Bill Phil

That is a concern however it is mostly a problem for electron/positron colliders due to the low mass of the particles. This is part of why a muon collider would be of great interest. The bigger issue for proton colliders is beam rigidity at higher energies - you need really strong magnets to turn the beam at higher energies or a huge radius. Maybe even both.

So I was wondering how to find the size of a circular particle collider with a given energy and magnetic field strength. Of course the main obstacle I've run into is the relativistic aspect of it. But nonetheless I would like to get a rough estimate for the necessary size of a collider for a given energy. Any help?

You could download GMAT and try to configure it to have the Kerbal solar system... I don’t recommend it though. Then again it might be a big pain. Plus you’d be planning a mission with n-body simulation...

The worst part about this program is the waste of talent. There are so many skilled engineers at MSFC but they’re stuck developing SLS.

It's a Casio, on a Plastic Beach...

The best proposal for this I've seen is StarTram, though I think Lofstrom Loops are a better design with more interesting engineering details - not to mention the ability to potentially build a full on orbital ring with similar, but more advanced technologies. It's not the cost of the fuel, it's the performance of the vehicle and the subsequent gains in payload mass or reduction in vehicle complexity. I remember the ratio is something like 10 kg on the rocket gets you 1kg of extra payload, for some recent designs at least. We can get rid of dozens, if not hundreds of tonnes on the rocket, potentially improving payload to LEO dramatically. Or conversely making the vehicle itself cheaper since its performance requirements are lower. Provided of course you aren't doing this low in the atmosphere. Basically reusable SSTOs become possible with relatively little starting velocity, even more so the faster you launch. And this is without any improvement in the rocket engines at all. I remember some analysis done a while ago that found that even a modest velocity allows for pretty big reductions in vehicle size, making SSTO vehicles like Venturestar far more practical with already existing technologies, which is the real advantage. It was the Maglifter concept- you can find it referenced on this page: https://en.wikipedia.org/wiki/Rocket_sled_launch#cite_note-MaglifterMankins-5 Remember the most expensive delta-v, in terms of propellant mass per unit velocity is the initial velocity. "For the launch of 25,000 pounds to LEO, a preliminary analysis of the addition of MagLifter (for the reference case of 10,000 feet, 600 mph, 45 degrees), results in a 25 % reduction in vehicle dry mass and a 33 % reduction in engine mass (assuming use of a Space Shuttle Main Engine, SSME, class propulsion system)." The gross mass (from a figure in the paper) was reduced by nearly 35%. This greatly alleviates some of the biggest problems with SSTOs, and its only 268 m/s. The required vehicle mass ratio was also reduced but not by a tremendous amount. Still, with faster velocities the vehicle could be even lighter. The only real obstacle to such an approach is dynamic pressure.

Rockets are actually a fairly limited technology - even antimatter rockets. Rather than using rocketry technology I think civilizations can be judged based on a few criteria: 1.) Heat rejection - how do they get rid of waste heat? We just dump it into the atmosphere which eventually takes care of it but at higher energies this will become less practical. More advanced species will likely have more advanced methods for waste heat management. 2.) Mastery of dynamic structures such as dynamic compression members, launch loops, and orbital rings. Such structures greatly expand a civilization’s ability to do things, and orbital rings in particular have some insane applications like suspending artificial surfaces over gas giants, stars, and black holes or even providing direct transport to other celestial bodies. 3.) Particle accelerator technology. The higher the collision energy any civilization is capable of will be beneficial, potentially allowing them to understand more of the universe such as GUTs and if they get to high enough energies maybe even quantum gravity or theories of everything. There’s a lot more, but those are some of the big ones in my mind.

Or you can use hyperdense matter to create a disk of high mass. Set up a tower to support an elevator with the crew quarters. Then find some way of accelerating the mass. I can’t remember who but someone called this a “balanced drive.” You use the elevator to set the local gravity to a level so that it balances with the ship’s acceleration, thus high accelerations are possible without turning the crew into paste.

I think the real solution to this is thrust curves. You should be able to design thrust curves (they can be really simple curves) for the boosters on your rockets. That way you get the thrust levels you want when you want them.

