Thursday, May 28, 2015

Visions of the future with Kim Stanley Robinson

Article published in The California Tech on 27 May 2015.


Visions of the future with Kim Stanley Robinson

Casey Handmer


Last month I sat down for an interview with celebrated Californian science fiction author Kim Stanley Robinson to explore his thoughts and visions of the future.


Casey Handmer How do you describe what you do? Why do you write science fiction?

Kim Stanley Robinson I write science fiction as a kind of realism, in most of my books. I do that because I think science fiction is the best literary form for realist art in our era.

CH While your 20 or so novels have been very well received, the most surprising thing about exploring them is that their style is less uniform and more experimental?

KSR  The narrator for most of [my latest novel,] Aurora, is an artificial intelligence that is running the starship. So that computer has to learn to write a novel. It runs through the history of English prose and novel techniques, starting with primitive realism. Finally, in the interstellar medium at the end of the novel there's just a stream of consciousness of the artificial intelligence. It was so much fun to write.

CH Your Mars trilogy is still remarkably scientifically accurate, despite being published more than 20 years ago. Nevertheless, about those windmills in Red Mars

KSR The first edition was full of errors ― I made about 300 corrections. After the 18th printing of Red Mars in paperback, there's a set of corrections listed at the end that have to fit the pages like a crossword puzzle, to keep the pages the same length.

CH Haha, I think "after the 18th printing" is the perfect answer to the pedants. It's art, you know. At some point you say, "I'm telling a story." I tell stories all the time. You don't tell exactly what happened. You take key things and relate the narrative, that's the important part.

KSR But with science fiction, you want to keep from throwing people out of it, or else people can get annoyed. Readers fall into a dream state of reading, but if they get cast out of it because of something being wrong, they can get angry, or amused, at the author. It splits according to the character of the reader.

CH I appreciate the effort to get the technical detail right; it's a colossal pain. Your work is rightly renowned for its attention to detail and very hard science fiction attributes. Why do you see technical accuracy as a necessary part of the craft?

KSR As an example, abandoning Earth [in the 2014 film Interstellar] is somewhat of a moral hazard. The general population is bad on these issues, in terms of what is possible and what is not. Science fiction has this general danger, because many people say, "Oh, that must be possible" because it got written up.

CH That's interesting; so science fiction authors have a social responsibility to build a realistic future world?

KSR It's very common for physicists to say that [because of future ecological disaster] 90% of humans will die. It's an absurd thing to say because it creates a general distrust and hatred of science. It's also a science fiction statement. When people say science fiction statements as though they were solidly scientific statements, like the nature of a physical law, then they're in the nature of a hoax which can be a dangerous hoax.

CH So sea levels will rise 15 feet over a decade, or a century?

KSR I know what you're saying, but we will adapt. We have to, just like we breathe. We are primates, we have done it all along. I object to the political program where [we] just give up, keep burning carbon because we like it, or we can't stop. It's defeatism, a pseudo-philosophy, a pseudo-realism.

CH Well, even if only a tiny fraction of humans will ever be able to leave the Earth, what is your view on human colonization of space?

KSR I like the idea of going to the moon; I like asteroids. And obviously, I like the idea of Mars. Whatever works, as far as I'm concerned. More is better; let's do it all. Robotic exploration, such as at JPL, is fine too. This idea that manned space exploration will save civilization and it has to be humans colonizing space and blah blah blah, the Wild West metaphor, all that is terribly lame thinking.

CH Seems more likely to be analogous to the Soviet expansion through the tundra.

KSR Good luck with that!

CH Technological and very expensive. But possible. So, what's next for you in terms of writing?

KSR I'm getting close to being done!

CH You set out a program 30 years ago?

KSR No, I just don't want to repeat myself. I'm interested to do all the subgenres of science fiction and make one significant contribution to each of the ones that I like. I've done an alternative history, I've done the solar system, I've done the planetary colonization, I've done time travel, I've done the prehistoric novel. I always thought that was a really important subgenre of science fiction because of archaeology, sociobiology and evolution. That was Shaman, my most recently published novel. And Aurora is what I have to say about going to the stars.

