So, to start my story, I need to make sure that my so called "Defenders of Earth" can leave Earth unnoticed (not yet sure), that's why I'm thinking of Cannons, 1000ft long, hidden beneath the earth. Then these cannons will fire the 20Ft diameter bullets at a 80 degree angle.

These bullets are composed of 4 layers:

This is the rough sketch of the compartments of the rocket.

enter image description here

  • Red Part is the Rocket Part (10 tonnes)
  • Blue Part is the Fuel Line (15 tonnes)
  • Green is the Thick plate (5 tonnes)
  • Orange is the content, which is a human in a exoskeleton armor (1 ton)

The weight of the bullet is 40 tonnes, with the rocket layer as the heaviest component. The rest of the weight is the rocket itself.

The sequence of launch will be:

  1. Cannon loads bullet
  2. Cannon Fire bullet
  3. Bullet "must" reach Mesosphere
  4. Bullet Rockets will fire
  5. Bullet "must" reach Exosphere
  6. "Package" will launch

Here are some variables that I am not sure of:

  1. Velocity of the exiting the muzzle of the cannon.
  2. Amount of gas the bullet rocket has
  3. etc... (other variables I have not yet think of)

assuming I handwave these variables, is it possible that this contraption can succesfully (and maybe secretly) launch a bullet shaped rocket into space?

BONUS: (But optional) If you can calculate the time of the travel that would be great! But if not, and yet have a answer, that will also be great!

Please don't ask me the materials the rocket is created. I have not yet think of this. But can I at least say that it is the same of what the space shuttle uses.


These bullets are supposed to be the transports for my story, I want them to actually survive the travel from ground to outerspace, with much reading about how does NASA does it. It seems I need to have some sort of staged flight? But can the I achieve it realistically with my contraption?

Any other Idea to launch the bullet is appreciated, as long as it involves a bullet shaped rocket.

The nanobots are out of the question since they will be weapons, and are not components of the rocket.

The armor of the packages (The humans, my defenders) are made from depleted uranium. I'm not sure if this info helps.

  • 11
    $\begingroup$ While there's nothing preventing this bullet to reach orbit, the acceleration is going to kill any human inside, though. $\endgroup$
    – Rekesoft
    May 24, 2018 at 8:01
  • 13
    $\begingroup$ You will have to read "From the Earth to the Moon" by Jules Verne. He already wrote the story on this in 1865 $\endgroup$
    – Tonny
    May 24, 2018 at 14:23
  • 5
    $\begingroup$ Don't make your "Gun/Cannon" a normal (explosive) gun. Instead make it a some kind of rail-gun (electromagnetic, steam, air, or whatever). Otherwise the explosive G-forces of you gun will kill any payload no matter how much exoskeleton they wear. With a rail-gun at least you can spread the g-forces out over 1000 ft. (not sure if this is enough, I haven't done the math) $\endgroup$ May 24, 2018 at 14:24
  • 12
    $\begingroup$ OMG, is that blue section supposed to be sticking out of the bottom like that? It's triggering my OCD something fierce. $\endgroup$ May 24, 2018 at 14:24
  • 5
    $\begingroup$ Seems like your railgun would have to be at least 200 miles long to be even remotely survivable (20Gs for the whole length). That doesn't seem like something that could be a secret. $\endgroup$ May 24, 2018 at 14:48

9 Answers 9


As others have noted, the 42000 g acceleration will make a hash of all but the most hardened payloads, making the project infeasible. As well, the blast from the "gun" and the high speed projectile screaming through the atmosphere into space will be rather noticeable as well.

Indeed, the only way to generate enough energy to actually launch more than a notional payload into orbit is likely nuclear energy. An underground test in the "Plum Bob" series accidentally (?) had the massive steel cap over the shaft blown off by the nuclear explosion, calculations suggested the cap was moving at 6X Earth escape velocity at launch. While it may be in the outer solar system today, the more likely result was it was vapourized by the incredible forces and air friction in the atmosphere.

More recently Brian Wang of "NextBigFuture" has advocated for a version of this (the "Wang Bullet") to shoot massive quantities of material like steel or even coal into space for colonization projects (the coal would provide carbon for various industrial or life support purposes).

