Colonists have set up a viable, long term lunar colony on the near-side of the moon in the mid-21st century. They are quickly reaching total self-sufficiency and the earth governments who sponsored the colony are getting itchy to maintain control.

Earlier control measures such as sending space marines to ensure a toe-hold on the Moon failed. The colonists shot down the troop carrier along with all the drones sent to provide covering fire. They are very good at shooting down anything that comes their way. The colonists are self-sufficient enough that a siege of the moon wouldn't work either.

Neither Earth nor the Moon can yet maneuver sizeable asteroids so bombardment by big rocks is out. Hypervelocity projectiles are insufficiently accurate to do the damage required. Lasers can be defeated by simply throwing lunar dust into the air. Guided nuclear warheads are agreed upon as the best option. Development begins on a W90 warhead.

How difficult would it be to build a guided nuclear warheads that would escape detection till it's too late? If a warhead can't be made completely undetectable, at what approximate range would it be detectable? (Too late is less than 15 minutes.)

The warhead should evade visual, thermal and radar detection. The Moon, thus far, only has detection facilities on the Moon itself. The colonists have access to x-band radar and sophisticated machine learning capabilities.

I'm aware of the maxim "There is no stealth in space." Push the technology as far as you can.

  • 3
    $\begingroup$ @CandiedOrange, when you have 16+ hours to deal with an incoming missle, the idea of how to avoid detection is non-trivial. Can we get the missle to the moon? Sure, that's easy. Can the moon stop it from landing? Maybe. This isn't a cut-and-dried question. $\endgroup$
    – JBH
    Apr 3, 2018 at 1:23
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    $\begingroup$ @jbh this is the same problem we have with planet killer asteroids. And they don't have anything against us. You really don't need stealth to make this a hard problem. $\endgroup$ Apr 3, 2018 at 1:29
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    $\begingroup$ "Maintaining control" is a goal that is not achieved by bombardment with nuclear weapons. Nukes just destroy, so there's nothing to control afterwards - the victor has no asset to take control of. $\endgroup$ Apr 3, 2018 at 2:30
  • 3
    $\begingroup$ @StephenG True, destruction by nukes isn't how you maintain control. However, a demonstrable threat of nuclear annihiliation is a valid control mechanism. $\endgroup$
    – Green
    Apr 3, 2018 at 17:30
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    $\begingroup$ "Guided nuclear warheads are agreed upon as the best option" ... why is that? I mean, earth have enough resources to make a laser beam powerful enough to fry something on the surface of the moon, and maintain such a beam for extended hours. Undetectable light-speed death, why are you ruling out this alternative? I assume because of the needs of your plot? $\endgroup$
    – msb
    Apr 3, 2018 at 20:57

12 Answers 12


Why not?

Make it a relatively dumb bomb on a timer, paint it black, give it radar absorbent plating, and (this is the important part) launch it from the far side of Earth.

Your delivery system can be whatever you want - mass driver, rockets, whatever - just make sure that all the thermal bloom associated with an atmospheric launch happens on the far side of the planet. No way for the lunar colonists to detect that unless they have satellites in Earth orbit... which would be a pretty major vulnerability. Craft the orbit of the new highly-stealthy piece of space debris so that it will arrive on the moon.

The lunar base, being a base, cannot dodge. You'll know where it is in a few weeks. The bomb emits virtually nothing. It's travelling at orbital velocity, and will presumably detonate in the many-megaton range. Counter that, helpless lunar colonists!

  • $\begingroup$ Comments are not for extended discussion; this conversation has been moved to chat. $\endgroup$ Apr 8, 2018 at 20:36

This is just to add some more details to jdunlop's answer.

I have done something like that quite a few times in Kerbal Space Program. Not because I wanted to bombard the game's equivalent to our Moon, but because I am cheap. Some missions require you to gather data from a certain altitude from the Mün's surface, but don't say anything about soft landing or returning, so a dumb impactor is the cheapest way to go.

If you want to go from a planet to a satellite of that planet, Hohmann is your homie. This is what a Hohmann transfer to the Moon looks like:

Much more fun than following a stairway to heaven

As you can see, a single burn is required to set you towards the Moon. A second burn is required if you want to orbit the Moon after that, but that would be no fun we don't want that.

