Bill Phil

Driving electric doesn't simply move the exhaust pipe everywhere - it's complicated and highly dependent on location. Coal is losing share as an electricity supply, but it is still in use in many areas. Fossil fuels are usually how electric demand is met - almost all renewable systems are too intermittent to provide baseload power. Only hydro and geothermal are capable of that. Efficiency? Uh oh. You see, higher efficiency has an interesting consequence - higher consumption. This is almost always the case, even has a name. Jevons paradox. So more efficient cars in the form of electrics will create an increase in demand for electric power - new capacity will need to be installed. There's about 270 million motor vehicles in the US. Electrifying a decent chunk of the market will lead to more demand for electricity. This is far more likely to be met by natural gas than any renewable system. Once range issues are dealt with this increase in efficiency might also lead to an increase in driving miles, or perhaps an increase in average speed. This will likely lead to an increase in carbon emissions due to an increase in the total power consumed by the grid through EVs. Electrifying other industries will likely have the same affect. Even energy storage systems benefit fossil fuel plants far more than renewable plants - coal and natural gas will be able to operate at or near their maximum capacity factor for the duration of their lifespan minus downtime. This will also lead to an increase in carbon emissions. Unless we do what France did and migrate to a majority nuclear power infrastructure. Efficiency will not save the world. This has to be addressed at every point in the process or it will literally be worse than it is now. We don't need to wait a few generations. The technology we have now is well suited to baseload power requirements. We let our nuclear industry die off in the past - it's no wonder new plants are so difficult to start up. Keep in mind that that "transportation" data likely includes many other sources beyond passenger vehicles. Indeed, semi trucks were responsible for 12.5% of US GHG emissions in 2013. Airplanes and shipping vessels are also large problems globally. Again, Jevons paradox applies. Electrifying semi trucks will likely lead to an increase in the use of semi trucks, and if the ultimate source of that energy is still fossil fuels (as it is likely to be) then total emissions are likely to still increase, potentially even faster. Interestingly Germany has been trying to develop their renewable industry - and the amount they've spent likely could have been used to build a large nuclear industry for most of the country. It's actually quite disheartening. Renewables are not the solution to our problems.

Perfect may be the enemy of good. But while an ICE is bad, electrics aren’t inherently better. There are numerous reasons for this. I won’t go into them because there’s already quite a lot of literature on the subject. Nuclear is better in almost every category than solar except for setup costs. Higher capacity factor, higher EROEI, less deaths per kwh, even less waste not to mention less required ground area. Meanwhile solar gets much more in subsidies per kwh despite not really being an effective power source. For many places (like where I live) nuclear is really the only option for low emission power. Solar power just doesn’t work out well here. Neither does wind or geothermal. Hydro is already used quite a bit here but it’s not enough. Thankfully we already have a nuclear plant - the first to generate a gigawatt of electricity and the second most powerful one in the US. Even the high setup costs may not be inherent with nuclear - a good chunk of the cost is the legal fees and so on associated with starting one. The issue isn’t oil - it’s coal. Oil isn’t actually all that common for electricity generation - about 1%. Coal is about 27%. And coal is much less efficient. If your EV is powered by coal then it’s worse than an ICE. If it’s powered by nuclear it’s far better.

"ZA WARUDO!" "KONO DIO DA!" -DIO "You're next line is :" -Joseph Joestar

Idk. I’ve heard so many stories from engineers at NASA about Boeing mucking up the works and almost deliberately increasing the required time and actively trying to delay the project.

The issue isn't acceleration (just build bigger, though of course that isn't easy at all). Acceleration requirements are decreased with distance. It's not the real issue. The real issue is getting out of the atmosphere. Dynamic pressure and hypersonic affects at sea level would be monstrous, so you have to build it high up. But that presents an even larger challenge. That said solutions do exist - though getting them to work would require a lot of engineering and R&D. Launch Loop is one example, and at least has the benefit of being able to use known materials (unlike a space elevator). I hope Starship works, but there's a good chance it won't. And even if it does rockets are a fairly inefficient use of energy. From an energy economics perspective they'll never be quite as good as non-rocket systems can be. Not to mention the pollution aspects, which are minor for now. But if the launch industry expands massively that'd be a lot of pollution we'd have to deal with, unless we stop using chemical rockets altogether.

-Keith Lofstrom, describing his work on electronics as silly as possible

Certainly. It would really change the game if it works out. Though I'm a bit skeptical that rockets will be how civilization breaks the chains of gravity - barring some major advances in the technology rocketry hit diminishing returns some time ago in terms of performance. Non-rocket systems seem to be much more capable, though they require more investment and technological development. At least rockets are a demonstrated technology - the question is lowering the costs. But I wonder if that's truly possible. That said there was some interesting mass driver research in the 30s that seems to have been buried.

