results.
That comet, fragmented as it was, left multiple impact marks in the atmosphere of Jupiter, including one that was twice the diameter of the Earth. That is impressive, and frankly intimidating, to contemplate. We are fortunate in the extreme that we have Jupiter and Saturn acting as cosmic shop-vacs, clearing much of the debris of the solar system before it reaches the inner orbits such as ours. However, from impact evidence on Earth, not every object is pulled in by our gas giants. If there are rocks out there lurking around that can blot out the Earth so effectively, I can’t imagine why we’d hesitate in getting off of our home rock and leaving more than one target for the cosmos to aim at.
As noted a few days ago here and elsewhere, ARM Option B is now the mission in play, and if it does anything at all to further our ability to get off-planet or divert inbound species-killer object, that’s outstanding.
NASA has decided to go with the Option B mission for the Asteroid Retrieval Mission (ARM).
Option B, for those who may not have been following the story, involves a robotic retrieval spacecraft that will grab a boulder from the surface of an asteroid, transport it back to the Moon, at which point a crewed mission would rendezvous with the boulder for study.
I have mixed feelings on this decision. On one hand, the idea of sending an Orion all the way out to meet the asteroid would have been an excellent test of true deep-space operations, so to go only as far as the Moon seems almost like wimping out. If we want to go to Mars, or even more importantly set up asteroid harvesting facilities, we’ll have to go that far and be out there for long enough to prove we can sustain such an effort.
On the other hand, it has been discussed that a logical melding of the robotic and crewed space missions would be useful for capitalizing on the advantages of both. Option B certainly seems to do just that. As such, I do see some optimism to be had. What has my fingers crossed is the hope that this plan is endorsed by the current president, will be so by the next, and that Congress supports it as well. If we are going to spend the time and money out of public funds to operate the manned space flight program, we all know we need a mission. It looks like we just got one.
Demonstrating large-scale solar electric propulsion (SEP) systems.
This is one of NASA’s main interests in the ARM mission — in the land of expensive launch vehicles, very high specific impulse propulsion, like you can get with SEPs, can make many missions a lot more affordable. Even with low-cost Earth-to-orbit transportation, SEPs probably make sense for a wide range of missions. Demonstrating the ability to use large-scale SEPs for tugging huge objects in heliocentric space, performing precision injection maneuvers, etc., might be very useful.
The goal of high-isp interplanetary transit is indeed what I would consider an enabling technology for colonizing our solar system. Without it, there just isn’t any way to get the mass of hardware and logistical items where you need them to survive in extraterrestrial locations, at least in near-term scouting missions. When ISRU can be reliably counted on at each location we colonize, that picture changes at least theoretically, for that local colony. However, we end up in the same situation again as we hop from location to location in our system, and we must be able to take our needs with us to each new place.
Now for crewed missions in general, we need high-isp capability to keep trip times low, and avoid the years-long travels that we have long taken as a given. SEP propulsion systems don’t address this directly, being ill-suited for long-term use in transporting crews and all the large systems they require. Developing SEP to a higher degree of sophistication does bolster the mission design for unmanned cargo systems, of course, and that would reduce the burden on crewed missions somewhat by offloading some of the logistical burden. Essentially, the SEP systems for colonization efforts would be relatively slow-moving uncrewed cargo ships sent ahead for later rendezvous with much faster crew carrier spacecraft. For the carriers, other bootstrapping rationales would be needed to co-develop technology like VASIRM, where the power density is much higher than that of solar-powered ion engines.
One of the tenets of the Outbound project is that Humanity already lives and works in space. We are surrounded by the environment that is keyed to our biology and allows us to live with at least a fighting chance for survival, but it is still only one environment, on one body in outer space. There are many more environments out there, and many more bodies in space. Through technology, we have already dipped our toes in, as Sagan said, and we know that adaptation is possible. If we survive ourselves, or terrestrial natural events, or even the vagaries of space threats that exist, we can get ourselves spread about the cosmos. Time, resources, and human industry are the only real design factors, and we have those.
Of course, the above is a philosophical argument. Not logically untrue at all, but vague. As an engineer, however, you can look at our species’ life in the universe as a systems engineering problem. Essentially, we are an imperfectly closed-loop system that is performance-limited by its nominally-closed nature. Said less-esoterically – Humans only live on Earth, and while it takes care of the bulk of our needs, staying home limits our potential. The definitions of our potential can be represented in many ways, of course. Many systems would have to come together to break out of our closed-loop construct, and those systems must be defined before our potentials can even be really hinted at.
With that in mind, I think it is high time to treat human Space Exploration and Exploitation (SE2) as a System of Systems puzzle. I am now looking at the high-level view of the system, and will progressively break it down into more and more subsystems, until there is a real framework to build upon to create a viable and understandable space-faring society. The work will not be easy, I have no illusions about that, and I will need to form a team of co-researchers and supporters to pull together what I expect will be a huge body of work. I think that’s all worth it, though. Let me elevate that: It is necessary.
Providing a good way of testing out a man-tended space habitat.
One of the ideas NASA is looking at incorporating into ARM is attaching a prototype deep-space habitat. This would allow visits of up to 60-day duration by crews of up to four. While there are other ways you could test something like this (such as Lagrangian point L1/L2 gateways), testing it in an operational environment would be useful, as would demonstrating the ability to do long-term habitation in close proximity to an asteroid.
Now, there are good reasons for testing habitations at Lagrange points, I grant you. For one thing, being able to establish the means of setting up waystations along a path or set of paths to service a greater exploration and exploitation of our solar system is invaluable. Having a predictable nexus for inbound/outbound spacecraft is better for a the kinds of manufacturing, materials processing, and even passenger-handling systems that have proven so effective for the past couple of centuries. And such waypoints’ efficiencies will be highly optimized by the systems themselves determining where they reside in space, not merely making do with what exists out in the heavens.
However, Goff is absolutely correct that testing habitat technologies would be well-served by setting up shop on asteroids first, for a couple of reasons:
Firstly, we don’t want to be endlessly floating in space watching as we glide past or around the objects we really want to set foot upon. Landing a habitat on an asteroid satisfies at least that human urge to explore. But, more than that, it allows a much smaller effort there to be extrapolated to more demanding landing and living missions to places like Mars, and we can learn a lot more with less fuss. A big driver in Mars landings is that we have a much more difficult time achieving safe entry and landing speeds from the planetary approach, as we lose most of the atmospheric braking advantage we enjoy landing on Earth. To fix that, we generally either have enormous parachute size (and mass) to catch what little air there is on Mars, or we carry even more enormous amounts of mass in the form of landing propellant. Airbag landings, while shown feasible for our robotic missions, are not reasonably safe enough or predictable enough to land human systems, up to and including the humans themselves.
In contrast, recent missions such as the Dawn orbiter mission to the dwarf planet Ceres and the Rosetta mission to Comet 67P show that we can indeed orbit exceedingly small objects in space where asteroids reside, and can even land on them. The propellant mass to perform those landings is quite small.
Secondly, by setting up crew-tended shop on asteroids, you can tackle more than one thing at a time. You can credibly test the habitat while the crew actually performs the needed inaugural experimentation needed to assay an asteroid. You end up learning more than one thing at a time that way.
So, until issues with landing downmass and technology for more demanding crewed missions are worked out, the habitats-on-asteroids mission profile allows for early-term validation of off-world living while concurrently pursuing industrial research.