Posts by John Robson 5250 publicly visible posts • joined 19 May 2008
You don't need the same pixel density as something handheld on something a few metres away.
4k at 50" is about 44" across, and 3840 pixels, that's under 90ppi.
A larger screen obviously has even lower density.
Of course Wii controllers aren't smashing into TVs as often any more... so this is probably limited to to rollable displays (which could be really quite nice in various circumstances, but are almost certainly niche to say the least)
You've got months to compress some atmosphere into storage - only need to puff off at high pressure once a (martian) year.
So a system that puffs every three weeks or so could do one segment each time.
Obviously massive complexity and weight penalty, and there are almost certainly issues which are more significant than the lack of atmosphere.
Well clearly if you don't use 9kWh a day then you won't benefit from a 9kWh battery - That's hardly surprising is it?
And clearly it depends on which tariff you have.
"I don't think the battery will be providing 100% efficiency, especially not in 16 years' time."
Well, my calculations were based off 85% RTE, which is a reasonable estimate for a battery with half decent battery management - and I stopped after 15 years. The likely behaviour is actually longer, but gently declining lifespan.
Taking a 9.5kWh battery, at just 85% efficiency...
I use 9.5kWh at 7.5p to charge it - cost 71p - I then don't have to use (85% of 9.5kWh at 39.4p) £3.18 each day - that's £99 per month.
You could suggest that I use a "normal" tariff as my "saving", I did... but even with the pre October prices (I was on a supplier of last resort tariff) the projected saving in terms of electricity using panels/battery is enough to finance the panels/battery (with the battery actually doing the heavy lifting). If I use the current "Energy company profit guarantee" rate then I expect to be paying substantially less for electricity and appropriate finance than I would be for electricity alone.
My usage pattern actually favours the use of a time of day tariff anyway, so I'm comfortable using that direct comparison.
Projected cost per kWh, inclusive of standing charge, goes from 35.9p to 9.6p.
Ok, so how much does a 9.5kWh battery cost... About £6k installed, with a ten year unlimited cycles warranty.
It's therefore paid for itself in less than half the warranty time, whilst also giving additional protection against power cuts and increasing the value of my property...
Assume that it lasts 50% more than is warranted, and you have a 200% ROI in 15 years - or about 5% compounded annually.
Of course it also enables full usage of a home solar array - and it helps if you have other reasons to be on a time of day tariff (like an EV, or a ZEB). But there are also other benefits (like power cut protection).
There is the final point that not everything has to have an R, or be an I. You fit a new kitchen or bathroom, do you decide on an ROI, or do you get something you want, and like. Like a new kitchen/bathroom installing panels/battery systems has a direct positive impact on property value as well.
Using solar/battery does more than just give you a financial return, it also improves the grid mix, and improves your energy resilience* (protected circuits).
* I'm not going to be keeping my battery with a minimum fill level to cover any possible power cut, but I am protected in the likely event of power cuts any time up to the late evening this winter. I won't be running my oven/kettle/microwave, but that's what a gas hob is for. The boiler will have power, as will the fridge/freezer and my IT equipment (which will be behind it's own small UPS as well, to deal with the automated, but not seamless, hand over onto an isolated circuit).
New company wanted me to start on a Friday (get the office and computer setup out of the way and hit the ground running on the Monday), old company wanted me to finish on the Friday...
Both sets of managers knew about it though - and it was for one day.
It did cross my mind that I could have simply not resigned my previous role, and I don't think anyone there would have noticed (large consulting firm I'd been TUPE'd into and then spent months not getting any work at all, to the extent that my manager frequently took weeks to answer emails about the processes involved) - but integrity put a stop to that idea...
"Raptor isn't performing at the level it needs to for it to be used on Starship"
Well, it's already comfortably over 300 bar pressure, and they've dropped the count of engines on the booster from earlier specs, so I'd take any rumours of serious underperformance with a grain of salt or two.
One thing we can be sure of... they'll always want more performance. When they start recovery they'll have to look at the performance/reliability trade off, and the more raw performance is available the better that tradeoff will be.
33 engines at about 225 tons of thrust is ~7000-7500 tons of thrust, for a vehicle that masses ~5000 tons.
That's a healthy TWR of 1.4.
Starship isn't vapourware. You're thinking of New Glenn.
Raptors are blowing up when they test them beyond previous limits - that's what test stands are for.
They have already flown a number of raptors quite successfully, so I'd not suggest that the raptors are the biggest issue.
SpaceX have a different philosophy from some of the more traditional rocket companies, but that has resulted in significantly cheaper launches, and in getting manned launches back to the western hemisphere whilst the traditional "we do all the work up front" company is still to launch, despite taking huge amounts more money to develop their system.
If a full stack fails then it won't detonate, it will be one heck of a fireball, but there won't be the mix for a detonation.
I'm not turning blue at all...
There are advantages to being outside the atmosphere beyond sharpness, adaptive optics are utterly ridiculous (that's a compliment) in both concept and execution, and make for excellent observations.
But being outside the atmosphere still offers better seeing and a wider availability of spectrum... The better seeing is probably wiped out by the sheer scale of mirrors that can be dealt with on the ground - though even the LBT mirrors are smaller than a starship fairing - and we've seen how well JWST managed to handle aligning segmented mirrors if we want to go even larger.
