Sunday, May 30, 2010

NASA FTDP, find out what it means to me

In 18 months time it is almost a law of nature that computer power will double. The same (with a smaller number of months) is true for DNA sequencing, and many other technologies follow exponential development curves. Why?

To many of us it seems like magic, but there's a lot of work that goes into achieving these modern miracles. In 18 months time a new chip manufacturing technology will be available because years ago engineers started working on it. Other engineers are now working on the technology which will be used 18 months later. Some future technology which isn't even envisioned yet will build on the work of these technologies that have come before. When we peg dates to them, this is a Technology Roadmap.

So, when some people talk about the NASA robotic exploration program being a success because it only develops technology as necessary to complete a mission, it ignores the primary driving factor of robotic capabilities: that law of computer power doubling every 18 months.

The NASA Flagship Technology Demonstration Program is an attempt to bring a modern technological development process to space technology. By identifying key enabling technologies, breaking them up in demonstrable milestones, and pegging dates to those milestones, a Technology Roadmap can be bootstrapped. The only missing piece is competition. Hopefully, NASA will structure the FTDP to encourage the greatest amount of competition from its contractors, including buying off-the-shelf components for flight demonstrations thus stimulating the private sector to adopt the Technology Roadmap to guide their own research and development and provide a framework for entrepreneurs to make a business case for "startups" in space technology.

With a healthy technology development industry to back it up, the consolidated Space Technology Roadmap makes planning missions with low risk a lot easier. Rather than absorbing technology development costs (as mission managers despise) and taking on all that risk, the missions can be structured around technologies that will be ready when the mission has passed design review. The robotic exploration program has become used to this kind of thinking for the reasons already described, the human exploration program can too.

The Radiation Exposure Numbers Game

The effect of prolonged radiation exposure on the human body is one of the potential show stoppers of long term human spaceflight. Yesterday we heard Zubrin present his traditional "don't worry about it" speech and another speaker refer to his reasoning as "the numbers game". By this, he meant that no-one in the audience is going to check those numbers so Zubrin can say whatever he wants. I think this speaker was missing the point. Let's look at what Bob was actually saying.


Zubrin's Assumptions

  • Six month transit times to Mars are available every 2 years
  • Radiation exposure on the Mars surface is negligible due to the availability of dirt for shielding
  • Solar radiation in deep space can be shielded against, so galactic cosmic radiation is all that matters
  • The GCR dose in LEO is about half that of deep space. It's about 55%
  • Mars crews would consist of 5 people
  • The ISS will continue to be crewed permanently by 7 people

Under these assumptions, a Mars program for 10 years results in a total crew dose of 5 * 10 / 2 * Deep_Space_Dose. Whereas the total crew dose for the ISS will be 7 * 10 * 0.55 * Deep_Space_Dose. If we normalize we get 25 < 38.5, so clearly Mars is a safer mission than ISS in terms of radiation dose, right?

Well no, we can argue with almost all of his assumptions. Transit times are more like 8 months. Radiation exposure on the Mars surface isn't negligible because astronauts will be doing lots of EVAs. Solar radiation shielding makes the galactic comic radiation dose worse, etc, etc. But I think this is the wrong way to go about it. Arguing about the assumptions draws us into the trap of thinking about overall program doses which are irrelevant.

What matters is the individual astronaut's lifetime dose. In the ISS program today, astronauts are limited to 9 months non-consecutive stays on the station (either three 3 month stays or a 6 month and a 3 month stay). Under the assumptions above, an individual crew member's dose in the Mars program is 1 * 1 * 1 = 1 normalized year. In the ISS program the crew member's dose is 1 * 0.75 * 0.55 = 0.4125 normalized years.

As such, an individual astronaut is more than twice as likely to die of cancer when they return from the Mars mission than an individual astronaut in the ISS program, and that's under the bad assumptions. In reality it's much worse.

Now that doesn't mean they shouldn't go. Even if it was absolutely certain that 10 years of your life would be cut off by cancer from going to Mars there would be a line of volunteers snaking out the door. What it means is that NASA is legally not allowed to send astronauts under the existing radiation exposure laws (which ISS strictly follows). It means those laws need to be changed or we need technology to make that radiation exposure less.

Saturday, May 29, 2010

Mars Direct vs FY11 NASA Direction

This morning Bob Zubrin will be arguing the case for Mars Direct over the NASA future direction. This is what I'd really like to be able to talk to him about but probably won't get a chance to. [About an hour after I wrote this post a friend of mine decided it would be hilarious to introduce me to Bob Zubrin and then run away. I started the conversation by saying that I thought he had too many strong, stupid and offensive opinions, but rather than punch me in the face or walk away he suggested we discuss our differences. And so we did.. for about 2 hours. He agreed with many of these points but insisted that new NASA administration won't actually be doing any of the stuff they say they will.. we'll see.]

There's a lot of common ground between the two plans but all the focus is, of course, on the differences. Dr Zubrin can't be happy that NASA is doing work that supports his plan, only being appointed the Space Czar will do.

