Sci-Fi: Practical Rocketry for the Bright Conference

 More notes on my draft optimistic hard sci-fi setting, the Bright Conference.

Arthur Gurin

Fuels and Engines

Rockets make people a bit weird. Some proposals feel like "Pro Tip: You can commute to work faster by taking amphetamines, driving through oncoming traffic, and firing a belt-fed machine gun." 

It's technically correct advice, but Isp isn't everything. Arriving at your destination is nice too. Normally, I'd go "Augh, hydrazine!" but after reading about some of the speculative engines and fuels out there I've started to say "Nice, safe, predictable, cuddly hydrazine. You'd never betray me." 

For the Bright Conference, I'm limiting technology to something with a real-world test or a thorough proof of concept, not just a sketch on a napkin or a thought experiment.  Anything at a Technology Readiness Level of 3 or above on this table is probably fine. This means no antimatter rockets, no fusion rockets, and no handwaved reactionless drives. I'm going to err on the side of plausibility.

For human exploration pods, liquid methane and liquid oxygen makes a lot of sense, with hydrazine or some other monopropellant used for reaction control. Other species may have other requirements, technology chains, etc, but they're still limited to the viable, and not just the possible.

You can make some rockets more efficient with cheap power. Where do you get cheap power? The local star is the obvious source. You've already got a giant fusion reactor. Why not use it?

Solar panels. Plenty of room for improvement, but panels add mass and cooling requirements.

Beamed power. If you're staying in a system for a long time, set up a solar power station and send the power to your ship. Microwaves, lasers, battery transfers: whatever works best.

Use a solar sail / magnetic brake to move from location to location slowly, which may not be a concern for species that travel efficiently. Humans do not travel efficiently.

Alternatively, use a nuclear reactor. Waste heat management is an issue (Damn you Carnot!), but this seems like a technology chain that could be optimized, given sufficient time. It also seems like a solid modular product. Buy an off-the-shelf nuclear brick with a built-in radiator, stick it on your spacecraft, and use an adapter to convert the output to your needs. No user-serviceable part inside.

Ditto for fuel cells. Hydrogen is a bit tricky to carry around unless you need it, and you can't get very much power out of one, but it's a neat trick.

Fusion reactors are possible, but only on an installation scale, and only when using the free fusion reactor in the sky isn't viable. They're usually next located near their hydrogen source, or used in gate devices.

You can use mass drivers (a.k.a gravel guns) to move an asteroid. Filling a system with high-velocity pellets might seem like someone else's problem, but that someone else inevitably becomes you, so this probably isn't a common or portable method.
Scott Scneider, Supernova (2000).
Not a great film, but great miniatures, and at least some sensible hard-ish sci-fi decision making.


No shields, no magic, no credible defense. This isn't a tactical sci-fi setting. It's a policy sci-fi setting.

Accidental impacts (micrometeorites, debris), general radiation, and solar storms make some form of armour useful, but not every component can be armoured.

Nuclear weapons are still viable (for different reasons than in an atmosphere), but conventional explosives, or even simple kinetic impacts, are still dangerous. If someone really wants you dead, they will find a way. The missile/drone/laser/plasma/shell always gets through. Spaceships are fragile. The most technologically advanced alien ship is unlikely to survive a few direct hits from an autocannon.

The choice is this: do you haul around a defensive system that you'll probably never use, and won't save you even if you do use it, or do you rely on reputation, risk/reward calculations, and unintended consequences?

Most species use dual purpose systems. Technology that could be weaponized, but has another useful function to justify its existence, and the cost of hauling it around. You don't need to pack a rocket launcher, you need to pack a hiking pole.

Probes/missiles are expensive. Each probe is a miniature spaceship, with its own fuel supply, maintenance costs, and duplicate (in miniature) of many systems aboard the main ship. Cut corners and your probe becomes unreliable or even a liability. It's the same problem faced by escape pods and shuttles. On the other hand, having more than one eye is very useful.

Lasers can be used for long-distance communication or accelerating small probes. Most high-velocity probes ride behind a laser, which sweeps dust from their route. It seems plausible that compact high-efficiency lasers could exist, but they aren't completely effective defensive weapons. You can turn an incoming bullet into an slightly warmer incoming bullet, while filling your ship with waste heat in the bargain.

High-density energy storage mediums can be turned into explosives, or at least inconveniently feisty devices, under the right conditions. Communications equipment can be used as electronic countermeasures. If you can transmit a signal, you can transmit a countersignal, noise, or lies.

