shynung

I'd like to ask something, but this one hasn't been answered.

Or one could forget the radiators, and accept the fact that the railgun or laser turret will destroy themselves after a single shot. Make the spaceships themselves disposable unmanned vehicles, meant to get as close as practical to the target, shoot a single railgun or laser charge, and blow themselves up afterwards. Like that, one just slashed 50% of mission deltaV (that thing's not coming back), along with ditching almost all of those graphene radiator panels.

So everybody wear pressure suits at launch? Must have been a tight fit.

I can understand that. Reminds me of RasterPropMonitor's multipurpose screens. Though, I don't get why would the astronauts need to wear gloves inside a pressurized capsule. So, maybe flight controls, along with other critical systems, would use large glove-friendly buttons. Stuff like general-purpose computers could be something like laptops or tablet PCs.

Whoops. Fixed. Still working on the attachment nodes. RL stuff is tying me down lately. So basically, large and heavy tanks that hold only small amounts of propellant despite their mass and size, and a relatively lightweight rocket engine. This, in addition to the engine not having a bottom attachment node, being bulky, and costing quite a fortune. Or, make the engines as expensive as the stock 3.75 m first-stage engine, but make the propellant tanks expensive and fragile. Didn't understand the bit about water circulation chamber, what would that be used for? Cooling?

The old Apollo computers don't have colored graphics, for one. The new ones also work faster than the old ones. And the touch screens. I mean, it's everywhere in people's pockets for a few years now (smartphones, iPads). I can't imagine a spacecraft designed in the 2010s to not have it.

A drone, as in UAV (or, more aptly, USV), is expected to fly back to be refueled and rearmed. This thing doesn't fly back after it delivered the zap; in fact, the reactor core powering it would probably explode mere seconds after it has fired, due to the lack of radiators in an effort to shave off weight, a consequence of its single-shot concept. This isn't a laser drone, it's a laser missile. To be precise, a guided missile carrying a weapons-grade laser as its offensive payload instead of explosives or kinetic energy. I think it's much better for the sensor ports to be inside separate optical turrets, much smaller than the main laser turret, and covered in separate ablative fairings. This way, it can traverse faster than the main turret, an obvious advantage when acquiring a target within a very limited time frame. It also means that the missile can carry several targeting turrets rather than relying on the main laser turret, which means the anti-sensor laser now has several eyes to blind, increasing the chances of the sensors acquiring a target before it gets blinded. Note that I used fairings, not shutters. An ablative fairing similar to aerodynamic fairings used in orbital booster rockets can be simpler to build and open than a shutter system. Coupled with the fact that the laser turret won't survive firing the laser (due to having no radiators, resulting in it, along with its power source, overheating to Hell), the ablative covering doesn't need to be closed again, rendering the point of shutters moot. I can even imagine a nastier version. Replace the directional optical sensor turrets with a passive omnidirectional sensor. When its fairing pops open, it lets itself get fired upon by anti-sensor lasers, thereby acquiring the position of the anti-sensor laser turrets. Train the main laser turret to this location, and pop the ablative fairing microseconds before firing. The target ship would have lost one of its laser turrets (possibly along with a few other things), opening the way to more devastating weapons that are more reliant on sensors.

Chlorine trifluoride (ClF3) chews through almost anything. I'm pretty sure there are other nastier stuff that one can make in labs, but I'll leave it there. Except the missile is a laser-carrying miniature unmanned spaceship. It doesn't have to be right next to the ship it's looking for, just close enough that light-speed lag is low enough so that quick targeting is possible. Despite the power requirements of laser weapons, it doesn't need radiators as big a larger ship would, because all it has to do is to pump out one good zap with its laser, and that's it; destruction of the reactor core or laser emitter/turret immediately afterwards is acceptable. It also doesn't need propellant to get back to where it came from, so it doesn't suffer too much from the rocket equation. Also, its sensors don't have to track the target all the time. It can instead receive targeting information from the ship that launched it, or even outright controlled from the launching ship. The sensors and emitters can be buried inside ablative armors able to shrug off whatever sensor-blinder laser the target may have, and pop open via explosive bolts at the moment just before firing. Like that, the vulnerable moments are the time frames between armor popping off and laser firing, and this can be reduced to milliseconds or even microseconds with the right equipment and the right firing sequence. Heck, mount several targeting sensors on separate disposable ablative armor fairing, and pop them open before the main laser fairing. Get enough targeting data with these sensors before the target's anti-sensor lasers blind them, then aim the main laser using this targeting data, while still covered by ablative fairing. This way, when the main laser's fairing popped off, it's already aimed at the target, reducing time from pop-off to laser fire even smaller. Like this, the only way a target can defend itself is to destroy the missile outright, using lasers meant for engaging other ships. If the target has only a few anti-ship lasers, a laser-missile swarm would ensure a few got close enough to unload a few zaps.