Could we add enough speed in one burn to reach the Moon?

Yes, we can! The russians did so for the first time in 1959, followed by US's Apollo missions:

The first space probe to successfully perform TLI [Trans-lunar injection] was the Soviet Union's Luna 1 on January 2, 1959. The first human-crewed mission to successfully perform this procedure, and thus becoming the first humans to leave the Earth's influence, was Apollo 8 on December 21, 1968.

For the Apollo lunar missions, the restartable J-2 engine in the third (S-IVB) stage of the Saturn V rocket performed TLI. This particular TLI burn lasted approximately 350 seconds(...)

So, with technology that is largely outdated today, we can accelerate humans from low Earth orbit to a Moon-impacting trajectory in less than six minutes. I have a feeling that by the time we colonize the Moon we should be able to accelerate a bomb towards the Moon in much less time.

Could we do it without being seen from the Moon?

Sure! Look at this essay from NASA, about the Apollo missions' launch windows (all emphasis are mine):

In order to accomplish this 'rendezvous' with a minimum expenditure of propellant, the injection (TLI) must occur very close to the extension of the earth-moon line at the time of the spacecrafts lunar arrival. This is termed the negative of the unit vector of the moons position (the position on the opposite side of the earth from the sub-lunar point), which is called the moons antipode. The optimum trajectory is very similar to a Hohmann transfer.

This minimum energy transfer trajectory would have placed the earth parking orbit perigee at the moons antipode if the moons mass did not perturb the trans lunar trajectory. However the moon does perturb the spacecrafts trans lunar trajectory, as shown in figure 5 above, and therefore the earth parking orbit perigee must lead the moons antipode by approximately 8 degrees to compensate. The apogee altitude of the osculating conic trans lunar trajectory was determined by the trans lunar flight time which defined the trajectory energy requirements at trans lunar injection (TLI).

To inject the spacecraft to the moon in the most efficient manner, an impulsive velocity (acceleration) would be added along the orbital velocity vector (direction), giving an injection at the perigee of the trans lunar conic. Since an impulsive (instant) addition of velocity is not possible, a finite burn time is required, and the actual injection position is on the order of 20° ahead on the antipode. The thrust from the S-IVB is directed approximately along the velocity vector, and as the velocity increases above orbital, the altitude and flight-path angle increase. For the Apollo lunar orbit rendezvous flight mode, by the time sufficient energy has been gained, the altitude has increased by 60 to 75 n. miles above that of the earth parking orbit and a positive flight-path angle of 6° had been attained. Since the conic trajectory is very nearly parabolic (eccentricity 0.97) the true anomaly is approximately equal to twice the flight-path angle, so perigee is approximately 12° to 14° behind the burn cut-off position. The TLI burn arc itself is 25°, so that ignition always occurs within a few degrees of the moons antipode.

Again, a rocket with current or better technology, and more specifically not carrying squishy humans would easily outperform the J-2 and Saturn V rockets used in the late 60's. All in all, the TLI would look like this...

Trans-lunar injection

... But the payload would not need to perform a full orbit around the Earth before the trans-lunar injection burn.

Can we make the payload stealthy?

Of course we can! First things first, drop the requirement that it has to be a nuke, that is wasteful and inelegant. You don't need a nuke to do some huge damage.

With current or near future technology, it would be quite feasible to send them lunarians:

  • A 100 meters wide lump of iron;
  • Hitting the ground at 45°;
  • And touching ground at 5 kilometers per second.

You may be thinking that a hundred meters is too much. It is for today, but not for a civilization that has built a self-sufficient colony on the moon.

One advantage of iron is that it will cool off in minutes after the TLI burn. If you need it to cool in less time, you can add a heat sink as part of the TLI stage, and you can make that stage turn around and return to Earth a minute after decoupling from the payload.

With no burns visible from the Moon, no radioactive material in it, and zero emissions, they would not see it until it is too close. As for how much damage that would do, I have used a simulator to drive my point:


Here is what the impact profile would look like. The Empire State building would fit inside the crater:

Oh the humanity!

I think the debris flying out of that would cause multiple smaller cratters to appear surrounding the main one. And since this is cheap and simple, you can just rinse and repeat. Have fun!

