by guest blogger Ken
Dan Lester is back, and with a vengeance. Mr. Lester works at UT Austin and has a strong interest in IR astronomy. He really wants an instrument in free-space (SAFIR), and is convinced that there are few astronomical applications that are better served by being on the Moon than in Free Space. Part of the issue is that it has been often proposed that IR telescopes be placed in the everdark craters at the Lunar poles, providing free cryogenic temperatures to the instruments. So there are competing architectures at play.
Dan Lester and Giulio Varsi have a compelling article over at The Space Review entitled “Destinations for exploration: more than just rocks?”, which calls for a re-examination of where we want to conduct our astronomical sciences. He makes a lot of good points, most of which I agree with, though as usual I don’t entirely agree with his conclusions, though in this case it is because I don’t think the authors take the argument far enough.
The authors open with the entirely reasonable question of whether the architecture that is being developed to implement the VSE is going to enable the capabilities to build, maintain and oversee facilities in free space as well? Both Jon and I are clearly both in favor of such a thing, and even the CBO Report called orbital construction something that NASA is just pushing into the future with the ESAS architecture. Or as I noted in the referenced post:
The report also makes the very salient point that for future NASA MARS missions the mass in LEO requirements have ranged from 470-1500mt. So once NASA is done with the Moon they STILL have to face the task of on-orbit assembly to meet their “next” objective (which the report also notes was not a requirement set in the VSE – these guys really did try to lay out all the facts and be impartial). All NASA’s doing with ESAS is pushing the learning curve farther into the future. Penny wise, pound foolish is an old folk wisdom that comes to mind.
Or as the authors note in the article:
On the one hand, NASA plans to have us travel vast distances to Mars while, on the other hand, it seems willing to abandon the very in-space construction and maintenance capabilities [learned from ISS and Hubble (and I would note some shuttle flights)] that may be necessary precursors to such long voyages.
They decry the lithocentrism of most space exploration and note that the vacuum of free space is the perfect reflection of the new Information Age. Wait, maybe I said that wrong. They think that operating outside of gravity wells reflects the free flow of electrons around the world in the Information Age. Or something like that. They question the marketability and feasibility of ISRU, though they do note that it would affect in-space operations, which NASA is abandoning, so they’re losing their justifications for going to the Moon to do ISRU in the first place. Good point.
I disagree, though, with their contention that most of the science objectives can be achieved robotically. A lot of folks smarter than me also think that humans have to go out with the robots to achieve maximum benefit from each. The authors do note that the Earth-Moon Lagrange points are connected to the Sun-Earth Lagrange points by low-energy trajectories, meaning that instruments like the JWST could be ‘kicked’ back to a facility at an EML point for servicing,a la Hubble, making it an enabling job site. I’m 100% in agreement, and have said the same thing many times, such as in my “Why Mars Again?” post where I noted:
From EML-1 we have an on-ramp to the Interplantary Superhighways which connect all of the lagrange points of the Solar system. We can have platforms out at the Sun-Jupiter L-2 point that periodically return to EML-1 for servicing and upgrade. We can have Asteroid Belt watchers at Sun-Mars L-1 and L-2 showing us the lay of the land there. We can have a communications platform at the Sun-Venus L-4 or L-5 point to provide communications around the Sun to Mars when its occulted. We can have Sun watchers at the Sun-Mercury L-2 point (okay, those might not be coming back). The point is that we can have a robust program of monitoring our near-space environment for threats, that can be upgraded as we learn more, and in a relatively simple and low-fuel-cost way.
The authors note a recent article in the Society of Logistical Engineers journal Logistics Spectrum. I think they are talking about this article here. (alternate site). It’s by some familiar names, but does make a number of very good points, such as:
-the Moon is 20 times further than any logistics support of a remote base on Earth
-Over 70% of the energy is getting over the first 200 miles from Earth
-They see 5 emerging enabling technologies:
*autonomous rendezvous & docking
*new autonomous payload transfer system
*new s/c2s/c cryogenic propellant tank transfer system
*autonomous propellant tank tapping system
*autonomous lunar payload offload system
-they propose staging at MEO and EML1. The system they suggest will initially transfer 800kg to the Lunar surface directly, 4x that if refueled at EML1, and 10x that if refueled in MEO and EML1.
-the development cost of a significant new launch capability represents at least 100 launches of existing EELVs and many years of Lunar transport operations
-they then go on to talk about PPPs and that sort of thing.
It’s an interesting article, and a nice find. That an article on Lunar Logistics would appear in a trade journal does kind of support the notion that the giggle factor is starting to go away a bit regarding private space efforts. The amount of cost associated with establishing the depot chain is one of the key drivers in getting ISRU established early.
