Assume there's a spaceship in earth orbit that its crew of 24 want to get to Mars, the crew are all humans and possess all of modern day knowledge and equipment, is it possible for said ship to make the (one way journey) without any electricity while the crew get there alive?

Think something like space Amish: no purposeful using of electricity regardless of how it's generated; if static (or any other type) electricity is created it's fine so long as it's not being actively used to operate the spaceship or anything in it... so no batteries but combustion & chemical reactions are fine. (Yes I am aware that Amish use some electricity; it's an analogy, not literal Amish.)

Necessary assumptions list:

  • The ship has been designed from the ground up without any electricity
  • How it got to earth orbit doesn't matter, it's already there
  • No magic
  • Modern day tech
  • No electricity can be used, this journey is sponsored by a super-rich man in order to win a bet (the rich do some crazy shit)
  • Price and efficiency are not an issue, it just needs to get there with the crew still alive
  • It doesn't need to land, Mars orbit is enough

I tried thinking of it by each component of the spaceship and this is what I got so far:

  • Rocket engine – shouldn't be much of an issue as it can be controlled with mechanical valves to control fuel flow with a chemical/mechanical ignition
  • Direction control – small puffs of compressed air to point the ship to the right direction should still be possible
  • Lighting – ideas?
  • Air life support – biological plants or algae air recycling? one of the biggest things I'm not sure of how well it will work
  • Waste disposal – mechanically powered vacuum pumps airlock and throw it all away
  • Food – it might be a months long journey but it's still short enough to allow non-perishables canned good and other dry kept food to be the only source of food needed so no cooling needed
  • Water – Some recycling and\or purifying should be possible with muscle power alone, will likely still need to carry more water from the start to compensate but seeing how price is not an issue the extra fuel costs are acceptable
  • $\begingroup$ An obvious question is why bother keeping the crew alive during the trip if it's one way and they're not landing just orbiting ? Isn't that a suicide mission ? Note also that no electricity will be very bad if anyone needs medical treatment. Communications are impossible (and hence tracking for navigation becomes problematic). All mechanical kit adds significant mass (a disaster) and all chemical processes add requirements for storage and processing (possibly very hazardous). "Not impossible" is not the same as "remotely practical or sane". $\endgroup$ Jun 6, 2019 at 4:13
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    $\begingroup$ "King David's Spaceship." $\endgroup$
    – JRE
    Jun 6, 2019 at 8:31
  • $\begingroup$ en.wikipedia.org/wiki/Optical_computing / photonic logic? Light is an electromagnetic wave (and/or a separate particle), but if you count this as "electricity" I think you'd have to count the electric fields in chemical processes, too. I mean electromagnetic force is one of the 4 fundamental forces of nature (vs. gravity and strong + weak nuclear forces), so it's not like you can avoid anything to do with it, if you want matter not to pass through other matter. Anyway, then you just need to power some lasers to drive the photonics, and build pure optical transducers for sensing. $\endgroup$ Jun 6, 2019 at 14:21
  • $\begingroup$ Is biotinkering an option? Animals (and humans) use electricity to function, so are you saying plants only? A ship by Groot, for Groot, of Groot? $\endgroup$ Jun 6, 2019 at 15:14
  • $\begingroup$ Why is it one-way? And whether they stay there or not, how do they prove they actually arrived at Mars so that the rich dingbat wins the bet? $\endgroup$
    – WGroleau
    Jun 6, 2019 at 15:16

10 Answers 10


Yes! And I shall do it by totally violating the low-tech spirit of your question!

The biggest part of the challenge is your desire to go to Mars. Mars is a helluva long way away. If you were going to the moon from Earth, then I'm pretty certain you'd be fine. But a trip that far, with this kind of challenge? Doesn't appeal!

Here's the key thing: no electricity doesn't mean no mod cons! Let me take you back to the old days of scifi, back when calculations were done by hand because there were no computers, and no solar panels. Classic Heinlein. Atomic rockets!

What you want is a bimodal nuclear rocket. Nuclear reactors don't actually need electricity to operate. Sure, they make things easier, but actually you can wheel the control rods in and out with hand-driven mechanisms. Nuclear rockets are decades old technology; almost as old as nuclear reactors themselves, which predated electronic control systems.