Could they really not see it coming?

We can barely predict where a falling space station will touch down, and it is not unusual for us to learn about a passing asteroid after it has passed by us.

Supposing they do see it coming, what can they do?

Lunarians' only hope is deflection. If you blow the payload up, the pieces will still have momentum going towards the moon, and the damage will be practically the same - only more spread throughout the land. Add to that, the Earth can simply keep spamming those things at them. At some point surrendering becomes cheaper than maintaining a permeable defense system just to fight an uphill battle.

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    $\begingroup$ "One advantage of iron is that it will cool off in minutes after the TLI burn" wouldn't it hold only within atmosphere? In space a mild steel would cool 1.8 * 10^-4 (1/r + 1/h) K m / s. So to cool from room temperature to half of temperature of background radiation it would take 2 years (unless I made an error in calculations). Until than it is 150-300 K light bulb in space. $\endgroup$ Apr 4, 2018 at 4:44
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    $\begingroup$ It can orbit the Earth a couple times before starting the transfer burn at the hidden side, so it will have plenty of time to cool down. $\endgroup$
    – vsz
    Apr 4, 2018 at 13:59
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    $\begingroup$ There's a very good reason to use a nuke instead of a huge lump of Iron like you're suggesting if being launched from the surface of the Earth. That calculation is for a 100m diameter sphere of Iron, not a bar as implied by "100 meter long", with a volume of 524,000 m^3 and a mass of 4.1 million tons. Putting that into orbit is just slightly more difficult than a nuke weighing a few dozen to a few hundred kg. If you want to throw asteroids around sneak out into interplanetary space/the asteroid belt and strap an engine of some sort onto a big rock to change its orbit. $\endgroup$ Apr 4, 2018 at 20:44
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    $\begingroup$ The other benefit of nukes over kinetic impactors is that you get a lot more bang for your lift buck. Lifting a million tons of iron off the planet is energetically expensive, no matter what your technology level. For about the same price, you could throw a thousand 100-ton 500MT bombs. $\endgroup$
    – jdunlop
    Apr 4, 2018 at 23:18
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    $\begingroup$ We cannot predict where space stations fall down because we don't know the complete layout of the upper atmosphere, and drag in the upper atmosphere is what causes the space station to deorbit in an highly non-linear fashion (drag causes lower orbit, which causes drag to increase, which causes lower orbit...). There is nothing equivalent going on in your case. That analogy is like saying "we don't know how many atoms are in a cookie, so they won't be able to see this coming" -- completely unrelated. $\endgroup$
    – Yakk
    Apr 5, 2018 at 14:51

Since the effect the EarthForce seems to want is total destruction, there are actually a multitude of ways to achieve the effect.

Firstly, since there is an effective missile defence screen, direct attacks with large, slow rockets is unlikely to be effective. What you might need is to suppress the defence grid with radiation weapons delivering energy at the speed of light. EMP, high energy microwaves and lasers are all available today, so sending drone weapons to blanket the near side of the Moon with with high energy radiation wherever a weapons or sensor emplacement is known or suspected is an obvious first step.

EMP can be generated with explosively driven devices, so large numbers of non nuclear rounds can be built and sent to cripple enemy electronic devices. Lasers and high power microwave generators will be larger and more vulnerable, but there is no size limits in principle, and astoundingly large generators and antenna or mirrors can be built in Earth orbit and slowly manoeuvred into firing positions. In principle an X-ray Free Electron Laser (FEL) can be built capable of delivering enough energy to vapourize metals, carbon fibre and ceramics in milliseconds at a distance of one light second (just slightly less than the distance from the Earth to the Moon), but a Ravening Beam of Death (RBoD) is somewhat beyond current day technology. So expect an active campaign to suppress any defensive systems, and take out surface installations like solar arrays and radiators.

Another weapons system which can bypass the defences of the Moon would be space based mass drivers or railguns. Even small projectiles can pack a massive punch if delivered at a great enough velocity, and small, high speed projectiles would be exceedingly difficult to track and destroy. The delivery systems will be space warships in their own right, the proposed "Have Sting" electromagnetic launcher from the SDI era was of a similar size (but greater mass) than the present ISS.

enter image description here

Have Sting compared to the space shuttle. Diagram by Scott Lowther

So even without stealth, we can engage the Lunar defence grid outside of their range and carve a path for the nuclear package to arrive.

But building and delivering laser and railgun weapons into cis lunar space is going to be expensive and time consuming, and you want something much faster and more compact? Never fear. Nuclear devices can be used to drive effects, being a very compact energy source in their own right. Since there is nothing to transmit the energy in a vacuum (unlike the atmosphere converting the intense x-ray radiation of a nuclear blast into an energetic shockwave), you would essentially have to land a nuclear device on the surface to truly destroy the moonbase. On the other hand, several different ways exist to convert the energy of nuclear explosions into useful effects.

In the Atomic Rockets "Conventional weapons" section, there are several different variations of nuclear "shaped charges".

Another device being investigated by both SDI architects and weapon designers is "a kind of nuclear shotgun with little pellets" named Prometheus. According to a Congressional report that was otherwise quite pessimistic about SDI, Prometheus "may have nearer-term applications for picking out warheads from decoys" (in the midcourse phase of ballistic-missile flight) than the Neutral Particle Beam (NPB), a leading contender for that role. Encouraged by experiments already conducted, SDI officials in 1987 ordered an acceleration of the Prometheus project for "concept verification," using funds from that year's $500 million supplemental SDI request.

One research engineer familiar with the project described the device as operating much like a rifle, using a polystyrene-filled barrel to help couple a plate to the "gunpowder-like" blast of a directed nuclear charge. After the impulse from the explosion generates an intense shock wave, the plate "fractionates" into millions of tiny particles. Of course, these would vaporize if in direct contact with the bomb, but as configured, the pellets have reportedly achieved speeds of 100 kilometers per second without vaporization.‡

Beyond "Shotguns", there are also nuclear Explosively Forged Projectiles (EFP's), useful for cracking open the underground base, Nuclear "Shaped Charges", similar in principle to a HEAT round, but projecting the molten metal "jet" at @ .03 c, and the Casaba Howitzer, which focuses the energy of the nuclear warhead into a star hot spindle moving at @ .1 c, delivering laser like energy to the target from a range of hundreds to thousands of kilometres.

enter image description here

Cross section of a "Nuclear Pulse Unit" from an ORION nuclear pulse drive. A CASABA Howitzer would be based on a similar unit

Once again, these can be delivered to just outside the range of the defence grid and then detonated, destroying any surface mounted sensors and launch or laser arrays, and then cracking open the base itself with a slug or jet moving at a large fraction of the speed of light.

As for obscuring the device, it simply has to be launched on a low energy ballistic trajectory, so its origin isn't made obvious by a rocket burn. The device can be protected in a conical shroud which deflects radar away from it, and kept cooled close to the background temperature of space by filling the shroud with liquid hydrogen and allowing it to slowly vent, carrying away waste heat.

enter image description here

Misty low observable shroud. The pointed end would be facing the Moon as it approached, and liquid hydrogen wold be slowly boiling off to keep it close to the temperature of the space background

So a deadly attack on the Moonbase would likely be delivered by either a small flotilla of spacecraft supressing the defences with radiation weapons and hypervelocity slugs, or a series of nuclear shaped charges which use the energy of the nuclear device to deliver high speed projectiles and energy to scour the surface and "crack open" the base to kill it. Nuclear weapons, or even scouting spacecraft to observe the target would be concealed within "Misty" shrouds, and cooled with liquid hydrogen to evade sensors until they came very close to the target. Considering shaped charged can be fired from thousands of kilometres away and deliver effects at fractions of light speed, you actually don't even have to get too close.


The Missiles will be launched in Earth's shadow and enter a trajectory that will hit the base (... near enough) without any burns outside that shadow. Probably high up, then entering an excentric elliptic orbit that will hit the Moon on the right spot. The hard part is, of course, stealth.

Radar - a radar absorptive coating should be doable with near future tech, or even curent one.

Occlusion - warheads are small, no big problem for stars. Course should not cross the Earth from Moon's perspective.

