Seret

Lots of satellites blink. That's the main way you spot them.

Life cycle analysis is routinely used for PV, and doesn't result in any unpleasant surprises.

I'm not a marine biologist but I'm pretty sure algal blooms only happen in nature due to an imbalance in the system, and are pretty lethal for a lot of marine life.

That's actually a really good point. It's not just the energy sector that emits GHGs.

The issue isn't efficiency really (although it's nice to have) it's that hydrogen just shifts the emissions elsewhere in the system. You still have to actually deal with them. That doesn't mean it's a bad idea. Centralising carbon emissions at power plants where low-carbon fuels or maybe CCS can be used would allow us to substantially decarbonise hard problems like transport. But until we've done that hydrogen isn't actually any cleaner than current options like oil.

Sure, but where do you get the hydrogen?

No, the theory is based on solid historical data. Some parts of the world (such as the US) have already gone through peak oil. The situation on the world scale is likely to have something of a longer tail due to things like tertiary recovery, but you can't fight the economics and the physical realities. The easy stuff gets dug up first, then it gets hard and expensive.

Was that directed at me? The fact remains that we're burning it faster than it's being created. Estimates of reserves always climb, if only because we develop new methods to locate and extract them. That doesn't change the fact that they're finite. Finite resource, rising open-ended demand; it's a no-brainer.

I do only use three mods: Kerbal Alarm clock: essential for running more than one interplanetary mission concurrently IMO Kerbal Engineer: numbers! Mechjeb: I chop and change between KER and MechJeb for data, so tend to have both installed. Can't be bothered with part mods, they're a hassle.

This. Even if you ignore climate change completely it's clear that our energy systems are unsustainable long-term. Energy demand continues to rise, and fuel reserves are finite. Our current system clearly only works as a temporary stepping stone on the way to something more rational. It's not a question of if we have to change our energy systems, just when. Why not start now and make a gradual transition instead of having a mad panic later?

How modest of him!

Ideally they aren't mutually exclusive. Profits and self-interest are extremely good motivators. Private industry drives lots of innovation. All the technology in the computer you're reading this on was developed by private companies. Most of the great engineers of history (eg: Ford, Brunel, Edison, Marconi) were working in the private sector.

One way to generate a long password that's easy to remember is to use a sentence. For example you could use: "I live in a blue house with my son. His name is Bob and he is 9 years old.", taking the first letter of each would generate "Iliabhwms.HniBahi9yo.". That's a reasonably strong password, and should satisfy any complexity requirements while being quite easy to remember.

You're right of course, but there are practical problems. Ideally we'd be taking a two-pronged approach: Stop emitting carbon Remove the excess carbon already in the cycle The problem is that we simply lack the competencies for the second part. That's slowly changing, ten or twenty years ago if you mentioned geoengineering people would think you were a crank, now it's at least being discussed. The problem is that it requires massive international cooperation, it's incredibly risky, and confidence is low. We unfortunately lack a scale version of the Earth to do testing, so you'd have to be damn sure of your models before you try it, because the problem with testing your assumptions live is that you need to do it at full scale to get any effects. Getting it wrong could be immensely destructive and we've already proved we don't understand the feedback systems in the biosphere well, so we need to approach it cautiously. It's not something we're going to be doing on a globally significant scale in ten years, or twenty, or probably even fifty. You only need to look at weather forecasting and the arguments over the IPCCs models to see how immature our understanding of the full range of processes (including complex feedback) in the biosphere. Our models are limited in power, although improving rapidly. However, the Butterfly Effect does restrict the distance we can model into the future, and that limits the confidence we can have in the idea of global-scale geoengineering. TL;DR: We can reduce emissions, we can't clean up the carbon. So we're doing what we can. A long time. The deep sea and seabed are the biggest sponge we have for carbon. One possible problem with ocean sequestration is that it looks likely that we'll start dredging up the methane hydrates at some point. IMO it's likely that we'll dig up and emit all the carbon we can get our hands on. As long as it's profitable to burn hydrocarbons people will do it. We need to develop alternatives that are financially attractive to prevent them from doing this. We need to prepare for the effects of emissions if they don't, and in the long run we need to find ways to remove and sequester the carbon they do emit. It's not going to be easy, and it's probably going to take centuries, but we really don't have a choice.

Loving the colloquial phrasing of the title and OP, btw

The camera view is set to the centre of mass, but thrust and especially lift could be handy.

Sure, but for the phase of development they're at currently they are fully funded. You can't say whether or not they'll get ongoing funding. SABRE is viable technology without Skylon, they've already monetised some of the patents (they're selling precoolers to industrial users) and there could be a market for SABRE engines to other customers. I agree with you that Skylon is probably vapourware like HOTOL before it, but it's not accurate to say that REL currently aren't managing to attract investors.

They actually do have funding so far, including from the UK government. There doesn't seem to be any reason to think that SABRE development is short of funds. AFAIK they've also got enough to cover the early work on Skylon they've been doing. Personally I'm still sceptical that Skylon will ever come to be, but there's interest and investment in SABRE so far, so who knows.

That might explain some of his behaviour, but I think a fair bit of it was just down to him being a jerk.

Indeed, but delivery of crew and replacement modules to the ISS is one of the SLS Design Reference Missions: Basically they're keeping SLS on the sideline in case the Commercial Crew Programme doesn't come through. That looks pretty unlikely to be the case though.

Unlikely. REL themselves stated that their schedule had slipped out to 2021-2022 as of three years ago. So about seven years is the lower bound, with the actual time likely to be somewhat longer. These projects always take longer than anticipated. Unfortunately it costs thousands of times more to get it to space than it does to plonk it on the ground. You'll produce far more electricity by spending the same money on ground-mounted PV than shooting it into space. The economic case against space-based PV gets even worse as the price of PV cells comes down (which it has) and the cost of mass to orbit doesn't.

What does your book of bad arguments say about correlation and causality?

Crowdfunding isn't a good business model for an ongoing business, it's good for raising capital for a product launch or a startup, but after that you need to have a conventional way of generating income. In space that either means you're in the business of satellites, or you're doing science and exploration with funds granted by a benevolent government. What would investors get for their money? There's a limit to how much money you can raise from pure benevolence.

AIUI lobbing things into LEO is the backup plan for it if the fancy payloads don't materialise.

That's the theory, the practice has proved somewhat more difficult. Eventually everybody will just have to bite the bullet and push through proper long-term storage facilities. I suspect most countries will have to build their own, I can't see many folks being keen to accept everybody else's waste. Even though fusion plants won't generate the high-level wastes we're stuck with those generated by existing fission plants.