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how could one transport people planetside into orbit when the planet the people are on has no infrastructure for launching stuff into orbit? (this includes rockets and railgunning things into orbit) I would really like to implement this into a story and I'm curious if there's even a glimmer of hope that I can do it without absolute handwavium.

the people being transported would be all types of people.

this should be a very quick affair, a pickup should arrive within a day.

any science fiction solutions allowed, just no magic.

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    $\begingroup$ Have you considered a skycrane ? $\endgroup$
    – ErikHall
    Feb 22 at 23:51
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    $\begingroup$ What is the tech level? $\endgroup$
    – Thorne
    Feb 23 at 0:15
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    $\begingroup$ Would it be possible for a shuttle of some kind to land on a body of water? This might simplify the infra-structure needed. $\endgroup$
    – FlaStorm32
    Feb 23 at 3:47
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    $\begingroup$ @FlaStorm32 not entirely possible, some waterless planets have colonies $\endgroup$
    – alkahest
    Feb 23 at 12:39
  • $\begingroup$ Added a second answer for if we're allowed to just railgun stuff into and out of orbit :) $\endgroup$ Apr 16 at 13:21

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There is an upper limit on how fast you can do this, but yes, with minimal handwavium, you might be able to do it.

How do we do it?

If you're allowing science fiction, let's handwave a nuclear fusion turbojet that allows for extremely efficient propulsion in and out of an atmosphere. You have virtually unlimited $I_{sp}$ and therefore fuel is no longer a concern. Then, you can include whatever landing gear you want so you can touch down just about anywhere. This isn't entirely based in sci-fi either: assuming you have compact nuclear fusion (which is bound to happen one of these days anyway), you just sit your fusion reactor next to a combination inert gas inlet/air intake and let physics do the work of propulsion. Out of atmosphere, you use the inert gas as propellant, and inside an atmosphere, you use air. Done!

Is that really realistic?

If we're talking about Earth, then we're considering a time at which there is a necessity to transport a volume of soldiers from the Earth's surface to orbit in under a day. That is certainly no time soon given the current laws regarding outer space, and so it's honestly not as implausible that we have our unobtainium engine figured out by then.

But how long does it take?

There is a minimum time that it takes to pick someone up. This is related to orbital velocity. Say you want to pick someone up from Earth's surface and bring them to the ISS. You can wait ~45 minutes (on average, given a 90-minute orbit) for the ISS to be in the right spot, then burn at 1 g all the way down till your orbital velocity is zero, at which point you'll be on the surface. Then, you burn back up at 1 g straight to the ISS where you deliver your troops to their vacation home (or warzone, or wherever). The ISS is moving at 7.66 kilometers per second, so you're going to need to accelerate twice that much (once going down, once going up) in order to complete the mission. Under ideal conditions, this will take around 26 minutes - more realistically, probably about 30. So, ostensibly, you could deliver troops to low Earth orbit in about 1:15:00.

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I'm not sure how you could do any kind of mass transport to orbit without any infrastructure, just look at airports.

Infrastructure can also refer to manufacturing. if the planet has no means to manufacture spacecraft then this is completely impossible.

I suppose you could build sea dragon-like vessels in shipyards and launch them out of the water to circumvent the need for a spaceport, but you're going to need manufacturing.

If the spacecraft are not made locally that opens up a lot more possibilities. I can imagine a fleet in orbit sending down some kind of military SSTOs that can land on rough terrain to pick people up.

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Assuming troops in orbit can survive and be useful you are talking about a rather high tech, well above what we have now. Are you sure you want them in orbit, not to get them to some other world? It would be helpful to (very generally) describe what kind of troops are they and what you want to do with them.

The obvious approach is to mostly avoid the tech side. There are just ordinary boring space ships delivering cargo to/from planet or refueling, you repurpose them to move troops. You send a representative to a nearby system to rent a few transports. You negotiate a deal with space trade guild/corporation. Advanced aliens suggest to help you for a price. You ask an enemy of your enemy to get assistance. Stuff like that.

If space ships can't enter the atmosphere they should use shuttles of some sort. Normally shuttles would be land based or parked in space station but, if you don't want the planet to have these capabilities they can come with the transport ships.

Shuttle can be rocket based. Or a space plane which climbs up as a plane and then uses space engines. Power source - chemical, fusion or fission reactor. Or some future tech like antimatter, anti gravitational engine, ion drive, beryllium sphere.

In general tech details are not particularly important for a story. It is a technobabble functionally equivalent to magic. It can be fun in small quantities, but focusing on it doesn't make much sense.

Heroes don't have to necessarily understand the tech. "WTF is that? - Oh, It's arkelian trader, you never seen one? - No. Not landing anyway. Awesome. How do they do it? - Trillion credits question. Damn aliens." and proceed to description of landing of an impressive landing of a miracle spaceship.

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  • $\begingroup$ absolutely sure I want them in orbit. warships with handwavium warp drives will receive them and teleport them elsewhere $\endgroup$
    – alkahest
    Feb 23 at 2:01
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One proposal for more efficient space ship launching is to use magnetic acceleration. Basically you build a curved track, put a specially designed maglev wagon on it which carries the payload you want to go into space (people in this case), then accelerate it along the track. At the end of the track it just releases and flies into space with minimal rocketry necessary just to steer after getting there.

Biggest problem is you kinda need to build it into a mountain as these tracks need to be long, have a shallow curve and preferably be as high as possible.

Other than that, the power necessary compared to the rocketfuel isn’t that big.

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Post-edit answer

If you allow orbital-scale railguns, then things get way easier. All you have to hand wave is a way for people to survive very high g-forces, like the "juice" from The Expanse that allows people to withstand upwards of 10 gs for extended periods of time.

Let's assume you have that, and that you can build a ship that can house people inside with inertial dampeners or juice boxes or something that lets them survive extreme g-forces. Then this is a very simple problem: an equatorial railgun to launch stuff up and a retrograde railgun to launch stuff down.

To launch into orbit, fire your human bullet through a railgun situated at high altitude parallel to the surface of the planet at that point. Then, after around 30 minutes of coasting out of the atmosphere to a low orbit, you can use a minimal-delta-$v$ burn at apoapsis to achieve low orbit. Done in half an hour!

To launch back from orbit (say, from a space station you just launched to), simply have another railgun of much smaller power oriented in the opposite direction of the station's velocity. The railgun actually only needs to supply the amount of delta-$v$ that the ship put in to get into orbit to get out of orbit; after another 30:00-45:00 wait, the ship re-enters the atmosphere.

As it turns out, more powerful railguns actually don't really help here. You just need enough delta-$v$ to get into and out of a nearly-circular orbit; it's much more expensive to go up than to go down, but that is to be expected, and you can launch from anywhere along the equator. If you're willing to have extra fuel on your bullet-ship to make an inclination change in your orbit, you could actually launch from anywhere; just burn normal to your orbit when you reach your orbital node and you've successfully achieved a roughly-circular orbit using a railgun. Getting back down to any point on the planet's surface, not just on the equator, can also be done; simply angle the railgun so your reentry point is roughly above your drop zone. This does make deploying a reentry pod to the poles more energy-expensive for the station, since plane-change $\mathrm{d}v$ must also be supplied by the station's railgun if you're deploying all the way up there, but it works in the most general case.

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