And finally, thermonuclear bombs can be made low-maintenance, relatively safe to store/hit with a hammer. You can't guarantee any given ship isn't carrying a small missile with a city-destroying warhead.

Side Note: Atomic Rockets and other hard sci-fi advice sites remind readers that most FTL systems can be casually turned into weapons mass destruction. This can be a problem for military sci-fi, but the Bright Conference says, "So? We have weapons of mass destruction."
Dave Malan

Human Astronauts

How do you train an ambassador who cannot be held accountable?

How do you prepare someone for a mission where death is very, very likely? Not deliberate murder, but accidental death from malfunctioning equipment, radiation, running out of fuel and air, or living a long, interesting, and terribly lonely life around some distant star.

How do you train someone for a situation that is almost entirely unknown? No mission control, no fixed criteria for sucess or failure. Just guesswork, improvisation, and staying calm under pressure. Playing the long game when you can't see the board.

Anyone running an ambassador training program also can't rely on the sci-fi standard youth indoctrination camp. You can't rely on secrecy and limited information. You need wholehearted consent. Your ambassadors will be out in the world, thinking for themselves, reading all the forbidden literature, uncovering all the leaks and war crimes, or running into another astronaut, alien, or adaptive artificial intelligence trained to argue philosophy.

An Excerpt: Training

"Moving on to proposal three. Hire some puzzle-makers and psychologists. Tell them to design some non-anthropocentric puzzles. Really hard ones."

"Should we ask an alien for advice?"

"Perhaps, if we can explain the concept to them. I'm sure other species have had the same problem. But they could bias the training."

"Noted. I think we should look at full-scale simulations as well."

"Like virtual reality?"

"No, that never works. I mean the sort of simulations that paramedics use. You arrive on scene, there's fake blood everywhere, an overturned car or a collapsed stage, and you need to triage. Like an obstacle course, except it's realistic."

"And instead of actors it's logic puzzles?"

"Or actors in alien costumes."

"Right. And our trainees have to navigate the scenario."

"On mescaline."


"Hear me out. We want our trainees to be used to bewildering situations, of clinging to rationality when the world is apparently going mad. So we dose them with mescaline, and perhaps a mild emetic, or something else to simulate zero-G sickness. I don't know, I'm not a doctor."


"Can someone explain how we'll get useful information out of this proposal? How are we evaluating trainees? Is this timed or..."

"It's holistic. The point is to see how they do under extremely adverse conditions designed to simulate, as best we can, the experience of being out there. Alangrave described visiting a station as 'being a mouse in a shopping mall designed by Escher.'"

"And trying to solve a rubix cube, on mescaline, while theater students dressed in rubber suits hit you with pool noodles is exactly like that, right? Come on. Proposal four..." 

Pack Only What You Need

In null gravity, humans aren't going to do a lot of walking Is leg amputation really such a radical proposal? Cybernetic eyes and cortical implants are science fiction, but chopping off legs is science fact. 30-40% a human's mass is legs, and you don't need legs in null gravity. Space agencies in the real world seem to agree. Launch mass is one concern, but maneuvering mass is also important, and a species surgically altering itself make space travel easier is not uncommon.

"We had a very pious and humane man, who gave them a most excellent sermon on this occasion, exhorting them not to kill us all at once. 'Cut off only one of the buttocks of each of those ladies,' said he, 'and you will fare extremely well; if you are under the necessity of having recourse to the same expedient again, you will find the like supply a few days hence. Heaven will approve of so charitable an action, and work your deliverance.'

-Voltaire, Candide

Closed-Loop Ecological Life Support

The ultimate goal is to turn a human into a closed cycle. The only input is energy. The only output is waste heat. Everything else is recycled. Unfortunately, humans require a lot of complex inputs and make a lot of weird outputs. There's no way to get a backpack-sized permanent life support system working for a human. Even with mildly handwaved tech, a full recycling setup would probably be too large to bolt to a one-person spacecraft. 

Since this is an RPG and not a manual, I can probably get away with saying "Feces centrifuge," "biosolids conversion algae," and "algae supplement pellet" and let you imagine the rest. Closed-loop recycling is both a psychological and an engineering problem. NASA claims the ISS is 80% efficient.

