Starships

As I posted earlier this year the most realistic concept is a pulsed fusion drive that can achieve 0,14c - but not 0,5c.

Additionaly for a travle lasting decades a very huge spaceship is required and it there has to be included a stable well working ecology to proved food.

The crew has to be numerous and political problems among the memebers are to be expected.

Repairs have to be made possible concerning each system included - ecology too.

The real spaceship cannot be imagined today - only unmanned ships.



Dipl.-Volkswirt (bdvb) Augustin (Political Economist)

I completely agree that there are some really big problems to achieve interstellar travel. But they can be overcome. You can build a space ship big enough - and you can accelerate it to high enough speed. The trick is, simply, to have enough reaction mass, and to launch it out the rear end of the ship at high enough velocity. The ion drive concept is probably the best bet we have currently, but other ideas will come.

As an aside, the theoretical maximum for any reaction drive in space is c. The real maximum is decided by the exhaust velocity of the drive, combined with the amount of reaction mass available.

There may be a complete larger problem I have been reminded to by the recent posts and articles about artificial suspension of animations and about ne wcooling technologies.

In the interstellar space - fa away from each star - the star ship permanently will loose temperature - it will be going to cool down and there is nearly no source of temperature. The only source could be a nuclear or a fusion reactor. But thsi reactor will have to have a risk reduced by a factor of one million at least. I am speaking of accidents like Tschernobyl not only - There mustn't be any shutdown that lasts longer than a few days.

Perhaps animation needs to be suspended until arrival at the next star having a habitable region where humans can exist in. There the suspension could be terminated until the star ship is to leave that star for the interstellar spave again.

This all just to list a relevant problem.



Dipl.-Volkswirt (bdvb) Augustin (Political Economist)

Nuclear reactors are safe. The biggest reason why Tschernobyl blow up, was that the moderator was carbon or graphite, which burns very well. Added to that no extra big walls or protective 'shell' and it was a disaster in the making. The French powersupply comes mainly from nuclear reactors, we have only 1 working left and the politicians want to close that one too. Nuclear fision has a bad name because of Tschernobyl. The real only reason not to built a reactor is that the wasteproducts will last for centuries and we dont have a clue if humans will be committed for such a long time. Let alone if anyone knows where the wasteproducts are after such a long time.

Another 'problem' with nuclear fision is that the uraniam required for this is pretty rare, and enriching the natural uranium takes a long time.

If you want to build suchs a hibernation ship within 20 years, nuclear fision is the only real option once you get out of the suns reach.

how fast will ion drive get us to the nearest star ?

Hello, Stefan,

I have no problems with nuclear reactors anyway here on Earth.

The problem with nuclear reactors at such a star ship would be that the ship would need three to four decades at least to the nearest star in the nieghbourhodd - Alpha Centauri.

This means the reactor will have to be working for these more than three decades without longer shutdowns, without damages by asteroids, without damage by human failure... and so on.

These are very much higher safety and availability requirements than those here on Earth.

That reactor would have to provide the energy to keep the temperature in the inner of that star ship at the earthian level if no hibernation is desired. In case of hibernation the star ship would have to maintain and control itself automatically completely - which to me seems to be no good concept given the current technologies and the technologies at the horizon.

At least interruptions of hibernation should be done - and then heat or warmth has to be available which is difficult after losing enegry to the interstellar space during several years.



Dipl.-Volkswirt (bdvb) Augustin (Political Economist)

How true! And probably the fission reactors would need refueling in less time than that. How well does enriched uranium store? Would it decay and become unsuitable for the reactor before it could be used? Would fuel reprocessing in flight be needed?

Reactor fuel is typically much less rich than it can be made for um, "other" uses... you can load aboard your ship fuel rods for each cycle in progressivlely higher grades of enrichment, then when the time to refuel arrives, the decay has resulted in replacement fuel of the appropriate grade.

I would still want two (possibly three) reactors for redundancy, as well as double (or more) the projected fuel quantity.

This might seem like a silly question.. but where do you think its best to contruct these starships.

- On earth
- In a massive hanger type thing in space
- On the moon or planet with less gravity

Im not sure if its practical to have a star ship blasting off from earth because of the weight and cost. Im assuming it would be a vehicle that would always remain in space and then little scout ships that are ferried along in hangers. Much like how we see in our space science fiction movies

Also im assuming that starships will mostly be built with advanced robots. large and nanoscale

Imo, for these kind of big projects where you gonna have to get massive ships, a spaceelevator will be needed in order to keep costs down and the programm running.