A nuclear rocket will give you excellent thrust (needed to move all the stupid rubbish you need instead of using electrical and electronic equipment) and good specific impulse (so you won't need too much fuel, and won't need to take a really long, boring, slow and probably fatal journey). Really, you just twizzle the control rods a bit, and twizzle the fuel flow valve a bit, and woosh. You'll need a good chronometer, a good space sextant, and probably a slide rule or two. Careful monitoring of core temperature (doesn't need electronics!) and timing of carefully pre-calibrated engine burns will get you where you need to go. Heinlein would be so proud of you.

A simple nuclear rocket will not, however, be running all the way to Mars. You'll be doing two burns... injection into your transfer orbit, and injection into Martian orbit. Maybe a mid-course correction because you're flying by the seat of your pants and didn't finesse your initial injection burn well enough. The rest of the time your rocket will sit idle, so you may as well bring a nuclear rocket that can be reconfigured to operate as a plain old thermal nuclear reactor when it isn't generating thrust and make use of all that uranium.

Given a supply of hot coolant from your reactor, suddenly you have access to chemical processes that require decent amounts of heat. One such process is carbon dioxide scrubbing, whereby you can regenerate your CO2 absorbing medium by heating it up whilst exposing it to vacuum, causing all the absorbed waste to outgas. No muscle power needed! You can generate hot, high-pressure steam for use in a reaction control system. Hell, if you really wanted to go all gonzo steampunk, you can use a steam-driven motor to rotate an artificial gravity centrifuge.

You've got a ready supply of heat for cooking and sterilising stuff or distilling and reclaiming water from your biological waste products.

Lighting has an easy solution: the sun! Your ship will be in full, bright sunlight for almost its entire trip. You can set up some big Mylar reflective panels outside, focussing light through windows in the hull. That's gonna be more than bright enough for all your needs... in fact, you'll need to bring some shutters or curtains with you because you'll want some dark places to sleep well. For emergencies, and for any occasions at departure or arrival when you'll be shaded from the sun by a planet, consider beta lights. They'll last more than long enough for your flight, and can be made in a range of colours and sizes, and fit the nuclear theme.

(You could doubly cheat by using a big reflector as a heliograph and a telescope to keep an eye on earth for flashing laser return signals. Communicate via Morse, get ground control to do your computation for you. Not essential, but, y'know, I feel like I have to point out extra opportunities to break the spirit of the rules!)



You can replace everything with either a chemical reaction or muscle power.

  • Ventilation: muscles

  • CO2 scrubbers: muscles + chemistry

  • Oxy: more tanks.

  • Heat: chemistry

  • Lights: chemistry

  • Computers: Babbage machines + sextants (although this one's a lot harder to swallow, you probably could do it)


Why on Earth would you want to?

Jack Ryan : Could you launch an ICBM horizontally?

Skip Tyler : Sure. Why would you want to?

(The Hunt for Red October)

You have all the modern-day tech but want a ship that's the equivalent of an interplanetary Kon Tiki? Why? Why, why, why, why, why? It would be easier to justify a hand-crank power generation system than this. Even Benjamin Sisko had solar power. I suppose you could write a "teenagers save the world again!" story about some kids who figure out how to get into orbit and make it to Mars without the help of electricity (or educated/experienced adults), but why?

In reality, I don't think it's possible to build the ship without electricity. I don't think you can manufacture even the hull plating to the specifications required for safe space flight without electricity. Or the space suits. Or the oxygen tanks. Or anything else. But, technically that's not what you asked.

Nevertheless, I think the weight required to replace all the electricity-requiring stuff would be astronomical. You need to carry the chemicals that are used for lighting, heat, ignition, etc. Those chemicals are consumed. That means weight — and a lot of it — at the beginning of the mission. And you had to get all that weight out of Earth's gravity well.

