Gassed!

Gassed

Super-Earths might be Dead from Gas…

Origin and loss of nebula-captured hydrogen envelopes from ‘sub’- to ‘super-Earths’ in the habitable zone of Sun-like stars

…rather surprising study of hydrogen-capture and loss from planets near Earth’s mass and orbit. Planets bigger than 0.1 Earth masses (i.e. Mars size and up) will capture the hydrogen-helium gas (H2/He) from the nebula that forms around young stars. The XUV (“soft x-rays”) light from young stars is enough to drive the primordial atmosphere away – but critical to future life on such planets, enough must escape to allow a secondary atmosphere, of heavier gases, to form. Below about 1.5 Earth masses, the planets can lose the primordial H2/He. Above that mass not enough is driven away to produce an “Earth-like” planet. Instead a “mini-Neptune” forms, with a deep H2/He atmosphere over a hot, rocky core.

But it’s not all bad news – small planets that were ejected from close to their stars by migrating gas giants, might retain sufficient H2/He to remain warm enough for liquid water, far from their original orbit. Such objects might be sprinkled through interstellar space, awaiting discovery.

Antimatter at Hand?

Marshall Eubanks has posited the presence of million tonne masses of stable quark matter inside solar system objects – potentially both matter and antimatter forms of it, with the antimatter version protected from annihilation by a 100 MeV Colour-Force potential well.

Powering Starships with Compact Condensed Quark Matter

While pure antimatter/matter propulsion promises high exhaust velocities (~c) the difficulties of achieving that ultimate performance are considerable. But what if we use something else for reaction mass and use antimatter to energise that? And, instead of using it in a rocket, we use a magnetic scoop to draw in reaction mass from the interstellar medium? This is the Ram-Augmented Interstellar ‘Rocket’ – though technically a rocket carries all its reaction mass – and it promises high performance without all the disadvantages of exponentially rising mass-ratios. Mixing 1% antimatter into the matter flow could, in theory, produce an exhaust velocity of ~0.2 c. Scooping and energising the equivalent mass of ~100 times the mass of the starship would allow a top-speed of 0.999999996 c to be achieved, before braking to a halt using half that mass. This would allow, at 1 gee acceleration, a journey of ~20,000 light-years. The nearby stars would be accessible at a much lower antimatter budget.

Quark Matter in the Solar System : Evidence for a Game-Changing Space Resource

Very Rapid Rotating asteroids might be held together by the additional gravity of a mm-sized million tonne quark nugget.

Primordial Capture of Dark Matter in the Formation of Planetary Systems

Evidence for Condensed Quark Matter in the Solar System

Observational Constraints on Ultra-Dense Dark Matter

Such quark nuggets would be made in the Big Bang potentially, if antimatter is squirrelled away in such a form, the explanation of the observed lack of free-antimatter in the Universe. The abundance of such ultra-dense tiny specks, to be compatible with microlensing observations, would be in the ‘interesting’ mass-range suggested by the Solar System evidence.

More Harold “Sonny” White Papers & Presentations Online

IXS Enterprise 2
Sonny presented at the Icarus Interstellar “Starship Congress 2013″ in Texas. His talk starts at 13:20 and ends 58:00 at Icarus Interstellar’s YouTube video of the event: Day Three of Starship Congress 2013. Note the interesting discussion of Q-Thrusters for interstellar missions (30 years to Alpha Centauri) and the “warp-drive” illustrations.

Sonny’s discussion of Metric Engineering began with a 2003 paper on the implications of the Alcubierre Metric, here in abstract: A Discussion of Space-Time Metric Engineering. A search on Google will find it at the publisher’s web-site for about $40 US, but a reformatted reprint (White 2003) might be found.

A citation search of the above paper presents two interesting derivative papers:

Artificial gravity field Which is a discussion of how one might use Metric Engineering to generate SF-style artificial gravity. Not easy, but intriguing nonetheless.

Conformal Gravity and the Alcubierre Warp Drive Metric explores an alternative formulation of gravity’s implications for the Alcubierre Metric and the feasibility of warp-drive. Conformal gravity offers the tantalising possibility of warp-drive without the need for NET amounts of negative energy/pressure.

Harold also collaborated with Eric Davis, an exotic propulsion Guru, to discuss the Higher-Dimensional version of the Alcubierre Metric: The Alcubierre Warp Drive in Higher Dimensional Spacetime. The work Harold did for this paper fed into the more recent series of papers on optimising the Warp-Drive’s properties to minimise the energy required. See the previous Crowlspace blog-post for details.

