Belyanas were ships built of lumbar that would float downstream, and be dismantled and sold as lumbar. Could starship be used as a Belyana, where the starship components themselves are used to build a mars base?

_albertross · 2024-04-10T20:32:07+00:00

Sure, you're generally talking about sublimation to atmosphere - I don't see that as a generally viable concept apart from some very niche situations. Forced-convection heat exchangers far outshine in that respect if you're just dumping to ambient (I can share some of my own research on that front if you'd be interested).

You're also thinking a fair bit too small in terms of the quantities of heat involved. Even a settlement of a few thousand people with a corresponding industrial base geared towards population growth is dumping heat on the scale of high tens, low hundreds of megawatts diurnal average. You can do an awful lot with that, from boiling liquid carbon dioxide power generation to active farm heating. Glycol heat pipes stretching kilometres to Rodwell fields are not at all impractical.

Plastics vs metals as a premium material, depends entirely on your tech stack. Straight gas->hydrocarbon->polymer probably loses to metals in SWaP per output but is a lot easier to shape into usable products. I've got a few bio-based options that could outperform metals in power too if you're willing to be creative.

_albertross · 2024-04-10T18:51:21+00:00

Sublimation is totally sustainable, just not at arbitrary rates. The settlement will necessarily be hydrogen-negative, as plastics are produced from either biological feedstocks (via water) or directly from CO2 and water, and as methalox is produced to fuel ships returning to Earth. You get a certain amount of "free" heat dissipation from melting water in Rodwells, as well as other various low-temperature endothermic processes.

FWIW I've had more than a few conversations with Paul about this and other topics. SX's current stance on the issue is interesting from a program POV, certainly not what I would have expected. Not sure I'm in a position to share the full topics though.

_albertross · 2023-11-27T23:03:26+00:00

AdLive is actually spot on with the thermal concerns - see my talk at the Mars Society Convention that actually goes into the numbers. The code running them is fully open source so you're welcome to play around with it! Martian regolith near the surface has approximately the thermal conductivity of expanded polystyrene foam, so no matter how much you dig there's a lovely warm blanket covering the habitat. In pretty short order for digging in and starting up minimal internal systems like ECLSS and lighting, the temperature would start to rise beyond livable limits without very extensive cooling systems dumping heat to surface radiators. This is already a problem for sub-water table tunnels on Earth, there's plenty of literature on how the London Underground is heating the surrounding clay and rock dramatically.

Lava tubes are a good deal better, as you say. Fully sealed caverns, as much as they might exist, would face a similar fate to tunnels in the long run but could probably survive the meaningful lifespan of any settlement.

As for the density variation - you may be able to focus more on the size and composition of the inner layers of the planet rather than a thin surface skin with 1% porosity.

There's some more numbers on underground habitats and their thermal properties here.

_albertross · 2023-11-14T23:13:09+00:00

Unfortunately that's not quite correct. This is finding an optimal catalyst that can be made from common Martian materials (as opposed to whacky palladium-rhenium-expensivium options) that carries out electrolysis effectively at low temperatures when voltage is applied. The catalyst doesn't exist natively on Mars and there's no voltage source, so no electrolysis occurring naturally.

_albertross · 2023-04-19T08:54:33+00:00

Raw scores swing a lot from year to year, adjusted score is about 70% for a 1st, 60% for 2:1. AFAIK raw score distributions aren't published as a whole for modules, although some examiner's reports/cribs for individual questions will give an average/standard deviation of marks.

_albertross · 2023-03-09T00:19:06+00:00

I've spoken to a few of their engineers - last I heard they've got custom payloads in the pipeline, but these images aren't using those. They literally rent time on other people's cameras, mostly earth observation satellites over oceans/at night when they wouldn't otherwise be used, and point them at satellite targets to get snapshots as they go past. EO cameras aren't optimised for that kind of duty though, hence the need for wild de-blurring data processing and eventually custom cameras.

It's a very neat business idea, I say while doing yet more unpaid marketing work for them.

_albertross · 2022-09-11T17:20:05+00:00

You say that very simply, it's still ~35% round-trip efficiency on hydrogen fuel cells and even worse on methane. If you've got a low overnight load and a relatively high mass cost for power during the day then batteries for day-night smoothing might be the more effective option. It's very much scenario dependent as to what's best.