And it would need to be a very slow voyage because without decent computers you're having to figure everything out by hand. Even a (very heavy!) Babbage machine can only do so much, so fast (hand cranking!). That means slow, gentle course corrections. Heaven help you when it comes time actually get down to Mars. But, I suppose you could pull a Felix Baumgartner and drop everything via parachute from low orbit (very low orbit... as in "don't get hit by the flaming space ship on your way down" low orbit).

And considering what it takes to do the limited space stuff we do today (with electricity), I would hope your passengers are both the luckiest people in history and good Church-going people.

Why on earth would you do this?

Oh, yeah... some idiot with more money than common sense wants to win a bet. Implausible. I'd bet the bet was for a whole dollar.

EDIT: BTW, I think the real problem is whether or not your space suit has enough oxygen for the walk between where you landed on Mars and where your equipment landed.

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    $\begingroup$ Muscle-driven CO2 scrubbers sound a bit like a losing proposition. $\endgroup$ Jun 5, 2019 at 21:34
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    $\begingroup$ @StarfishPrime oh, it could be done. Have enough scrubbers such that the CO2 being generated turning the crank didn't overwhelm the scrubbers. That's my point about weight - you'd need so much stuff you wouldn't normally need that the whole idea is ludicrous. But I suspect it could be done. $\endgroup$
    – JBH
    Jun 5, 2019 at 21:35
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    $\begingroup$ I think Babbage machines problem can be mitigated by making a lot of prepared calculations. The spaceship will pack volumes of tables listing "If at the time X your instrument reading is Y, do engine burn for Z seconds". $\endgroup$
    – Alexander
    Jun 5, 2019 at 21:37
  • $\begingroup$ @Alexander, possibly, but I'd like to point out that the Apollo missions didn't do this, and they had a good reason to if they could. But the real problem is, what happens if anything goes wrong? (oh, like a center-engine cut-out...). Now you're reworking all your math from the ground up. Granted, you'd have plenty of time. Note that you could make the babbage machine from plastic. Hope nothing breaks or strips, though. $\endgroup$
    – JBH
    Jun 5, 2019 at 21:39
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    $\begingroup$ @JBH most accidents would leave the ship somewhere on a predictable orbit. The problem would be only to find an entry in the table that correspond to this orbit. $\endgroup$
    – Alexander
    Jun 5, 2019 at 21:43

It is possible

and it doesn't even need special or new engineering.

I will not take into account:

  • how you get your vehicle into orbit around earth
  • what the purpose/motivation of this mission is
  • the funding
  • if electricity was used to manufacture the vehicle

Rocket engine:

You can use the basic principle of any rocket engine being currently used. You would only need to change the electric solenoid valves for mechanical/hydraulic ones. The hydraulics of your space ship can be powered by chemical reaction (your rocket fuel) or pure mechanical.

Direction Control:

Maneuvering is an easy one. Thrust vectoring, powered by your hydraulics, will be your coarse steering mechanism with cold gas thrusters (compressed gas) for fine adjustments. This is how most space ships/rockets do it today.


Your main source will likely be sun light, with simple reflectors to light up certain areas. If the sun has got a day off and decides to not emit light you can use chemical reactions/algae/phosphorescence.

Air life support

Carbon scrubbers need heat which you can produce with chemical reactions or use waste heat from other components from your ship, e. g. your rocket engine.

Waste disposal

Just toss it out there are no rules about littering outside of earths orbit.


You can have non perishable food but you can also just use a refrigerator. There are quite cheap gas powered fridges for camping you can buy on amazon, why not but one of those on your space ship?


Filtering water can be done by distilling and filters which both only need heat or pressure. Pressure can be created by brute mechanical force.


A lot of look up charts for most possible situations/maneuvers and a mechanical calculator/computer for manual calculations.


But why even bother to do math? Your Amish astronauts are way to cool for that. You can use focused light beams and Morse code (or a more mission specialized language) to communicate with someone (on earth/in earth orbit) who provides you with information. And keep in mind that your crazy rich person probably wants to stay in contact with the space ship to know how everything is going.

