would it help to slow yourself down every now and then or go down in a spiral manouver?

basically, any method less risky than plunging straight down

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Spiraling works to keep things on track, such as nuclear warheads. Thats why gun barrels sometimes have rifiling, the spin keeps the bullet on a straighter course. You dont want to do that in a manned spacecraft, it'll make your passengers sick.

This is a good video:

This is more about nuclear weapons:

The method would have to include a way for the ship to slow down significantly.
If you had a powerful enough counter gravity generator that would work.
The reason for heat build up is due to speed, so anything that slows down a ship in reentry effectively counters the heat build up.

The above linked video on the Apollo re-entries is great. There really aren’t many different things you can do to avoid the hottest parts of re-entry. Basically there you have to have a way to survive I the heat. The above Apollo video talks about using ablative heat shields which work great but are one-time use. Once you are past the hottest re-entry phases is where you really start to have options.

Type and shape of spacecraft is another big issue. Are you dealing with a lifting body (like the space shuttle) or not, basically does it have wings. If the craft can glide or is capable of powered flight then you can do wide maneuvers to bleed off speed once the craft is deeper in the atmosphere. The shuttle for example would make large S turns after the hottest re-entry phases to bleed off speed. Maneuvering like that though isn’t a really good idea during the hot parts though because of stresses and heating up more of the ship.

Fuel is another big concern. Doing something like a suicide burn, waiting till very late to fire engines to slow for landing is actually one of the most fuel efficient methods. If I remember right I believe the space-x falcon heavy boosters use this method on landing. You can be constantly firing engines to slow down the whole way in but it will require enormously larger amounts of fuel if the craft cannot glide in atmosphere (assuming the planet in question has a thick enough atmosphere).

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Pick a planet without an atmosphere. No air, no friction!

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IRL: Provide a giant surface area facing the ground with heat resistant plates, (Apollo)
Glide in on wings (Half of space shuttle)
Suicide burn (space x)
parachutes ( mars landers)

possible but not built: Skyhook
orbital ring
space elevator

Scifi: powered landing all the way
anti grav drives
teleport
portals.

If you're looking to land on a planet with the lowest risk of burning up. You will want a spaceship that can change its shape from the shape optimized for space travel to a shape optimized to glide down on wings at less than mach 10.
This will mean you will be in a straight line, around, and around a planet as you slowly descend for hours.
Anything above mach 10, and you're asking for heat that can melt your wings/ship. I've read Isaac Asimov do this in some of his stories.
Now depending on how hard of Science Fiction you want to go with, you will have to keep in mind the slower you are the faster you will descend causing friction and Heat.
If you go too fast, you have a chance of bouncing off the atmosphere.
If you use rocket assist descent, then you might as well go straight down in a traditional Rocket which will take you hours, and you will be backing down to the surface.
IE you will be facing space, and using a lot of fuel, or if you have anti-grav technology you can just slowly descend without rocket assist.
I hope this helps with your story.

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Bullets and Nuclear Bombs use an Axial Spiral, spinning around their axis. Spacecraft use an Orbital Spiral (continually decreasing altitude) which can vary in size from a complete circling (or multiple circlings) of the planet to one just a few miles wide with a constant turn, much like a corkscrew (depending on your drive system and ship design).

It mostly depends on your level of technology. (NASA would love to have some the technology that lets you launch, land, and re-use your entire spaceship like in those old movies).

And how much bolognium you have.

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Why are you tagging me, Obsi is the one that needs the information

Also, it depends on why you're landing, and how urgently you need to be on the surface. Depending on your tech level, a straight-down descent at 80 degrees can be done if your goal is to be down as quickly as possible. If you have force-shields (either tech-based or magical) and anti-gravity (again, tech-based or magical), you can pretty much choose how you're going to descend and how fast or slow you want to go. If you're stuck using real-world physics, then it gets more complicated...

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If you are part of a civilization of arseholes, you could consider a powered landing by any type of torchship or open-cycle atomic rocket. You could even do an elevator landing with these means, never subjected to a hard reentry or high g's, all with real-world physics.
If your arsehole civilization was establishing a colony inside the planet, consider aiming your reentry at a wasteland, then flying atmospherically away from the wasteland to land in the spaceport in the next valley, while the fallout of hundreds, thousands of reentries makes that one valley glow in the dark.

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Actually, you could very much do an 80º reentry with real world physics and relatively low g's experienced by the passengers. It would just be the ultimate arsehole move: you build a heavy, heavy heat shield out of lunar regolith, do your straight-down plunge, then jettison your shield on the upper stratosphere while you deploy your first drogue chute. You then land safely and comfortably while your shield creates a crater or air-bursts with the power of a small nuke. And if you wanted to be even more of an arse bandit, rather than picking lunar regolith, you could have carried your own rock from Earth if you initially took off using an Orion drive or other type of non-contained atomic rocket.

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If you are part of a civilization of arseholes, you could consider a powered landing by any type of torchship or open-cycle atomic rocket. You could even do an elevator landing with these means, never subjected to a hard reentry or high g's, all with real-world physics.