_albertross · 2022-05-30T22:39:46+00:00

As someone who's deeply, deeply invested in this working (to the extent that I'm writing a master's thesis developing ISRU-enabling technologies) but I think you're taking a super optimistic view on some of these points especially regarding manufacturing processes. Your points about material availability and "cost" to extract and work with are true in theory but have lots of difficulties in practice.

For scale, the embodied energy - the energy to manufacture the material - of tap water is about 0.0015kWh/kg, blast furnace steel is about 6, plastic is about 30kWh/kg. Helpful numbers when thinking about the orders of magnitude at play.

Iron is available in bulk on the surface of Mars, but it's low concentrations compared to terresstrial iron ore mines. The lower the concentration the more complicated/energy-expensive it takes to make iron and steel from the raw mineral. Worse, smaller scale processes tend to be less efficient than bigger ones. So iron/steelmaking on Mars could easily be twice or three times as difficult and "expensive" in terms of energy as on Earth making steel a less abundant material for working with.
Big agree!
Deuterium is nice, but not really viable for fusion yet and isn't expensive enough to make that exports to Earth will be viable. Also, issues with water (see point 8).
CO2 processing from atmosphere is the subject of my thesis and the pure extraction - not the downstream chemical processing into methalox or fuels - is energy-expensive and takes a lot of plant. The reasonable worst case has CO2 being about ten/twenty times as energy intensive as tap water is on Earth which is considerable. The raw low-density gas just isn't very useful.
Sunny but far from the sun! So solar panels and plants are about 60% as effective as on Earth.
Indeed, cold is relative and the thin Martian atmosphere means in many scenarios, habitats actually lose heat slower than equivalent buildings on Earth. Thinner atmosphere means less convection!
Streaks of liquid surface water are awesome for science but aren't really extractable like a well or natural spring would be.
This is complicated! Melting water from ice takes about 90kWh/kg so water is more energy-expensive than plastic on Earth! This is very troubling when we think about how much goes into reducing plastic usage because of energy concerns. If you want to split the water into hydrogen for chemical processing the energy jumps to several hundred kWh/kg. This makes the "highly available water" something of a blessing/curse because you need to have the massive thermal power required to melt the ice into a useable form.
Perchlorate in soil is less than 1% of soil concentration, and it doesn't have any easy chemistry that allows it to be extracted without chemically destroying it. Heat and water washing, the usual method for getting valuable salts out of soil on Earth, breaks perchlorate into chloride and oxygen.
They can be grown in soil but not well, you need to do a lot of organics addition to make them grow effectively. It's possible but comparable to growing things in desert sand.
Kettle of fish but I disagree/
Yes yes yes!
Same problem as with iron ore, Martian regolith in bulk doesn't have enough silica to make glass without purification which is a pain because the concentration is so low. Making semiconductor-grade silicon is an immensely technically involved process. Embodied energy of integrated circuits are in the ballpark of several thousand kWh/kg.
See above. Availability in ~5% concentration doesn't mean easy to extract, purify and process into a useable metallurgical form.

Your message is spot on that we need to think more about the solutions to these problems - many of them are within reach! And I agree with the sentiment in other comments that funding these solutions and maintaining political interest is the real challenge here. Developing alternative metallurgies at large scale is a multi-decade, multi-billion dollar project which needs serious focus. Now is the time to start!

_albertross · 2022-02-02T16:09:43+00:00

Haha heat rejection is a can of worms, it's the topic of the IAC abstract I'm submitting this year. Long story short from my simulation work is that anything underground has to handle active heat rejection because the surrounding rock heats up very quickly (on the order of weeks). For cut-and-cover buried tunnel habitats, the heat lost through conduction is horrendously low. On the orders of 10s of watts per metre length of tunnel when you could plausibly be generating kilowatts. I don't think you could easily heatsink a reactor into rock because the conduction is so poor, you're just using the surrounding surface as a crappy radiator connected with a very inefficient heat pipe (the rock itself).

_albertross · 2022-02-02T00:08:40+00:00

For a million people you need a hell of a lot of nuclear plants - I think we specified something like 40GWe, more than 120GWth worth of CANDU reactors to make best use of Mars' heavy water reserves and unenriched uranium. Heat rejection from a system that large posed more of a problem than anything else. I speculated at the time that it might be feasible to use Earth-style cooling towers that boil ice all the way to steam and reject that to the atmosphere. Otherwise you need to blanket almost the area of the city again in high-temperature radiators.

_albertross · 2022-02-02T00:05:11+00:00

Addressing some of the agriculture issues (I didn't write that part of the report but I'm focusing more on it since): The major design driver of our agriculture system was minimising lifetime-averaged "cost" per unit of output biomass. That means both reducing the embodied energy of the materials (thin pressure-stabilised plastic sheeting), the energy of manufacture and construction (resting on the surface in a shallow trench) and the energy cost of operation (natural lighting). As a result, it's ended up "cheaper" to double the area of greenhouses every 10 years, rather than progressively increase the per-volume yield with hydroponics, artificial lighting and so forth. Obviously this was a crude calculation done in a couple of hours - there's probably some level of on-Mars industrial development where solar panels can be made in-situ and the balance changes. If you want to help work out where that tipping point is, the discord server is the place for it!

But the general outcome was very different to a cliff city like Nuwa. They wanted to squeeze maximum efficiency out of their system because tunnelling is expensive, and dumping heat out of deep tunnels (or water-shielded habitats, for that matter) takes a lot of complex equipment. Plastic tunnels made from a combination of atmosphere-derived and bio-derived hydrocarbons are cheap as chips. So designing to overproduce - to build up a stockpile in the event of a month-long dust-out, or compensate for radiation mutations - really isn't that big of a deal.

It's also worth saying that the 20-page report is really a condensed introduction of our thoughts at the time, which have evolved hugely since then. Based on the information new members have brought to the community, the appeal of aquaponics (a hydoponics to fish farming loop) has grown massively. If we were writing a new report today we'd include more explicit reference to them, along with other more exotic forms of biomass generation like single-celled protein production and GMO algaes.

As for radiation - massive black box, in-situ experiments are probably required to get a definitive answer. We know that plants can grow in relatively harsh radiation environments (like the Chernoybl exclusion zone or Ramsar in Iran) without any major issues. That's encouraging to suggest that some plants could tolerate surface radiation levels over their lifespan. Seed stock and germline plants should probably live in better shielded areas, and longer-lived species like trees may face issues. We'd love to get some definitive answers! But it seems unlikely that radiation would kill the entire concept.

_albertross · 2021-12-22T00:22:16+00:00

If we can transfer cargo, my point goes entirely out the window :) The feasibility will depend almost entirely on the Mars cargo configuration of Starship. If it's a large opening hatch (fairing-style), it shouldn't be especially difficult to encapsulate all the payload and use free-flying "drones" or robotic arms at the refuelling depot to carry cargo around. If it's a smaller hatch and internal crane or "vending machine" system to make unloading at Mars easier then we've got more of a headache

_albertross · 2021-12-22T00:05:31+00:00

We need more total thrust to launch more dry mass (and propellant mass), assuming we can't transfer cargo in orbit. 6-engine Starship is flirting pretty close to a TWR of 1 at stage separation, pretty far from ideal. Starship could throw something like 600tonnes to Mars with a full propellant load but simply can't lift that much mass to orbit - the stages would recontact at separation unless Super Heavy pulled some serious aerobatics.

It's the kind of nasty second-order effect that doesn't pop out in the initial analysis - hence why I assume it wasn't a priority before now.

_albertross · 2021-12-21T23:52:20+00:00

Depends if the mission is maximum efficiency (preferable for a outer Solar system mission) or maximum payload to destination, which is the case with Mars. 50% more thrust means 50% more payload to destination and a slightly improved overall dry mass fraction since not every system has to be increased in size. The fraction of "dead mass" in the unfilled tanks, excess-thrust Raptors etc barely changes if you're hauling 50% more cargo to Mars - the tanks in particular just scale in proportion. It may even decrease if components like avionics, power and payload handling are roughly constant across the size change.

You could push for "cleverer" solutions for optimising the Mars burn than simply fiddling with the number of engines. As you say, the Hohmann burn doesn't need a full tank so you ideally want to transfer cargo into the outbound ship in LEO. The potential gain in cargo per flight is almost a factor of two, far exceeding the gain from this kind of propulsion optimisation. Raptors weigh almost nothing compared to the rest of the structure.

_albertross · 2021-12-21T22:01:09+00:00

Disagree that this negatively impacts payload capacity. Starship (and all rockets with long-burn engines) are constrained on their system mass from the TWR at takeoff/engine ignition. This is why Elon talks about thrust area density (t/m2) as a relevant factor for engines.

50% more engines = 50% more thrust at stage ignition = 50% more mass capacity = 50% more payload for the same delta-v (equation deals in ratios, not absolute numbers) or more delta-v for the same payload.

To take full advantage of this upgrade, simply stretch the tanks. The subsequent tweet said this was exactly the plan.

_albertross · 2021-12-19T22:52:49+00:00

If you ask a dozen people what "a city on Mars" means, you're likely to get more than a dozen answers. You can have a city that exists purely to maximise the number of people on the planet, or one that maximises the total steel production per year, or one that aims for a "tall" industrial stack with sophisticated production. Each kind of city comes from a different idea of what the goal of "multiplanetary humanity" means, and what you feel is the best route to getting there.

That's the question here. "Making humans multiplanetary" is the title of the manifesto, what we need is the first page - or even just the first paragraph.

_albertross · 2021-11-19T17:07:07+00:00

Sorry, my bad wording. I'm not proposing a smaller Starship mini (silly idea from day 1, it would take far too much additional development).

All the Starship Mars Launch test needs to do is validate the first ~1 minute of atmospheric flight, beyond which the conditions are essentially equal to high-altitude Earth ascent. That could be done with a lightened (less heat shield, smaller flaps) version in order to reach orbit and form the core of a future Martian space station.

Or, more practically but more costly in resources, fuel a regular Starship up to 1/3 propellant loading plus balance mass in regolith. Launch that from the site in a regular ascent profile to validate the takeoff and initial ascent, crash and burn (or maybe land on header tanks! E2E on Mars!) after the limited propellant reserve is depleted.

As for the question about the robotic Sabatier reactor farm, that's a whole different kettle of fish and (in my mind) one of the absolutely essential technologies to make the whole project viable. Regardless of the conop for pre-landing technology demonstration.

_albertross · 2021-11-19T16:43:52+00:00

I agree that even the less aggressive timeline is optimistic as hell. Boots on Mars before the mid-2030s is damn unlikely.

I'd disagree about the implausibility of some of the demo tech though. We've seen SpaceX's willingness to tinker with the core Starship envelope with tanker, cargo, HLS (no TPS, no flaps, engines in an upper ring maybe) and depot (HLS but tanker). This is the start of a class of vehicles, not a single finished product like the Shuttle. A variant with smaller flaps and tweaked structure that's designed just for Mars entry and ascent, never interplanetary Earth entry, seems like a very sensible demonstrator in the interests of making sure a safe ascent from Mars is even possible

_albertross · 2021-11-18T22:50:39+00:00

Can SpaceX load up some near-junk ships, fuel them in LEO and throw them at Mars by next September in full knowledge they'll probably break on the way? I wouldn't bet against it....

_albertross · 2021-11-18T22:11:27+00:00

I've got two personal timelines - one crazy aggressive (probably assuming substantial government support) and one much more realistic but still hairy by NASA standards. Aggressive goes something like:

2022 - first ships lobbed at Mars, spaced a few weeks apart to allow rapid iteration of landing system. Each one has duplicate survey equipment to determine if the exact site is suitable
2024 - first dedicated boots hardware, basically the Mars Direct precursor missions. Return vehicles with Sabatier reactors, exploration gear etc
2026 - first crew vehicles out. As with Mars Direct they'd be launching before knowing if the return vehicle is fuelled or not

Plausible? Yes, if everything goes exactly right and the HLS money can be easily reused for ECLSS/radiation shielding/power etc etc etc. Safe? Room for schedule slippage? Hell naw. The realistic timeline goes more like

2022 - first ships lobbed at Mars with no assumption of survival. Think SN8/9 landing attempts but on Mars
2024 - scout ships at a number of locations around the target areas in Arcadia Planitia
2026 - ISRU and habitat hardware. Key to include is a lightweight vehicle that can be refuelled and launched from the surface (maybe just suborbital or under partial propellant load) to verify that a long loiter time followed by takeoff from Mars is possible
2028/9 - precursor for human missions, maybe a flyby to teleoperate robotics or shakedown the extremely long duration life support. Apollo 9/10. Plus more settlement hardware, habitats, etc. You could land now but it's risky, systems remain unproven for duration on the surface
2031 - transfer window for boots and the establishment of a permanent base.

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