Well the idea would be to propel a huge ship. One could adapt mini-mag Orion to the concept - that way at least the propulsion units aren’t full blown nuclear weapons. Though eventually you get more propulsion from the direct momentum exchange between the propulsion unit and the vehicle.

That’s kinda sorta what Lightcraft is.

0.1c assumes fusion bombs. That said it is possible using catapulted bombs that the vehicle doesn't carry within itself... Of course that would imply being able to sling atom bombs at near 0.1c. Yikes.

Higher thrust - and lower total impulse. It has 26 tonnes for TLI Block 1 - almost half of the Saturn V’s. Block 1b is 40 tonnes or less. Only Block 2 - which may never be developed, approaches the Saturn V’s performance, at 45 tonnes. Meanwhile the Saturn V could deliver over 48 tonnes to TLI. Block 2 requires advanced boosters - there’s a real chance it will never happen. The use of liquid hydrogen in this way is immensely inefficient - gravity losses are larger and the stage delta-v split is inefficient. The higher thrust is all from the SRBs - which have a shorter burn time than the S-IC and provide less total impulse even with the core added. SLS is less powerful.

I’ve talked with some of the engineers - it’s a real mess. Boeing has been very problematic for the engineers so far. I’ve forgotten the specific issues but it’s been a huge problem plaguing SLS since the beginning. It’s actually going to be one of the cheapest super heavy launchers in terms of development costs. Of course SpaceX may change that but we’ll have to wait. SLS is less powerful than the Saturn V - the claim that it’s more powerful is just false. It also has issues with poorly done hardware installation and even hydrostatic pressure. The core is too tall. It doesn’t have enough engines either. Even the software is having issues. The idea of using “off the shelf” technology didn’t pan out - they had to redesign almost everything and each RS-25 performs slightly differently. But the real killer is launch cadence. The expected launch rate is so small and the payload capacity so limited as to make the thing almost useless for beyond LEO.

NASA regularly assists SpaceX and SpaceX is a major NASA contractor. NASA doesn’t build rockets. At most it designs them and then contracts out the actual construction - but even the engineering has contractors involved.

No, the Moon is a bad source for Helium-3. Uranium and Thorium are more abundant by orders of magnitude and in similar abundances as Earth's surface. The concentration of Helium-3 on the Moon is so miniscule that it may not even be an energy positive process, and no matter what the energy return on investment will be tiny. No, there's really nothing in space worth bringing back. That said a mature industry in space would be awesome and could enable some very interesting missions. Well Mini-Mag Orion could open up Jupiter exploration, and if not it would certainly open up Asteroid Belt exploration. Not sci-fi at all. Though a mature industry in space would certainly help.

It's not about how cool it is (it is cool in my mind though). It's about how important Mars will be in the solar system. Settling Mars is certainly cool and has a romantic allure (especially since a number of old sci-fi books are set on Mars). This isn't the place to have that discussion anyways. It just seems to me that Starship is more likely to lead to orbital habitats than Mars settlement - and even then both are not likely to happen. Space settlement is very hard to do. So difficult that we literally do not have the technology. We likely have the science and most of the understanding to do it, but not the technology. And developing that technology may take the better part of this century. Or longer. Maybe we'll get lucky and the technology will be developed relatively soon, but I doubt it. In the interim we should be developing an industrial capacity in space - allowing construction of large objects and efficient transportation around the Earth-Moon system. Hopefully both Starship and whatever BO does will help with this. Not quite. Terraforming Mars for example requires massive amounts of oxygen and nitrogen (more per square meter than Earth due to the lower gravity) and likely massive reprocessing of the soil. Imagine doing that for 150 million square kilometers! For a comparable area of space habitats you can have less oxygen and nitrogen per square meter and it is much easier to landscape. Essentially you're comparing making one giant thing with millions of smaller things - eventually you may see amortization with the difficulties and costs for making the smaller things. Indeed in the best case scenario you can also build the equivalent area faster - if a habitat has 100 square kilometers and is capable of building another in ten years (and we also expand the resource acquisition to support this manufacturing) then one habitat will result in the equivalent area of Mars in a few centuries whereas terraforming Mars may require over a thousand years and even then people may require breathing masks to go outside. But then here's the thing - the space settlements don't have to stop there. Another few doubling periods and you've already built more area than Mars can provide. Of course a 10 year doubling period is quite optimistic, but the point stands - building a planet's worth of orbital habitats is likely easier to do than terraforming planets. Plus you can build even more area. Terraforming Mars piecemeal may be possible and may be done but there's a gravity issue and you only get 1 Mars worth of area out of it in the end. Yes both concepts are beyond current needs to an extreme. But the orbital habitat concept has more room to expand and can be built anywhere in the solar system, if the materials are provided. Plus it can be used to settle any star system so long as it has asteroids or other easily accessible matter sources. Also the required mass for building an equivalent area to Mars with orbital habitats would represent about 4.1E-5 times the Moon's mass. Dismantling the Moon could enable us to build 20 thousand times Mars's current land area (which is roughly equal to Earth's land area). Of course that's a bad idea (for Earth's ecosystems) and would require a massive infrastructure, but we could build an equivalent area to Mars without having to do much beyond Earth's gravity well (you'd need to probably grab asteroids to get enough nitrogen and water among other volatiles - but there's plenty of oxygen on the Moon at least).