CH You need warp drive or lots of antimatter. The speeds and energies involved ― there are certain physical limits which are hard to get away from.

KSR I don't think it's going to work, but fortunately there's more to Aurora than that!

CH It seems like a long shot with any current or projected technology. But we don't know enough to see far enough to know that it will always be impossible.

KSR Technology is a challenge which is a physics thing. There's a tendency for physicists to talk about physics and all other things in terms of physics, which everything ultimately comes down to. But the problems for interstellar travel for humans are biological, sociological, ecological, and psychological. On all these levels, it's in terrible, terrible trouble.

CH We are just thinking meat ― it's too many orders of magnitude beyond our ancestral activities. More locally, though, for the first time in the history of the universe, as far as we know, humans have enough industrial capacity and coordination to colonize other planets. Do you think we'll be able to colonize Mars before something else goes seriously wrong?

KSR The best analogy for Mars is not the New World, so colonization is not the right word. A better analogy is Antarctica, so yes, we can set up scientific stations there, similar to McMurdo and other Antarctic stations, any time we decide to pay to do it, with the years of work needed also. We are definitely robust enough to do that, and JPL would be a big leader, as it has been. But colonization implies many people, and therefore terraforming, really, to make that place livable. So that's a 10,000-year project, maybe, worth doing when we have a stable civilization here on Earth. Worth thinking about now, too. The long perspective is often useful.

CH One consistent theme of your work has been an exploration of post-capitalist societies. Post-capitalism as a term sounds a lot stranger than it should be, but people aren't often thinking about a future system. In your view, what are the key strengths and weaknesses of capitalism as a system?

KSR Its strength is that it is a legal system and as such can in theory be modified for the better by legislating different laws. This is an advance over the sheer force and nepotism of feudal and earlier economics. It has another strength that is at the same time a weakness, which is that it crowdsources human desires to make prices for goods and services, so that what people want tends to create prices in a market.

CH What's wrong with that?

KSR The problem is people can want impossible things ― possible for individuals maybe, but impossible for group and planet over time. Thus we systemically underprice most commodities and services because the pressure of supply and demand favors buyers over sellers. The worst underpricing involves natural resources, externalized in accounting but not reality, and human labor, which is scared into cheap misery. But as these are the two most important resources, pricing both at predatory dumping prices…

CH Predatory dumping?

KSR Charging less than it costs to make to drive competitors out of business, means that we live in a multi-generational Ponzi scheme, and it's the generations to come who will take the hit. That hit is starting now. Another weakness is the way the laws of capitalism unconsciously reproduce laws of gravity such that accumulated capital has more power to accumulate than smaller masses of it. So the rich get richer and the poor poorer, as demonstrated by [Thomas] Piketty, though also recognized in [other, older economic systems].

CH Caltech students do not have much political power, but they are at the forefront of technological innovation. We've already seen some examples of IT-leveraged economic innovation, such as Uber, Airbnb, bitcoin, etc., that have circumvented or short-circuited our largely moribund legislature. Some wildly successful Silicon Valley companies have succeeded mostly in enriching themselves, but the capacity still exists for the next generation of engineers to have a prominent voice in the future they design and build for the rest of us. Do you think it's possible for a less wasteful, less greedy economic model to outcompete capitalism on its own turf?

KSR Yes to that last, except with this cavil: capital can try to buy the legislatures that make the laws that run capitalism, in which case, any other system will be handicapped because the rules make the game. So the question becomes, "Is democracy real, or does accumulated capital, or oligarchy, run our governments?" This is the battle being fought in our political life now, everywhere.

CH Can the dreams of post-capitalist America left be realized through technology rather than policy?

KSR More generally, how can we price goods and services if we decide that the market systemically underprices things and is destroying the biosphere and human lives?  Especially when there is currently no central planning system that could work to replace the market? This to me is the big "technological" question, and I do think it's a scientific question in systems design involving feedbacks of all kinds, as well as a political question.

CH Where does Caltech fit in this?