Some back-of-a-napkin math suggests that a perfect plant/algae based CO2->O2 recycling system (i.e. algae in tubes) is probably not portable, or stable for 1 astronaut. Since cryogenic storage of large quantities of O2 and N2 is viable, this system does not need to be 100% efficient.

A human Bright Conference pod usually uses three systems:

  • Alien bioengineered algae pods. Mostly used to supplement food. CO2, power, and water in, O2 and sucrose out... but nowhere near enough to close the loop. It could if humans were more efficient, but we aren't.
  • A regenerative metal-organic CO2 scrubber. CO2 buildup will kill you faster than you'll run out of O2.
  • A sealed chemical scrubber in case of a fire, power loss, or other catastrophe. Peel the top off the tube, get an extra few hours of life.

We can't eat alien snacks, and they can't eat our snacks. You have to pack a lunch.

The Vital Ingredients (a.k.a. There Is Such A Thing As A Free Lunch)

"Vital Ingredients" is a mistranslation, but it stuck. The theory goes that most newly contacted planet-bound species need time to adapt to the level playing field of null gravity and hard vacuum. An altruistic well-established species can set up a buffet (or bird feeder) of raw materials. A traveling species can replenish supplies for free (or under the terms of a very generous supply-limiting contact). It costs the altruistic species very little and earns them an enormous amount of goodwill.

It not something you can count on, but it does exist. There's usually a term to prevent permanent freeloading, but some species don't mind if their buffet attracts permanent residents. A buffet can create a space station and a culture. Locating these buffets could be a mission for the PCs. Not all are equally useful.

A Vital Ingredients buffet usually includes a few tanks of bioengineered algae-analogues to upgrade raw materials. Almost nothing on the buffet is something humans consider food. Aside from oxygen and water, ethanol is usually available. Tbe joke runs that you can starve to death sober or you can starve to death drunk.

Luckily, some alien species have fancy algae-analogues that will upgrade methane, acetic acid, or other common buffet items into glucose or starch, and a handful of vital amino acids. The life support package of well-equipped Living Module may include a few of jars of these cultivated organisms, in the optimistic hope that the module will be useful for decades.

Back-Of-The-Napkin Math

NASA (values are per day)

For 1 person-year:

  • Water (80% efficient recycling): 1.3 tonnes. Call it 1.5 tonnes. Note that this only counts biologically necessary water. ISS astronauts use a lot more water for hygiene.
  • Oxygen (no recycling): 0.3 tonnes. Call it 0.5 tonnesfor safety and to provide extra O2 to flush the filters. Doesn't count fuel oxygen.
  • Food (with minimal water) (negligible recycling): 0.2 tonnes. Call it 0.3 tonnes, or 0.5 tonnes if you want to be generous. 

Artificial Gravity

There are no magic gravity plates in the Bright Conference. You have to get your gravity from Sir Isaac Newton. The assumption is that exploration is sufficiently dangerous that long-term health effects of null gravity are probably not what will kill you. Living Modules contain exercise equipment, but spun gravity rings are not viable at the moment. If you make it back to Earth - and it's a very big if - a long hospital visit will be mandatory.


No showers. Just a wash cloth and centrifuge, or wet wipes, or perhaps, as a luxury, a plastic bag you can climb into. Pre-launch, consider permanent hair removal from some areas (or your whole body; it'll save time), cauterization of nail beds (see below), and freezing your gametes (if you want to have offspring).

Human spaceships require constant maintenance. Sterilize the vent filters. Suck up skin flakes and dust with a tiny vaccum wand. Wipe down surfaces with your limited supply of biocide. A UV sterilization lamp might not be the worst idea. Could help with vitamin D and, possibly, the blues. While most gates are near stars, "near" is a relative term.

Human Spacecraft

The Bright Conference is a 5-minutes-into-the-future setting. If we can't do it now, then I can't include it.

Spacecraft are designed to use Hitchhiker Waivers. Humanity cannot currently afford to pay the Gatekeepers, but other species will occasionally pick up a low-mass ship or two and take them along, with no assumption of liability on the other side. Humans can also negotiate travel arrangements with alien species directly, usually with better terms.

I'm thinking around 20 tonnes is a good value for a one-person one-year ship.  

Excursion Module

A spacesuit with a backpack. The backpack partially swings to the side to reveal a hatch. You attach the hatch to your living module and climb out, like a spider shedding its exoskeleton. A spacesuit isn't clothes. It's a small uncomfortable room with pockets for your limbs. 