Wikipedia covers the Interferometer Test for space warps in the lab here: White–Juday warp-field interferometer. Present status of the experiment is encouraging, but not conclusive. Sources of noise need to be pinned down and minimised or analysed and removed via post-data analysis.

Recently (last month, almost in time for Christmas) this intriguing paper discussing Sonny’s 2003 paper appeared: The Alcubierre Warp Drive using Lorentz Boosts according to the Harold White Spacetime Metric potential ?. Fernando Loup and Daniel Rocha are warp-drive enthusiasts, not mainstream Relativists, but have produced interesting bodies of work over time. Best read critically.

Finally I should mention the EMDrive controversy and its possible relevance to the Q-Thruster. A patent lawyer, Robert Shawyer, has developed and promoted a propellantless drive based on the behaviour of microwaves in a convergent reflective cavity. He believes it provides thrust without propellant being expelled – its claimed thrust level is much too high for it to be a radio “photon-rocket” (unlike some supposedly propellantless drives that have appeared over the years). Shawyer has claimed interest and experimental validation from Chinese researchers, even though many mainstream physicists (including Greg Egan, the Australian SF writer who is a mathematician by training) have computed the relevant fields of the microwave cavity to demonstrate NO net thrust.

However, there may be a theoretical “out”, which might apply further to other proposed Thrusters. Fernando Minotti discusses one version of gravitation theory in which such thrusts might be produced: Scalar-tensor theories and asymmetric resonant cavities. While the EMDrive probably doesn’t work, another Thruster concept, developed by Cannae, might. Unfortunately their web-site is down so I can’t direct you to their rather interesting material. Whether it’ll produce real results in proper testing conditions *might* come from work at Sonny’s Eagleworks Lab.

Road-Map

Harold “Sonny” White Papers & Presentations Online

Space-Warp

NETS 2012 presentation: http://www.lpi.usra.edu/meetings/nets2012/pdf/3082.pdf

Von Braun Symposium 2009: http://www.astronautical.org/sites/default/files/vonbraun/2009/Von_Braun_Symposium_2009-10-21_7b_White.pdf

Space Times 2009 write-up, starts page 8: http://www.astronautical.org/sites/default/files/spacetimes/spacetimes_48-6.pdf

STAIF 2007 Presentation: http://forum.nasaspaceflight.com/index.php?action=dlattach;topic=13020.0;attach=173105

Harold White’s papers at the NASA Technical Reports Server:

IXS Enterprise 3IXS Enterprise, based on Sonny’s Warp concepts

Eagleworks/Warp-Drive Papers:
Eagleworks Laboratories: Advanced Propulsion Physics Research
100 YSS 2011 Paper: Warp Field Mechanics 101
100 YSS 2012 Paper: Warp Field Mechanics 102: Energy Optimization

Mainstream NASA Papers:
Spacecraft Applications for Aneutronic Fusion and Direct Energy Conversion
Technology Area Roadmap for In Space Propulsion Technologies (1)
Technology Area Roadmap for In-Space Propulsion Technologies (2)
Roadmap for In-Space Propulsion Technology

Limits of Life

Earth as we know it today, is transient. The atmosphere has changed significantly since the earliest days. Soon after formation a dense atmosphere of carbon dioxide and water is suspected, though fortunately Earth was cool enough for the oceans to condense. After nitrogen levels rose and the carbon dioxide was mostly buried, the Earth was without free oxygen. The Sun was 25% less luminous, thus some sort of greenhouse gas kept Earth warm enough for liquid water rather than frozen oceans. Carbon dioxide, methane and hydrogen are suspected.

But beyond those what is the range of the possible?

William Bains discusses the issues and describes a possible silicon biosphere here: Many Chemistries Could Be Used to Build Living Systems. He discusses this in more detail on his web-page: The nature of life. Engagingly, doing polysilanol chemistry in liquid nitrogen sounds like fun, in a chilly, frost-bite prone way…

The National Academy of Science produced this book about 6 years ago, which discusses the issues of alternative atmospheres: The Limits of Organic Life in Planetary Systems

Also there’s this paper by Johnson Haas which discusses a biosphere based on halides as the active gases: The potential feasibility of chlorinic photosynthesis on exoplanets. While chlorine is “rare” in cosmic terms, there’s enough in our oceans to replace oxygen has the active gas in our atmosphere, thus “rare” should not be confused with “available”. Chlorine is definitely available.