What does Mars really offer us? Some more land area? No, it's completely uninhabitable - without our intervention. If we're going to do that though then we'll get so much more bang for our buck by building artificial habitats that rotate to provide artificial gravity (plus you get access to a full 1g of gravity). A simple calculation using the mass of the Asteroid belt shows that we can build over 700 times the land area of Earth from just that mass. Mars is a drop in the bucket in comparison. Obviously such a large endeavor will take an immense amount of time and effort but Mars just doesn't offer that much and suffers the same issues as Earth in addition to low gravity and less area - not much habitable area (all of which will be artificial). And since all artificial habitats (no matter the location) will be artificial, orbit is just easier. Another thing to consider is relative difficulty - the largest object in Earth orbit is the ISS at over 400 tonnes. Meanwhile the largest object on Mars is around 1 tonne. Now this may change with Starship but no matter what happens Starship will also vastly reduce the costs for Earth orbit as well as Mars and the Moon - assuming everything goes perfectly. This means that larger objects in Earth orbit will be possible. It also means a lunar infrastructure could be done somewhat easier. This ends up making orbital habitats around Earth an even more likely prospect, especially since the technology can be somewhat related to orbital hotels - if such an industry ever comes to fruition. Recently Al Globus found that the radiation environment in equatorial LEO is fairly mild due to avoiding the South Atlantic Anomaly (where radiation spikes). If we wanted to compare the costs and difficulty of putting a settlement of equal size into either location then it will be much easier to put it into ELEO than on Mars, and this only becomes more true with the introduction of Starship. Not to mention the advantages of being close to Earth - emergencies are easier to deal with, people can return to Earth, maybe visit relatives, and so on (provided Starship can actually make space access cheap enough). I've said before that the ISS is the second most habitable place in the solar system - and even then it's a very far second to Earth. I'd take a space city over Mars any day. At least then I have a better chance of coming back to Earth if things go awry.

Mars isn't that much of a gateway - it's one of many possible destinations. Earth orbit is more of a gateway than any other location. From there both Venus and Mars aren't far in terms of delta-v. And there's actually quite a lot we can do as a civilization in just the Earth-Moon system. Indeed the thermodynamics of civilization may necessitate activities that are quite interesting in this "region" of the solar system. And if beamed propulsion or even just advanced nuclear propulsion is developed and the required energy infrastructure with it then transportation in the solar system becomes easier (in a relative sense since we will be a more energy rich society - hopefully). Interstellar vehicles are... difficult. We're talking immense energies (for both low mass high velocity vehicles and high mass low velocity vehicles, the scaling relationship isn't very nice). I really feel that colonization of Mars will ultimately be a footnote. Orbital habitats just have so much more to offer an energy rich society than any planet. It'll happen eventually, but I doubt it'll be a major event. Rather it'll be a long process that coincides with other efforts but brings less benefits. Economics may never work out for space settlement. However thermodynamics will eventually rear its ugly head if our energy use grows (and since standard of living correlates quite well to energy use per capita I would argue it should grow, but with less damaging sources). Eventually our civilization may overload Earth's heat rejection capacity. Before that ever happens I would argue that we should be a space-based civilization - with major industries no longer on the planet and perhaps even major populations as well. This is because if we want to stay on the planet and remain a high energy society we will need to invent some way to increase Earth's heat rejection capacity - it's not impossible but it seems even less economically sound than expansion into space. That is to say that methods for launching large volumes of mass into space (and at survivable accelerations) are much easier to develop than a massive thermal control system for the entire planet. Of course civilization may collapse long before it ever threatens to overload Earth's heat rejection capacity. Essentially it may be more costly to remain on Earth than to expand into space - a few centuries or maybe even millennia from now. On a more SpaceX related note: Hope Crew Dragon turns out well. Would be awesome to have more manned vehicles up.