General informations:

  • Your space ship will be a heavy and big one because you need to carry a lot of additional fuel to replace electricity.
  • Mechanical power can be easily created with a steam engine (powered by rocket fuel) or a sterling engine which can use heat to output mechanical power.
  • Mechanical systems are more prone to wear so maybe have a some spares?
  • most electric systems/components have a direct mechanical alternative/precursor, but they are in most cases bigger and less efficient.
  • You can even automate all of your system with a precise clock and mechanical triggers such as strings/wires
  • If you just want to get into any orbit around Mars, you don't even need to be that precise about your maneuvers.
  • Your space ship will be assembled out of multiple modules (because of size and weight) if you want to use any of the currently available (and planned) launchers. (Getting things into orbit is harder then getting to another orbit)
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    $\begingroup$ Wow, communications. I had assumed we'd have to do without that one, but Morse is a great idea. I suppose we could blink an entire city if necessary. $\endgroup$ Jun 6, 2019 at 11:45
  • $\begingroup$ @EmilioMBumachar Earth can use a laser if they are able to track the space craft precise enough or the spacecraft as good "big" enough of a receiver. Or you could use a telescope on the space ship to look towards earth but that is probably harder to align precisely without electronics/tracking $\endgroup$
    – GittingGud
    Jun 6, 2019 at 11:49
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    $\begingroup$ Heck, if the crazy rich person wants to do this responsibly, they'll probably send along a conventional chase spacecraft that can rendezvous and recover the crew on short notice if anything goes irreparably wrong. The other wagering party can use it as a staging point for his observers. $\endgroup$
    – notovny
    Jun 6, 2019 at 19:12
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    $\begingroup$ Life support, waste disposal, food, and water can all be handled more simply, in a single stroke, by having the right amount of green plants on board to make a balanced ecosystem (cycling O2/CO2, using waste as fertilizer, and growing food). Possibly even including some meat production via insects, or fish grown in a hydroponic/aquaculture combo setup. And feel free to get arbitrarily detailed regarding the system of mirrors, optical pathways, etc., used to capture and direct the right amount of sunlight to sustain the whole thing. $\endgroup$
    – dgould
    Jun 6, 2019 at 22:41
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    $\begingroup$ Are you thinking a hypergolic propellant here since electric arc is out, plasma torch is out (Uses electricity for ionisation), there is using a pyrotechnic charge I guess but as it can't be an electric detonator you would be looking at something shock sensitive that might not be a great thing for this purpose vibration from earlier burns could potentially prematurely detonate stored charges perhaps. $\endgroup$
    – MttJocy
    Jun 7, 2019 at 19:19

Rocket Engine
Direction control

Both of these are chemical processes. While we use electronics to control them, there is no reason you couldn't use mechanical things like valves. The result might make Rube Goldberg blush, but it is not impossible.


There's a big fusion plant at the center of the Solar System that is constantly producing light. If you want light, you can use windows and mirrors (to concentrate the light where you need it).

Also, fossil fuel lamps work.

Air life support

Same way you manage it now, only without electrical controls. This might lean more towards using plants, as the windows will keep them producing oxygen twenty-four hours a day. But you could use chemicals instead.

Waste disposal

Compost it or incinerate it. Maybe incinerate then compost it.


Plants in a greenhouse. Maybe some animals. Freeze dry or can stuff. Note that if the stuff starts cold and then gets exposed to space, it will stay cold. Pull it in as needed.

Albert Einstein was a coinventor of a heat powered refrigerator. Not much point in our world, but it was designed for a no electricity world.


Look at seawater greenhouses. These use sunlight to evaporate water and then condense clean water from the vapor. This process uses no electricity and can be used with sewage water instead of seawater.

All this may waste space more than we would choose, but there's plenty of space. Given enough money and fuel, any amount of mass can be moved.

If you have a problem with heat, you can radiate it away. Conduction and convection won't work but radiation will. This will happen naturally. If that's not fast enough, you could take along ice (outside the ship) and bring it into the ship for cooling. Dump hot vapor to get rid of heat immediately.

If you are too cold, burn fossil fuels. You're in space. More trouble with getting carbon dioxide than getting rid of it.

