Spacescifi

[snip] You know (or should) I am discussing blast lasers mounted on spaceships. The associated mass/weight of equipment for cooling and powering such a beast would lower it's total thrust greatly. No matter the rocket engine used ro push it. Thrust lowers automatically when mass pushed is high. Why is it we have so we have such a high propellant to mass ratio with rockets? [snip]

Asteroid mining never pays for the expenses unless the expenses are ALREADY paid. QED: people already living in massive rotating space habitats with constant 1g acceleration scifi spaceships that either do not use propellant or are ridiculously efficient with it.

As was I. Lasers are poor at blasting stuff unless you have lots of cooling equipment. My point is simply that it is very ineficient to use lasers for blast mining at all. At best they are not bad for burning, but blasting? Too much mass required. Low thrust. I don't care what your ship's drive is, if it is a rocket with known propellant and engines, even nuclear, thrust will suffer. A lot. That's my whole reason for this thread.

Lasers run into the same problem as fusion torchships. The amount of mass equipment to reject the heat of pulse lasers with blast ability will be so much that any ship carrying it will have poor thrust. By poor I mean so poor it should be a station in orbit, not a spaceship. And definitely not flying around looking for asteroids. The one type of laser that I think is portable and can pulse blast...but only once, is the bomb pumped laser. The kind you stand away from. Which either requires using rocket fuel or waiting patiently or jyst firing the BPL through mag rails, albeit not real fast as you don't need a lot of speed.

It was worth a try Hey! What if the cylinder had air inside and a hovering flying drone shot bullets at the forward wall but never landed? Granted...I know, recoil. But what if the entire ships was shaped like a torus (donut)? And two drones, in on each side, fired simultaneously at the front wall? The recoil shoots them back, but if the ship is BIG and spacious enough that the drones can fly and curve around as much as they want with without hitting the walls. Only up to a point, since eventually the rear wall will catch up to them...I think if they keep shooting at the forward walls. I am guessing. It's interesting.

Hmmm. Take a cylinder of steel with an astronaut wearing magnet boots. He has a rubber ball with a lead core, so it's a heavy ball. He walks to the middle of the cylinder, lifts off the floor, and throws the ball as hard as he can at the front wall. The front wall has sticky adhesive. The ball does NOT bounce back. The astronaut floats toward the ceiling and flips to reaatach his boots. Then runs forward a bit so he does not fall to tge rear wall. Does THAT impart forward impulse? Hardly practical. Just curious

Thank you Terwin. In simple terms, you cannot get forward mpulse with a closed system because the back wall will hit you and cancel out any forward impulse you gain. Unless we broke physics. You would have to cancel out the g-force from acceleration felt ONLY from inside the ship's hull that are caused from outer hull accelleration only, but let it remain with the outer hull. With that, you could hit the forward inner wall and that would be enough to push the ship forward.

Ya know...when you're serious, you're either brilliant or hilarious, this time the former. So true, classic scifi starships who laugh at delta V would be equipped with boring bots and bomb bots. Bore bot bores deep, flies out, bomb but flies in and drops bomb, leaves. Detonate. Boom, a bunch of smaller rocks that are easier to a haul back to base. I recommend just storing whatever dust the bore bot kicks up, since covering it will lead to all the dust eventually falling back toward the botvand clogging whatever engines got it down in the first place. Don't lose a bot. They cost $$$. Antimatter catalyzed nukes 500 of em (small nukes that pack as big a punch as normal size nukes thanks to AM). That't the only way.

I know. My point is that if we take ANY classic scifi starship from a video game especially or a movie that laughs at delta V...it makes in-situ asteroid mining obsolete. It is easier to just haul bigger rock than can fit in your cargo bay and ship it to a moon base for processing than do it yourself. Funny how scifi tropes either get obliterated or inverted when the implications of scifi tropes are played out faithfully and logically. Actually asteroid processing in such a system would be mainly for shipping to space habitat stations in deep space or in la grange point orbits. I think it is the height of silly to use Earth resources to supply a space habitat when you have high thrust virtually endless constant acceleration starships at beck and call that can even do FTL warp. The ENTIRE universe is your resource. Use it. Not your precious homeworld! You need tech at scifi trope level to even justify a manned asteroid operation being common. If tech is so IRL that delta V is actually a big concern, manned missions bring little to no benefit as in-situ mining does not care about humans rotting for lack of gravity and proper food supply. Unless you manage to pull a Watney and grow veggies from your number twos, sunlight, and asteroid soil LOL.