The helmet has a ranging laser and one or more visors. Inside, there are a few display screens, a water tube, a microphone, and speakers. 

The backpack has a battery, radio, radiator, tiny solar panel, air tank, water tank, gyroscope, and propulsion system. The backpack stays outside the living module. If it breaks, the astronaut can use the entire living module as a sort of giant backpack.

Gloves are the worst. Human hands are not designed for space. Portable robotic analogues are not viable yet. EVA work means losing your fingernails. Getting your nailbeds cauterized before you go to space might not be the worst idea. Fine manipulation is almost impossible. 

Side Note: Real-world spacecraft typically use a high-pressure low-oxygen mix for habitats (to prevent flash fires) and a low-pressure high-oxygen mix for EVA suits (to prevent the suit from popping and to allow astronauts to bend their limbs). For the Bright Conference, I'm assuming a high-pressure suit could be designed with current-generation materials (and a blank cheque). If not, I'd need to add a decompression / bends procedure for every EVA.

The backpack has a control arm for the maneuvering unit. Compressed nitrogen or CO2, very limited delta-v. If you can, stay tethered. If you can't, you may need to ask for a push back to your spacecraft. How embarrassing.

Living Module

A small pressurized room with a bed (a sort of sack), a toilet, a bunch of computers, the high-maintenance bits of the life support system, and a lot of storage. "Snug" and  "cozy" might be applicable if you're feeling generous, "a coffin with pockets" if you're not.

Forward-thinking designers add a second hatch. It's not an airlock, but a second Excursion Module can dock, or you can dock hatch-to-hatch and link two or more Living Modules in a chain (though it'll be an ugly unbalanced mess of panels and radiators). It'd be nice if humanity settled on a universal standard for hatch designs. Spirit of cooperation and all that..

Service Module

All the other parts that make a spacecraft possible, but do not require human interaction or regular maintenance. A robotic arm with a camera may be useful. Propulsion system. Reaction control system. Solar panels, heat radiator, main battery. Tanks. And adapters. So many adapters.

How Many Crew?

One is the loneliest number. A Bright Conference astronaut is, arguably, the most expensive and vital part of a mission. Given the chance of death and failure, why risk two astronauts when one will do? Loneliness is also an incentive to seek contact and make connections. Either make friends or go mad.

Pair-bonded humans form a common cultural unit. Two astronauts can also keep each other honest (in ideology or chores ). On the other hand, two can be as bad as one. Personal space does not scale.

Three is an interesting number. Three allows for luxurious watch rotations. You can have a human active and communicating at all times.

Reza Afshar

The Kardashev Scale

A few species in the Bright Conference have managed to hit Kardashev II, through Dyson Swarm-like constructions. Megastructures can give a civilization a goal. They are also required for ultra high-end research and manufacturing.

Given the age of the galaxy, sensible species might expect more Kardashev II+es around the place. The most plausible answer is the inherent instability of organized life. A 10,000 year construction project has a lot of room for error, sabotage, changes of priority, etc. Civilization may not collapse, but it wobbles a fair bit. There's no stable plateau.

Data on failure is available. Learn what to do, what not to do... but who's lying to you, and why? Aside from differences of perspective, philosophy, and judgement, there's a temptation to insert false and misleading data. Pretend to fail. Pretend to succeed for non-obvious reasons. It's another reason for contact (and potentially a secret the PCs can discover) Xenoarchaeology is more than just looting and resource reclamation.

Some species aim for a timeless, god-like, inscrutable reputation so that other species leave them alone. In a setting without magical technology, this is tricky. Some species deliberately erase their past and start anew.

Paul Pepera

Getting It Wrong

Post-contact, every washed-up billionaire with access to a rocket wanted to explore life outside our solar system. They signed Hitchhiker Waivers, strapped their tiny improvised capsules to the hulls of outgoing alien ships, and disappeared. Very few made it back. The decision-making process of a coddled wealthy sociopath is not useful in the Bright Conference. On Earth, you can fail gently. There's always the secret bank account, the equity in your house, the friends in high places, the speaking circuit, or the consultant route. If all else fails, there's ditch water and roasted rats.

In space, trapped in a refurbished Soyuz capsule three hundred light years from Earth with twelve days of oxygen and no one willing to pay the exorbitant costs to return an unprepared Hitchhiker to their backwater planet, failure feels very sharp indeed.

