5 ms·

Not really relevant but, if we we had an arbitrarily super fast spacecraft, how would we prevent it from hitting a small rock and exploding?

simlevesque 7y ago
Maybe they we will be able to detect a marble from hundreds of thousands of miles in the empty space with new radar/lidar tech.
- ztjio 7y ago
  LIDAR can't even see the moon.
alpha_squared 7y ago
Ultimately, you can't. Space is really, really, really big and empty, though. Unimaginably so, which would make an incident be some really bad luck. In something like the lightsails, you'd just launch multiple simultaneously. Space is so big and empty that even for something like the asteroid belt you could pass through any point randomly and on average be thousands of kilometers from the nearest rock. Perhaps even tens of thousands.
- ceejayoz 7y ago
  High hundreds of thousands, if not a million or two, actually. https://physics.stackexchange.com/questions/26712/what-is-the-average-distance-between-objects-in-our-asteroid-belt https://physics.stackexchange.com/questions/26712/what-is-th... Space is BIG.
- Cogito 7y ago
  Space is big. It's extremely unlikely to get close to any object while randomly passing through its orbit. Unfortunately, space becomes a lot smaller once you want to park yourself in a similar orbit to another object. Don't get me wrong, it's still massive, but since orbits trace out a path the problem becomes figuring out if two paths intercept rather than if two points intercept. This is why access to 'space' will not really be impacted in the case of a Kessler cascade; you can go through low earth orbits on the way to somewhere else, but if you tried to stay in low earth orbit you'd almost certainly be hit by something.
- b_tterc_p 7y ago
  Is this true about tiny pebbles as well as asteroids? I would think a tiny rock would cause immense damage at high speeds.
- Gustomaximus 7y ago
  Is it though? To try and quantify risk I looked up how many metoeites hit the earth each day and its 18,000 to 84,000 that are over 10 grams. Whiile the earth is obviously much bigger than a space craft, you would think should there be a bunch of craft flying around in the future, theres a fair odds of it happening every few years. Also for example, the ISS has already been hit a couple of times: https://www.iflscience.com/space/an-astronaut-used-his-finger-to-plug-that-leak-on-the-international-space-station/ https://www.iflscience.com/space/an-astronaut-used-his-finge... If we have thousands or 10's of thousands of craft in space in the future I would suspect this will be a very real issue on a semi regular basis. Take what I say with a healthy dose of skeptism as not an expert or even well researched, but logically on above seems quite a reasonable risk.
  - ben-schaaf 7y ago
    Things tend to collect around large gravity wells, that's just kinda how that works. I don't think you can compare the ISS in LEO to something traveling within or without the solar system.
cpeterso 7y ago
Navigational deflector shields :) https://memory-alpha.fandom.com/wiki/Navigational_deflector https://memory-alpha.fandom.com/wiki/Navigational_deflector
azernik 7y ago
At those speeds, you've got to worry about running into particle radiation anyway.
mabbo 7y ago
Why would it explode? More likely, the small rock would put a hole into the spaceship. This isn't a disaster. The spaceship residents would notice a gradually decreasing amount of pressure, assess where the leak is, and put a piece of duct tape over the hole. Remember kids, real life isn't like the movies.
- jblow 7y ago
  Because it’s the equivalent of a stationary space ship being shot by a projectile traveling at the speed of the original space ship. If that is any remotely relativistic speed, duct tape is not going to fix the problem, because your space ship is now a hot gas.
- Cogito 7y ago
  The kinetic energies involved can be huge. In the same way that an object won't explode when hit by a subsonic 9mm round with ~0.5kJ of muzzle energy ('just' causing a leak and decreasing amount of blood pressure) it will when hit by a 0.50 calibre round with 14-20kJ of muzzle energy. For two objects in low earth orbit, travelling in opposite directions, the speed of impact can be over 14km/s - or 98000kJ per kg. At that speed even a relatively small object is going to cause a massive explosion when it hits you.
  - db48x 7y ago
    Whipple shields are cheap and effective. The impact does indeed impart a lot of kinetic energy, but on a thin sacrificial layer. This breaks the projectile into thousands or millions of tinier projectiles in an expanding cone of debris. As each of those smaller projectiles carries much less kinetic energy, and they impact your craft over a much larger area, the damage to the hull is minimized or even eliminated. Since a solar sail is just a huge sheet of plastic coated in aluminum, any impact with the sail will tend to leave just a pinhole, or possibly a tear. You do need to design your sail with ripstops, but the total area lost to the pinholes will tend to be quite small.
- scotty79 7y ago
  Actually that's exactly sounds like a movie series Expanse. Space combat scene. They even depressurize the ship in anticipation of getting holes in it.
nine_k 7y ago
At something like 0.25 c hitting interstellar hydrogen becomes a major source of gamma radiation.

