Solving the debris hazzard at high C speed.

[Admiral_Ritt]

Yes, I know we are not likely to travelling this fast in this Century or the
next, because of the energy considerations etc.

Still, I think some other barrier besides the difficulty achieving high speeds is out there, and my estimate is that .45 C is going to be near the limit. Why?

As empty as interstellar space is there is still a chance your space vehicle will come across something large enough (whatever it is) it needs time
detect and dodge.

The facts: even a 1 Gram impactor at .45 C will cause an explosion
close to 9 TeraJoule: For reference at 2 KT nuclear device is 8 Terajoules

What approaches do you think would work:

 

[Urwumpe]

Since there are no options left:

Maybe such future spacecraft will make use of external propulsion systems, which eject the fuel forward, but then work on the gas cloud that surrounds them. If you manage to get a thin 100 km atmosphere in front of the spacecraft, most smaller particles will simply burn up like very fast meteors and only reach the spacecraft at a small fraction of the usual speed. But that kind of propulsion has its own complications right now.

But since we are far away from even 0.01c, why not imagine magic?

 

[Admiral_Ritt]

Magic to you...inevitable in deep time.

Nevertheless, even if there aren't manned .45 C missions.
There might be large probes sent out at those speeds
Unless they are cheap and made of [ingredient that is tough and will irritate skeptics as well], you might still think about protection.

 

[Urwumpe]

There might be large probes sent out at those speeds

Yes - in the more or less distant future.

Today, the speed record is 0.0001c relative to the sun. And just mere 0.00006605 c relative to Earth. Even just getting one order of magnitude more would require technologies currently not available to us (but thinkable). Two orders of magnitude is right now impossible to engineer. Four orders of magnitude would be in the realm of magic to us right now.

 

[Admiral_Ritt]

If I can talk about what would be possible now, if we had the funding
and the nuclear test ban treaty was altered to allow fusion/fission devices
to propel a probe to alpha centauri things get more tractable.

A modern design using fusion with "Momentum Limited Orion". (See Dyson, Orion designs) could be built.

But Strangely enough, at 8%-10% C You still have a protection problem.
So the question still stands, how can you protect such a probe?

One way you might try is to have your probe disassemble and recombine to form a flat lattice once under high C speeds. the Flat Lattice has a lot of redundancy and self repair mechanisms. The flat lattice would allow for temporary holes, in case of a large threat, or in case of a small undetectable small debris, to just absorb and repair the damage.
I picture the lattice to be about 10000 M Sq. and maybe a couple of cm thick

 

[Urwumpe]

If I can talk about what would be possible now, if we had the funding
and the nuclear test ban treaty was altered to allow fusion/fission devices
to propel a probe to alpha centauri things get more tractable.

Sorry, but that explanation is cheap The comprehensive nuclear test ban treaty does neither ban nuclear reactors or nuclear devices in space, nor does it ban nuclear thermal rocket engines, neither fission nor fusion.

It only bans nuclear explosions like by Orion type drives for a good reason there - it would make our other satellites go nuts - right next to people with nervous fingers on the red button.

The legal devices are just technologically too risky to explore further right now, and often politically infavorable, should they ever fail and crash somewhere.

 

[Andy44]

Sorry, but that explanation is cheap The comprehensive nuclear test ban treaty does neither ban nuclear reactors or nuclear devices in space, nor does it ban nuclear thermal rocket engines, neither fission nor fusion.

It only bans nuclear explosions like by Orion type drives for a good reason there - it would make our other satellites go nuts - right next to people with nervous fingers on the red button.

The legal devices are just technologically too risky to explore further right now, and often politically infavorable, should they ever fail and crash somewhere.

Getting off topic. The assumption is that our vehicle can, in fact, reach relativistic speeds.

How do we protect it?

For a brute force approach I would place a massive shield a few km in front of the main vehicle, pehaps. Deploy it after accelerating, and retrieve and stow it when it's time to accelerate again. Not without its problems, of course.

 

[Urwumpe]

Getting off topic. The assumption is that our vehicle can, in fact, reach relativistic speeds.

How do we protect it?

For a brute force approach I would place a massive shield a few km in front of the main vehicle, pehaps. Deploy it after accelerating, and retrieve and stow it when it's time to accelerate again. Not without its problems, of course.

Protection is generally proportional to density - so a light massive shield would be hard. You would have to find a way to increase its "apparent density" some how.

 

[Admiral_Ritt]

yeah, I was trying to have that conversation on
protection, I and can only be so polite before, I have to
say, don't follow the thread if it bothers you.