The discussion should not go too focussed on the reactors - the question is if nuclear reactors and even fusion reactors are sufficient to get rid of the losses of temperature into the very cold interstellar space. Please note that even at Titan - being 1.2 billion km away and far away from interstellar space - has a temperature of -180° C only despite its atmosphere of Earth-like thickness. A star ship would have to travel through interstellar space for decades - fuel of the reactors isn't the first or most important problem. The first and most important problem is the technology to create sufficinet energy, temperature, warmth to replace that amount of temperature that will be lost into the cold interstellar space - these losses may be the biggest dangewr by far.

The place of construction will be space or something like a hangar in space. I could imagine that several asteroids will be modified and combined to build a star ship - they will be mined and the mining products will be used in place to build the vehicle. The remainders of the mined asteroids will be integrated into the vehicle because the caves can be used as habitats, rooms and so on.



Dipl.-Volkswirt (bdvb) Augustin (Political Economist)

Ideally, for any type of true spaceship -- not an aerospace vehicle or lander (or anything else that comes in physical contact with a planet or moon or other large stellar object) -- should be constructed in orbit, as there is no reason to expose it to the ravages of atmosphere and gravity. So I vote for option #2: orbital shipyard.

Absolutely! The biggest problem will be getting rid of the waste heat generated by the reactors. Designs for nuclear powered space craft include very large radiators for cooling. Believe me, the cold will be no problem at all.

Mr. Cambell is right... you won't lose that much heat by radiative processes. If you use a reactor (which I am sure you must for such a purpose), your primary issue will not be freezing to death, (which is what it sounds like Ekkehard is worried about) it will be boiling. There isn't much matter in interstellar space in which to dump your waste heat, heck, there isn't even enough in interplanetary space. I read an article recently about Prometheus (NASA's nuclear propulsion project) in which the reactor engineers (whom have honed their skills building aquatic vessels) were specifically making the statement that one of the biggest challenges is dumping excess heat, and that you don't have the luxury of using the ocean like you can in a submarine.

Hello, SawSS1Jun21,

if I don't misunderstand you and if I don't misunderstand Peter too then you are taking my post from the opposite side to Peter and peter seems to take it from that side I have in mind.

The initial point of my thoughts is that a star ship flying through the extremely wide and cold interstellar space for decades will loose its temperature into the interstellar space that way that a satellite or rocket orbiting Earth looses the heat got by the sun into space when that side that has been faced to the sun before is faced to the dark space now.

This means that without a source of temperture and heat the star ship will become frozen perhaps - the saturnian moon Titan is an example of this. Titan shows that at a distance of 12 billion kilometers the sunlight is far too weak to provide any sufficient temperature from an external stellar source.

Mars is an example of a planet that has lost by far the most of its initial internal temperature - and both these examples are extremely huge compared to a star ship engineers may be able to construct and build. The difference in size means that the star
ship will loose its temperature extremly faster than a planet. Satellites orbiting Earth provide a basis of experiences - satellites orbiting Mars, Jupiter, Saturn and probes crossing the interplanetary space provide an additional source of experiences too.

These thought of mine assume that the star ship has no equipment or technology withe the primary purpose to provied sufficient heat during the decades of flight thruogh the interstellar space - that time the star ship is farae away than 150 million kilometers from any sun-like star. And the distance from stars like Sirius needs to be very much farer to prevent the danger of the larger amount of deadly radiation of these stars the astronauts, crew, colonists etc. would be faced to else. At the safe distance it may be too cold yet.

These thought mean that keeping the internal temperature of a star ship has to be considered urgently.

Currently I don't know any source of temperature than a conventional nuclear reactor or a fusion reactor - a technology that doesn't work yet. And I have no informations that anyone has calculated if such reactors produce ship-wide temperature-amounts that replace the losses to the interstellar space. What is the rate of loss per second and cubemeter to the interstellar space without a source that primarily should provide temperature and what is the rate of temperature per second and cubemeter provided by such reactors? Is the freedom of interruption sufficient or s a significant number of backup-reactors required that mean a substantial increase of mass which would mean a substantial increase of the propellant requirements? What new and better temperature providing technolgies are required and imaginable? And so on.

The problem of temperature losses to the interstellar space need consideration.



Dipl.-Volkswirt (bdvb) Augustin (Political Economist)