Missile warheads can be much more variable than simple fragmentation charges. A missile could be built to have some sort of single-use ultra-capacitor that burns out after discharge, and have enough stored energy to power many kinds of payloads. Things like mini-railguns that fire kinetic impactors, small laser cannons, EMP generators, or even stuff like asphalt cement ejectors (gunks up exposed sensors, radiators, and solar panels), high-voltage electrostatic nets (shorts out sensors/antennas sticking out), or maybe chemical payloads designed to heavily corrode metals. In the end, missiles (as in, self-correcting munitions) are just small spacecrafts intended to get close to the target and do things that harm or impair the target. How it actually does it is something that's very flexible, and can be adjusted to counter various types of defensive measures.

It works. It's mass-efficient compared to things like winged orbiters (Space Shuttle, Dreamchaser). It's self-stabilizing in reentry conditions. Also, not everything's old tech. The new capsules have fancy computers and LED lights. Touchscreens too, from what I read.

I smell missile warheads.

You can minimize the frame strain from firing a big gun if you design the ship right. One way is to built the ship around the gun, rather than simply bolting it to the frame. Case in point: A-10 Warthog. A similar concept can be used for a space warship, by building the ship around a giant railgun. The railgun's 'barrel' / rail system effectively becomes the ship's frame.

Yep. Though, to be fair, aerial superiority can be achieved by either fighter jets or AA systems. So even a combatant group not having an access to aircrafts could deny the use of their opponent's air assets.

Maybe you meant chamber temperature, since a nuclear salt-water rocket doesn't actually have a reactor core. Right now, engine heat production config is 4 times of LV-N's. Does this need adjustment? Also, uploaded engine models to github repo.

Nuclear pulse propulsion is 1960s technology. We know how it's supposed to work enough to be able to build one today. It's just that no one's crazy enough to actually give this a try. Maybe when some alien race decided to try to slag our planet someone will be able to brush the issues aside and build a nuclear pulse battleship, like the one in Niven's Footfall. Hard for us not to, since this is a space-themed video game forum.

Assuming the combatants has laser weapons, there's hardly any reason why would this scenario be true. Even then, missiles/autonomous spacecrafts could simply spend their entire deltaV budget to close the distance, engage, and be thrown away immediately after that. Very improbable. Any active spacecraft would emit more heat than a similarly-sized space junk. Electronics, even low-powered ones, create heat when operating, which means IR emissions. Unless the vast majority of orbiting space junks are RTGs, anyone with a decent passive IR sensor would know which ones are active ships. Also, assuming that tiny ships mean unmanned satellites, that means they have radio, otherwise they can't be controlled. Identifying friend from foe via radio (IFF, transponders) has existed for several decades now.

Because a single battle is just a single confrontation between two opposing fleets. Space warships zapping each other with lasers for years at a time would be a silly waste of energy. A laser gunfight between two warships would end immediately when one side either attempts to flee, surrenders, or gets destroyed. Looking at realistic energy requirements for ship-destroying laser weapons, efficiency limitations of thermal-electric energy conversions, and the fragility of high-performance (=large) radiator panels, I think it's safe to predict that warship laser gunfights would last somewhere between minutes to hours, depending on internal heat sink capacity. Wars, on the other hand, can last for years.

The fuel in a Bussard ramjet depends more on design. A Bussard ramjet can use plutonium as a fuel to heat the the propellant it scoops up. Fusioning the propellant is entirely optional; what's mandatory is that energy must be injected into scooped propellant stream somehow.

Of course it won't. NASA is an agency, not a program; agencies cannot be 'cancelled'. What's more likely to happen, given the current situation as I see it, is that NASA is going to be told to do things that may not actually bring any meaningful progress. The SLS program, for instance, might get cancelled the moment they are flight-ready, and get replaced by some other program to keep the engineers busy, so those engineers will pay taxes, buy stuff (=boost economy), and vote. The SLS itself may never get the chance to show their full capabilities; maybe a few test flights to (try to) convince people that all that hard work finally paid off, but no actual missions planned for it.

