Main concerns in a Proxima Speedster.

[Oberonian]

Dudes you are about to get a treat now.

I have been pondering a ship that could go to Proxima Centauri in 8 years....and coming back in similar time.

I have run into small obstacle. I realized that if you use solar power to run the engines...you may run outa time in accelerating it...as the g-forces are too great for human to endure for a very long time like a year.

I figured you need another station like ISS that is running constantly a path between sun and the planet Jupiter. It would have to go really really fast....before launching the Proxima Speedster....at 0,2 C minimum.

There the crew is switched and the acceleration can continue.

Do you see the picture.

Ship takes off from earth just like any other ship with two chemical rocket stages.

I know this is sci-fi as it is...but it may give a hint about what is coming in 30-50 years as propulsion systems evolve. Human does not much evolve in that period.

Do you find the second station ( Interstellar Station ) in this scheme as a plausible solution ?

[Hobbes-22]

A station that moves at a speed of 0.2C will not be in orbit: it's going so fast that even a close pass to the Sun won't change its course by a significant amount. So you'll need to use thrust (and lots of it) to change its course.

We're many orders of magnitude away from being able to accelerate a grain of sand to 0.2 C. Accelerating a space station to such speed is even harder, making it go around corners is harder still.
I think you're underestimating how impossible this is.

[Oberonian]

A station that moves at a speed of 0.2C will not be in orbit: it's going so fast that even a close pass to the Sun won't change its course by a significant amount. So you'll need to use thrust (and lots of it) to change its course.

We're many orders of magnitude away from being able to accelerate a grain of sand to 0.2 C. Accelerating a space station to such speed is even harder, making it go around corners is harder still.
I think you're underestimating how impossible this is.

Okay could 5% of C be obtainable ?

I might become sci-fi writer if my plans don't work out as planned.

[Hobbes-22]

If you want the station to be in orbit (i.e. it'll stay in that orbit without course adjustments), its speed will be in the region of 30 km/s, or 0.0003 C.
The fastest speed achievable with current technology is about 60 km/s (this is the target of the JPL Interstellar Mission proposal).

5% of C would require something like Project Orion (giant spaceship powered by nuclear bombs. Current technology, but an investment that would make the Apollo program look cheap).

[laszlo]

The Parker Solar Probe only got up to around 0.04% c and it holds the record for fastest spacecraft relative to the Sun.

Never mind the science fiction writing, it's already been done. Doc Smith had his characters going at thousands of times the speed of light over 100 years ago. Stick with the real world and you'll do something a lot more interesting 

Moving spacecraft at significant percentages of c is described by 2 fundamental equations - Tsiolkovsky's rocket equation and Einstein's relativistic mass equations. The two work together almost fiendishly to make accelerating a rocket to even a low percentage of the speed of light almost impossible. Unless someone figures out a different kind of propulsion, spacecraft will have to stay slow relative to light.

If a rocket powerful enough to accelerate to a good percentage of c is developed, its environmental effects would be so catastrophic that it could never operate close to an inhabited planet so you'd still have the problem of getting it out to a safe distance in a reasonable time.

Have fun.

[Frogstar_Robot]

A surprisingly good answer found on Q&A site :

Matter-antimatter annihilation is theoretically the ideal mechanism for long-distance space travel. The process will supposedly turn pure matter into pure radiation energy, which will have the exhaust velocity = c, the speed of light. Assuming 100% efficiency for the rocket engine and a spacecraft and engine that constitute a 1000-ton payload, then here are the numbers:

We start at Earth and accelerate with 1 g [the acceleration of the Earth’s gravity] for half the distance and then turn the rocket end-for-end to use it as a 1-g brake until we reach the star.

Total fuel mass at start of trip: 38,000 tons
Rocket engine power at start: 116,000 terawatts [about 80,000 times the total electric power output of the entire US!]

Rocket flight time to Prox Cen: 3.56 years
Flight time seen from Earth: 5.93 years
Antimatter fuel required: 19,000 tons

Antimatter does not occur naturally; every bit would have to be produced and stored on Earth. If the entire electric power output in the US were used to create and store antimatter with 100% efficiency, the generation time would be 27,000 years!

One more item of interest: Space is not a pure vacuum. It contains particles [mostly hydrogen atoms] at an estimated density of one atom per cubic centimeter. Constant collision with these particles [called the interstellar medium] at the halfway point would produce 28,000 watts of heat and radiation per square foot of cross-sectional area of the spacecraft. That would pose a severe problem for the astronauts.

These results show that an antimatter trip to Prox Cen is hopelessly beyond any conceivable technology at present.

Space is big. ISTR if you run the numbers for a fusion drive, you'll need about 3 supertankers worth of fuel.

That's why SF authors casually refer to warp drives or "sleep pods" and avoid any detailed explanations.

[laszlo]

A surprisingly good answer found on Q&A site :

Matter-antimatter annihilation is theoretically the ideal mechanism for long-distance space travel. The process will supposedly turn pure matter into pure radiation energy, which will have the exhaust velocity = c, the speed of light.the speed of light. Assuming 100% efficiency for the rocket engine ...

Bogus.
1. It's not just exhaust velocity that matters otherwise flashlights would take off at the speed of light when turned on.
2. No proposed anti-matter rocket is anywhere near 100% efficient
3. The constant 1 g acceleration he posits ignores relativistic mass changes so the actual energy required is much more that he suggests

[Frogstar_Robot]

A surprisingly good answer found on Q&A site :

Matter-antimatter annihilation is theoretically the ideal mechanism for long-distance space travel. The process will supposedly turn pure matter into pure radiation energy, which will have the exhaust velocity = c, the speed of light.the speed of light. Assuming 100% efficiency for the rocket engine ...

Bogus.
1. It's not just exhaust velocity that matters otherwise flashlights would take off at the speed of light when turned on.
2. No proposed anti-matter rocket is anywhere near 100% efficient
3. The constant 1 g acceleration he posits ignores relativistic mass changes so the actual energy required is much more that he suggests

You totally missed the point, never mind.

[KelvinZero]

Okay could 5% of C be obtainable ?

I might become sci-fi writer if my plans don't work out as planned.

Is that a threat?

You might want to look at..
https://www.centauri-dreams.org/2019/03/04/pondering-the-dyson-slingshot/

You actually can get interstellar scale velocities from scenarios like that, though obviously we don't have anything like that available in our vicinity.

Im not sure what speed you could maintain zipping around jupiter, but it would be not greater than the velocity of something orbiting just above jupiter's atmosphere. That would not be too hard to calculate. Acceleration = V²/R where
Acceleration = surface gravity of jupiter
R = radius of jupiter
.. then solve for V .. or something like that.. I expect it is a lot higher than orbiting earth but very tiny compared to light speed.

btw, our fastest spacecraft ever was the Parker Solar Probe which achieved 692,000 km/h as it dipped into the sun's gravity well. I think the speed of light is about a billion km/h .. so I guess it got to not far of a thousandth of the speed of light.. pretty impressive!

[Paul451]

Bit late, but...

I have run into small obstacle.

You don't want to do that at relativistic velocity.

I realized that if you use solar power to run the engines...you may run outa time in accelerating it...as the g-forces are too great

If you mean solar sails. Then you're running out of sunlight. So how about using a Stellaser (Stellar Laser)? That gives you a much brighter light source when natural light is running out. It might also help sweep out lighter material like gas and dust in the interstellar corridor, reducing impact on the front to the interstellar ship which, at even low relativistic velocity, will sand blast a solar sail to nothing while irradiating the crew.

The idea is that you have large solar sails hanging over the sun at intervals around it, using sunlight to balance their position (called "statites"). Part of the light they reflect is bounced back and forth between pairs of mirrors, lined up so it passes through the plasma of the sun's outer layers. This creates a pseudo-laser, using the sun's plasma (and energy) as a lasing medium, increasing the power and coherence of the reflected light at each pass. (Simplistic diagrams below.)

Effort would need to be taken to balance the lateral thrust on the statites caused by the beam itself, so presumably you'd need a ring of them around the sun, each reflecting to two others in the equal and opposite direction. Some of the coherent beam can then be bled off by the Stellaser statites to create narrow focused, stupidly high-powered lasers which can be sent into the rest of the solar system to power industry and settlements, and to allow solar sails as primary, high speed transport, especially in the outer solar system and through the Kuiper Belt and Oort Cloud.

It can also be used to push interstellar solar sails, and both power and propulsion remain available during their whole trip.

Obviously the first mission to Proxima would be to build another Stellaser there, to slow down incoming ships and power their return, as well as provide the next leg to Alpha Centauri. That first mission would be slower, because it would take much, much longer to slow down, so it would probably unmanned.

Additionally, your interstellar travellers should probably be travelling as a fleet, not a single ship. Redundancy, specialisation, the ability to escape other people.

before launching the Proxima Speedster....at 0,2 C minimum.

Also, 0.2c is not fast enough to get to Proxima in 8 years. You need slightly more than 0.5c.