Which brings us to the NRC report on “The Scientific Context for Exploration of the Moon”. I had some commentary on the draft version of the NRC report last year, and the final version fleshes it out pretty thoroughly. Notably, Daniel Lester is one of the committee members who prepared the report, and his influence can be found in chapter six – Observations and Science Potentially Enabled by the VSE. The idea of astronomy from the Moon is an old one, in part because of the obvious differences from the traditional terrestrial scopes: lack of atmosphere, less seismic activity, extreme cold/sensitivity during night viewing. Physics Today had a pro/con debate last year on Build astronomical observatories on the Moon? between Mr. Lester and Paul Lowman Jr at Goddard. Dr. Lowman is one of the lecturers at the NASA Academy, and I still have his handouts somewhere in a back corner of the Lunar Library. The debate raises a lot of really good points, and I think Dr. Lowman makes some good points about the laser reflectometers left by the Apollo astronauts are still returning readable signals to the McDonald Observatory (with which Dr. Lester is associated in the NRC report), calling into question the severity of the levitating dust issue. But the whole question of astronomy is really just a side argument in the much larger context of science from the moon versus science from free space.
My personal feelings are that we know how to build on rock. We’ve done a lot of it here on Earth, and pretty much everything we’ve learned to do here will be even better on the Moon. The wild cards are free space instruments. The Hubble isn’t an interferometer. Dr. Lester admits in the Physics Today artice that “Design studies of formation flying…make astronomers optimistic that precision fringe tracking for such large-baseline free-space interferometry is achievable.” Okay, but we do know now how to build on rock, and do interferometry on rock. Not that we shouldn’t develop the capability for more sophisticated free-space observations, but my conservative side says let’s start with what we know, and build going forward. I will note the efforts of ESA’s Cluster suite of instruments, which is building lessons-learned in formation flying. A good start, but we’re still pretty darn close to the starting line in that regard.
My preference is for things like a slow sky survey from each of the Lunar poles, radio scopes on the far side, and maybe some others at different locations. For free-space I’d like to see more small-body searching scopes, first pointing sunward, and then outward. This is part of the reason that I differ with Dr. Lester. My interests are local both temporally and spatially. I have much more interest in the small bodies of the Solar system than in things like galaxies 14Bn light years away in time and space. Dr. Lester is interested in the cosmological stuff and fundamental research in that field. This skews our perceptions of what sorts of instrumentation are necessary/likely/possible. Dr. Lester sees scopes at SEL-2 looking into the depths of the Universe. I see scopes at EML1, SEL1, SEL2, SVL4, SVL5, SML2, SML3, SML4, SML5, SJL1, SJL2, and so on looking at the small bodies and characterizing them, watching the Oort Cloud and Kuiper Belt for disturbances and incomings.
Stuff that is relevant now for the kinds of things humans want to do in the near future. Fundamental research is important. Let me repeat that so that everyone understands that I understand. Fundamental research is important. We should never completely stop doing it. Nevertheless there are a variety of compelling priorities and we have to be careful how we allocate resources to achieve the greatest number of goals. I think that Solar system studies are more relevant to the implementation of things like the VSE, and should therefore have priority over instrumentation not dedicated to Solar system studies. I also want free-space instruments, just of a different sort, spread over a larger number of alithic destinations. That’s what I meant when I said I didn’t think the authors took their argument far enough. Because with the right plan of attack we can all get most of what we want.
They’re spot on about EML1, a location that more and more folks are realizing is an absolutely phenomenal phenomenon, and I maintain that we are truly blessed to have an on-ramp to the Interplanetary Superhighways (IPS) so close to home. No other Solar planet can make that claim by anywhere close to what we have. I’ve said before that if there was one thing that could sway me (an atheist) towards some kind of intelligent design, it would be the closeness of our Moon (essentially a double planet system, some maintain) and the gravitational warps that give rise to the saddleback of EML1.
In the first stages of free-space astronomical instrument architecture development, you would want to use EML1 to give the instruments a last go-over before deploying them onto the IPS to their respective stations:
Sun-watchers at SEL1 (I think the most important suite of instrumentation)
Deep-space watchers at SEL2
Relay stations at the Venus Equilaterals (SVL4 & 5)
Forwarding of asteroid belt watch instrumentation to the SML1 Marsport (for forward deployment to SML2, 3, 4 & 5)
Kuiper Belt and Oort Cloud watchers at SJL2 and SSL2
Sun-watcher at SMercL2
and so forth. A comprehensive suite of instruments that addresses everyone’s interests.
What will happen is that as more and more instruments deploy, a regular stream of returning instruments will be coming in for servicing, upgrade & refueling. So you’re developing an economy of technical services for a really robust program of data collection. My goal is to do it commercially, while providing both security and scientific benefits.
I am happy to see more constituencies looking at the EML1 option. The fact that it gives 24/7 access to the entire surface of the Moon for about the same dV (about 2.52 km/s) is of partiular interest to me. We can do sorties to anywhere we want to go from EML1 once we get a fuel depot established. Which plays into the whole development of ISRU as a priority thing so that we can start shipping LOX at least from the Moon.
I’m currently reading through “The Modern Moon” by Charles Woods, and his comprehensive overview of the face of the Moon identifies a number of compelling destinations for sorties. Reading this book, and the NRC report on the science rationales for the Moon, really make clear that there is a lot of really solid science to do right here in our backyard. Science that also feeds into my commercial goals for cislunar space, and science that helps answer planetary security questions. I can’t believe we’re letting ourselves wait so long to get back there.