Interstellar probes/travel

[Grond]

No idea if anyone else on the forum is interested in astronomy or interstellar travel etc... but I find this concept to be really cool. Its essentially Silicone Valley or computer revolution meet interstellar travel.

https://www.youtube.com/watch?v=VRpl1KQCr6M

https://www.youtube.com/watch?v=RoCm6vZDDiQ

This new probe design- photon or laser driven nanocraft is really revolutionary compared to traditional chemical rockets. It also shows that to some degree sci-fi is slowly becoming reality 

[Wylder Treejumper]

@Grond: Ah yes, photonically propelled nanocraft. Of course, the main problem is building, powering and cooling the laser array- lasers take a lot of energy and generate a lot of heat. Needless to say, it would be very expensive- but also exponentially faster than anything we have right now, able to travel at about .3C, if I recall correctly.

I want to be an astrospace engineer, so this sort of thing is right in my wheelhouse. If you like photonic propulsion, take a look at this article, which details using photonic propulsion in the intermediate future for large-scale craft, like large probes, or supply or crewed planetary missions.

Currently, my ambition is to work for SpaceX. I would love to design the ship that takes man to Mars.

[Grond]

Cool! Yup the top speed according to Dr. Lubin for a nanocraft would be .3C. Obviously bigger probes would go slower. I took a look at that article and the only thing I am skeptical about is that manned interstellar flights could become a reality in 70-100 years. I think sending the first interstellar probe- nanocraft or maybe slightly scaled up nanocraft would be more realistic in that time frame. I think Dr. Lubin stated that 1 teraton would be required for a manned photonic driven probe. That's about the energy released by the meteor impact that wiped out the dinosaurs...

In terms of photonically propelled nanocraft, I believe Milner  stated that he estimates that the final cost for developing Breakthrough Starshot would be 5-10 billion. Now these projects usually tend to run over budget but still even if it was twice the initial estimate it would still be feasible. Especially if one or better yet several governments get on board. It is also the most technologically and financially realistic option for interstellar travel we have at the moment. Chemical rockets can't reach relativistic speeds. While there are numerous problems with nuclear propulsion. While theoretically the technology to build an Orion style spacecraft, which uses hydrogen bombs for thrust or "fuel", does exist its highly unlikely to materialize in the near future. First you'd need around 300,000 MT to get to the nearest star- Proxima Centauri. The entire estimated global nuclear arsenal is about 15,000 MT. Secondly that spacecraft would be enormous and unbelievably expensive- easily in the tens of trillions. Which makes it cost prohibitive and also politically impossible because of the fuel and the nuclear test ban treaty. Its top speed was estimated at .05C.

The other option is a Daedalus style nuclear fusion powered spacecraft. First our technological capabilities for controlled fusion are greatly lacking and nowhere near the levels required to build such a craft. The amount of fuel required is huge- we would need to mine the atmospheres of the gas giants for deuterium and tritium. The estimate cost of such a craft was over 150 trillion, not economically feasible. Top estimated speed was 0.1C. The problem is that most of the weight of these spacecraft would be in their fuel. So in essence a lot of energy is expanded by the fuel propelling itself. With photonic driven craft this isn't a problem- the fuel source stays on earth.

Another advantage is that with a laser array or photonic propelled system- you can literally launch thousands of nanocraft in a year. Its also estimated that such a laser array would require the amount of energy produced by a large nuclear power plant. This is many magnitudes of power less than either Orion or Daedalus style spacecraft. Also the cost to build and develop such a system is far "cheaper" and "easier" than these other two options/concepts. Plus Orion or Daedalus is really only a one time venture given the enormous costs, while nanocrafts can literally be sent in all directions. Given the low cost of mass producing them and the comparably low amounts of energy required to propel one to relativistic speeds. Plus if one gets damaged or destroyed its no big deal, with an Orion or Daedalus type craft it would be a disaster.

Well basically what I'm trying to say is that I think photonically propelled nanocraft and later spacecraft are the future of interstellar exploration.

[Wylder Treejumper]

Yes, I don't agree with that estimate either. I say, take the stated timeline given for new space exploration technologies to mature, and increase it by 50-200% (The more advanced the technology, the greater the increase- probably 200% or more in this case). A lot of times, these scientists rely on the development of other new technologies to make advancement of their technologies possible, which throws off the entire timeline. For example, I doubt we can exponentially increase the efficiency of solar power in such a short amount of time. I believe improved miniaturized fission generators are a more likely option. I'm also waiting for graphene microsupercapacitators (hows that word for a mouthful?) and harnessable nuclear fusion technologies to develop. In the long term, I believe anti-matter reactors will likely be the main source of power generation and storage. Anti-matter puts an incredible amount of energy into a very small package- the only problem is, of course, utilizing and storing that energy without immolating ourselves.

SSTOs are the immediate future- SpaceX and BlueOrigin have already developed them into practicality. They cut the cost of spaceflight enormously, allowing us to build orbital infrastructure much more easily. I believe things will stop there for a while, until perhaps nuclear thermal rockets are built. That gets rid of chemical rockets beyond Earth's atmosphere. Ion engines are then a possibility, but their high efficiency is more than compensated for by their low thrust, making them useless for ELO+ launches. And I would assume that is when fusion propulsion comes in. Very powerful, can be built with infrastructure pulled up to LEO by SSTOs, and once it gets up to speed it can go indefinitely. I'm not sure about the scale, because that technology is so far off, but I imagine it would be useful for a variety of craft scales.

Photonic propulsion ought to be quickly developed for nanocraft, because it will allow us to explore distant locations on a much shorter time-scale than anything else- given, they are nanocraft, so they can only do so much, but it is still much better than what we can get through telescopy. I don't believe large craft photonic propulsion is practicable anywhere in the foreseeable future. I call its development after fusion drive.

I also don't really believe in building large interstellar crafts like the Orion- and Daedalus-class ships you were speaking of, simply because they are cumbersome. Once warp drive is available, in the really far-away future, that may be different, but the possibility of them being unable to complete their missions just seems like too great of a risk vs. payoff, at least without extensive exploration and experimentation.