KSR So it is not outside the Caltech purview by any means to be asking, "How can we realistically change the global system to something more sustainable?" and then regard [capitalist] economics not as a field itself but rather a meta-field, a very big and important social science that can benefit from rigorous studies from the hard science angles. The Caltech political economists can do a projective project of designing stepwise reforms to a sustainable post-capitalism. I imagine something like first anti-austerity, back to Keynesian macroeconomics. Then social democracy, Scandinavian style. Then socialism, meaning public utility districts in USA-speak. Then some X system that we can only call post-capitalism at this point, because it doesn't exist yet; but it needs to be sustainable, and just.

CH Well that's certainly thought-provoking stuff! Thank you for your time, and perhaps we'll see you hiking in the Sierras.



Tuesday, April 28, 2015

Next Generation Mars Lander and Return Vehicle

Next Generation Mars Lander and Return Vehicle
Concept development: Casey Handmer

Wyverngif.gif

What is this?


This is a new spacecraft concept capable of landing on the surface of Mars and eventually returning to Earth in essentially complete form. This spacecraft, the Wide lifting bodY Vehicle for Earth ReturN or WYVERN, is envisioned as a versatile chassis capable of a wide variety of missions with minimal changes. While many sizes are possible, such a spacecraft must meet the following requirements:
  • Low ballistic coefficient. Mass/heat shield area < 250kg
  • Rocket powered soft landing without parachutes or inflatable components, for reliability.
  • A stable, low form factor on the surface, even on sloped ground.
  • Capability to be launched from Earth in one piece, without assembly or fueling in orbit microgravity.
  • Reusability. The spacecraft should be capable of flying a configuration which permits return to Earth for reuse, utilizing the Martian atmosphere to synthesize fuel for the return flight.
  • A monolithic heat shield (no hatches, windows, doors, etc) that is not ejected, so it can be reused on return to Earth.
  • Adequate fuel capacity for single stage return to Earth, requiring approximately 7.8km/s of delta-V.
  • Significant cargo down mass capability, ideally measured in 10s of tonnes, and a large fraction of launch mass.
  • In-Situ Resource Utilization (ISRU) capability.


How is it done today - what are limits of current practice?



Currently, spacecraft are landed on Mars using Apollo-derived truncated conical capsules, parachutes, rockets, and airbags or skycranes. Current limitations include:
  • Mass - Mars Science Laboratory (Curiosity) represents the largest payload to date, of approximately 900kg, and represents an upper limit on the capabilities of aeroshell, parachute, Earth-launched payload fairings, and rocket landing system. Specifically, 900kg is not nearly enough to land humans.
  • Locations - Mars’ thin atmosphere greatly restricts the sites where it is possible to land, effectively eliminating the ⅔ of the surface that is above datum.
  • Return capability - no existing or proposed Mars spacecraft can leave the surface. Even proposed sample return missions use bespoke staged solid fuel systems with minuscule upmass capability (<10kg)


What’s new in WYVERN - why will it succeed?



Specific innovations include:
  • Form factor - we exploit the differing requirements of various stages of the mission to provide a long, wide, and flat form factor that acts as a lifting body during entry.
  • Descent and landing profile - by orienting the spacecraft to enter the atmosphere on its back, then roll 180 degrees before a rocket powered landing, the spacecraft is always in a stable configuration and ideally positioned on the surface to protect the heat shield while enabling loading and unloading of cargo.
  • No parachutes or inflatables - hypersonic parachutes for large payloads are difficult to test, heavy, too unreliable for human cargo, and ultimately unnecessary.
  • Very large included delta-V - with 7.8km/s of delta-V in launch configuration, the spacecraft is capable of returning to Earth from the surface of Mars with up to 25% of dry mass as cargo. Detailed mass tabulation is included below.
  • Reusable, multipurpose airframe saves development costs for different missions while also being scalable.
  • Unparalleled cargo capacity given rocket launch mass - 20% of low earth orbit capability vs 5% for MSL.


Who cares? What difference will it make?



Current and planned missions to Mars both robotic and crewed are fundamentally limited by the requirement of multiple unique specialized spacecraft, each of which requires separate design, testing, and all of which form single points of failure. None of these spacecraft are particularly versatile, few form a fundamental design which can be updated or improved without substantial redesign and development costs.


