I designed a crewed interstellar spacecraft

a reply to: Alfa015015

A special coating that can withstand the impact of hitting micro-asteroids traveling at velocities of 25%+ lightspeed???

I don't think material science has progressed that far mate, nor lightly to do so any time soon.

Ablative armor just is not going to cut that mustard im afraid.

All credit for trying. Lots of issues to be overcome and technology to be created, but we'll get there in the end.

The problem with prolonged space flight is the negative physiological impact on humans. Somehow these will need to be addressed.

originally posted by: andy06shake
a reply to: Alfa015015

A special coating that can withstand the impact of hitting micro-asteroids traveling at velocities of 25%+ lightspeed???

I don't think material science has progressed that far mate, nor lightly to do so any time soon.

Ablative armor just is not going to cut that mustard im afraid.

Micro-asteroids are thought to be rare in the ISM (InterStellar medium). They aren't rare in our solar system so you wouldn't want to travel at 25% light speed through our solar system.

It doesn't take a micro-asteroid to cause damage, just a grain of dust creates explosive damage at 20% the speed of light. This has been considered for the Breakthrough Starshot initiative which aims to send small spacecraft at ~20% lightspeed to Alpha Centauri, in this paper:

The Interaction of Relativistic Spacecrafts with the Interstellar Medium

The authors of that paper seem to say erosion by dust is a bigger problem than larger particles which can destroy the spacecraft completely, because those larger particles are so rare.

From page 14 of the pre-print:

Interstellar dust can produce numerous craters on the spacecraft surface as a result of explosive evaporation following each dust grain encounter. This effect can erode the entire surface of the spacecraft to a thickness of ∼ 0.5 mm after it has swept a gas column of N H ∼ 3 × 10^17 cm^−2 for v ∼ 0.2c...

We estimated that an encounter with a dust grain larger than 15 µm will completely destroy gram-scale spacecrafts. Given the low abundance of very big grains in the ISM, their effect is likely to be unimportant.

If I'm interpreting their paper correctly (I'm likely off a bit on this, so read the paper to see their actual maths and particle density estimates), they expect if 10 million of these tiny spacecraft were sent to Alpha Centauri, maybe one of them would be completely destroyed by a larger particle, but not much more than that and for the rest, erosion by dust would be the big problem. The project talks about sending only 1000 spacecraft so the chances of an encounter with a destructive large particle are correspondingly lower for that quantity.

They don't think particle damage to the spacecraft is an insoluble problem, but it's definitely a problem that needs to be addressed carefully:

We have identified several ways to protect the spacecraft, a needle-like configuration as well as materials suitable for the lightsail and protective layers using the obtained quantitative estimates.

I suspect we won't know how accurate their estimates are until we actually try to do it.

If you fire the lazer off a mirror, that will cancel out every action has an opposite reaction, or it will meet the rule.

The light reflecting back doesn’t have an opposite reaction anymore and you have a space ship 🚀

a reply to: Forensick

LASER.

Light Amplification by Stimulated Emission of Radiation.

originally posted by: Arbitrageur

originally posted by: Alfa015015
The laser system would be placed outside the spacecraft, probably in some Lagrange point.
The only laser in the spacecraft is the photon rocket, which is necessary to decelerate.

The first screenshot from your animation is at about 31 seconds. It's hard to see the source off in the distance, but the laser light is striking the sail.

Then at about 40 seconds it looks like the source of the light is coming from the spacecraft, doesn't it? Did the man making your animations make a mistake to show it this way?

These animation screenshots don't seem to show what you described in your reply.

No mistake.
In the first animation, the light sail is accelerated by a laser placed in a Lagrange point.
In the second one, the spacecraft uses a photon rocket to decelerate.

originally posted by: Forensick
If you fire the lazer off a mirror, that will cancel out every action has an opposite reaction, or it will meet the rule.

The light reflecting back doesn’t have an opposite reaction anymore and you have a space ship 🚀

The laser would be located in a Lagrange point, outside the spacecraft.

a reply to: paraphi

Thanks!

originally posted by: andy06shake
a reply to: Alfa015015

A special coating that can withstand the impact of hitting micro-asteroids traveling at velocities of 25%+ lightspeed???

I don't think material science has progressed that far mate, nor lightly to do so any time soon.

Ablative armor just is not going to cut that mustard im afraid.

It hasn't been created yet, that's true.

Breakthrough Initiatives is now researching on this.

a reply to: Alfa015015

The craft would need to be made form material or matter that could absorb the impact of any micro-asteroids or particulate matter encountered on the course of the journey.

And that could convert the kinetic force to another form of energy, or even store the energy, to be used for breaking or other purposes.

Given the limitations of our material science, and the energy release associated with collisions of objects at 25%+ lightspeed, that's going to have to be a rather robust material with almost magical associated properties.

Why wouldn't they just shield the craft electromagnetically, small antimatter reactor to power it up?

a reply to: myss427

Well for a start you would be required to produce and store antimatter in sufficient quantities to power any electromagnetic shield.

And if you can do that then you can also propel the craft via some kind of Antimatter rocket which could theoretically reach a speed of around 72 million mph.

No need for any solar sails/light sails or any other form of propulsion if you have antimatter in a bottle.

a reply to: Alfa015015

In the second one, the spacecraft uses a photon rocket to decelerate.

Have you calculated the energy requirements? Should be pretty straight Forward.

Get it? Forward? Forward shows his work. You used half of his, do you have the rest? It just seems like a "photon rocket" is going to require a lot of juice.

a reply to: Alfa015015

I think it would need to add a lot more weight to deal with cooling the reactor. The vacuum of space is a horrible conductor for heat dissipation. I may be wrong but I think the reactor on the carrier draws seawater to help with cooling.

a reply to: Grimpachi

That's a fission reactor. I guess the possible future hypothetical fusion reactor might do away with that somehow. Or maybe big ol' radiator fins might work.

It's sort of disappointing that nuclear aircraft carriers are actually steam powered. The reactor just boils water. The excess heat is removed by a heat exchanger.

a reply to: Phage

To be fair even with a hypothetical fusion reactor it would still be turning some type of steam engine or maybe they would use salt. The same principle I believe.

a reply to: Grimpachi

With 100% efficiency all the power would be directed to the photon rocket (It's gonna take a lot. "Somebody" should do the calcs.)

Anything less, big ol' fins. Radiate that heat.


Screw it, just use a Libby Drive. Push the button, pull the switch, cut the beam. Make it march!

originally posted by: Phage
a reply to: Forensick

LASER.

Light Amplification by Stimulated Emission of Radiation.

Pedantic:

Phage

a reply to: Forensick

I bet you'll never write lazer again.

a reply to: Phage

The HALL Ion thruster being tested seems like a winner. I also read that there are some designs with some kind of scoop in front to continuously refill the "tank" for the Ion thrusters when orbiting planets with atmospheres.

Not going to win any drag races unless it is against other Ion engines but I like their ability to run extended periods.