Don't need fusion for that. Z-Pinch fission can get up to 20 thousand seconds, and fusion boosted fission (using fusion reactions to increase the neutron flux to increase fission burnup rate) could get above 100 thousand seconds. Could even make it like VASIMR/LANTR - adding in an "afterburner" to get more thrust when it's useful. Of course most of that usefulness is either escaping a gravity well or launching from a planet - which is probably never going to happen with nuclear propulsion.

Then wait for a sale. You can hide the struts pretty well if you’re careful.

Neil Peart stands alone. Rest in Peace

In free fall no force is felt except tidal forces, which can be minimized. As an answer to the OP: 100 km/s at 1g is about 10 thousand seconds. Or about 2.8 hours.

You don't need a pressure suit, true. But making a suit that's heated enough to let a human survive that environment... It's 94 kelvin on the surface... Only about 30 kelvin above the temperature range for high temperature superconductors.

In actuality you can apply the necessary amount of power. You can't apply it to a mirror based photon sail, true. Such sails are temperature limited when it comes to their maximum accelerations. I suggest you read the literature regarding SailBeam before simply stating it as "bogus." It's well researched and the physics are well understood. It's far from miraculous - indeed it's very mundane. In fact, it's so mundane that the technology is likely going to be developed this century, if only on accident. The weird quantum stuff doesn't happen at this scale. We're still comfortably macroscopic. You're right, there isn't a turret in existence that can do that. But we're not talking about the here and now. We're speculating about the technology future civilizations will possess. We already have an incentive to develop the necessary technology for such a beam - beamrider systems would effectively be the same technology. Not only that but you don't have to aim at an incoming fleet - just lay its easily predictable trajectory with stationary particles (relative to the star system) which the enemy vessels will collide with at large velocities. Anything that survives that gets melted by lasers or whatever needs to be done. Funny you should say that. You see, under some definitions of "megastructure" the Great Wall of China is a megastructure - I would certainly call that possible with current technology. Not only that but you seem to have a strange notion - we're not discussing interstellar warfare between civilizations with our level of technology. We're discussing interstellar warfare with civilizations beyond us in almost every way conceivable - though still limited to the physics we know today. We're speculating using known science and physics about what more advanced civilizations will be capable of. You've also misunderstood - orbital habitats are not necessarily megastructures. Some of the smallest designs for orbital habitats are not much larger than the ISS's length in terms of their diameter. And since there's a good chance the starship you ride in on will come with such a habitat for the journey there really is no reason to even land on planets. At least initially. You may want to later on to get access to more resources - after you've already established a fairly well sized industrial base in space. We're talking about advanced and energy rich civilizations on levels beyond us - interstellar warfare becomes useless because of the easily foreseeable technological development that comes along with access to that level of energy. Each and every star system becomes an impenetrable fortress and the energy (and matter) required to wage interstellar war are extremely wasteful. The cost of interstellar war is high - downright gargantuan. The benefits are null. Interstellar war is useless. Not only that but the required technical understanding to construct various megastructures already exists - we only need engineering. For example dynamic orbital rings are likely within our technology, but the likelihood of such a system being built is low due to geopolitical issues. Not to mention constructs such as McKendree Cylinders - we understand them well (at least structurally) but we just don't have the industry to build them. Meanwhile other examples are far beyond current technology. No, X-ray lasers pumped by nukes are "bogus", and even then they aren't bogus, they're more difficult to develop than the scientists thought. Still very possible and a potential technology for a more advanced civilization. More conventional lasers pumped by bombs may be more practical. Antimatter isn't a power source. It's an energy storage mechanism. A terrible one at that. Let me lay it down like this: The required energy to produce antimatter is on the order of the mass-energy of the amount of antimatter you want. Due to inefficiencies this number is vastly higher. The required energy is immense. Meanwhile conventional nukes are much easier to make, and have less risk of accidentally going off. By most measures - they're a better weapon. They're cheaper - so you get more boom for the buck, both in terms of energy return on investment and in terms of actual money. Actually the highest energy density is black holes - but using them as weapons will be difficult for obvious reasons. I suspect civilizations will not make antimatter - it's volatile, expensive, and has limited use beyond rocketry. Meanwhile other concepts are far more effective at accelerating vehicles to high energies and much more affordable too; both in terms of energy use and complexity. Not only that but as a weapon you'd get more bang for your buck if you just used high acceleration RKVs. Antimatter systems may actually be less useful than you think since the required containment technology may be quite large and massive. Indeed antimatter's uses will likely be starting fusion warheads or perhaps making "microfusion" warheads. If warheads actually remain as a useful technology. Essentially it boils down to this: Antimatter is actually a very bad choice for almost any potential application. Better alternatives exist. Due to these alternative technologies and others star systems are naturally fortified against invaders. If not they can be easily fortified. RKVs are impractical as well across interstellar distances. Thus interstellar war is useless.