The proposed design will form a basic chassis with raw capabilities that can be customized in many directions without requiring redesign of the mission-critical components: entry, descent and landing, propulsion, guidance, navigation and control, and so on. Mass analysis below indicates that as a one-way lander with 50T gross mass, it can deliver ~25T to the surface. With in-situ resource utilization for return fuel manufacture, it can deliver ~15T and return ~5T to Earth, as well as the reusable spacecraft. It can also readily perform missions in the Earth-moon system.


What are key unknowns?


  • Minimum viable structural mass. While using a pressurized methane/oxygen tank as a structural backbone, is it possible to complete the rest of the structure with enough margin for landing and launch? Preliminary mass analysis included below suggests it is possible.
  • The design requires the development or adaptation of high Isp (380s) methane-oxygen engines each delivering a relatively small ~130kN of thrust.
  • Returning the spacecraft to Earth requires the synthesis of fuel and oxidiser on the surface of Mars, which in turn requires a substantial quantity of electrical power, totalling approximately 150kWyears for the 50T design reference. Realistically, this can only be provided by a space reactor such as the SAFE-400. Such reactors have been developed but never flown.


How much time and money is required?



The spacecraft is estimated to be similar in weight and materials to a mid-size jet aircraft such as the 737, with commensurate development and construction costs. With cost of development amortized over many missions, this represents a substantial (> order of magnitude) improvement in cost over other proposed Mars mission architectures, such as SEI or Constellation, which involve much more complicated conops, greater mass, and less versatility.


Preliminary analysis


I'm a physicist, not an expert digital modeler or authority on hypersonic aerodynamics. Nevertheless, it is possible to present a rough sketch of WYVERN in various configurations.
Entry configuration:
WyvernModelEntryConfig.png
The central blue cylinder is fuel tank, mostly empty during the outbound voyage, with several magenta domes partitioning it into different sections. Green cones are rocket engines. Blue triangles are tails to shift center of drag behind center of mass. Brown marks the edge of the vehicle envelope, with a basic flattened triconic profile and heat shield on the bottom.


WYVERN in landing/launch configuration:
WyvernModelLandingConfig.png
Here, WYVERN has inverted to land with engines facing down, and heat shield facing up. With clearance beneath and a spread, stable posture, WYVERN is ideally suited for the loading and unloading of cargo without a crane and/or 15 floors of stairs.

delta-V summary

Earth surface - LEO: 9.3-10km/s. 9.3 for KSC to non polar orbit.

LEO-Earth C3: 3.3km/s. (Optional solar electric propulsion)
Earth C3-TMI: 1km/s (180 day trajectory, for 2 year free-return).
Total from booster(s): 13.6km/s


TMI-Mars surface: aero direct entry + mid course corrections + terminal velocity to landing ~0.83km/s.
Total from WYVERN outbound: 0.83km/s


Mars surface-LMO: 4.1km/s.
Flat ascent penalty: 0.03km/s (for having rockets fire perpendicular to axis).
LMO-Mars C3: 1.4km/s
Mars C3-TEI: 1.5km/s (190 day trajectory, 0.9km/s minimum for 280 day trajectory)
TEI-Earth surface: aerobraking + mid course corrections + terminal velocity to landing ~0.8km/s.
Total from WYVERN+ISRU: 7.83km/s.


A single stage flight from Mars’ surface to Earth’s surface requires approximately 7.8km/s of delta-V, at best. Given eight advanced methane-oxygen engines with an Isp of 380s, the requisite mass ratio is 8:1. That is, a mass of x landing on Earth requires a launch mass of 8x, or 7x in fuel and oxygen. An initial:final mass ratio of 8:1 (for soft-cryo props) is small by comparison with the 23:1 ratio achieved by modern booster rockets, such as the Falcon 9 first stage.

Mass allocation

By combining the structural elements of fuel tanks and airframe, WYVERN achieves a much lower dry mass than more conventional designs.