To make this efficient, you would probably need to fill the shaft with water so the x-ray output of the bomb turns it into plasma and effectively couples the energy of the bomb into the projectile.

So yes, you could launch "bullets" into space with kiloton bombs, but it won't be "unnoticed" in any sense of the word......

  • $\begingroup$ Did I get this right, instead of my cannon, I have to use a Railgun, using the same technology to drive a bullet train, can the bullet reach further if I use this? $\endgroup$
    – Mr.J
    May 25, 2018 at 5:35
  • $\begingroup$ Any technology which can accelerate the "bullet" can be used so long as the acceleration is spread over a long enough time frame that the human passenger can survive, Electromagnetic sleds seem suitable, but will need to be very long, since even trained humans can only handle 9 g, and it is safer and more sensible to have much lower g forces (maximum is probably 3 g) for safety and comfort. $\endgroup$
    – Thucydides
    May 25, 2018 at 9:33
  • $\begingroup$ Any suggestions on how can my humans survive? $\endgroup$
    – Mr.J
    Jun 1, 2018 at 2:04
  • $\begingroup$ Your humans survive by being launched at under 9*g* (and preferably 3 g) using a rocket, or very long launching sled to reach orbital or near orbital velocity. Go to the Atomic Rockets website for some preliminary research: projectrho.com/public_html/rocket $\endgroup$
    – Thucydides
    Jun 2, 2018 at 2:31

The human will die instantly if blown out of the cannon

(Note: skip to "Launch Detection" for how to address the changed focus of the question.)

A back of the envelope (literally) calculation full of approximations shows that in order for the bullet to reach the mesosphere (50 km ASL) on a ballistic arc, launched from sea level, it needs to be launched at around 1200 metres per second. Note that this will just reach an altitude of 50 km after 80-90 seconds and start falling back, the rocket will need to do all the work of getting anywhere after this.

Assuming perfectly smooth acceleration over a barrel length of 300 metres (1000 ft), acceleration will be on the order of 2300 metres per second squared for almost half a second. While all my numbers could be off by as much as 50% in either direction (lots of approximations) 230 G is simply not survivable. Even by adding all plausible (and some implausible) favourable factors, humans can't get into space this way in any condition to achieve a mission.

Single stage to orbit - not that easy...

The main difficulty in getting into orbit is not achieving the required altitude but reaching the required orbital velocity of over 9.4 km/sec. Escape velocity is 11.2 km/sec. This is not practical with current technologies (which is why multi-stage rockets are used to get to orbit in the real world).

Is there an alternative?

All you are launching is a single soldier in exoskeleton armour. This doesn't look like a long range or long duration mission, more like a special forces job in earth orbit. In that case - why send a fragile human? Send a drone (or 3 smaller ones), controlled from groundside. The drone will need some pre-programmed routines, but lightspeed delay is minimal, especially if in low-earth orbit. (Although you will need to keep switching to a new retransmission station with line of sight as the drone orbits.) This allows you to use your payload for mission-critical capabilities instead of life support and means you no longer need to worry about how to retrieve the operator at the end of the mission. However, given that you have clarified that the crucial element of the story is to deliver four humans into space unnoticed, the following section will examine how to do this.

Launch detection and covert options

Assumptions regarding the enemy, designated Red Force:
1. Red force has finite forces that are in total control of Earth orbital space.
2. Red force has satellites in orbit with ground observation capabilities sensors equivalent to current United States surveillance satellites.
3. Red force has other sensor capabilities equivalent to current United States capabilities.
4. Red force has both space-to-surface and space-to-space weaponry equivalent to current Earth prototypes or near-future concepts, primarily mass drivers or missiles.

As other answers have covered, it would require a linear accelerator hundreds of kilometres long to launch a person into orbit without fatal acceleration levels. Building such a linear accelerator (overcoming massive engineering challenges) without being detected and attacked from orbit would be extremely difficult, time consuming and hideously expensive. So let's look at other options using conventional launch vehicles.