The real benefit is the availability of spectrum either side of the visible.
If, and it's a big if at this point, Starship really does get the cost down to Musk levels of optimism... then the cost stops being a significant issue (you're paying a pretty penny for a mirror, at that point the transport costs are high to basically anywhere you really want it, starship might not be the most expensive option).
The plan is generally to not get all the way to orbital velocity, but to get out of the pesky atmosphere (or at least high in it) without having to burn fuel (which you had to carry, and therefore burn more fuel to carry the fuel...).
Those fuel savings are very, very real.
Whether or not spinlaunch ever manage to put payloads into orbit we do at least know that the maths works.
Well as someone with a disability that makes driving much more difficult even simple lane keeping substantially reduces the cognitive load associated with driving.
If we could get a vehicle that would even just do motorway driving for us that would be a huge benefit, and it would actually be a benefit to get that on all vehicles - motorways would rapidly become even safer, and flow better.
Additionally the roads around motorways would become safer as well, since people would be much fresher and more alert.
15kW is about right for motorway driving.
350kW (the current spec) is more than twenty times as fast, so for every hour you spend driving you need to spend less than three minutes charging*.
* Obviously assumes that the battery and the mobile half of the charger can deal with 350kW - but that's the point, the charge cable is already capable of delivering more power than most cars can handle. We don't need a beefier cable, we have the charging infrastructure already, it's better battery management that is the next big thing.
Charge rates much beyond the current 350kW aren't really necessary... we're already battery limited, 350kW is 20+ miles per minute (350kW * 3m/kWh = 1400 miles/hour)
Most cars can't take that much current even when it's available (half of the charger is in the car, half is on the side of the road).
If stopping every three hours for ten minutes is too much then you probably shouldn't have a license.
One major reason for this is that an existing thermal plant (coal, gas, biomass, whatever) can "simply" have several of these delivered, and replace the boiler with steam from these.
Although reading the article... the actual reactor is 4' * 7', so the generation might well be on board the 40' container.
Possible - but for the devices in question it's unlikely.
USB-c handles up to 240W power delivery, and 40GBps of data transfer.
I think we'll be ok for a few years.
The real issue is that noone is going to want to think about designing the next connector - for anything, not just for portable devices.
My astro lecturer gave us a complete set of notes at the start of the course... with a handful of deliberate mistakes and a selection of blanks.
Enough to keep you in the lectures listening, but also enough that your attention was on what was being said rather than on writing.
"Air source is cheaper to install, but relies on a decent source of heat in the outside to work effectively (i.e. energy in to drive the reverse 'fridge needs to be less than the heat pumped into the house). In warmer climes it's OK, since the outside air is relatively warm & more humid. As it gets colder you have to drive the pump harder (more energy in) to gain an effective temperature difference, and as it drops below zero you get icing on the unit and even less efficiency, and ultimately a barely-warm house and no hot water, or lukewarm water at best and no household heating. It's very limited in applicability"
Thank goodness you worked that out before they installed them all over scandanavia!
What matters is the choice of heat pump, the refrigerant and design make a huge difference to the designed operating temperature.
As for folks in poorly insulated homes - the answer there is to bloody insulate them. It doesn't matter what heating system you use if you lose all the heat in five minutes.
Air source heat pumps are pretty much silent, they use a very large, very slow fan, and take up a relatively small amount of space - particularly in new builds which should be designed around the ASHP unit.
They also remove the need for a boiler inside the house...
Orion('s boilerplate model) has... but that's the payload not the rocket.
IIRC this capsule isn't a full Orion spec capsule.
**We** all know it's a less well built shuttle, but the claim is that it's all new...
"NASA's Space Launch System might look like a mishmash of heritage Space Shuttle parts but it's all new hardware"
https://www.theregister.com/2022/09/05/nasa_sls_northrop_grumman/
(Unfortunately not a quote with attribution, so...)
I don't recall the ICS having had a flight test of any sort either.
The odds are good that SLS will get to orbit first, but SS/SH will certainly not be beaten to landing by SLS.
Always amazes me that times when the "only" political decision is one that actually makes no sense doesn't bring parties together to go "Look, we know there is widespread fear around this - but it's actually the safest way we have to generate power. If we all keep that line and explain it then we can carry on doing the right thing"
It had been rumoured... I was somewhat shocked when Lis Truss referred to him as King Charles III before any announcement from Clarence house, and even more when the BBC picked it from that as an official source.
We'll likely never know whether he had intended to use George but decided against rocking the boat at such a time or whether he was always going to use Charles.
Getting back is relatively easy - you can aerobrake to lose most of the velocity.
Shuttle: $54k/kg
Falcon9: $6k/kg
Starship: Target: $10/kg (not 10k, 10)
I suspect Musk's aim of $10/kg is somewhat optimistic, but another factor of ten reduction is plausible.
So shuttle cargo better be worth it's weight in gold (currently $54,784)
Falcon 9 cargo is valued about as titanium (currently $5k ish?, hard to find)
Starship might be worth as much as silver (currently $589) or a little bit more than copper ($7)
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