The answers can be much more complex, however. And they depend on what exactly the situation is. Aliens: is it intelligent life? Simple life? Is it closeby? Far away? Are they “sufficiently advanced”? And so on and so forth. Propulsion tech: depends. A lot. We may end up building orbital settlements and abandon finding habitable planets. Waste heat: we could theoretically construct an orbital ring setup to carry waste heat from Earth into space to radiate it away. Or we could expand just to more efficiently radiate waste heat. Now that is an interesting reason to colonize space...

I don’t think world building in sci fi should be about fixing society. Rather it should be about the impact of scientific advances or even the laws of physics themselves on human society. For example, what would happen if we discovered aliens? What would happen if we advanced in propulsion technology fairly rapidly? What would happen if humanity’s waste heat became a problem in and of itself? And so on. When it comes to “fixing” society, that may best be left to utopian/dystopian fiction. Some of the best ones are built around ideas to fix society. After getting the concepts straightened out you think about how they’ll affect people - and you can pretty easily make a decent dystopia.

Rotation is probably our best bet.

I don't know about better life expectancy on the Moon and Mars. Earth will remain the most developed place in the solar system for quite some time. Though this can change over time, as it always does. Actually the slight increase in radiation could be beneficial, if the hormesis model has any weight behind it... I don't really think solid bodies like the Moon and Mars are suitable for settlement. Sure it could be done but we're talking about places that are far away (in the case of Mars, this is true both in terms of distance and energy, but mostly true just in the case of energy for the Moon - but it has low gravity which could be problematic). Similar to how Antarctica isn't inhabited, I doubt the Moon and Mars will be anytime soon. It will probably happen eventually (and who knows? maybe Musk's crusade to colonize Mars will actually bear fruit...) but likely after some time. Research facilities will likely be established - but orbital settlements are so advantageous that planets and moons look pretty lackluster in comparison. The biggest advantage is probably ease. If we were to do an analysis of settlements on the Moon, Mars, and in orbital space (specifically Equatorial Low Earth Orbit (or ELEO) for now, but eventually we might be able to dispel the Van Allen radiation belts - freeing up a lot more orbital real estate...) we would likely find that the mass requirements for a given population size are pretty close - this is because the Moon and Mars settlements can use local regolith as radiation protection and the radiation doses in ELEO are actually pretty mild - as well as life support mass likely scaling with population more directly than other factors. However - the energy and logistical requirements requirements would be far different. The largest object ever landed on Mars is about 1 tonne (Curiosity). The largest on the Moon is about 15 tonnes (Apollo LM). But the largest in LEO? Over 400 tonnes (ISS). Of course SpaceX might be able to change the game a bit but it seems like it'd be far easier to build a settlement in ELEO than anywhere else. Eventually the industry for building settlements can mature and extraterrestrial resources can be acquired to provide shielding (provided some kind of powered shielding method isn't developed - there are some ideas for this), expanding the locales where settlements can be built. There's an entire asteroid belt, Kuiper Belt, and Oort Cloud out there...

Did you read the link? You can get a pretty wide selection of food - probably better quality than most food on Earth too.

Actually this is something I think about a lot for space colonization. Interestingly some of the best literature on space farming comes from research into orbital space colonies. You should look into that. I can’t link anything right now (on mobile) but there is a lot of good stuff. Since water is so important I’ve seen recommendations to use aeroponics whenever possible. The whole system is lighter than hydroponics (important for space colonization) and can actually have pretty great yields. If you’re already growing fish then aquaponics makes sense. However if we manage to mature cultured meat technology and apply it to fish then growing fish won’t be strictly necessary. Of course not every plant is great for aeroponics but it seems like it can work well. I managed to find this link: https://space.nss.org/colonies-in-space-chapter-9-up-on-the-farm/ This is a description of how ten thousand space colonists could be fed - though I’m not fully sure if the numbers work out. I think the proposal is to feed ten thousand people with 100 acres - might be possible with high yields, full year growing season, optimized environment, and so on. But it may be tough. Going vertical might free up more area as well. There’s other stuff as well. I suggest giving it a good read through.

The problem Cernan experienced was a cooling issue. As he labored to maneuver in space - which was by no means perfected at the time - his visor began to fog up. The air cooled suit was problematic for the purpose of doing useful work during EVAs.

Some small solid motors might be installed to deorbit each rod. The lateral velocity is what makes it dangerous - though it’s not as powerful as a nuclear bomb/warhead it is powerful enough to take out pretty decently sized targets. There was some though to using them as anti tank weapons but the accuracy required and the lack of maneuvering capability rendered that impractical.