Heat - the biggest problem. Each warhead could be cooled pre-launch, then launched together with a powerful heat pump that will cool it further in orbit. The challenge will be to build a nuke that works at really low temperatures, thermal shrinkage and the chemistry of the explosives might pose a problem. How low? Theoretically we want 4K, temeperature of the cosmic microwave background. Realistically, since intensity of thermal radiation scales with the fourth power of temperature, we 'just' need to come below the detection treshold of Moon's IR scanners. The missiles will likely spend a day at least en route, plenty of time to become heated up by the sun. So I am stealing an idea from the short story "A Soldier of the City" (dunno by whom): each missile has a large shield, pointed at the Moon. The front side is cooled to be 'cold enough' to evade detection, and is large enough to hide the large radiators pointig backwards, dumping the excess heat.

From the above, it follows that times of full Moon (when the missiles will fly away from the sun, towards the Moon) is the best attack window, as the cold shield will be out of direct solar radtiation then.

Depending on the sensors the Moon people have, an interesting discussion can be had about course: making out a small target (<10 m) in front of the sun is hard, unless one has a special instrument built for looking at the sun and handling its intense emission. I suspect that any lunar colony will be very interested in solar storms, so I'd guess they have instrumentation that can maybe make out a cold spot in front of the sun. So the missile fleet will use cold space as a backdrop.

Of course, the Moon militia will have read this post (or A Soldier of the City, which is all in all a better read) and will launch micro observation satellites (or buy info from earthbound stargazers) all over the Earth-Luna system ASAP, missiles as described above would be quite visible from the sides and rear.

But terran militaries will anticipate this, and construct warheads with internal heatdumps: the missile starts with a large tank of liquid helium (or another medium with lots of energy intensive phase changes at very low tempreatures), the heat pumps will try to cool the whole surface and dump the heat into the internal tank. These would be perfectly dark from all around, but would require trajectories that reach the target quickly.

One could park a fleet at the Earth-Moon L3 point (from Luna: behind Earth). They would barrel towards Luna on a trajectory that goes close by Earth, gathering speed and using external heat radiators while behind the Earth (for an observer on Luna), and coast once outside of it. Of course this gives a rather small area in space for the Moon militia to point their surveillance sats at.

Last not least, the Moon militia can always burrow deeper into the moon, to hide bunkers, protect civilians and guarantee a second strike capability. So the sanest option (but probably not the one you'll base your story on) will be to find a peaceful modus vivendi between Earth and Moon. In Kim Stanley Robinson's Red/Green/Blue Mars trilogy, they needed 200 years (IIRC) and three fat books to manage, maybe your lunans be quicker.

  • $\begingroup$ It should be noted that "in the earth's shadow" is not correct. You want it to be opposite of the moon's position, which isn't necessarily shadowed. $\endgroup$
    – thanby
    Apr 3, 2018 at 14:58
  • $\begingroup$ That's what I meant, but you are correct so I clarified this sentence ... $\endgroup$
    – mart
    Apr 3, 2018 at 15:15
  • $\begingroup$ Heatpumps dont work in space. As there is nowhere to pump to. $\endgroup$
    – joojaa
    Apr 3, 2018 at 20:52
  • $\begingroup$ You pump to a radiator, and radiate the heat away. Which is why I went into a little detail about how to hide the radiator from moon based observers. $\endgroup$
    – mart
    Apr 4, 2018 at 7:09
  • $\begingroup$ yes only works if you know where the observers are though i.e. the moon can;t have any observation posts orbiting another body or they might see the hot end of your projectile $\endgroup$
    – jk.
    Apr 5, 2018 at 8:58

Compensate With Tactics, not Tech

Missile launches have crazy impressive launch signatures which are easily detected from space. The lunar defenders can watch anything that is launched from earth into space and the earth-governments can't really do anything to stop them from doing so. Either earth to lunar launched nukes, or earth orbital to lunar launch signatures are basically impossible to disguise. Whats worse, the lunar defenders literally have days to prepare a response for anything they watch leave earths atmosphere or it's orbit.