If a satellite has its sensors watching an area, there is no real way to disguise a missile or spacecraft launch. Any currently existing rocket which is efficient enough to get a payload into orbit will produce a massive thermal signature. It's the same as being in a very dark room, yet the tiny indicator lights on appliances are easily visible. The only way to mask them is to put something thermally opaque between the sensor and the thermal source (not practical), increase the temperature of the entire region to match the temperature of the rocket exhaust (not survivable), wait for the observer to stop watching (maybe) or poke out the eyes of the observer (ahhhh!).

The Defenders need to be tracking the enemy satellites in order to make this work - no alternative. If they are lucky there is an existing hole in the Red Force satellite coverage that they can take advantage of, somewhere that is not being directly observed for a few minutes every so often. If such locations do exist then they are probably in bad locations for launches - it would be all too easy to keep the entire equatorial area under observation, for example. If there is no practical location that they can take advantage of then they need to get into the anti-satellite business using either rockets, cannon or lasers.

So there is a use for the cannon - a bunch of depleted uranium marbles in a casing can survive a savage acceleration and only need to reach the satellite's altitude for a moment - then the satellite's > 9km/s speed will provide all the kinetic energy necessary to destroy it. Ditto for a rocket, no great performance required. Regarding lasers, I am suggesting tracking the satellite with a laser powerful enough to dazzle the onboard sensors, not something powerful enough to cause material damage. If at all possible, hit additional satellites covering different areas at the same time, otherwise Red Force can focus all its reserve sensors on the one area.

While the eyes are poked out or looking elsewhere is the time to launch. All four humans launch in a single 2-stage vehicle with a bullet-shaped final stage. At roughly the same time five smaller rockets also launch. The smaller rockets will deliberately have the same acceleration profile as the primary and cube-corner radar reflectors to give them the same radar signature. Once they are out of the atmosphere they will inflate "caps" at the front to give them the same visual profile as well. (This is assuming that the Defenders are on a budget and cannot afford to waste six full-size launch vehicles.)

Now switch to Red Force's viewpoint for a while. They just lost a few satellites or their imaging, refocus other sensors on the area and pick up six bogeys as they clear the atmosphere. It looks like the Defenders had trouble getting quality components because one suffers a catastrophic failure at first-stage separation. The other five continue on but as they get close to an intercept course on an important Red Force target two more malfunction - the lead one explodes into tiny fragments and the last one loses thrust and starts venting fuel on one side, throwing it into a flat spin. The three remaining rockets accelerate towards the Red Force target to ram it but miss, either as a result of more poor engineering or point defence fire. Red Force has emerged victorious, albeit fairly easily against the ragtag Earthlings...

Switching back to the Defenders' viewpoint - the rocket that failed at first stage separation was to make the subsequent malfunctions believable. The second rocket to go will explode into prefragmented pieces designed to provide maximum visual and radar distractions, with the direction of shrapnel release to provide masking without endangering the humans. The four humans were aboard the third rocket - the rocket's spin was carefully planned to be in a plane that will give them the vector they need to reach their target (or get close enough for low-impulse thrusters to do the rest) if they release at the correct point in the rotation. The humans' armour is as non-reflective to visual and radar wavelengths as possible and includes thermal masking - I strongly recommend it is made of carbon composites as much as possible instead of depleted uranium. Provided they keep tight emissions control, the humans will look far less interesting and important than the thousands of bits of space debris in the area.

I acknowledge the influence of the late Nigel D Findley in the plan presented above - see p127 of the Aztlan sourcebook for Shadowrun 2nd Ed.

Edit 1 - previous alternative

Recent events in Hawai'i have inspired an enhanced solution, albeit with no research to back it up. While it would be a really bad idea due to the geological instability of the area, let's posit an undersea tunnel linking O'ahu to the Island of Hawai'i. Hidden from prying orbital eyes, this tunnel could be repurposed into a linear accelerator a few hundred kilometres long, with the normal exit on the Island of Hawai'i extended and aimed upwards, albeit in a gentle curve. There are lots of engineering difficulties, such as evacuating all the air in the tunnel in front of the bullet, but these are not inherently impossible if the tunnel has sufficient integrity. Time the launch to coincide with a volcanic eruption (predicted or induced) and the Defenders can launch their projectile with hot ash covering any thermal signature and the eruption covering for the shockwave.