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    $\begingroup$ The offspring of Einstein's refrigerator are still in use. They're used in off-grid situations--it's simpler and more fuel efficient to run your refrigerator directly on propane combustion than using a generator to make electricity to run a conventional refrigerator. $\endgroup$ Jun 6, 2019 at 1:50

Yes, but only if no rendezvous is needed

Rendezvous is bringing two spacecraft close together in orbit, position, and velocity. Docking is the actual physical contact between two spacecraft. Unless the spacecraft already were together (e.g. Apollo TDE manuever), you need to rendezvous before you can dock.

How close do you need to get to rendezvous? Wikipedia claims that the last phase before docking is 100-10 m. The first man to perform a successful rendezvous, Wally Schirra, stated:

Somebody said ... when you come to within three miles (5 km), you've rendezvoused. If anybody thinks they've pulled a rendezvous off at three miles (5 km), have fun! This is when we started doing our work. I don't think rendezvous is over until you are stopped – completely stopped – with no relative motion between the two vehicles, at a range of approximately 120 feet (37 m). That's rendezvous! From there on, it's stationkeeping. That's when you can go back and play the game of driving a car or driving an airplane or pushing a skateboard – it's about that simple.

Although there are plenty of examples of manual docking, no rendezvous has ever been successful without an advanced electronic computer. The calculations required for rendezvous are so complicated that Buzz Aldrin earned his doctoral degree from MIT in 1963 on the subject. Not even the on-board computers of Apollo had the processing power to perform these calculations; they were instead done by IBM mainframes back in Houston, and the parameters then radioed to the spacecraft. Without electricity, there will be no mainframe computers, no radar, and no communication with the spacecraft. No "clockwork computer" (or hand calculations) is going to be able to perform these calculations.

Supporting evidence that no rendezvous has been successful without a computer:

  • The Soviets attempted rendezvous twice with Vostok and failed. Vostok 3 and 4 were in 1962, and Vostok 5 and 6 were in 1963. Vostok lacked maneuvering thrusters to adjust its orbit to match that of its twin. The initial separation distances were in the range of 5 to 6.5 kilometers (3.1 to 4.0 mi), and slowly diverged to thousands of kilometers (over a thousand miles) over the course of the missions.

  • US astronaut Jim McDivitt tried to maneuver his Gemini 4 craft to meet its spent Titan II launch vehicle's upper stage on June 3, 1965. Although he was able to make visual contact with the target, the rendezvous failed. He was in orbit behind the target, and assumed that thrusting toward the target would bring them together. Orbital mechanics doesn't work that way, and thrusting toward the target merely made them farther apart.

  • The first successful rendezvous occurred on December 15, 1965 when Schirra maneuvered the Gemini 6 spacecraft within 1 foot (30 cm) of its sister craft Gemini 7.

    Schirra put Gemini 6A's computer in charge of the rendezvous.

  • The first rendezvous with docking was Gemini 8. "At 55 nautical miles (102 km) they gave the computer automatic control."

  • The first unmanned docking was the Soviet Cosmos 186/188 and was automated.

  • Soyuz 2/3 had the Igla automated rendezvous system. It attempted manual docking and failed.

  • Soyuz 4/5 also had the Igla automated rendezvous system. It was successful and two cosmonauts exchanged vehicles.

  • During the early years of Apollo development, Von Braun and other officials pushed the "direct" approach with a single spacecraft making the whole trip, arguing that there was no way that a lander ascending from the lunar surface could ever rendezvous with a spacecraft in lunar orbit. Quoting an interview with Robert Gilruth, the first director of the MSC in Houston:

    DeVorkin: In direct descent you needed an enormous booster. In earth orbit rendezvous, you needed two Saturn launchers to meet in orbit. In lunar orbit rendezvous, you needed only one Saturn launcher, but you had to have, correct me if I'm wrong, extremely finely tuned abilities to do celestial navigation, because the lunar orbit rendezvous was being done at the greatest distance, was the critical path. The most difficult thing to conquer.

    Gilruth: But that had onboard navigation.

    DeVorkin: Had it been developed yet? To what degree were the computers ready and available?

    Gilruth: Well, that's true, we were the people that made IBM. There's no question about it. We put the computer age ahead ten years with Apollo, because we really did use IBM and built them up in order to do this program.