Hitchhiking: An Excerpt

The system was more beautiful than he imagined. A binary star, and the glittering arc of a space station. A line of solar panels and reflectors, black as midnight on the inside, glowing red on the outside, with glittering silver supports and docks. The Kurslek ship that had accepted their Hitchhiker Waiver took them within a few hundred kilometers of the station, then let them go and changed course to dock with the massive solar collector.

The novelty of the view faded within a few hours, though, given the cost of this little adventure, Brandon milked every flicker of joy for all it was worth. After taking thousands of nearly identical photos and drafting a few nuggets of wisdom, he had his new assistant Flynn tap out an open Hitchhiker request using the translator program and waited. And waited.

And waited.

Brandon felt like the two-person pod was shrinking. His doctors had told him that he couldn't take uppers or levelers with the antinausea meds, and he'd downed the backup bottle of celebratory champagne hours ago. Masturbation was out. "Are you sure it worked?" he asked, yet again.

"Yes. You can see the receipt ping from the Kurslek ship, the Gatekeeper station, the solar station, and even a mining outpost. They heard us. They just haven't replied." Flynn was hired because he was supposedly an expert on this sort of thing.

"Why not?"

"Because nobody in the system wants to go to Earth right now," Flynn said. "Once again, if they wanted to go, they'd tell us how long we'd have to wait. But they don't. So they haven't."

"Do they know we're running out of air?" Brandon growled. 

Flynn shrugged.

"Give me that," Brandon said, reaching for the tablet. Flynn dutifully handed it over, and, with smirk of authority, Brandon selected the Kurslek ship from the dropdown menu and typed, "Take me home right now."

"Clause requires statement: Consequence." The statement was printed in yellow. No transmission.

Brandon typed again. "Take me home right now or I will die."

"Clause requires statement: Consequence."

"Fucking thing is broken," he said. 

"It's not. If you want to issue a demand in Galactistandard you need to offer something or state the consequences of a failure to accept. It can't be implied." Flynn didn't sound worried, just bored.

"But the consequences are that I, we, will die."


"And... humanity will take revenge?"

"No they won't. We signed a Hitchhiker Waiver. Didn't you read it? We are on our own."

To his credit, Brandon had read the waiver, in both a literal Galactistandard translation and in a summary presented by a lawyer. He just hadn't believed it. He stared at Flynn with growing rage, then tapped at the pad.

"Statement: Clarification: Unless we are returned to Earth we will die in 72 hours." 

The app accepted the statement, translated it into a much longer string of Galactistandard, and beamed it to the Kurslek ship.

Six long minutes later, the ship replied. "Statement: [this ship] is not returning to the [Sol system]. Statement: Overriding Fact: Transmission from [this system] to [Sol system] is not possible for [9.8 days]."

"What the fuck," Brandon said. "Why not?"

Flynn put his hand on the tablet. "That's how gates work. It has something to do with relativity. The Gatekeepers won't allow quick return tickets."

"So you knew? Why didn't you tell me?"

"Back in college, my roommate signed up for one of your brain hacking trials. Remember, the miracle slow-release neurotransmitter booster? He was supposed to get a paycheck and expand the frontiers of science. Instead he had a massive stroke and died, along with everyone else who signed up."

"They signed a waiver," Brandon said automatically.

Galactic Rest Frame

Gatekeepers arbitrarily allow passage. They rarely allow multiple quick trips, and almost never allow a leap-and-return journey. 

There are several explanations:

  • It's a method of preventing war. Everyone has time to think about their actions.
  • Two vessels colliding in the same gate is catastrophic.
  • The Gatekeepers wish to appear more inscrutable than they really are.
  • It has something to do with relativity.
Stellar velocities are low. They're similar to the escape velocities of a planet. For most stars, doing the Lorentz calculations is a bit silly. With rounding, we're all in the same boat.

Let's take the worst case scenario. The fastest star we've measured is whipping around a black hole at 8% of the speed of light. That's a mild Lorentz factor of 1.003. And an oddly convenient bit of math: for every year and a day you spend orbiting that star, a year and one day passes on Earth. That's not a lot of time to get up to relativity-based shenanigans. "Behold my twin! Their birthday is in February but mine is... slightly later in February! Dun dun dunnnn!"

Relativity though experiments include often include phrases like "an appreciable faction of the speed of light relative to one or more observers", as if rocket fuel is free. It's possible get a rocket up to those speeds, of course, but it's not easy. Saying "some high fraction of the speed of light" makes thought experiments interesting. Actually getting to some high fraction of the speed of light, without handwaving the material costs or inventing magic engines, is trickier. 