So, what the earth government needs to do is use covert ops. Instead of crazy expensive new tech development they modify how they use what they already have. Hyper velocity rail guns are fired at the moon colony, but these projectiles are different, they detonate into clouds of hyper-velocity sand just outside the lunar defense envelope. These high velocity clouds of sand scour sensor lenses, and laser or other weapons emplacements sensor arrays blurring or even outright destroying any ability they have to detect objects. The only way to preserve sensors and weapons targeting lenses is to shutter them, thus also rendering them blind. Only microseconds behind the impact of these hyper velocity dust could bursts there is another wave of hyper-velocity projectiles containing nuclear warheads. Constellations of small limited use drones launched to arrive just outside the defensive envelope at precisely the right moment for the sand-blaster rounds to hit are also in play. These are simple and cheap drones, maybe only with enough power to fire one laser-pulse or a single conventional nuclear missile, or to simply explode in shotgun-like blasts of chaff and flares and further assorted sensor clutter. There are a TON of them. They each have a very specific target. The laser drones target and fire on the shuttered, ablated, or destroyed sensor arrays and defensive weapons emplacements further degrading defensive capability and increasing likelihood of a successful strike by one of the drone launched conventional nuclear missiles. Since we are dealing with swarms of drone craft launching nukes, and waves of hyper-velocity rail-gun fired nuclear warheads only a few, maybe even only one has to successfully penetrate the defensive network for the strike to be a success.

Developing super secret sneaky tech is very expensive and takes decades, this doesn't make it a non-viable option mind you, but if the colonists just torched a troop carrier your earth government will want a way to retaliate NOW, not 15 years and 800 billion dollars of research and development later.

Hell, go for a psychological option and have all the "nukes" that make it through the defenses be just regular conventional explosive warheads. Follow them up with a radio broadcast demanding surrender and promising live nuclear warheads are due to arrive soon. This way you have a chance to recapture your crazy expensive colony before nuking it to oblivion.

  • $\begingroup$ Anything heading to the Moon will be, since Earth escape velocity is 40,000kph, hypervelocity. $\endgroup$
    – RonJohn
    Apr 3, 2018 at 3:48

Our preeminent and loquacious benefactor, Xanax the First (may His edifactory sardonicism calm us forever!), had declared the lunar colony of the moribund nation of Anathemia to be obstructive of his grand view of the universal glory! It must be erased from existence!

The problem, of course, is that with a 9 hour transit time our nuclear missles are easily seen and even more easily shot down long before their radiative bloom can cleanse the lunar surface.

Your task, and it is imperative that you take it, is to present to His Ultimate Pacification a plan for delivering the metaphor of his wrath and vengence in a guaranteed manner. We love you Xanax!

photons are not your friend

  • While it's unlikely to detect an object as small as an ICBM from the color of its shell metal, it's not impossible. Therefore, the missle must be painted matte black.

  • But that's not enough. As the missle passes in front of stars, they will be occluded. This either requires the missle to be fairly small, or the surface must be designed with an imaging surface that will present the starfield, or something similar, toward the lunar surface.

  • The inner shell must be black-body (I believe this is the correct term) absorbing to ensure no radiation from the nuclear mass or the engine is lost for detection.

  • The outer shell must also be absorbing to ensure that incoming radiative scans (radar, etc.) don't reflect. However, I think this should be a bit more comprehensive. What happens if the scan expects to detect the international space station ... but doesn't? The absence of something that should be there is as revealing as the presence of something that shouldn't be there. Therefore, the missle might need to be smart enough to know where it is in alignment with detected scan sources and reflect enough signal to ensure a false positive.

  • The shape of the missle should balance the need to project false images to protect its approach with the need to minimize its detection signature.

  • The missles need to leave the lunar orbital plane, ideally by so great a distance that the Earth is no longer behind the missles should a line be drawn from any point on the moon, through the missle, and beyond. It is much simpler to compensate for the occluded light of distant stars than the occluded light of the Earth itself. If possible, this same argument should be applied to the Sun such that the missles are not in line between the moon and the Sun.

The heat bloom is a massive problem

  • The launch isn't the biggest problem. Keep up a steady satelite launch program that allows you to mix in your nukes and you're in business. It's hard to track a single tree in a forest. Over the course of time, a few "satelites" go down or are discontinued (powered down) leaving, at best, only a radar signature to track. But how small an object in orbit around Earth can be tracked from the moon? My point is, it shouldn't be a problem to mask the launch.