I realise this is nowhere near the original specifications of the OP's cannon. However, it does give a vaguely plausible mechanism for an undetected, human-survivable launch, with the added drama of requiring precise timing to avoid the bullet being destroyed by airborne debris from the eruption.

  • $\begingroup$ The fragile human is the plot of the story, there will be actually 4 of these "bullets" to be fired. I'm thinking of creating a story as realistic as possible, with nanotech the only fantasy thing. $\endgroup$
    – Mr.J
    May 25, 2018 at 8:17
  • $\begingroup$ @Mr J - Thanks, that helps. Suggest you put that information into the question, including whether all four humans are being launched from the one location and what the limits of the nanotech are. $\endgroup$ May 25, 2018 at 9:35
  • $\begingroup$ A curve allows you to accelerate the craft slower but doesn't protect the occupants when the track curves up. $\endgroup$ May 28, 2018 at 4:33
  • $\begingroup$ @KerrAvon2055 any suggestions on how my humans can survive? $\endgroup$
    – Mr.J
    Jun 1, 2018 at 2:05
  • $\begingroup$ @Mr.J the edit I've just made is the best I can come up with. Let me know if any of my assumptions are invalid - I've been viewing it as a Footfall-like scenario (Niven and Pournelle) $\endgroup$ Jun 1, 2018 at 12:55

You've got a space gun.

There's no doubt this idea could work, as the article I linked will tell you. So essentially yes, this contraption of yours is entirely possible (as for whether or not you can use a Space Gun to launch a projectile unnoticed into space, well that might be a good idea to ask in another question, since that seems right up this site's alley)


There is no doubt that you could create a contraption like that that could send the bullet-shaped rocket into mesosphere, or even space. The problem is how safe would the cargo be. If you were trying to fire it so that by the time it leaves the 1000ft canon it has escape velocity, 11.2km/s, (which is still not enough to reach the atmosphere as friction will slow you down to a much smaller terminal velocity) your heroes would experience aroun 42000g of acceleration which would most definitely kill them. There is no way to get around this as even the thickest armor wouldn't help their brain smushing down into their skull. If your story isn't very futuristic sci-fi, the best bet for your heroes are old-fashioned rockets, which can thrust continously instead.

  • $\begingroup$ Hmm, I'm getting 21,000 Gs when I do the calculation. One of us is off by a factor of 2 somewhere. $\endgroup$ May 24, 2018 at 14:41

Since this is not tagged with Hard-science i'm not gonna do the math, but the space gun is not a bad idea.

Most here realised the gun would suqash most payloads before reaching orbit, but there is 2 factors missing, 1 they are trying to "shoot" the payload in to orbit reaching the full escape velocity at the muzzle, but the "bullet" has a rocket propulsion system build in, thus lowering the need for full orbital insertion att the muzzle. (the delta-v to reach space at 100 km would be about 1.4 km/s about 1/10th of orbital speed, to reach 300 km you need about 7 km/s and you have keplers law to help with the insertion burn)

The second is that the atmosphere is too high. But if you are able to rise the muzzle to a higher ground the atmosphere would be thinner and and again less drag would be needed.

Ex. the atmosphere is about 14 psi at ground level but at the top of mount everest it is almost 1/3 at 4.8 psi. The reason you don't launch from a higher place is that the trouble of moving the rocket that high is not worth the small return but in this case the barrel is about 10 km anyway and you don't have propulsion on the way up

While your heroes might not be able to launch from mount everest the accelerator needs to be long and your citadell could be aprox 10 km tall, with the space gun barrel down the center. An alternative would be to launch from a plane having a space gun on the plane gives a bit of velocity and speed, the launch would be harder to detect. But that will give other complications.

Once up there the capsuile would make the capture burn and your hero would be in space.


If you fire a bullet and want it to reach space, you basically need to give it Earth escape velocity of 11 km/s. After that, it doesn't matter which angle you use to fire it, as long as it doesn't hit the ground. (actually it does matter when you take into account atmospheric drag)

As bonus, handwaving a cannon to fire a projectile at that velocity will take out the need of a more complex structure of the bullet. You may want to keep some steering capability.