A much older discussion, though still pertinent, is John Campbell’s discussion of hydrogen breathing life on Jupiter, from the 1930s: Other Eyes Watching. While our model of Jupiter has changed, there has been much discussion of biospheres on hydrogen rich planets in recent years – even Earth is suspected of quite high hydrogen partial pressures in the past. Hydrogen greenhouse planets could provide liquid-water conditions for photosynthetic life all the way out to Saturn. Past that point, the Rayleigh scattering of light makes photosynthesis too hard for life to pursue, so liquid water biospheres further out would need to run on more exotic energy sources. In the right parts of the Galaxy, capture of dark matter and its possible self annihilation could warm planets to provide more clement conditions for life.

Ammonia is often touted as a replacement for water as a biological fluid in cold conditions – there’s at least one astrobiology group experimenting with precursors to biomolecules in ammonia as the replacement solvent. Under pressure, the temperature range for ammonia becomes wider, so ammonia-based life need not be “cold” life.

While ammonia is analogous to water, as they’re both polar molecules, non-polar liquids like carbon dioxide and methane have been discussed as homes for some kind of life. Super-critical carbon dioxide – i.e. warmer than 31 C – has also been discussed as a medium of interesting chemistry relevant to life, but our ignorance of the limits of chemistry hobble our imaginations.

Stephen Baxter, the British SF writer, made the interesting suggestion of metallic life arising from even more exotic liquid environments – oceans made of iron carbonyl, which decomposes at relatively low temperatures into iron metal and carbon monoxide. His “robotic” aliens, the Gaijin (“alien” in Japanese), are initially believed to be artificial, but instead evolved on such an exotic world, in his novel “Manifold: Space”.

A Local Source of Bulk Antimatter?

An interesting preprint, pending publication in the 2013 100 YSS proceedings, on viXra:

Powering Starships with Compact Condensed Quark Matter

Author: Thomas Marshall Eubanks

Compact Composite Objects (CCOs), nuggets of dense Color-Flavor-Locked Superconducting quark matter created before or during the Quantum Chromo- Dynamics phase transition in the early universe, could provide a natural explanation for both Dark Matter (DM) and the observed cosmological baryon asymmetry, without requiring modifications to fundamental physics. This hypothesis implies a relic CCO population in the Solar System, captured during its formation, which would lead to a population of “strange asteroids,” bodies with mm-radii quark matter cores and ordinary matter (rock or ice) mantles. This hypothesis is supported by the observed population of small Very Fast Rotating (VFR) asteroids (bodies with rotation periods as short as 25 sec); the VFR data are consistent with a population of strange asteroids with core masses of order 10^10 – 10^11 kg. If the VFR asteroids are indeed strange asteroids their CCO cores could be mined using the techniques being developed for asteroid mining. Besides being intrinsically of great scientific interest, CCO cores could also serve as very powerful sources of energy, releasing a substantial fraction of the mass energy of incident particles as their quarks are absorbed into the QCD superfluid. Through a process analogous to Andreev reflection in superconductors[7], even normal matter CCOs could be used as antimatter factories, potentially providing as much as 10^9 kg of antimatter per CCO. While of course speculative, this energy source, if realized, would be suitable for propelling starships to a substantial fraction of the speed of light, and could be found, extracted and exploited in our Solar System with existing and near-term developments in technology.

As an “anti-arXiv”, viXra tends to be much maligned – though a browse of the bombastic proclamations by a gaggle of pseudoscientists does cause one to distrust almost everything. However in this case there’s merit to the idea.

Alternatively the researcher has put the paper up here: https://www.academia.edu/5092209/Powering_Starships_with_Compact_Condensed_Quark_Matter

The implications of discovering such CCOs would be tremendous for interstellar propulsion – a compact, steady supply of antimatter. Of course the antimatter would need to be used effectively – for very fast starships, this concept from Friedwardt Winterberg is relevant:

Matter-Antimatter GeV Gamma Ray Laser Rocket Propulsion

What’s not so obvious is coupling matter-antimatter reactions to reaction mass, as required by energy economising on missions with lower mission velocities. A gamma-ray beam won’t mix with just any old matter thrown into the rocket engine.