Component
Mass (kg)
Analogous existing hardware and mass
Fuel/ox tank
5600
Falcon 9 second stage dry mass 4900kg
Non tank structure
5000
40’ shipping container 3800kg steel
Main rockets
8x125
RL-10 has similar thrust and use parameters
RCS
500
Dragon Draco RC system
Solar array
1000
50kW at Mars orbit with 100W/kg at LEO
Heat shield
2400
300m^2 of PICA-X
Avionics/GNC
200

ISRU - Reactor (nuc)
500
SAFE-400 120kW reactor
ISRU - Feedstock
8500
7500 H2 for 150000 CH4/O2 + margin
ISRU - Reactor (chem)
500

Fuel/Ox mass
150000
21400kg gross mass to Earth. 180m^3 storage
Spare/cargo upmass
5700
15700 dry mass
Spare/cargo downmass
15800
50000kg entry mass includes 10000kg EDL fuel and 9500 kg ISRU components


Mass summaries throughout duration of full mission


Note that these figures are for the Mars lander only. They do not include the mass of the LEO-TMI booster(s), outlined in the configuration section.
Mission stage
Mass (kg)
Explanation
Low Earth orbit
50000
Falcon heavy launch
Trans-Mars Injection
50000
TMI with separately launched booster
Mars Atmospheric Entry
50000

Mars surface after landing
40000
10000kg for 830m/s delta-V during landing
ISRU fuel
30000
Methane, taking volume 71m^3
ISRU oxygen
120000
Basic stoichiometric ratio, 105m^3
Pre Mars launch dry mass
21400
Structure and return cargo
Pre Mars launch gross mass
171400
Requires 6x110kN thrust minimum to lift off
Trans Earth Injection
26200
4800kg of props remain for Earth EDL
Earth atmospheric entry
26200

Earth surface after landing
21400
800m/s of delta-V remain for landing

ISRU components

The ISRU unit consists of a chemical reactor, a nuclear reactor, associated plumbing, and hydrogen feedstock. It generates methane and oxygen via the Sabatier reaction and Reverse Water Gas Shift reaction according to well understood principles. In the context of a manned mission, the reactor would be deployed by remote control on the surface prior to fueling and activation. A solar array can provide auxiliary power during cruise or on the surface, though does not produce nearly enough power to complete ISRU within the ~500 day window between landing and return to Earth. A scaled down WYVERN for sample return could use a large, disposable solar array on the surface for ISRU power. If the mission profile calls for two WYVERNs; one Earth return vehicle to land two years earlier and produce fuel before the crew transport WYVERN arrives, then the reactor only needs to go with the first vehicle, and can stay on the surface, fueling the crew transport vehicle after the mission has concluded. Later, the crew transport vehicle could fly additional samples back or function as a backup.

Entry, descent and landing profile
WYVERN employs an innovative, back first entry profile. WYVERN’s heat shield forms the roof of the spacecraft in standard landing configuration. With a hypersonic L/D ratio of ~2.5, WYVERN is capable of skip entry and substantial cross-range performance. During supersonic cruise at terminal velocity (~500m/s), WYVERN completes a 180 degree roll, pitch up maneuver, and retropropulsive descent and landing using four clusters of 2 130kN redundant high Isp methane oxygen motors analogous to Dragon V2. Powered flight continues for around a minute, first decelerating at full power, then descending under controlled flight to a soft landing. In more detail, with a peak thrust of 8x130kN and an initial mass of 50T, WYVERN can decelerate at 21ms-2(much greater than Mars’ surface gravity of 3.8ms-2), taking roughly 30 seconds to slow down from terminal velocity to begin a powered descent at reduced thrust.
WyvernProfile.png
A basic simulation of WYVERN entry using banking to suppress hypersonic skipping until around 1000m/s, where the barrel roll may be performed during a natural peak in the trajectory. MSL’s entry profile, computed using the same simulation and publicly available data, is included in red for comparison.

Launch profile
WYVERN launches from Mars in its horizontal configuration. Mars’ atmosphere is thin enough that there is no substantial performance impedance from climbing to orbital speed with the flat side up. Total delta-V loss is less than 30m/s compared to vertical orientation, or -6m/s for no atmosphere.

Internal configuration

Different internal configurations can be built within the framework formed by the aeroshell, central fuel tank, and propulsion units.