True...I was trying to avoid getting into the details so I misspoke.

[snip] Space manufacturing. Is. Hard. Also expensive. The ISS is primarily a research outpost for manned spaceflight science data. They would have to retrofit the station in order to really make it an industrial base. Challenge #1: Refining ore in Earth often involves water. Shipping water to and from the ISS regularly would be expensive, but possible. There are also many other components, like the need for a centrifuge due to the lack of gravity and making sure the whole station won't spin opposite when the industrial centrifuge starts spinning. Challenge #2: Heavy station's deorbit faster. Weight still matters. If the ISS is heavy industry in LEO, we would have to reboost it more often. It's a cost factor, meaning if we are'nt even breaking even profit-wise...you already know. I actually covered this in: https://forum.kerbalspaceprogram.com/index.php?/topic/197139-doa-scifi-tropes/page/4/

Translating scifi tropes into reality I do not really support unless we CAN do it and it is worth the cost. Scifi is and was for me merely wish fullfillment, an escape, and to be anything more than that an author adds idealogies he supports as well as frowns on. May even teach a lesson or truth that crosses cultural bounds that everyone can agree on. It is not prophecy.

It sounded good at first anyway. I thought that if one part of the ship weighed heavier than the other that the impact might impart impulse. I thought magnets may help but they also do the whole newtonian thing.

The concept: Springs. Gas. A heavy metal plate, and another plate of less weight to absorb the impact from the heavy metal plate, perhaps coated with rubber, and definitely with pistons to absorb the impact force. Propulsion: The pusher plate is propelled via gas jet thrusters using stored gas. The plate is extended away from the ship as the coiled springs stretch. The gas does not escape into space because a fabric sheath stretches out along with the heavy plate as it extends. The gas stops firing and wham! The plate smashes into the impulse receiver plate providing forward impulse. Granted, you cannot reach orbit with this, but once in orbit I think it could be useful. Could this work? Is there ANY reason in known physics why it would not? Because this seems like a way to NOT expend propellant and still get impulse, and it is a WHOLE lot easier than fission, fusion, antimatter and what have you. The gas would also be recaptured when the plate ran low by suction fans inside the propulsion plate. Want more impulse? Make tighter coiled or longer springs I presume. What do you think? Is this KISS at work? Did I just unknowingly invent the reactionless drive (not actually but no propellant is lost so..)?

Actually to be honest, it is easier to live off our own solar system than go interstellar The only good reason to mount a manned interstellar mission of the OP, even of we could (we cannot), is if our sun will go nova. Even then there is distinct possibility that that won't be enough. Since last I checked the safe distance from a supernova is 100 LY. That is death rays moving at the speed of light! A nova should have a shorter safe range that, but if it is measured off in LY then a STL ship of ours has precarious chances to escape to say the least. A headstart would be it's only chance, and the next system over may be too close. That's a LOOONG haul to the next system or however many it takes to be safe from a nova.

Ya know....perhaps in situ mining at all would be obsolete in a space opera settings? I mean, the spaceships in popular media have virtually endless high thrust delta V, they do not seem to skimp on thrusting maneuvers at all. So with those, which are also the most common type in space sims, it would be a lot more economical to just haul asteroids to the nearest base or station designed exclusively for asteroid processing. Known science does not reward any space vehicle that tries to excel in ALL areas it can possibly find itself in. It rewards specific fine tuning in one or just a few areas. I reckon even IRL asteroid haulers to and from asteroid processing stations could make a lot more sense than loadimg whatever one can in their cargo bay, as cargo bay space is limited, space itself is virtually unlimited. What am saying is that your cargo bay is NOT the limit neither should it be your limit. Your limit is whatever max amount of rock your much your ship can push with decent thrust. With known science, it would take no less than either a lot of fleet to push asteroids around...at great propellant cost I might add, unless waiting decades is ok. Or using laser propelled sails attached to asteroids which would take decades anyway. Using space opera logic? You could fly up to a space rock and push it with decent constant acceleration all the way back to base! It might be a quarter of 1g due to the extra mass penalty on thrust due to the space rock, but some g-force on the crew is a WHOLE lot better than the zero g conditions miners would find themselves in IRL. Mining takes time, but asterould hauling using space opera constabt acceleration would be a lot FASTER.