Star Mummies…

Rameses II - Mummy

How will we adapt to interstellar travel? Rocket Pioneer, Robert Goddard, speculated on interstellar travel back in 1918. He saw two options – if we can release atomic energy then asteroids or small moons could be used as large starships travelling at reasonable speeds. Alternatively, if atomic energy proved impossible, he pondered…

[…]will it be possible to reduce the protoplasm in the human body to the granular state, so that it can withstand the intense cold of interstellar space? It would probably be necessary to dessicate the body, more or less, before this state could be produced. Awakening may have to be done very slowly. It might be necessary to have people evolve, through a number of generations, for this purpose.

In the latter case he suggested solar-boosted hydrogen/oxygen rockets, with interstellar speeds of just ~5-15 km/s. That’s 60,000-20,000 years per light-year. The pilot would need to ‘wake’ occasionally for course corrections – though Goddard had suggested an automatic navigation system back in 1907-1909 using photo-cells, a system used on the “Mariner” probes – so would be re-animated every 10,000 years on trips to nearby stars, and every 1,000,000 years or so, for longer trips.

Goddard had worked on solar-powered ion rockets back in 1909. But he didn’t consider light’s own pressure to push solar-sails. If he had, then the 1,000 year missions to Alpha Centauri suggested by Greg Matloff would’ve seemed a natural improvement over the deca-millennial missions chemical rockets implied.

Of course we know atomic energy can be harnessed – if we so dare. Yet the idea of flying between the stars as mummified cryogenic life-forms has a strange allure. To travel the stars so, we would needs become like human-sized ‘tardigrades’ or ‘brine-shrimp’, both of which can undergo reversible cryptobiosis in a mostly dessicated state. Even if we can’t do so (reversibly – it’s not too difficult to make it permanent), might there not be intelligences “Out There” who have done so? What if we found one of their slow sail-ships? Would it seem like a funerary barge, filled with strange freeze-dried corpses?

Fusion Rockets to Mars… Part 2

John Slough’s Fusion Driven Rocket could reach Mars in 30 days, though for the first missions a more achievable 90 day flight time, and 210 day Round-Trip time, is touted.

Roadmap to a Fusion-Driven Rocket with a 90 day trip from Earth to Mars [pptx slides from Pancotti]

Mission Design Architecture for the Fusion Driven Rocket [paper from 2012 describing the architecture of such a mission]

The Fusion Driven Rocket [NIAC Phase II presentation by Slough, Pancotti & team]

The following diagram illustrates the propulsion system basics:

mars-fusion-drive-4

To achieve fusion, the fusing material needs a rapid input of energy and high density conditions – conflicting demands as the energy wants to drive the materials apart. Such conditions can be achieved briefly by dynamic means – in this case, by imploding metal foils (“liners”) onto a small Field-Reversed Configuration (FRC) ‘plasmoid’ composed of fusion fuel. A plasmoid is a self-shaped structure of plasma (ionised matter is ‘plasma’), which in an FRC pulls itself ever tighter via its own magnetic fields. Thus it naturally drives itself towards high density, until it loses too much energy to radiation and unravels. Before the plasmoid does so, it is compressed by magnetically imploding liners to fusion conditions for long enough to react a significant fraction of the fuel, releasing much more energy than the liners input into the plasmoid. Much more.

For the initial design, as described, the Fusion-Driven Rocket’s ignition system is driven by a solar-array, with no attempt at extracting fusion energy from the plasma stream. Eventually an auxillary power source not restricted to Sunlight will be needed for the Outer Planets, but to get to Mars and the asteroids, a solar array is the least development heavy power-source. The fusion reactions occur once a minute or so, due to the charging time of the compression system, and the current design is very conservative in system components – the solar arrays get 0.2 kW/kg, while the capacitor system stores 1 kJ/kg and so on. Thus a deliberately conservative design based on what we can build now – the only novelty being the fusion engine.

That final NIAC presentation has this rather optimistic development timeline:

FDR RoadMap

…the optimistic point being that it’ll be a “NASA Mars Flight Program” that implements the Fusion-Driven Rocket. I wonder.

Fusion Rockets to Mars… Part 1

While there are perfectly workable concepts for sending humans to Mars by using chemical or nuclear thermal rockets (NTRs), neither option gives spectacular performance. Initial Mass in Low Earth Orbit (IMLEO) is the relevant performance metric and fortunately there’s several quasi-complete designs using both chemical propulsion and NERVA class nuclear thermal propulsion that we can refer to.

