It's for a short story I'm writing

There are probably tons of micro meteors that you would encounter on the way. You would also need enough food and water to make a two way trip, assuming a return trip. Tools and materials to repair any damage that occurs to your spacecraft while en route.

Not really. Like, micrometeors and other debris exist, but the craft is presumably built to deal with that. The modal probe to the outer planets just goes through the asteroid belt without much care, or may have a trajectory chosen specifically so it goes near an asteroid to observe it.

Something that comes to mind is how much Δv the craft has (and what that implies for what sort of trajectory is chosen and travel time). There are thermal and power concerns, though again this is normally dealt with in the design phase.

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What kind of tools would be used to repair the damage?

Wouldn't there be damage to a solar panel? Or something like that.

There can be (IIRC, there are a few holes in some of the ISS' panels), though that's more of "make sure you have a sufficiently tough structure that it can take the hits and still provide spare power".

Also, er, I was assuming that you'd use a nuclear reactor or something given how far from the sun Neptune is.

I'm writing a short story, I came up with a conceit.

What other debris can harm the spacecraft?

Well, I guess I would have an arc welder and some plates to repair any damage to the hull. Depending on how fast you're going dust and micro meteors could wreak havoc on a space craft. I don't think that stuff would be detectable because of their small size. This is why one of the tropes in Sci Fi space books and movies are shields. One way to look at it is what would you have on a sub for emergencies. You don't want water flooding into your hull any more than you want air escaping. The same could be said for a spacecraft.

Another thing to consider is size. The Titanic for example collided with an iceberg with relatively low speed. Because of the mass of the two objects it caused a lot of damage. Conversely smaller objects traveling at high velocity could also cause lots of damage. You may be able to detect and avoid an asteroid tens of yards across but something smaller may go unseen until it punctures your craft. Ideally you would have pressure sensors aboard your craft to detect any leaks or drops in cabin pressure.

Btw I have no education in science after high school. I just like to read a lot.

I mean we’ve sent unmanned ships there and further, they don’t seem to be suffering any crazy amounts of damage

Well, it wouldn't be bombarded with meteors, because meteors are an atmospheric phenomenon.

Where's the spacecraft's origin? a planet's (Earth's?) surface? Then it first needs to get into orbit (I think it's 4.72 lbs of fuel/oxidizer per pound of cargo using current technology?). Once in orbit it needs to handle the planetary orbital debris. Then it'll leave the Van Allen belt, which protects against radiation, which makes the metal brittle. If it passes by Jupiter to pick up speed, it'll be exposed to the second highest source of x-rays in the solar system. Any spacecraft powerful enough to travel to another star system is not going to try using a Hohmann Transfer method...

It's not a given that a space craft will travel through the asteroid belt- it could easily pass at an angle to the solar plane, bypassing the asteroid belt. The next part is getting through the terminal shock and Heliopause. Apparently this is rather difficult for the voyager spacecraft. Not sure why, but apparently the voyager spacecraft has been bumping up against it for years. After that, we're effectively in "Interstellar Space", but we still need to get through the Oort cloud, which spans ~1/2 the distance to alpha centauri. Once in this region of space you're subjected to even more radiation than craft inside the solar system.

Depending on the type of transportation used, that matters as well. Current Warp theory states that if it were possible to travel at near-light speeds (or faster if you're into the whole Alcubierre drive and its improvements over the years), an accumulation of particles collects at the front of the ship and, bombarded with higher energy over the course of the distance travelled, become highly energetic. A sudden stop would impart momentum to the ionized particles at the front, effectively turning them into a bullet. So you get ALL the way to the planet, stop, and then potentially blow it up by shooting the shit out of it with a massive ion cannon, propelled by the energy picked up by your ship (turning around would have the same effect on earth).

.... I just realized you're talking only about neptune. Fuck it... I'm not deleting all that.

I will say, though, that Jupiter puts out a fuckton of xrays, and neptune is #3 xray producer in the solar system IIRC. So a spacewalk is probably out of the question around jupiter or neptune.

Because of the distance, solar power is likely not a good option for power, so some internal power source would be required.

How about asteroids?

Also, while more mundane than meteors, your target is also moving. I assume this is solvable by math but it still must be considered.

Even in the asteroid belt, the asteroids are so far apart that you are unlikely to even see one, let alone have one hit you. Space is really big and mostly empty. The Voyager probes have been travelling through space for decades with no repairs and are still doing fine.

I mean, I'd avoid flying it through Saturn's ring plane, the ring arcs around Neptune, or especially close to a comet, but space is in general pretty empty.

Well for my story, an asteroid will impact the spacecraft

As a NASA mission designer, there would never be solar panels on a Neptune mission.

I'm writing a short story, what would be some plausible obstacles en route to an earth-like planet?

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I know that, I'm just talking about another short story I want to write.

Asteroids are not a concern. Real asteroids are not like the movies or the classic game. They are spread far apart. Even in the main belt between Mars and Jupiter they average ~1,000,000 km apart. There are a lot of them, so by happenstance you could pass relatively close to one, as New Horizons flew by an asteroid at a distance of over 100,000 km on its way to Jupiter and Pluto. (Or you could expend a potentially significant amount of fuel to deliberately fly by one at a closer but still-safe distance, as Galileo flew within 2,400 km of 243 Ida on its way to Jupiter.)

Micrometeroids are somewhat more of a concern, but mainly in low orbit around a massive object like Earth or Neptune, much less in deep space. (Neptune has faint dusty orbital rings.) For that, something like a Whipple shield would greatly reduce the risk and damage from micrometeoroids and other debris up to ~1 cm in size. (Earth has both natural and artificial debris orbiting it, so shielding is especially important for the ISS, which is spending decades in low Earth orbit.)

Look at The Martian. Most of the problems are things breaking unexpectedly. But FYI, the flight operations team is usually cut back somewhat in deep space because nothing is expected to happen.

Well I think you have your answer. They don't calculate a problem in the asteroid belt because there is less than a 0.000001% of a collision happening. But it could happen.

I expect acknowledgements for contributing this key plot point lmao

Naw, but my dad does. Can't even sit on the toilet some days.

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Joking aside, there are a lot of micrometeoroids out there, but relatively few asteroids. There have been experiments on spacecraft to detect the impacts.

For example, both Pioneer 10 and Pioneer 11, which were deep spacecraft that ventured into that part of the solar system had micrometeoroid detection systems. I don't know what the results were, but I know they did register some impacts.

As far as the larger debris, it's instructive that we've been sending spacecraft to the outer solar system and beyond since the 1970's and we've never had one disabled by a meteroid or asteroid impact. Space is just vastly huge and almost (but not quite) completely empty.

The real danger would be in the asteroid belt between the orbit of Mars and Jupiter, and there are also other areas of heightened concerns like the Jupiter trojans.

Hello u/Responsible_Trick644, your submission "En Route to Neptune" has been removed from r/space because:

• Such questions should be asked in the "All space questions" thread stickied at the top of the sub.

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That is great for your story, I guess. Real life odds would be less than a one in a billion chance for it to happen though.

https://en.wikipedia.org/wiki/Asteroid_belt