Indeed it's possible. I'd stick a large toroid MHD generator and have the rocket exhaust fly through it just after leaving the nozzle. Problem is, it works only on charged exhaust gases, and it saps a lot of thrust. Assuming identical mass flow, your thrust/weight ratio and specific impulse just went down the drain.

I was afraid something like this was going to happen. Sad to know it has happened for a very long time, but nothing I can do from here. At least my copy of KSP hasn't failed on me yet.

So basically, it doesn't really matter whether some NASA program was making progress or not. It's just to keep them busy, so to speak.

For the first trip, maybe, since the Sherpas probably have to carry their mining equipment to their O2/fuel collection point. But they don't have to bring it back home; they can leave the O2 mining rig there, for future Sherpas to use them later. Sure, some things would have to be replaced, machinery oiled, consumables replaced, but the bulk of the rig mostly stays in place. The tanker that carried O2/fuel doesn't go very far, either; just back-and forth from mining spot/surface to Camp 3/EML2. Also, the assumed mining spot shouldn't be past the summit on the other side of the mountain, otherwise that would correspond to the mining spot being farther than Mars. Lunar surface is closer to EML2 (despite going down a gravity well) than Mars orbit, taking about 2.5 km/s of deltaV, as opposed to about 5.2 km/s for going to Mars orbit. Then again, you're right that it depends on what's being mined, Water or O2 might be close to break-even, but stuff like nuclear fuels might be something else. Also, moving an asteroid to a stable orbit isn't an easy endeavor, because the useful (large) ones are massive. It'll take plenty of propellant to move it to EML2, but at least the tug doesn't have to carry the mining rig with it. Might be a good idea, but depends on what will the miners get from the asteroid.

Now imagine that the cost of carrying O2 from Base Camp was much higher, in terms of energy. The hiker would have to carry a lot of food (and breathe a lot of atmospheric O2) just to carry that O2 all the way to the summit. Meanwhile, the Sherpas found a place near Camp 3 that has some O2 in a form that they could bottle (say someone airdropped an air liquiefier/separator device). This O2 source is lower than Camp 3, but higher than Base Camp, so they spent less energy (food and O2) getting that O2 to Camp 3, where people line up to get it. Suppose that the Sherpas and the hikers work for the same company, whose mission was to mine something from the summit of Mount Everest which cannot be found somewhere else, call it Everesite for now. Suppose that the hikers and Sherpas have to use O2 all the way from base camp to the summit. Which is cheaper, in terms of energy spent: carrying their entire supply of O2 all the way from Base Camp to the summit (which means lugging around big and heavy O2 tanks), or carrying just enough O2 to get to Camp 3, refill their O2 there, and continue the rest of their journey using O2 taken from refill site? Replace O2 with rocket propellant, hikers and Sherpas with spacecrafts, Base Camp with the launch pad, Camp 3 with EML2, O2 refilling site with the Lunar surface, and the summit with Mars.

There are things that an ASAT missile cannot reach easily: anything with a solid defense. Current crop of ASAT are for things like spy satellites which doesn't have any kind of defense system, and has very little armor for them to defend with; adding armor makes it heavier, and in spacecrafts, every gram counts. However, suppose you have something up there that is literally worth waging war upon, say a really big asteroid with high concentrations of rare elements, or maybe a space station dedicated to some top-secret stuff that can't be done on Earth for some reason. Bringing in armor would be just as difficult as the spy-sat, since reasonably-tough armor plates are quite heavy. It's also, unlike the satellites, cannot simply be launched en masse, hoping that at least a few survives; space stations and/or asteroids takes a lot of energy to deploy (in the case of asteroids, either deploying the machinery to them, or deploying tugs that move them to the machinery). In short, only a few of these things can exist, due to cost constraints. So what would a defending general do? Similar to how today's ships have less armor that WWII battleships, but just as difficult, of not more, to hit: Close-In Weapon Systems. Basically, stick a few quick-firing autocannons or pulsed laser emitters mounted on a turret, designed to shoot down any incoming projectiles and/or ships that comes within range. Trying to get through this kind of defense would require either lasers, particle cannons, huge swarms of ASATs, or a big, armored space battleship, like the Orion example posted. The first two can be countered by ablative armor (can be made lighter than solid, anti-kinetic armor) and ship-generated magnetic fields (strength depends of available power, only works against charged particles, neutral particles are unaffected), respectively, while the latter two are quite expensive in terms of material. Basically, if there's something worth defending in space that can't be easily replaced, it would probably have CIWS. These are the tough nuts that are too unlikely to be destroyed by a simple ASAT.