simlevesque 7y ago

Maybe they we will be able to detect a marble from hundreds of thousands of miles in the empty space with new radar/lidar tech.

ztjio 7y ago
LIDAR can't even see the moon.

alpha_squared 7y ago

Ultimately, you can't. Space is really, really, really big and empty, though. Unimaginably so, which would make an incident be some really bad luck. In something like the lightsails, you'd just launch multiple simultaneously. Space is so big and empty that even for something like the asteroid belt you could pass through any point randomly and on average be thousands of kilometers from the nearest rock. Perhaps even tens of thousands.

ceejayoz 7y ago
High hundreds of thousands, if not a million or two, actually. https://physics.stackexchange.com/questions/26712/what-is-the-average-distance-between-objects-in-our-asteroid-belt https://physics.stackexchange.com/questions/26712/what-is-th... Space is BIG.
Cogito 7y ago
Space is big. It's extremely unlikely to get close to any object while randomly passing through its orbit. Unfortunately, space becomes a lot smaller once you want to park yourself in a similar orbit to another object. Don't get me wrong, it's still massive, but since orbits trace out a path the problem becomes figuring out if two paths intercept rather than if two points intercept. This is why access to 'space' will not really be impacted in the case of a Kessler cascade; you can go through low earth orbits on the way to somewhere else, but if you tried to stay in low earth orbit you'd almost certainly be hit by something.
b_tterc_p 7y ago
Is this true about tiny pebbles as well as asteroids? I would think a tiny rock would cause immense damage at high speeds.
Gustomaximus 7y ago
Is it though? To try and quantify risk I looked up how many metoeites hit the earth each day and its 18,000 to 84,000 that are over 10 grams. Whiile the earth is obviously much bigger than a space craft, you would think should there be a bunch of craft flying around in the future, theres a fair odds of it happening every few years. Also for example, the ISS has already been hit a couple of times: https://www.iflscience.com/space/an-astronaut-used-his-finger-to-plug-that-leak-on-the-international-space-station/ https://www.iflscience.com/space/an-astronaut-used-his-finge... If we have thousands or 10's of thousands of craft in space in the future I would suspect this will be a very real issue on a semi regular basis. Take what I say with a healthy dose of skeptism as not an expert or even well researched, but logically on above seems quite a reasonable risk.
- ben-schaaf 7y ago
  Things tend to collect around large gravity wells, that's just kinda how that works. I don't think you can compare the ISS in LEO to something traveling within or without the solar system.

cpeterso 7y ago

Navigational deflector shields :) https://memory-alpha.fandom.com/wiki/Navigational_deflector https://memory-alpha.fandom.com/wiki/Navigational_deflector

azernik 7y ago

At those speeds, you've got to worry about running into particle radiation anyway.

mabbo 7y ago

Why would it explode? More likely, the small rock would put a hole into the spaceship. This isn't a disaster. The spaceship residents would notice a gradually decreasing amount of pressure, assess where the leak is, and put a piece of duct tape over the hole. Remember kids, real life isn't like the movies.

jblow 7y ago
Because it’s the equivalent of a stationary space ship being shot by a projectile traveling at the speed of the original space ship. If that is any remotely relativistic speed, duct tape is not going to fix the problem, because your space ship is now a hot gas.
Cogito 7y ago
The kinetic energies involved can be huge. In the same way that an object won't explode when hit by a subsonic 9mm round with ~0.5kJ of muzzle energy ('just' causing a leak and decreasing amount of blood pressure) it will when hit by a 0.50 calibre round with 14-20kJ of muzzle energy. For two objects in low earth orbit, travelling in opposite directions, the speed of impact can be over 14km/s - or 98000kJ per kg. At that speed even a relatively small object is going to cause a massive explosion when it hits you.
- db48x 7y ago
  Whipple shields are cheap and effective. The impact does indeed impart a lot of kinetic energy, but on a thin sacrificial layer. This breaks the projectile into thousands or millions of tinier projectiles in an expanding cone of debris. As each of those smaller projectiles carries much less kinetic energy, and they impact your craft over a much larger area, the damage to the hull is minimized or even eliminated. Since a solar sail is just a huge sheet of plastic coated in aluminum, any impact with the sail will tend to leave just a pinhole, or possibly a tear. You do need to design your sail with ripstops, but the total area lost to the pinholes will tend to be quite small.
scotty79 7y ago
Actually that's exactly sounds like a movie series Expanse. Space combat scene. They even depressurize the ship in anticipation of getting holes in it.

nine_k 7y ago

At something like 0.25 c hitting interstellar hydrogen becomes a major source of gamma radiation.