    DeVorkin: Let's go back and talk about your comment about IBM, and how NASA made IBM what it is today.

    Gilruth: I think I would say that they had a lot of talent. They would have become successful no matter what, but we did help them by giving them such a challenging project as Apollo was, which required the utmost in computer development. I'm not a computer expert, although I had some very good people in that work. Without those computers, we never could have solved all those equations in such short time, that we could direct these things into proper orbits.

  • The Apollo transposition/docking/extraction (TDE) manuever started with the spacecraft already matched in position and velocity. The maximum separation was only 150 feet, so it's not a rendezvous. However, it was done manually.

  • Apollo trans-lunar injection and trans-Earth injection aren't a rendezvous (no second craft). In addition, their parameters were calculated by computers at mission control, including Apollo 13's manual burn.

  • The movie Apollo 13 shows some hand calculations. This was a rotation of the two spacecraft coordinate systems, so the the gimbal angles could be transferred from one spacecraft to another. The X-axes point in opposite directions, and the Y/Z axes are rotated because they couldn't perfectly align the roll angles of the two spacecraft when docking. These calculations had nothing to do with with calculating trajectory, thrust, or any other maneuver of the spacecraft. The fact that you saw a bunch of guys doing calculations with slide rules does not imply that every spacecraft calculation can be done that way.

  • Soyuz and the Space Shuttle used computers to rendezvous with other spacecraft.

Other answers have made arguments about the other systems of the spacecraft being feasible. However, no clockwork computer or manual calculations will enable you to rendezvous two spacecraft. Therefore, you must design your spacecraft accordingly.

  • $\begingroup$ You're ignoring photonic logic / optical computing (en.wikipedia.org/wiki/Optical_computing). I posted an answer about it because it seems everyone else is ignoring it, too. For pure number crunching, it's plausible now or near future, if humans are around to input numbers and read results, and press the right buttons at the right time. $\endgroup$ Jun 6, 2019 at 18:37
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    $\begingroup$ I'm undecided which way I should vote this. On the one hand, you're correct that you can't compute a rendezvous in real time without electronics (but you can fly a precomputed one). On the other hand, you're using a great deal of misinformation to back up your point (eg. the Apollo AGC certainly could compute and fly a rendezvous; the reason why they used Houston's numbers is Houston had better tracking data, making for a more efficient flight. Gemini 4 wasn't a failed rendezvous, it was failed station-keeping, where point-and-burn done right would have worked.) $\endgroup$
    – Mark
    Jun 6, 2019 at 22:18
  • $\begingroup$ A mechanical computer most certainly could calculate a rendezvous in a reasonable amount of time, we've been building mechanical computers to extrapolate orbital mechanics for centuries. Such a computer would just be extremely complex and not good for anything else. It's getting the tracking data to the required level of precision that's going to be difficult without radar... $\endgroup$
    – Perkins
    Jun 7, 2019 at 22:40

I don't have a complete answer, but there's one major thing most other answer have missed:

For comms / computing, I was thinking photonics, aka https://en.wikipedia.org/wiki/Optical_computing, if we can power lasers without electricity. Perhaps radioactive decay could pump atoms into an excited state, ready for stimulated emission. Or bright light from a thermal source.

Other unsolved problems: transducers for input and output:

  • let photonic logic control the engines and other physical things directly
  • get sensor input

Microphones should be relatively easy; sound an modulate the angle or position of a mirror which changes where the light reflect, or changes which wavelength resonates in an optical cavity.

Receiving digital comms by laser should should be ok. But camera imaging is less obvious.

Definitely the hardest part is physical outputs, without actual electricity to create electric or magnetic forces. Light does not have much momentum. We might need humans to push buttons when they see lights.

Aiming a comm laser might be possible with some kind of phased-array technique where aiming is based on phase of light, not physical motion of optical components.

Light is an electromagnetic wave (and/or a separate particle), but if you count this as "electricity" I think you'd have to count the electric fields in chemical processes, too.

Electromagnetic force is one of the 4 fundamental forces of nature (vs. gravity and strong + weak nuclear forces), so it's not like you can avoid anything to do with it, if you want matter not to pass through other matter.