Those are show stoppers...impossible for us as of now. Compact fusion: The only compact fusion we know of involves our nukes. Controlling that compactly involves machines...which are anything but compact. High heat does not like compact...it WILL vaporize everything. Cryo-sleep: Perhaps I mentioned it before but frogs do this because their blood won't freeze over. Ours does. To make us do cryosleep and survive you have to reengineer our body so that is no longer a Mark I human. That is how far you would have to go. Bears hibernate, but I don't think they freeze over. Only cold blooded animals freeze over and live that I am aware of. And humans who do have cold blooded disorders have a whole host of health issues anyway. Artificial gravity: Easier, but requires a lot of range. Other key challenges: Food. Relationships. Conclusion: Like I have said before, we are NOT ready. Even if we were, as far as I can tell the only sensible reason to go that far is if Earth is dying and it is not going any where. Even if it did...by then we should have better options than the OP proposal I would hope. Something that does not involve reengineering human bodies to be cold blooded.

There is also a reason for the adoration. The most obvious is marketing...and simply put, THEY know and expect S and V to sell. You know what I mean.

True...a miner would either need unlimited delta v with good thrust or the ability to generate both gravity and antigravity to get away with chasing blown up rock without consequence. Still, when what you want is deep inside the asteroid, a bit of cannon fire can help. This a lone miner scenario. Now if you had a whole fleet of miners with diamond blade circular saws attacking a 3k asteroid, that may take less time to turn a profit. As is, unless the stuff is really valuable asteroid mining makes little sense to even involve people at all. Just bots. If people are out asteroid mining in space because travel is THAT efficient, then they likely already have either gravity/antigravity tech or virtually unlimited high thrust delta v. It makes no sense otherwise in a setting as far as I am concerned. Incidentally, with a localized 1g gravity field pod you could capture all that debris easily...but that is scifi I know. Then again...you know me.

Personally I think playing 3-D asteroids sim firing tank shell at them while doing newtonian manevers would be quite fun. Especially because it shows truth for once. I dislike it when fiction has people believing stuff that is either super hard or impossible is the opposite. Especially when we have good alternatives that work even BETTER. Unlike FTL or interstellar travel where we have no alternative besides a very specific set of stories. You don't need fancy plasma blasters or high powered lasers for blasting space rocks. Since neither are good at blasting anything but stuff that is already prone to combust, which a space rock is not. Tank guns will do nicely for blasting. Barring that good ole fashioned nukes will. Now that would be a fun game!

Depends on who you ask. Zubrin? It's a worse case scenario bug. Dissenters? Feature. Either way, it would be a high price to pay for having spaceship with Xasers (x-ray lasers). Ha...perhaps that's why no one rich is willing to openly support NSWR lasers. Nevermind all the radiation it creates.

Actually I just realized we don't even need railguns to break up an asteroid. Railguns are long range, highspeed slugs. If a mining vessel is closing in for an intercept, a railgun is overkill, in both the power required and the speed generated. Besides, railgun rails erode over time and the current flow can even melt the rails if high enough. This is not a real issue for sea ships that have plenty of spare rails and plenty of water to transfer waste heat to. When closing to intercept an asteroid or any other solid object you wish to blast to bits, old reliable tech works just fine. And by old and reliable I mean tank cannon guns. Mounted on a miner spaceship. Still not enough blast? Add nuclear explosive tank shells as ammunition for the tank cannon. Joe Schmuckateli knows what I am talking about.

I think you are on to something. If military forces have tested lasers of this sort it is mos definitely classified, since if anything goes horribly wrong your entire laser facility goes up in a nuclear fireball.

Thanks for the knowledge! Yeah...lasers ARE useful. If you have the patience. For gamers they would have to time warp the lasing while occasionally monitoring crew food supply just make sure they don't starve LOL while waiting. In real life yeah, totally kills lasers as space weapons apart from the bomb pumped lasers which won't be cheap by any means anyway. Too weak, and take too long.

The interesting data is the required radius or length of a spaceship or tether pods to do 1g rotation at 1 RPM (one revolution per min). 100 meter disc spaceship radius OR 100 meter long tether pods or 100 meter long spaceship with crew only living on the ends. Take your pick out of three. Elon's spaceship is slightly over 100 meters long, so he has the option of rotating tge entire ship and putting tge crew at the ends or extending 100 meter tether pods before spin. The first option is arguably less complex. This ONLY works if his spaceship is over 100 meters long AFTER staging detachment. If not he can't.