In another universe this may have been a hit, but we don’t even know its name.

Yeah, solar collectors can't avoid the dark from happening. But they don't experience night time, they experience eclipses. These only happen during specific times of the year, and for minutes at a time. Easy to deal with from a practical standpoint, just add slightly more capacity and then use storage systems. ... Microwave ovens are entirely different from a microwave beam for transmitting. You see, microwave ovens are designed to heat water and other molecules common in foodstuffs. This means that they operate at one of many frequency those molecules are sensitive to, usually one of the optimum frequencies. A microwave beam for power transmission will operate at the optimum safe frequencies for that purpose - which means that no, they will not (and likely can not, aside from photon collisions) cause anything within the beam to cook. Not to mention that you're talking 2.2 kilowatts of power spread over a rather small area for a microwave oven. The design irradiance for a microwave beam transmission system would be much smaller and less dangerous, not to mention less likely to cause dielectric heating. The rectenna can intercept nearly the entirety of the beam energy, and can do so efficiently. It appears as though you have not devoted much time to researching microwave beam power transmission. I suggest you do so, there are numerous interesting aspects to look into, but nothing has been found to be game breaking - save for the cost of putting payloads in orbit. I was under the impression we were discussing laser facilities stationed in space. Such facilities on Earth would, again, just be massive targets - practically useless for warfare. All they could shoot down would be spacecraft and some aircraft, but missiles and artillery could easily take it out from beyond visual range. Then why are there numerous government backed programs around the world trying to develop space based solar power systems? I mean, they're probably not going to result in anything, but the intent is there. The answer is simple: space based solar power is not a military threat, and can never be (as soon as it is it'll be dealt with). The beam energies for such systems are not and can not be significant threats. This is because power generating beams are inherently different from weaponized beams. Beams for propulsion carry a much larger threat with them but they also make easy targets due to them being large facilities. And yet even then there is research, both theoretical and practical, into beamed propulsion. The only way to truly travel at significant fractions of the speed of light (above gamma = 2) will require beamed propulsion of some sort, as rockets are simply not up to the task due to the rocket equation. (Either that or some kind of Robert Forward gravitational accelerator, which is "indistinguishable from magic", but could actually work, if the assumptions turn out true)

Actually that's impulse, a change in momentum. Thrust per mass of propellant isn't really measurable... thrust per unit mass per second is possible though. Of course that's just specific impulse again... OP: Thrust is determined by exhaust velocity and mass flow. But there's a tradeoff - usually when you have a higher exhaust velocity you have a lower mass flow. So to maximize thrust you'll need to look at high thrust low specific impulse propellants - such as solid rockets.

Assuming the spot size of the beam is small enough that the area power density is high enough to cause damage. Not only that but if we had particle beam propulsion and particle beam weapons there would be suitable countermeasures employed to protect assets. For example, we can already shoot down satellites we don't like, but we don't. Why? Because there are consequences. And if such weapons were developed and employed countermeasures would be developed as well. And consider that the beam projector can also be destroyed, quite easily I might add. I'm afraid you've misunderstood the point of space based solar power. It isn't about having higher intensity, rather it's about avoiding the interruptions for ground based solar power. Namely, avoiding night time, clouds, and cosine losses. For example, where I live the annual average solar irradiance is something like 200 watts per square meter. Compare this to solar irradiance at 1 AU - nearly 1400 watts per square meter. Just going through the atmosphere cuts into the solar irradiance. (And I live in a place that gets decently hot at that, it's just that night time lowers the average). You do concentrate the energy into a beam - but a microwave beam. Microwave rectennas can be built to catch the energy of this beam and be spread over a fairly large area, but leave the area beneath them unharmed and still usable. Not only that but you don't need a high intensity beam, nor do you want one. It would be too dangerous. You still get advantages: no night time for the panels in orbit and so on. But you don't want to beam it down at such an intensity that it can actually harm anything. Why would you use lasers? You could use Casaba Howitzers, slug throwers, missiles. No one said you had to station these weapons far away. A small flotilla of ships standing by is preferable. We already have access to immensely powerful systems. Beamed power will be more powerful still and the question of how to control that power is indeed an important one. I'm confident we'll find ways to deal with it.

Solid core NTRs, yes. Gas core might require cooling to get better performance.

Wait, what? I never thought I'd see this...