Lets really go retro and propose a steam powers space craft. A nuclear power plant generates steam and the steam is used either directly for things like cooking, indirectly by rotating turbines to circulate air, or through heat transfer.

As for lighting, your are in space and sun is always visible. Make sure your space craft has windows.



Because you need computers to control the ship, because you need precision, real-time measurements of the ship's position and orientation in space, and because you need high-precision timing to fire your rockets.

When you are in low-earth orbit, you are going pretty fast, approximately once around the earth in 90 minutes. In other words, you are moving across the earth's surface at 4° per minute, or 4 arcminutes per second.

From this orbit, you need to get into a transfer orbit that takes you towards mars. This is done by accelerating at the right moment in your orbit, making it so elliptical that it becomes a parabola, or even a hyperbola. To get to mars, you need a hyperbola within earth's reference system that happens to turn into a ellipse around the sun when you leave earth's gravitational field. The farthest point from the sun of this ellipse needs to be on the orbit of mars, and you need to arrive at that farthest point exactly when mars does. That's right, you fire your engine, get your direction, and then you float for more than 500 million km through space for over half a year, and hope that you arrive just at the right time and place.

The direction with which you leave earth depends on when you fire your engines within your orbit. Fire one second too late or too early, and your course will be off by 4 arcminutes. That is, you'll arrive about 4 arcminutes on mars' orbit before or after mars is at your point of rendezvous. The orbit of mars has a radius of 230 million kilometers, so 4 arcminutes are $230\cdot10^9m \cdot 2\pi \cdot\frac{4}{360\cdot60} \approx 268\cdot10^6m$, i.e. you've missed mars approximately by about a light second.

Likewise, the ship's orientation when its engines are fired needs to be right to a few arc seconds at most, the more precise, the better. Of course, you can measure your orientation with manual means, but while your astronauts will be working on calculating the correct time and duration of the firing, they will move inside their ship, and will introduce a significant error into its orientation.

The apollo missions had two flight computers on board (https://en.wikipedia.org/wiki/Apollo_Guidance_Computer), one in the command module, one in the lander. Each of these beasts weighted 32kg, and they were not included because it was so hip to fly with electronic guidance, they were included because they were a must. You have to have a very good reason for carrying along 64kg of inert mass when you are doing a rocket flight to the moon and back. And that reason was precise control of the rocket engines so that the astronauts actually got where they were supposed to go.

  • $\begingroup$ Upvoted, even though I think that the premise of the question (achieve ANY orbit around mars) can be achieved with slow burns and successive refinement burns. The Apollos needed the computers to achieve precise landings at the specified targets. $\endgroup$ Jun 15, 2019 at 18:46
  • $\begingroup$ This answer depends on a logical fallacy, specifically that the solutions used for the Apollo missions are the only suitable solutions. That only digital computers can be used when accurate predictive algorithms were implemented in analog computers for Fire Control Systems in WW1. And with the creation of micro mechanical machines their precision and accuracy would be astounding. Nothing prevents everything needed for a space ship to be steam and hydraulic powered, except the exorbitant cost and weight. $\endgroup$
    – EDL
    Jul 15, 2019 at 3:35
  • $\begingroup$ @EDL A fire control system basically needs to calculate a parabola (somewhat skewed because of air resistance). And if you get it wrong, well you loose a grenade, see the offset, correct, and place the next one on target. Celestial mechanics are quite a bit more complex. As I said, it all starts with having to start the engine with sub-second precision. Of course, you can try to build a Z1 and use that to perform the function of the Apollo guidance computer, but your engine firing will be brutally imprecise compared to electronic guidance due to the low clock frequency of mechanical devices. $\endgroup$ Jul 15, 2019 at 6:57

I believe that most of the issues involved in a non-electric spaceship have been addressed... for pretty much every electric technology in use on a spaceship, there exists a non-electric alternative.

However, I would debate that a photonic-based calculator is truly modern day technology. True... Some photonic circuit modules have been produced, but I disagree that the technology is ready for use in space as of now.

So, while we can have chemical and reflected light, and mechanical and hydraulic/ pneumatic control systems, a photonic processor is taking things a step beyond current day technology.