Common Ground

  • "Mars as destination" - Mars is the declared destination of both programs. That's a big deal, there's lots of other places that could be the destination. Considering that NASA has long been banned from considering Mars the destination, that's something worth celebrating.
  • Nuclear Power qualified for use in space - Both plans make critical use of fission nuclear power.
  • Entry, Descent and Landing in the Mars atmosphere - Landing on Mars is hard and precision landing of large payloads (double digit tons) is required for any human Mars program.
  • In-situ utilization of the Mars atmosphere for a preplaced ascent stage - This is a Zubrin original idea that has been whole-heartedly adopted by NASA.
  • Long stays for conjunction - Zubin famously made the case for staying on the Mars surface for long stays to reduce the duration of transit to months instead of years, again adopted by NASA as a standard.

But there are differences and, although they shouldn't be focused on they should be acknowledged.

Disagreement
  • Mission mode - obviously, Mars Direct is a direct mode, whereas the new plan (and most other Mars plans) leaves from LEO. The future NASA plans also call for aerobraking into Mars orbit.
  • Zero-g mitigation - Mars Direct famously proposed the use of a tethered spinning habitat, a risky proposition. Whereas the future NASA plan is what I call Charlie Bolden's Magic Rocket - reducing the transit time so zero-g isn't a major issue.
  • Radiation mitigation - the reduction in transit time also helps here. The Mars Direct plan has always been a combination of crew selection (all smokers, make em quit, ha ha), shielding with supplies (there's not enough and as you eat them..) and just outright denial.

But today's session will probably focus on commercial crew and asteroid missions.. in other, words, irrelevant politics.

Friday, May 28, 2010

Gravity Plating Part 2

In an earlier post I described a system for generating zero-g in the laboratory and how this might be used to generate a standard gravity on-orbit and for deep space missions. Today, Narayanan Ramachandran of NASA-Marshall gave a talk at ISDC and I had the opportunity to ask him a few revealing questions. As I expected, there is few technical problems with operating a system such as this in space. Superconducting magnets of sufficient size to levitate a human exist and, although they cost a lot for laboratory use, they are chump change for a human spaceflight program. The power requirements are not excessive for the advanced solar power systems NASA is planning to bring online over the next few years, or for the in-space nuclear power systems that may become available eventually. There was also some discussion about how much gravity humans need to maintain healthy bones, which was the primary motivation for the technology. Not for the first time I'm tempted to look up suppliers and crunch the numbers for an earth-bound entertainment use of this technology - zero-g at sea level anyone?

Wednesday, May 19, 2010

Hitching Rides

Too many times I have read the claim that with the retirement of the Space Shuttle this year NASA will be "hitching rides with the Russians" to the International Space Station. A number of writers have taken it upon themselves to stress that Shuttle retirement was a decision made by the Bush administration, not by the Obama administration, and although this is true I think it is really beside the point.

It has always been the plan to fly expedition members to the ISS on the Soyuz. That was the deal, the Shuttle builds the station and the Soyuz rotates the crew. Since late 2000, that's exactly what the Soyuz has done, and a permanent human presence has been maintained on the ISS. Every time the Shuttle flies to the ISS it is for a visit, of no more than 10 days as that is the limit of on-orbit endurance of the Shuttle.

If the shuttle wasn't retiring this year the missions they would be doing would be resupply - and maybe some more experimental hardware installations - the same kind of stuff they do now. What they wouldn't be doing, couldn't be doing, is delivering crew to stay on the station for any significant length of time.

Now, I can understand journalists, politicians, and dipshits on the Internet bemoaning the retirement of the Shuttle as the end of how NASA gets expedition members to the ISS - a position that is simply false in fact, as well as impractical on merit - but I have no idea why sensible educated people who have any idea how the ISS program operates would repeat this stupid meme; unless they are deliberately being dishonest.

Friday, May 14, 2010

Planetary Protection

Planetary protection is something for which, I think, a broad base of support exists. It has many facets:

  • earth monitoring
  • solar monitoring
  • potentially hazardous NEO monitoring
  • basic science for the understanding of the sun and asteroid/comet composition
  • high performance computer simulation and prediction of solar and NEO threats
  • technology development and demonstration for the purposeful diversion of NEO threats
  • harnessing of solar power
  • utilization of extraterrestrial resources; and
  • eventual migration of polluting industry off-earth.

Quite a number of these are best done using robotic tools, satellites for example, but some of them are what we could call "exploration" and can be done most effectively, in terms of time, with human missions – and time matters. Every day we don’t have a good understanding of NEO composition, for example, we’re in danger of incorrectly characterizing those threats.

When we start recognizing that external threats to the earth are real and require constant diligence to avoid, the argument for getting all the eggs out of the one basket starts to become less pie-in-the-sky and more sensible precaution.