First design is Wernher von Braun’s 1969 design, using NERVA class NTRs, which sent a crew of 12 to Mars – and brought them back – in two separate vehicles, landing six on the surface in two 50 ton Mars Excursion Modules (MEMs), all for an IMLEO of 726 tons per vehicle, or 1452 tons total.

Encyclopedia Astronautica: Von Braun Mars Expedition – 1969

Von Braun 1969

The second design, using chemical rockets, was developed by NASA in 1971, with the same crew (6) and MEM (50 tons) as a single Von Braun NTR vehicle. Total IMLEO was 1900 tons.

Encyclopedia Astronautica: NASA Mars Expedition 1971

A more recent design, developed by Robert Parkinson, launched a crew of five towards Mars in three vehicles based on Shuttle-era technology – the European Space Agency’s Spacelab module (which actually flew) and the Orbital Transfer Vehicle (which was studied extensively, but never launched.) Two of the vehicles, Orbiter 1 & 2, massed just over ~210 tons each, while the unmanned Lander Assembly, carrying the MEM, massed 194 tons. Total IMLEO would be 615 tons.

Mars in 1995! (1980-1981)

Mars-in-95-Rover1
[Artwork by David Hardy]

I am deliberately avoiding Robert Zubrin’s “Mars Direct” in this discussion, as it requires In Situ Resource Utilization (ISRU) to fuel up the Mars Return Vehicle, thus skewing the comparison. However incorporating ISRU is, in principle, possible for the design I wish to discuss next: the Fusion Driven Rocket.

Fusion Driven Rocket
Fusion Driven Rocket

Revised Habitable Zone… a Revisit.

Ravi Kumar Kopparapu and colleagues [Habitable Zones Around Main-Sequence Stars: New Estimates] have revised the 20-year old work of Kasting, Whitmire and Reynolds [Habitable Zones Around Main-Sequence Stars], with two seemingly minor changes with surprising effects.

Firstly, they’ve extended the range covered by the model to include stars below the 3700 K limit of the previous work, towards the much cooler 2600 K realm of very low mass Red Dwarfs. The very coldest hydrogen-fusing stars are still white-hot – Red Dwarfs drop down to just ~2300 K at the H-fusing limit of 0.08 solar masses, and 2600 K is hit by 0.09 solar mass stars. Secondly, they’ve improved the modeling of the greenhouse effect created by CO2, which has produced some startling changes in results. Earth ends up near the inner edge of the Habitable Zone – instead of 0.95 AU, the inner edge for a Solar-like star is ~0.99 AU and is even further out for redder stars. Ravi has provided a calculator of the effects on his web-site…

Hab Zone Calculator

…the default is the Sun, with an effective Temperature of 5780 K and 1 Solar Luminosity, and an Inner and Outer Edge of the Habitable Zone of 0.9928 and 1.6886 AU. Push the Calculator to 7200 K and the Edges become 0.9451 to 1.5285 AU. Drop the temperature to 2600 K and the range changes to 1.0883 to 2.1238 AU. So what’s going on? Why the changes? The peak radiation frequency of the spectrum is proportional to the effective temperature – hotter stars peak towards the ultraviolet, while cooler stars peak towards the infra-red. Planetary atmospheres are more effective scatterers of higher frequencies than lower frequencies – the cause of the blue daylight sky – and this means under a bluer spectrum, a planet is cooler, or warmer under a redder spectrum.

The Inner Edge is hit when the surface temperature runs away from our temperate ~288 K (15 C) and climbs towards 340 K (67 C), causing a wet stratosphere and eventual dessication of the planet via hydrogen loss. The Outer Edge is reached when no amount of extra carbon dioxide can further increase the surface temperature – adding more just reflects heat away. In fact at 35 bars the CO2 will condense into liquid at 273 K, but becomes opaque at lower pressures before then.

Interestingly if Venus was as far from the Sun as Mars most of its atmosphere (~90 bars CO2, 2 bars N2) would begin condensing rapidly. A turbulent atmosphere, full of convecting plumes, would carry heat away from the hot surface to space… rapidly. In a couple of decades, the place would probably find an equilibrium at something close to CO2’s critical point, about 304 K – just 31 C. An ocean of liquid carbon dioxide about 120 metres deep would form, though much of it would eventually percolate into the regolith creating a very exotic “ground-water”. Ultimately bright CO2 clouds might form and drive the temperatures lower, towards full condensation of the atmosphere…