However, all is not lost. There is at least one alternative technology that may substitute: Rod Logoc and Fluidics. Of the two, fluidics has already been used to build functional circuitry, and has also been shown to be able to be scaled down.

A fluidic computer is essentially a block of specially shaped gates, into which a fluid such as a liquid or a gas is pumped. The shape of the gates determines the behavior - other than the data input and outputs and the fluid pump, there are no moving solid parts, only moving fluid, so fluidics are very reliable. They are also far less susceptible to external electromagnetic interference than electronics.

As for the fluid pump, that could be chemical-powered, powered by a Stirling engine that operates between the sunlit and shaded sides of the spacecraft, or even hand-cranked.


Your problem can be split in two parts, getting there and surviving the trip.

Getting there

Most "exotic" propulsion systems require lots of electronics for control, or just are based in electric effects themselves. Going with 2019 tech level, what's in rutine use today for commercial spaceships should be your best bet.

Most ships use liquid fuel rocket engines. Those are efficient for the long range, but they have a few caveats for your mission: They require fine control of the burn if you dont want them to blow up, and the massive ammounts of fuel and oxidiser require pretty big pumps, which will need to be electric in a spaceship. The other problem with this approach is that this kind of engine doesn't like reignitions, and you will probably need to do a lot of correction burns along the trip.

Your next option is the hypergolic, it is less efficient and also needs pumping, but at least the control is very simple and can be done via mechanical means. You can do the pumping by having compressed gas push the liquids; won't do for the big trans-martian injection burn and the capture but would probably be OK for the correction burns along the trip.

For the big burn, I would go with the scariest of all: solid boosters. Those can be ignited via a hypergolic mix, and once they start burning there's no control needed because there's no way to control them; they burn until expended.

So, using a staged approach, I'd have a solid first stage for the trans-martian injection, followed by a hypergolic second stage for mid course corrections and a final solid stage for the mars capture.

As you won't have a control computer or anything that can compensate for asymetric trust, you'll need to have one of each, perfectly aligned with the center of your ship.

You'll also need to calculate your burns as precisely as possible. The most critical is the trans-martian injection one, it is the longest and also the one that has a bigger potential to screw your whole mission if done wrong. As you will be starting for an already known orbit around Earth, it is also the easier to calculate; you can even have it precalculated using a computer if that's allowed by the rules.

Your engines will need to be throttled down so that they burn slowly during a long time. A pilot seating in the front of the ship will use an optical finder to align the ship with a star and steer it if it spins off course; the slower the burn the easier it will be to align the ship.

For the attitude control, you could also have hypergolic thrusters like most spaceships do, but unless perfectly balanced, they will also propel you off course. A flywheel on a gimbal is the perfect option. Your 24 crewmembers can put their muscles to the work; orient the flyweel in the right direction, start spinning it and watch your ship counterrotate until it finds the right orientation.

The navigation shouldn't be that difficult, but it will need a lot of slider rule time. Observe the planets, find them in precalcualted tables and figure out how well you are doing. Correct your course accordingly.


The easier first: Don't bother with a recycling system, just bring enough water and low-residue food to last the trip. You will need to keep it aboard, though. Anything you expel from the ship will either alter your course if you do it with some force, or just stick around if you dont, surrounding you in a cloud of residue that will cloud your windows and difficult all your maneuvers. It would also alter the ship mass in unpredictable ways, so better bring it along.

For warmth you can just do like Mark Watney and bring a few plutonium pellets, they will radiate enough heat to keep your ship at a reasonable temperature. You don't want to be too warm to avoid people sweating, the water is better kept inside their bodies.

Another consideration is clothing. You won't be able to wash it so you'll do as the ISS and bring enough clean clothes for all the crew.

Air quality will be trickier; you can do as old spaceship did and have a pure O2 atmosphere, but you'll need to get rid of excess CO2, and have something that does that efficently; I personally have no idea how to do that without electricity and avoiding outgassing.

Finally, you'll have 24 people in crammed, smelly qarters for 9 months. You better figure out how to keep them entertained without electronics.


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