  • But once we're in space, a lovely heat bloom would be trivial to track from the moon. But we had to reach 7 miles-per-second just to escape Earth's gravity. That's ony twice what the missles want in the first place. That means the missle is traveling to the moon in 9 hours rather than 16. This means all we really need is thrusters, and for that we can live with compressed air. No heat bloom for course corrections.

One might be tempted to believe that with the addition of more fuel, the missle could achieve speeds that would render the need for stealth moot. The reality is that the fuel also increases mass making it more difficult to accelerate the missle. It also increases missle volume making it easier to detect and destroy. While a bit more fuel to reduce the transit time to, say, 6 hours may be preferrable. That would be a practical limit.

  • One last major burst of air as the missle nears its target in an effort to avoid the consequences of any early detection is preferable.

  • The engine and liquid fuel tanks should be jettisoned for incineration on the far side of the planet to make the actual missle as small as possible.

One missle isn't difficult. An hundred is a bit more of a challenge

  • A large group of missles would easily occlude light and increase overall mass to simple radar detection. Therefore, as early as possible and in tandem with the need to leave the lunar orbital plane mentioned earlier, the missles need to be spread apart.

This report being submitted during the Season of Adjur upon the second day of the Festival of Bequeathment unto the noble brow of the Lord of Mendelin for His consideration and approval as directed by my superiors in favor within the Hall of Adjudiciary Contentment that the will of Xanax the First be bound to eternity. Xanax!

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    $\begingroup$ Being small, cold and black is good enough. It probably wont pass in front of bright stars. It's a long way from the telescopes. $\endgroup$ Apr 3, 2018 at 19:45

Arguably the best way to hide such a thing would be to simply disguise it as something else. A nuclear weapon is simply a payload of a rocket - a rocket which might be carrying any number of things, such as supplies or scientific equipment. The ability to detect any spurious radiation from the warhead itself would be too late to stop it. Sure at a certain point they would probably extrapolate its trajectory and figure out that's a problem, but it might be too late. You can go from "huh, the moon is a long way away" to "wow we're impacting it at high velocity" pretty quick: https://www.youtube.com/watch?v=dE8pe2EYlZA


We have stealth planes so a stealth missile isn't that far a stretch.

If you don't mind waiting, you'd fire the missile on such a path that it would reach the moon out of view and orbit until close and then blast in at the last second giving them no time to react.

If you consider we miss a lot of asteroids which aren't stealth. A missile painted black and following a trajectory already established so it doesn't have to use its rockets would be very hard to spot. If it used a stealth fighter like design with the radar blocking paint, it would be virtually impossible.

  • 2
    $\begingroup$ Stealth bombers have benefit of being nearly the same temperature as the surrounding area so masking a few interesting wave-lights is all that is needed. Asteroids have exactly the same temperature.On the other hand missiles after lunch are 300 K lightbulbs against 2K background. Spotting them in IR should be easy (IR should be a color of 300K black body IIRC). $\endgroup$ Apr 4, 2018 at 3:54

You don't waste time and resources trying to invent something that's supposedly maybe undetectable, because we already have the technology to solve the problem of "enemy can shoot down our missiles": penetration aids.

In short, you build a lot of rockets with range to get to the moon, equip each with a few small nuclear warheads and a stupid amount of penaids, and launch them so all reach the lunar colony at the same time.

The sheer number of projectiles essentially guarantees that a significant number will impact the colony, and also that one of those that impacts will be a nuke. Yes, using penaids lowers the actual payload weight and thus limits the yield of the nukes, but you don't need a powerful nuke to do a lot of damage.

For example, each of the UK's Chevaline weapons contained 3 nuclear warheads of 200kt each and 27 penaids. A single submarine was able to carry 16 of these, which means if all were launched simultaneously, the target would have 480 projectiles to deal with. 200kt sounds like very little, but as this article demonstrates, a warhead of such "limited" capacity would still devastate an area of ~5km diameter. If the target should happen to be in a vacuum, the radiation emitted by the blast would be the most deadly aspect.