Actually, an open-cycle fusion (OCFu) drive would be far safer than an open-cycle fission (OCFi) drive (much less -if any- radiation), and a closed-cycle fusion (CCFu) drive is even better (much less shielding needed, and your fuel can also be your propellant in vacuum - In atmosphere, no spewing radiation out the thrust-vent of your craft, just masses of super-heated atmosphere).

If anyone here remembers the extremely-well-illustrated and written comic series Albedo Anthropomorphics (showing my age here), their Aerodynes/shuttles use an extremely-clean CCF system and an MHDT drive for their ships.

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Actually, you could very much do an 80º reentry with real world physics and relatively low g's experienced by the passengers. It would just be the ultimate arsehole move: you build a heavy, heavy heat shield out of lunar regolith, do your straight-down plunge, then jettison your shield on the upper stratosphere while you deploy your first drogue chute. You then land safely and comfortably while your shield creates a crater or air-bursts with the power of a small nuke.

That might be quite good for a combined orbital-strike/military invasion mission. Alternately, have a shield that will, on command, blow apart once braking is over and have it do a similar strike on a location: You get a massive bombardment (aerial claymore mine) as well as a huge pressure-wave strike proceeding it. I could imagine something like that being developed for a Starship Troopers-style scenario.

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and a closed-cycle fusion (CCFu) drive is even better (much less shielding needed, and your fuel can also be your propellant in vacuum

Actually, if you could choose, you would use Hydrogen as fuel, then Xenon as a propellant. Xenon specifically because it has a high atomic mass, thus most efficient (specific thrust/power used) when shot from an electric rocket, and because it doesn't interact chemically with its environment, thus it would cause less erosion to the exhaust (whether used in an ion drive or in a plasma drive). Your next best propellants would be water distilled either from sea water or comet ice (depending whether you're taking off from planet or space).

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Actually, if you could choose, you would use Hydrogen as fuel, then Xenon as a propellant. Xenon specifically because it has a high atomic mass, thus most efficient (specific thrust/power used) when shot from an electric rocket, and because it doesn't interact chemically with its environment, thus it would cause less erosion to the exhaust (whether used in an ion drive or in a plasma drive). Your next best propellants would be water distilled either from sea water or comet ice (depending whether you're taking off from planet or space).

It also depends if you can justify having both onboard. Hydrogen is far easier to distill and contain as opposed to Xenon, and you only need hydrogen as a propellant when out-of-atmosphere. Otherwise, you only need to super-heat air by passing it around a fusion reactor's heat exchanger to propel an aerodyne, as opposed to a proper space/starship. I have also read of ammonia being used as a propellant (2001), and water taken from extra-terrestrial sources (2069). And while using Xenon from an electric/ion thruster (as opposed to a 'rocket') could be 'considerably' more efficient, how costly is it to produce and transport

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Hydrogen is far easier to distill and contain as opposed to Xenon

Isolate, yeah.
Contain, nope. Pure hydrogen is actually impossible to truly contain. It has to do with the sheer size of the hydrogen diatom as opposed to anything else. As to hydrogen everything looks like a sieve, H² seeps through anything if pressurized. I understand that you could galvanize the inside of your regular metallic tank with either lithium or beryllium, but that barely slows hydrogen down from seeping through your steel or aluminium tank otherwise.
It is kind of like keeping charge in a lead-acid battery: the only way to keep it topped is to recharge it every now and then.

I have also read of ammonia being used as a propellant

That falls under "comet ice". Comet Ice is composed of CH⁴ (methane), NH³ (ammonia) and H²O (water). If you had space habitats, Moon colonies or similar, harvesting light elements from comets and using them all would likely separate them all, then use the least precious of them as propellant. Alternatively, if you are capturing comet ice exclusively for propellant, you could harvest or get rid of the methane (carbon apparently doesn't like being turned into plasma), then have some torchships designed for methane, and some others for water.

how costly is it to produce and transport

Xenon, like argon and krypton, is a by-product of the production of cryogenic fluids (nitrogen and oxygen). As long as industry needs cryogenic fluids, we'll have some. Helium is much harder.
As to transporting it: no harder than transporting any other pressurized gas. Easier, really, being a fully inert gas.

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How about a conceptual seperation of re-entry and landing. Entry onto the planet is considered complete at 31,000 ft, because that's roughly how high commercial airplanes fly. Then you just fly around for a bit and land like a plane does.

Maybe the wings only extend when re-entry is complete.

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Technically, the best possible landing technique was considered a pipe dream up to around 2012, when SpaceX demonstrated the first ever powered landing.
A powered landing can be as soft and unprotected as you can, worrying about the heat of your own exhaust rather than the heat of a violent reentry. The most extreme powered landing would be an elevator landing: you ride your engines all the way down, letting you descend with as few gees as you may want.

Here's SpaceX' last test of the Falcon Heavy System. As you can see, it is powerful enough to send a car to Mars, yet all three first stage boosters power landed, ready for another go: