Unmanned Expedition to the Wolf 1061c

[Ivan Tuzikov]

Unmanned Expedition to the https://en.wikipedia.org/wiki/Wolf_1061c

 

Let’s consider that mankind is able to build a version of: https://en.wikipedia.org/wiki/Fusion_rocket

Namely:

The NASA/MSFC Human Outer Planets Exploration (HOPE) group has investigated a manned MTF propulsion spacecraft capable of delivering a 163933-kilogram payload to Jupiter's moon Callisto using 106-165 metric tons of propellant (hydrogen plus either D-T or D-He3 fusion fuel) in 249–330 days.^[5] This design would thus be considerably smaller and more fuel efficient due to its higher exhaust velocity (700 km/s).

 

In 2006, the United States was estimated to have a production capacity of 11 million tons of hydrogen. https://en.wikipedia.org/wiki/Hydrogen_production

 

To travel to the Wolf 1061c, 700 km/s design (the rocket) would take 428 years to travel 1 light year (l.y.) and 5906.4 years to travel full distance of 13.8 l.y. and deliver 164 tons payload.

 

In Wikipedia example 165 tons of properllant are needed for 330 days travel, so 182 tons per year, which means that about 1075000 tons of fuel for 5906 years one-way trip.

 

Let us assume that the rocket holds 2 robotic spacecrafts (orbiter for planet exploration and space radio communicator) and a robot-operator.

 

The orbiter studies the planet for some time (for example, 10 years) and constantly sends the data to the communicator that orbits the Wolf 1061 star and uses it as gravitational lens to relay data back to the Solar system. The robot-operator controls the whole process.

 

When we take into account such hypothetical plan I wonder about materials, equipment, devices, electronics – diffusion of materials. Will these 2 spacecrafts survive the journey in off-state and under maintenance of the robot-operator. And for how long the robot-operator and the electronics and mechanicsms of the rocket are expected to last?

 

In short: can the above-listed equipment still be operable after 5906 years of space travel?

Edited February 12, 2016 by Ivan Tuzikov

[Ophiolite]

Interesting questions. Did your reference to diffusion include the loss of hydrogen through the walls of the tanks? Hydrogen can permeate almost anything. 6,000 years might be quick enough though. Any materials scientists out there have an expert view on this?

[fiveworlds]

To travel to the Wolf 1061c, 700 km/s design (the rocket) would take 428 years to travel 1 light year (l.y.) and 5906.4 years to travel full distance of 13.8 l.y. and deliver 164 tons payload.

 

Using the unmanned spacecraft speed record.

 

393927289812

6067008

64929.4

177.89

711.55 years for 4 light years.

 

I think we should first figure how fast we can actually go. I know there have been predictions that if we go too fast we will die etc but so far that hasn't happened.

Edited February 12, 2016 by fiveworlds

[swansont]

 

In Wikipedia example 165 tons of properllant are needed for 330 days travel, so 182 tons per year, which means that about 1075000 tons of fuel for 5906 years one-way trip.

 

 

I don't think a linear extrapolation works here. You need to also propel the extra fuel, which requires even more fuel.

[Ivan Tuzikov]

Interesting questions. Did your reference to diffusion include the loss of hydrogen through the walls of the tanks? Hydrogen can permeate almost anything. 6,000 years might be quick enough though. Any materials scientists out there have an expert view on this?

I also reference to diffusion processes in electronic chips and other complex equipment.

 

 

I think we should first figure how fast we can actually go. I know there have been predictions that if we go too fast we will die etc but so far that hasn't happened.

Well, I've picked up the most speedy design from wiki. As for "speed records" https://en.wikipedia.org/wiki/List_of_vehicle_speed_records#Spacecraftthe fastest is 252,792 km/h relative to the Sun or 70 km/s, ten times slower than the proposed rocket.

Edited February 12, 2016 by Ivan Tuzikov

[fiveworlds]

Well, I've picked up the most speedy design from wiki. As for "speed records" https://en.wikipedia...ords#Spacecraftthe fastest is 252,792 km/h relative to the Sun or 70 km/s, ten times slower than the proposed rocket.

 

Right so I double checked my math and I forgot a number. It is working out at 4269 years per light year.

 

[latex]\frac{Speed\; of \: light \: in\: seconds \; *\; Seconds\: in\: an\: hour \;*\; Seconds\: in\: a\: minute\; * \; hours\: in\: a\: day\; *\; 365}{speed\: of\: spacecraft\: in\: km\: per\: hour\;*\;24\;*\;365\;*\;1000}[/latex]

Edited February 12, 2016 by fiveworlds

[Ivan Tuzikov]

Again, and what about durability of materials that constitute complex electronic and electro-mechanical systems?

[Ivan Tuzikov]

I don't quite understand the specific impulse notion. If one uses 10 engines with the same thrust would it be 700 km/s x 10 = 7000 km/s?

[pavelcherepan]

 

 

I don't quite understand the specific impulse notion.

 

Specific impulse if measured in seconds is the time that an engine can produce a thrust of 1 N using 1 kg of fuel. There is a direct relationship between SI and exhaust velocity, i.e. the higher your exhaust velocity is, the higher your SI will be.

 

 

 

If one uses 10 engines with the same thrust would it be 700 km/s x 10 = 7000 km/s?

 

Not quite. With 10 engines you'll have a higher TWR and higher acceleration, but at the same time you'll use your fuel faster and in fact the final velocity with a 10-engine setup will be lower than with just 1 engine because you'll have to use fuel to propel the mass of those other 9 engines. Stick to 1 engine.

 

EDIT: You could actually put a ten-engine design to a good use if you use the thrust of all 10 engines when you're in the inner Solar System and as close as possible to the Sun and then jettison 9 engines and continue accelerating using the remaining 1. That way you could make a good use of the Oberth effect and use your fuel more efficiently.

Edited February 18, 2016 by pavelcherepan

[Enthalpy]

The NASA/MSFC Human Outer Planets Exploration (HOPE) group has investigated a manned MTF propulsion spacecraft capable of delivering a 163933-kilogram payload to Jupiter's moon Callisto using 106-165 metric tons of propellant (hydrogen plus either D-T or D-He3 fusion fuel) in 249–330 days.^[5]

Yes, Nasa has money for fiction.

Technology is about making things real. That's much harder. T and ³He for instance aren't real technology, nor fusion.

In 2006, the United States was estimated to have a production capacity of 11 million tons of hydrogen.

And? There is no tritium in it, nor ³He. So what's the point?

 

By the way, the same reason makes fusion energy on Earth pointless - until someone finds a means to regenerate it at the fusion reactor, or produce it by other means... But cleanly please. Lead+lithium blankets are as dirty as uranium fission.

To travel to the Wolf 1061c, 700 km/s design (the rocket) would take 428 years to travel 1 light year (l.y.) and 5906.4 years to travel full distance of 13.8 l.y. and deliver 164 tons payload.

 

In Wikipedia example 165 tons of properllant are needed for 330 days travel, so 182 tons per year, which means that about 1075000 tons of fuel for 5906 years one-way trip.

13.8 ly looks correct. If humans wanted to wait for 5900 years, which I doubt, the necessary speed would be 0.0023c or 700km/s.

 

Fuel expelled at 700km/s too would be used only to accelerate here and then to brake at destination. The vessel's mass would be divided by exp(700e3/700e3) at both locations

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

so 250t there (payload +engine +tanks +everything) would need 680t en route and 1847t at start, of which 1847-250=1597t are propellant.

 

Though, seeking reasonable travel time results in impossible masses, even with nuclear fusion. Bad news but hard reality. We'll stay in the Solar system for long.

the communicator that orbits the Wolf 1061 star and uses it as gravitational lens to relay data back to the Solar system.

I doubt about that one too. Lensing is as efficient on radiowaves as on light. We better have a quasar or a galaxy group to observe lensing and the effect is a tiny angle, not the angle of a star seen by an orbiting spacecraft.

 

If our Sun did bring usable gravitational lensing, we would now it already. No better there.

I wonder about materials, equipment, devices, electronics – diffusion of materials. Will these 2 spacecrafts survive the journey in off-state and under maintenance of the robot-operator. And for how long the robot-operator and the electronics and mechanicsms of the rocket are expected to last?

 

In short: can the above-listed equipment still be operable after 5906 years of space travel?

Space environment isn't very hard. UV light, but you can shadow it, and you travel away from the Sun anyway. Particles aren't a big constraint for hardware from what we expect there (Jupiter orbit would be a different story). No vibrations.

 

Essentially, hardware lasts in space longer than on Earth. But we have never built electronic equipment and tested it 6000 years later.

 

Don't worry about diffusion nor ageing in general. I'm confident this can be brought under control.

 

To my eyes, it's basically a matter of civilization. Not only will the technical standards be forgotten by then (Pioneer data was difficult to read after 30 years: find a magnetic band recorder, find what the encoding standards were, find the docs telling what the data means...). And much worse, nobody will care then about what we do now. Even in a century in fact.

Again, and what about durability of materials that constitute complex electronic and electro-mechanical systems?

No worry. At room temperature they're essentially eternal.

Plastics are destroyed by UV. A few ones are by ionizing particles but that's a small worry.

Electronic components are nearly eternal at room temperature, small current and normal voltage.

 

I don't worry about hydrogen diffusion. It does happen at 200-300°C through metals and at room temperature through rubber. Through plastics, it's noticed because measurements are so sensitive, but for a tank purpose it's small. Through proper metal at 20K, nothing will happen. If needed, put a double envelope and suck possible leaks from the room between them.

[Janus]

In Wikipedia example 165 tons of properllant are needed for 330 days travel, so 182 tons per year, which means that about 1075000 tons of fuel for 5906 years one-way trip.

No. swansont has already alluded to this. Fuel requirement don't scale that way. 165 metric tons of fuel for a 163933 kg ship works out to a mass ratio of ~2 ( the mass ratio is the mass of the fully fueled ship divided by the mass of the ship alone)

The rocket equation gives the change in velocity as

 

[math]\Delta v = V_e \ln(Mass ratio)[/math]

 

With an exhaust velocity of 700 km/sec, this gives a velocity change of ~485 km/sec. 1075000 metric tons of fuel for the same ship gives a mass ratio of 6558.6 (that's 6657.6 kg of fuel for every kg of ship) This will give you a velocity change of 6152 km/sec. 6152 km/sec is 2% of c, and at that speed it would only take 673 yrs to travel 13.8 ly. To travel the same distance in 5906 years requires a speed of ~.023% of c or ~701 m/s, which can be achieved with a mass ratio of 2.722, or 282.3 metric tons of fuel.