Tuesday, May 11, 2010

Gravity Plating

A common plot device in science fiction like Star Trek that allows crew to walk around in full gravity on spaceships is Gravity Plating. The idea is simply that the ship is plated with some magical technology that dramatically decreases the strain on the show's special effects budget :)

Having just this technology would have a major effect on NASA's future long duration missions asteroids, Mars and beyond, not to mention stays on the International Space Station.

Serious discussions of artificial gravity generation today are based on the concept of rotating the habitation module. Either a big torus like in 2001 A Space Odyssey, Mission To Mars, Red Planet, and Babylon 5 or, more practical, using a long tether between the habitat and a counterweight, say the expended trans-mars injection stage. Both options are incredibly difficult to do and dangerous. As such, their discussion in NASA circles has been virtually taboo for decades.

Which is why recently, while thinking about gravity plating in science fiction, that I was reminded of some NASA work announced last year that may be applicable. The work involves levitating mice. Perhaps the research got funded because its counter-intuitive to think of levitation as a means for producing artificial gravity. In fact, the research is studying the physiological impact of prolonged microgravity, and possible medical countermeasures.. the kind of work they do on the ISS, but presumably a lot cheaper.

So what do levitating mice have to do with gravity plating?

Imagine the levitating mouse experiment in zero-g. The mouse would already be "levitating", as would everything else, so what would it experience as it approaches a superconducting magnet that is firmly attached to the station? If the "ceiling" of the mouse's cage is the superconducting magnet, the mouse will experience a repulsive force towards the "floor" of the cage.

Diamagnetic repulsion requires a very strong magnetic field, typically in the range of 16 teslas, and so create significant problems if ferromagnetic materials are nearby. Superconducting magnets currently are very heavy and require cryogenic cooling. So, unfortunately, this may also be too dangerous for use by NASA in future spacecraft.

Thursday, May 06, 2010

Birds Of A Feather

Scott "Doc" Horowitz recently [1] published a rant on The Mars Society, and among the stupidity was this gem:
The COTS providers (Orbital and SpaceX) were awarded firm fixed price contracts totaling $3.5B to deliver approximately 40MT of cargo to the ISS. This, plus the $500M already invested in COTS, results in a cost of $100,000/kilo ($45,000/lb) to deliver cargo to ISS. If the Ares I/Orion were flown at a similar rate (6 flights/year) the fully-burdened government cost for delivering cargo to ISS would be about $70,000/kilo ($32,000/lb)!

Totally ignoring that there was no cargo block for Orion, what about the estimated $35B to $40B that Ares I + Orion is expected to cost? How about adding that in?

It's just like how Zubrin claims that NASA's budget today is the same as it was during Apollo [2].. by cherry picking 13 years from the Apollo period [3] (and in some retellings the 90s too) and then defining "the same" as 21% more. [4]

You'd think that completely objective proof that someone is wrong would be sufficient to discredit them but our community has been so diluted by politics and subjective opinion that we don't hold anyone to their claims anymore.

We're supposed to accept that Zubrin is just making a point that the budget excuse is irrelevant, and hey, I don't completely disagree with him, NASA can blow $9B on Constellation with virtually nothing to show for it, so a little NASA bashing isn't out of line, but the argument Zubrin presents immediately after this mathematical sleight-of-hand is that "during the past 13 years, no new technologies of major significance were developed." Of course, by "major significance" Zubrin means things like space suits [5], in space life support systems [6] and rocket engines [7].

So next time you hear Zubrin talk, and I guarantee that it'll be the same old shtick, think of Doc Horowitz - the kind of person who assumes his audience is clueless.

[Edit]

I spoke to Zubrin about this post.. he said I really should mention that the people he was arguing against were saying that NASA's budget was something like four times as much as it is today. Obviously these people are also wrong. Even at the peak of Apollo spending (which is what I think is really relevant) it was only 1.87 times as much as NASA's budget today. Although, I guess, if you were to compare the amount of the peak Apollo budget that was actually being spent on the human spaceflight program, and the amount today that is being spent on the human spaceflight program, you could get something like 4 times... but that's entirely Zubrin's point - the priority during Apollo was human spaceflight and today it isn't. To both camps I say: use real numbers and don't throw away the decimal point to make your point.

1. http://www.marssociety.org/portal/a-trajectory-to-nowhere-by-scott-doc-horowitz/

2. "In today’s dollars, NASA’s average budget from 1961 to 1973 was about $18 billion per year. That is about the same as NASA’s current budget." - Zubrin, http://www.marssociety.org/portal/zubrinoped-space-news-2-10/

3. NASA budget from 1961 to 1973, in constant 2007 dollars, $282.865B. NASA budget in 2010, in constant 2007 dollars, $17.912B. http://en.wikipedia.org/wiki/NASA_Budget

4. $282.865B / 13 = $21.759B, which is 21.48% more than $17.912B.

5. http://en.wikipedia.org/wiki/Mark_III_%28space_suit%29

6. http://en.wikipedia.org/wiki/ISS_ECLSS#Water%20recovery%20systems

7. http://www.nasa.gov/mission_pages/constellation/main/lox_methane_engine.html