This isn't the place for this debate, but we can do it in miniature. A megastructure can be quite large indeed, perhaps on the scale of Banks's Orbitals - or very down to Earth in scale; perhaps only a few kilometers in size. The definition isn't very well established. Planets are not the place for an expanding technological civilization - Gerard K. O'Neill and numerous others found this result in the late 1960s and early 1970s. "Habitable" planets are unlikely to ever be found, at least not anytime soon. By "habitable" I mean something that can be settled with little effort beyond landing on it. While it is true that you have resources on hand, this is also true for asteroids. Simply co-orbit with an asteroid of sufficient size and untold billions of tonnes can be easily retrieved from it. Atmosphere only does so much to protect the populace - an efficient radar and laser system can easily protect an orbital habitat from meteoroids and any orbital habitat will have extensive radiation shielding. Deep gravity wells aren't strictly the problem when you have advanced technology, the lack of area is. Not living area, mind you. Radiative area. The principle issue with advanced civilizations is waste heat and getting rid of it. Space-based civilizations in orbital habitats can not only build more living area (thousands of times more using just asteroids) but also more efficiently rid themselves of waste heat. Many megastructures do require cannibalizing a planet's worth of mass - but many more do not. For example, some people might call a Stanford Torus a megastructure, others may not. In any case, it is far easier to find and station-keep with an asteroid than land on a planet - one requires a completely different system from the vehicle that crossed interstellar space, one could use the same technology. Generally reducing system complexity is of high importance (though any settlement mission will be one of high complexity). Terraforming is an immensely wasteful and resource intensive process that requires an industrialized, if not settled, solar system - at least with current technology. It is far cheaper to build orbital habitats from asteroids. That is to say all of the advantages you mention also apply to orbital habitats, and other advantages do as well. Planets also make easier military targets (thousands of kilometers in diameter, predictable trajectories years in advance), not to mention a civilization may eventually desire to dismantle the planet in question in order to gain more resources. If it's suitably energy-rich then this is a more efficient use of the planet than settling it. No, it doesn't contradict my point. RKVs across interstellar distances are indeed effectively useless. No, the best thing to get them to those energies is not antimatter propulsion - indeed antimatter propulsion is an immensely wasteful concept. You already have the energy to create the necessary antimatter and the industry to create large numbers of particle accelerators to mass produce antimatter if you're even considering it - so why not use particle beams and magnetic sails? Some concepts enable ridiculous accelerations and there's no theoretical limit to vehicle energy, only physical ones like how much energy is available. Jordin Kare proposed the "SailBeam" concept that can accelerate objects fast enough to reach relativistic energies in less than a second (whether or not this is the proper frame or the frame of the accelerator wasn't clear to me - though the difference doesn't matter at that point). Antimatter is only something an energy rich civilization would use - and by then it has better options. Space to orbit weapons are irrelevant - as both the launchers and the targets are in space and in orbit. I suspect you meant surface to orbit weapons. Such weapons are also irrelevant to a civilization that lives entirely in space and only maintains a presence on planets to research and harvest them. Indeed attacking planets may actually help your enemy as it would disassemble it for them - unless you put enough energy into it so that large amounts of the planet's mass exceed stellar escape velocity. Antimatter is not the ultimate weapon even as the warhead of a rather conventional missile - yes you can get large yields with small amounts of mass, but the relative expense makes antimatter useless as a weapon since thermonuclear warheads or even just fusion boosted fission warheads are immensely cheaper. Indeed bomb pumped lasers may eventually be developed. But this still only applies to planetary or maybe interplanetary warfare, once you're an energy rich civilization war becomes very wasteful and increasingly useless. Yes, the best way to conduct interstellar war is with fleets sent to the target. Which are then promptly destroyed by the target system's beam-launchers, lasers, or specially built defense systems. Beam-launchers and propulsion lasers also make suitable weapons. Not to mention short-range RKVs using a derivative of Kare's SailBeam. The fleet will be easily visible, with limited options to maneuver and thus easily predictable trajectories. Even just flooding the region with "stationary" particles would deal immense damage to the attacking fleet. And since the attacking fleet will always have less in terms of resources than the target system the target system will always win. Interstellar warfare is wasteful and useless.