 

[statickid]

What about many layers of some kind of rigid foam (or whatever) with spaces between them? Not sure why this design concept comes to mind, but it's my first reaction thought. Since this ship no doubt has an astronomical budget, there could be a hundred or hundreds of thin layers. I'm imagining the point being to get the impacting particle to break up and disperse while also giving it a material to impart energy into.

 

[TMac3000]

Protection is generally proportional to density - so a light massive shield would be hard. You would have to find a way to increase its "apparent density" some how.

Wouldn't it's mass increase as you approach c? That it would make it more protective.

 

[Urwumpe]

Wouldn't it's mass increase as you approach c? That it would make it more protective.

Not sure if it really works that way... interesting question.

 

[RisingFury]

Getting off topic. The assumption is that our vehicle can, in fact, reach relativistic speeds.

How do we protect it?

For a brute force approach I would place a massive shield a few km in front of the main vehicle, pehaps. Deploy it after accelerating, and retrieve and stow it when it's time to accelerate again. Not without its problems, of course.

Protection is generally proportional to density - so a light massive shield would be hard. You would have to find a way to increase its "apparent density" some how.

Maybe density wouldn't be needed. We really have no knowledge of how a relatively large particle would interact with ANY surface at that relative speed. It's possible that the portion of the shield would be completely destroyed, along with the impacting object.

 

[statickid]

Due to the magical nature of the rigid foam (nano lattice?), the whole shield structure has less mass than the ship.

*Ship assets frankensteined from Sketchup Warehouse model


EDIT: This ship also doubles as a planet destroying mega weapon-- simply jettison the shield in the direction of the offending planet before changing course or slowing down.

 

[Andy44]

This ship also doubles as a planet destroying mega weapon-- simply jettison the shield in the direction of the offending planet before changing course or slowing down.

LOL That pretty much applies to any relativistic vehicle.

Scroll down to "relativistic attack": http://www.projectrho.com/public_html/rocket/planetaryattack.php

 

[Admiral_Ritt]

TMAC3000 AND STATICKID
as far as I know relativistic Mass increase is a factor at much higher speeds.

Momentum P = M*V / Sqrt[1 - (V^2 / 1-C^2) ]

For our example.
the Sqrt factor is for .45 C. M*V / .89 which does increse the energy needed to increase speed a bit more than 10%.

but that is nothing compared to trying accellerate to higher speeds
from 90% C.

Sqrt Factor for .90 C. is MV / .43 which more than doubles the energy need to push to higher speeds, compared to non-relativistic speeds.

STATICKID:

Are u sure your foam will not explode outward with so much force that
alot of the foam will splash out, so you would have to refill/reform your
"Shield"? smaller strikes would be no problem, but just how much does
the supply of foam for the trip weigh?

And if it's too thin maybe it will just Heat up the Offending object until it
becomes part solid part plasma.

In general a shield is a good low tech idea:

For larger hazzards, that .45 C speed will hopefully give you time to detect an object and change your course to miss an obstacle entirely. If it's too large to evade, you would the victim of the worst luck in the universe.

It's the hard to detect smaller debris that is trully the issue.

What about an anti-ballistic system: that could detect close up and have time to hit the object you are going to run into with some mass. hopefully the explosion is far enough away from the ship and nothing is left but smaller sand sized grains. Does it really come down to how good your radar is? Maybe So.

 

[Andy44]

Well, if you can get to these great speeds, you already have power to burn, enough for say, a whopping laser that can be used on incoming debris.

There is going to be a practical limit on the size of incoming object you can withstand or fend off. Grain of sand, you may be fine, but something like a soccer ball might be too big for even a big laser to vaporize in time, depending on how early you can detect it.

 

[Michael_Chr]

LOL That pretty much applies to any relativistic vehicle.

Scroll down to "relativistic attack": http://www.projectrho.com/public_html/rocket/planetaryattack.php

Good thing we are not around after anyone - that we know of - have vehicles that can move at relativistic speeds (as it appears).

The problem is off course the ones we dont know of (oooops...that tinfoil hat had slipped on again...):lol:

 

[Ravenous]

I'd build a thick layer of ice blocks at the front. It would be eroded after a while though... (Idea stolen from The Songs of Distant Earth.)

 

[MaverickSawyer]

I'd build a thick layer of ice blocks at the front. It would be eroded after a while though... (Idea stolen from The Songs of Distant Earth.)

Yeah, that's how I'd do it, myself. Clarke was remarkably prescient about many elements of space... geosynch satellites, space elevators, ice shields for high-C ships...