Possible configurations include
  • Self contained sample return mission with ISRU. Capable of delivering 15T to the surface, returning 5T of samples and/or mission hardware. 15T could include several rovers with specialized instruments, a substantial drill rig, even a small synchrotron.
  • Self contained crewed mission with ISRU. With 15T down mass and 5T return mass, a single WYVERN is capable of supporting a crew of 4 or 5 for a complete 2.5 year mission.
  • One way crewed mission. Remove the ISRU mass penalty and receive 10 additional tons of down mass, to possibly include more crew, more supplies, or more Mars cars.
  • Earth-return vehicle (ERV) crewed mission. Launched autonomously to Mars, the ERV WYVERN produces fuel on the surface before the crewed WYVERN departs from Earth. With 15T of spare down-mass, the ERV can also deliver substantial cargo in support of a surface mission.
  • One way cargo. Without ERV hardware, WYVERN is capable of delivering 25T to the surface of Mars, and also contains roughly 350m^3 of pressurizable volume.
  • Self contained crewed mission without ISRU. If return fuel is present on Mars’ surface, either prelaunched or premade, WYVERN can complete a mission without bringing ISRU hardware, with 25T of down mass and 5T of upmass.
  • Orbital shuttle. WYVERN could readily function as a shuttle to deliver payloads to or from Mars orbit from the surface. Downmass remains at 25T, upmass increases due to the decreased delta-V required. Surface to Low Mars Orbit is 4.1km/s, allowing a cargo upmass of 58T, given an incremental engine upgrade. Surface to Mars C3 and back to surface, such as required to dock with a large interplanetary spacecraft in a highly eccentric orbit, is 6.3km/s, allowing an upmass of 20T. Intermediate missions fall between these two extremes.
  • Trans Mars Injection booster. If WYVERN was launched to LEO from Earth by Falcon Heavy, it would require a vacuum booster stage to get to Mars. Three WYVERN-based booster stages, each launched with 125T of fuel by (possibly boosted) Falcon Heavy (preserving 55T after self-boosting to orbit), could dock with the crewed WYVERN in LEO and boost it to Mars. Two booster WYVERNs would fall back to Earth and land immediately, while the last booster WYVERN and the crewed WYVERN would then fly to Mars, where the booster stage would aerobrake or use a fly by (or both) to return to Earth via free-return or a Venus conjunction-class orbit, in time for re-use in the next launch window. Alternatively, a single booster with electric propulsion could gradually lift WYVERN into cis-Lunar space, before adding crew and burning chemically to TMI.
  • Lunar lander. With 150T fuel capacity, WYVERN could also land on the Earth’s moon and return in a single stage. If fueled on the moon, WYVERN could transport 120T of cargo from the moon to Earth, though could propulsively land with only 90T without engine modifications. If flying from trans-Lunar Injection to the moon’s surface and back to Earth’s surface, a fully fueled WYVERN could transport 35T of cargo. This cargo could be increased for non-time sensitive payloads by using 3-body interactions in the Earth-moon system.


Scaling

Given a more capable Earth-LEO booster, the WYVERN design can be readily scaled up. Released information suggests a SpaceX BFR LEO capability of 200T. This would enable direct launch of one WYVERN to TMI, or a similar profile to that outlined above with a single WYVERN scaled up by a factor of 4, which would transport 100T cargo to the surface. The only relevant design constraint in scaling is ballistic coefficient, which dictates that a high capacity Mars lander must be, on average, no thicker than a few meters in the transverse direction.

Radiation
With 8.5T of H2, 8T of O2, and 2T of CH4, as well as stores of water or food, there are ample quantities of low atomic mass nuclei to form a radiation shield for coronal mass ejection-type radiation during the outbound voyage. On the return voyage, reduced quantities of fuel and oxidiser (1T CH4, 4T O2 plus consumables) still allow for adequate radiation shielding of roughly 25g/cm^2 of shield wall.
Solar radiation fills the half-space in the direction of the solar magnetic field, where a gyroradius of about 1000km prevents a strictly ‘line of sight’ shielding methodology.