Speed is expensive and risky. In the absence of gate tech, it's far more efficient to develop some form of stasis (biological, AI inheritors, etc.) and slow-boat your way around a system or between the stars.

Gate tech is heavy. It's difficult to miniaturize and very energy-inefficient at low transported volumes. No ansibles. The smallest gates are used on scout probes, and they still weigh 500kg and only work once before melting. Species have tried to make smaller ones, of course, butthe investment to make them at all is enormous.

And if you do try to use a gate to send information into the past, the experiment will fail. Someone leaves the lenscap on the detector. The rocket explodes. The gate hits the wrong receiver. Funding gets cut at the last minute. Civilizations still try of course (because physicists can't believe it, and frankly, you can't blame them), but it never works.


  1. It just doesn't do to fuck with Flynn's friends, apparently.

    This has been pretty interesting to follow along with so far. Looking forward to more.

  2. Two useful things about fuel cells are that their exhaust is water (potentially filling any gaps in recycling) and the oxygen that they react with hydrogen can be used to extend life support in an emergency.

    Most vessels designed so far don't have very long endurance unless they're docked at a space station. A week to two weeks is pretty normal. After Columbia was lost, part of the ensuing analysis was determining how long it could have stayed in orbit waiting for a rescue. They determined the absolute maximum was around 34 days if the astronauts went to minimal activity to reduce oxygen use and power was cut to a minimum so that extra oxygen was available from the fuel cell gases. Even that was only possible because Columbia was the only shuttle with the Extended Duration Orbiter pallet that increased the fuel cell gases to 180% of what other orbiters could carry. That also didn't account for airlock losses in case of a rescue, which would have dropped the endurance to around 31 days. While the limited advances of technology in Bright Conference could allow for more miniaturization, my feeling is a multi-month spaceship for a human is going to be a fair bit bigger than 20 tons.

    1. Fuel cells are great, it's true, but only if you're carrying hydrogen. Not a bad plan for a shorter-duration mission, where you can round up for leaks, but it might not be the best idea to base your life support loop on a molecule that really doesn't want to stay in a tank. Also cuts down on refrigeration costs/risks if all you need to keep cold is your oxygen. Could theoretically build some sort of methane/O2 fuel cell, but that seems like a mess.

      I really should look into NASA rescue calculations. The shuttle was an extremely weird spacecraft for mass calculations (and in general) but 31 days x 7 people is a good start. A 7 tonne Soyuz MS can allegedly support 30 person days, but has no recycling loops.

      Bright Future pods (the 20 tonne / 1 person vague sketch in this post) are basically mini space stations with a suitlock and a small engine. No heat shield or parachutes for reentry. The 20 tonnes is an early calibration value. If I go to 30 tonnes, not the end of the world. 100 tonnes, something has gone awry.

    2. Another point of comparison might be the Tianhe core module. Strip off the airlock and docking adapters, shrink the diameter, and add a maneuvering pack to the back.

    3. I've been looking at a bunch of things that were either flying in the 1990s or proposed in the 1990s for another game, and here's the mass, payload, crew, and endurance for spacecraft I've been able to find at least semi-reliable data on:
      Hermes - 21 tonnes total, 3 tonnes cargo, 3 crew, 40 days
      TKS - 17.5 tonnes total, 12.6 tonnes cargo, 3 crew, 7 days
      LKS - 19.95 tonnes total, 4 tonnes cargo, 2 or 3 crew, 10 days
      Soyuz-TM - 7.1 tonnes total, 0.03 tonnes cargo, 3 crew, 10 days
      HL-20 - 10.9 tonnes total, 0.545 tonnes cargo, 2 crew + 8 passengers, 3 days
      HL-42 - 28.7 tonnes total, 4.3 tonnes cargo, 4 crew, 3(ish) days
      Multi-Role Capsule - 7 tonnes total, 0.5 tonnes cargo, 6 crew, 4 days

      All of these are designed for re-entry, of course, which skews their masses higher than an orbital-only system. I'm hard-pressed to think of a small, crewed, non-re-entering system. Any two of the three I can get to, even the crewed non-re-entering with cyclers (which are big).