Resources would not be a problem because, guess what, we already have thousands of ICBMs with thousands of nuclear warheads sitting there ready to be reused. In fact I'd wager that current ICBMs could, with some modification, be repurposed almost as-is to hit the moon - all they need is a bit more power to get into a lunar trajectory, and perhaps a new more efficient type of fuel could supply that? Alternatively just scrap the ICBMs and use those raw materials to build your moonkiller missiles.

I'm no general, but if I had to choose between a single "undetectable" weapon that didn't exist yet and could still be shot down; or a large number of proven, easy-to-manufacture weapons that are effectively guaranteed to hit the target... well, I know which option I'd take.


Everyone thinks so complicated.

They are quickly reaching

Means they are not yet 100% self sufficient. Hide the nuke in one of the last supply drops, done.


As far as I know, "no stealth in space" is for manned, actively fuel/computer using operating systems. If you used vacuüm tubes with a magnetic rail system (and on the moon its easy to get it vacuüm) you could launch projectiles out of the moon's gravitywell and into the earth's gravitywell where gravity will do the rest with practically no working cirquitry. It would be harder to make sure the projectile remains undetected as it enters the atmosphere but depending on the speed it might already be within the 15 minute range.

The Moon is likely going to be build for space exploration and exploitation (like astroid mining) in the first place so the space industry there would be big and the people living there some of the smartest hardworking and physically capable people you can find. So they'll have a huge advantage. Missiles from earth would either need to be under constant acceleration for the moon or would be launched when the moon is incapable of seeing the launch site after which the missile is going in increasing orbits until it gets close to the moon, making it easier to detect incoming projectiles as they are either burning fuel or coming from a specific direction at calculable intervals.

Another thing is radiation. The Moon people would be completely set to deal with all the radiation in space, so all the fallout of nukes would be far less impacting (but the low population and depressurization would counter this quickly).

  • $\begingroup$ Just a minor point - vacuum tubes don't generate any less by way of EMR than ICs. Rather quite a bit more, in fact. $\endgroup$
    – jdunlop
    Apr 4, 2018 at 1:06
  • $\begingroup$ @jdunlop but they generate it over a much larger distance, they arent connected to the projectile themselves, the rails are inside the tube which any sensible pereon is going to heavily shield against both detection and solar flares and the like and when fitted into other infrastructure such as vacuüm tubes for transportation across the surface its more difficult to detect what exactly is happening. $\endgroup$
    – Demigan
    Apr 4, 2018 at 6:49

Just throwing in some ideas for others to process further (and maybe approve or disapprove with sources):

  • Wait for a time when Earth and Moon travel through an asteroid belt. Place a warhead concealed as rubble/asteroid in earths shadow into belt just barely outside of collusion course to the moon, so it wont be considered a threat by lunar scanners. When closest, start thrusters and hope it can reach surface.

  • Nuclear explosions in earths atmosphere cause an EMP. What happens with nuclear explosions in orbit near the moon? A successfull EMP against the moon would render it defenseless. A second direct warhead or troop carriers now should be able to make contact.

  • For centuries there have always been ways to win against impenetrable defenses: weakening it from the inside via sabotage, espionage, infiltration, distraction, psychological warfare and so on. The weakspot of human civilisation is the human himself. Let your warhead do the rest

Edit: unfortunately unable to comment this instead of answering due to lack of reputation (new stack guy here)

  • $\begingroup$ This looks a bit more like an extended comment than an answer now. $\endgroup$
    – Mołot
    Apr 3, 2018 at 14:37
  • 6
    $\begingroup$ 1. Earth and the Moon don't travel through asteroid belts. 2. An NEMP requires a decent magnetic field and an atmosphere to be effective over long range. The Moon has neither. $\endgroup$ Apr 3, 2018 at 15:47
  • $\begingroup$ if you cannot comment, instead of answering with a comment (which will make you lose more reputation) just gain reputation first $\endgroup$
    – L.Dutch
    Apr 3, 2018 at 16:57
  • $\begingroup$ @KeithMorrison meteor showers are pretty much little asteroid belts. It still doesn't work out for a number of reasons like the size of objects, the directions they travel, and the sparsity, but there is natural space junk we pass through. $\endgroup$
    – user25818
    Apr 3, 2018 at 17:27

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