  • $\begingroup$ Is it even possible to "Ignore" the escape velocity? I know that every space instruments leaving earth does this, but can I ignore it without handwaving anything else? $\endgroup$
    – Mr.J
    May 24, 2018 at 6:22
  • 3
    $\begingroup$ @Mr.J, what do you mean with ignoring? If it's slower than that it will be pulled back by gravitation, else it will continue its trajectory $\endgroup$
    – L.Dutch
    May 24, 2018 at 6:24
  • $\begingroup$ @Mr.J most space mission do not actually escape earth but just reach some orbit. this requires less velocity but does require chnages in velocity after launch (otherwise your orbit has to intersect your launch point i.e. you hit the ground again) $\endgroup$
    – jk.
    May 24, 2018 at 15:07

In general, the best way to get a military payload into space without anyone noticing it is to put it in a big box labeled "telecom satellite" and just launch it on a rocket. There are enough commercial and scientific launches with various payloads and orbital destinations that you could probably hide in the traffic, or at least convince a reader that that's plausible.

If you want to leave Earth orbit, there's really no stealthy way of doing it (at least not yet; if at some point in the future there are regular commercial trips to, say, Mars, camouflage becomes a viable option again). At the end of the day, it's a lot easier to spot a hot, fast-moving object in empty space than it is to hide it, no matter what mechanism you come up with to put it there.


Borrowing some tech notes from The Forever War, you could use make your passengers incompressible, thus protecting them from most or maybe all of the acceleration you're subjecting the craft to. Disclaimer: I'm not sure how deeply into the fiction side of Science Fiction that particular measure is, it makes sense logically but it may or may not work when real-world physics is involved.

Alternatively if you want a bullet shaped object you could use a giant Gyrojet, it's a rocket, but it's also a bullet, in this case you're basically using a single stage Earth-to-Orbit vehicle. It would burn propellant the whole way down the barrel and out into space, thus smoothing out point accelerations to something tolerable. Secrecy is maintained by location, whatever the launch method you need to out the launch facility out of the way to prevent observation anyway.

There are some super-tech methods available to you, inertial dampers and that sort of thing but they throw up other problems, usually more than they're worth.



Yes, you could do something like this.

No, the system you proposed definitely could not do this without killing the human(s) inside. The acceleration I derive from your numbers (if you assume constant acceleration - which is a bad assumption for conventional guns), is an acceleration of ~7000 g's for about 0.1 seconds. 7000 g's is guaranteed to turn your crew into red jelly at the back of the capsule.



Years ago I wrote up description of how the Ram Accelerator technology could be used to accomplish this goal. Researchers have used experimental Ram Accelerators for decades. We could probably build one now that could launch things into orbit.

enter image description here


However, the facility would be very large and expensive. In order to not squishify your human passengers, the launcher barrel needs to be many MANY miles long. On my blog I limited the launcher to 3 g's of acceleration and discovered such a launcher requires a launch tube of 362 km about 225 miles!

Note that a straight up "space gun" can't apply an even g load. The passengers would experience most of the g load up front and get squished. That's what makes the Ram Accelerator a much better technology for human passengers.


This technology also requires an apogee kick motor. Basically, it can put the hero on a ballistic course with its highest point in space. However, once you get there, you must apply some additional delta V to circularize the orbit or your projectile will crash back to Earth. Your projectile will survive the trip as a single stage or possibly 2 stages (if you plan to do external scramjet burning after leaving the end of the tube).

  • Stage 1: ram accelerator burns fuel/oxy mix in the tube.
  • Stage 2: external scramjet burns onboard fuel with atmospheric oxygen
  • Stage 3: apogee kick rocket to circularize the orbit.

These stages do not require dropping prior stages. However, it seems to me that dropping the Stage 2: external scramjet fuel tank would probably be a good idea.


Assuming an 8,000 m/s exit velocity,

  • Time to end of tunnel, 4.5 minutes
  • Time to Apogee after exiting tunnel, 25 seconds.

Vessel shape

The ram accelerator vessel would NOT look like a conventional bullet. It would possess a shock cone in front and an aerospike in the back.

enter image description here

From University of Washington ram accelerator lab website.


You either get a small facility with thousands of g's of acceleration, only suitable for bulk materials OR you need a gargantuan facility able to launch humans without killing them.

You can't get both characteristics in the same facility.


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