      I'm not that familiar with Tianhe, but based on the frequency and masses of the Tianzhou resupply missions, it's using about 1 tonne per month of supplies. I would guess that reducing crew and improving recycling could lower that amount. I'm not sure if manifests are available anywhere saying what's being sent up (I somewhat doubt it, but I've been wrong before), but at a minimum it gives a real-world data point to work from.

    4. Very handy! As you've said though, reentry (especially with wings) skews the mass. And anything in the proposal stage is going to be a bit fuzzy. I'm sure the math is a lot better than ours, but with the Hermes, for example, that 40 day number is probably an early development goal and not a final realistic result.

      I'll see what I can dig up on the resupply manifests. 1/3rd tonne / month / person isn't completely nuts, especially if their water recycling is in testing/development mode and not in operational mode, the payloads include experiments, etc.

  3. >I'm assuming a high-pressure suit could be designed with current-generation materials

    There was a project few years go to replace balloon spacesuits with elastic ones. You compensate the pressure not with the air but because a lot of wires run along the surface of the suit, tighten up when you go to vacuum and and compress the suit. No idea what happened to the project but it is a 5 minute technology.

  4. So if this is to be gamified, will the players be taking the role of ambassadors? Certainly seems very different from standard adventuring, but I love the strange, lonely, claustrophobic-yet-vast idea of being stuck in one of those pods!

    1. Very different, but hopefully the next post will help with a few gameable aspects.

  5. I am surprised gravity isn't handled by the Battletech method - generate through thrust. Gets you there faster, AND you get the satisfaction of having gravity.

    Obviously more fuel intensive, but some of your mentioned fuel sources sound like they might be able to handle it. And surely it is simpler to just burn at 0.1 G all the time than to burn hard and then coast.

    1. Ah, that's because Battletech has magic rockets. http://www.projectrho.com/public_html/rocket/torchships.php#constantaccel Real rockets have burn times measured in minutes (or long ion-based engines with acceleration measured in small fractions of a metre per second). The rocket is a tyrant.

      Constant acceleration also doesn't work in orbit (or, it can, but it's a _very_ weird procedure. Instead of falling at the planet and missing, you run at the planet and miss. It lets you orbit a planet faster than freefall, but it's not realistic in any way. Fun, though.).

      It doesn't work if you want to park at a station, unless that station is also constantly accelerating. We also don't know what the minimum g is to avoid bone density loss. 0.1g may not be enough.

      The best advice I've got: try Kerbal Space Program (the original, the new one isn't quite stable yet) and see for yourself how hard it is to manage even 0.1g of constant acceleration.

  6. I've got to be honest, the heavy emphasis on how awful space travel is doesn't feel very optimistic to me.

    I get that some of that is coming from hard scifi sources, but stuff like "to pass through a wormhole gate you have to sign an alien waiver saying it's OK if you die horribly, and a substantial fraction of explorers do" isn't. It seems pretty dystopian. At least for the presumably-PC explorers living in tiny pods with no legs; maybe not for the folks back home, who you haven't elaborated on (beyond this snippet where a billionaire kills a ton of people with unethical human experiments because they also signed waivers, but I guess maybe the implication is that Earth became a utopia after all the billionaires got themselves killed this way?)

    There's nothing wrong with dystopian fiction about exploited PCs scraping by in an uncaring universe, obviously, I just wonder if maybe you've lost track a bit of the original objective? Or maybe I misinterpreted what it was?

    1. Space travel is awful in a lot of ways, but the upside, and this can't be understated, is that you get to go to space.

      Hitchhiker Waivers are basically the alien saying "Look, I don't know you, I don't know your species, I can't tell if you're sick or if your ship is well-built or what. But I will take you where I'm going, for free, and drop you off. After that you're on your own." Hitchhiker Waivers are also designed to be extremely clear on all points (unlike, say, a medical liability waiver).

      In the example, Brandon could have investigated his destination, figured out the chances of returning, prepared for the risks, etc. He did not. The sort of person who thinks hiring a rocket scientist makes you a rocket scientist may not be great at evaluating the consequences of his actions. Unfortunately, the loss of a few billionaire did not make Earth into a utopia.

      The "no legs" thing is more of a digression about payload optimization. It's possible a program would say "to go to space you need to let us chop off your legs", but the sort of person who signs up for that deal might not be the ideal long-term candidate.

      "Exploited PCs" is definitely iffy. I don't think any exploration program would send out people who weren't extremely motivated and highly trained volunteers. "Uncaring universe" is correct.