* Posts by John Robson

5142 publicly visible posts • joined 19 May 2008

Anyone want an International Space Station? Slightly used

John Robson Silver badge

Re: Mir

Yes skylab was, but it didn't land - components did... and equivalent components exist on the ISS.

I even said split it up, you just don't need to throw it apart, orbital mechanics will separate the modules and they will probably come down across such a long reentry path that it's inevitable that a substantial piece of something will land somewhere populated.

John Robson Silver badge

Re: Mir

At which point you don't need to do anything - just split the station up - no need to fling anything anywhere, it will de orbit, and if you're so sure all the pieces are sufficiently small... no harm done.

But if you look at what landed from skylab... it was things like individual oxygen tanks that landed, and whilst we were lucky that that was deposited in a pretty isolated area (albeit less isolated than the deep ocean) you don't want to take that chance with the whole of the ISS.

You want to be very deliberate about where you deorbit each piece.

John Robson Silver badge

Re: Mir

Canadarm isn't really able to "fling", and of course lowering the orbit of one module would raise the orbit of the rest, making each successive module harder to "fling".

I expect disconnection and individual controlled reentry is the plan - but someone might come up with something more interesting.

Scott Manley

Basically you can change orbit slightly, and things will de orbit, but not in a controlled manner (not important for small things)

The Moon or bust, says NASA, after successful SLS/Orion test flight

John Robson Silver badge

Re: That is how it is done

They also tested an EVA as a method of transferring in the event of a docking tunnel failure... so they had two methods available.

John Robson Silver badge

Those planes have to actively fly a parabola, since there is so much pesky air in the way

John Robson Silver badge

So they are - my error.

Even 30% cheaper is still more expensive than a single reuse, so I'm still not convinced.

John Robson Silver badge

It was one of the proposals... but I'm sure there would have been enough proposals put forward to come up with a workable plan if they had wanted to.

Those engines are marvels of engineering, it really does seem to be a shame in today's world to simply ditch them.

I appreciate that reuse wasn't seriously an option in 2011, but we're a little way on from that now, and to be throwing away engines that you've forgotten how to build is so badly self limiting.

John Robson Silver badge

Re: Breaking things

That's in the library now...

John Robson Silver badge

Who said it had to be caught by helicopter?

John Robson Silver badge
Facepalm

If only the engines were built to be reusable...

John Robson Silver badge

Re: build an emergency egress system at the launchpad

SpaceX have, I think, just used their abort system - if things go wrong, let's get the crew out of there *really* fast, not have them unstrap, clamber to the door then take a zipline to a bunker.

John Robson Silver badge

Since SLS is currently utterly reliant on SpaceX's Starship to actually get to the moon (rather than just near it)...

I would actually pick the dragon, it's a well proven ship to get to orbit - and if I recall correctly the heatshield was originally designed to cope with lunar reentry. SpaceX agree: "The Dragon spacecraft is capable of carrying up to 7 passengers to and from Earth orbit, and beyond" That 'and beyond' is important.

Of course the current heatshield might not (mass being expensive and all), but it's a relatively small change to a well known system.

John Robson Silver badge
Boffin

Re: Caining it Moonward

"The Artrmis mission remember, was coming in hot - damn, hot, real hot! Hotter than a hot thing on planet Hot. Beyond known heat stress data is what I'm getting at."

Well, entry velocity was 24,581 mph for Artemis 1 vs 24,816 mph for Apollo 10 - that means Apollo had ~2% more energy to deal with per unit mass.

Artemis is only ~10% more massive ~20t -> ~22.5t (i.e. 10% more energy)

Apollo was only 80% the diameter (4m vs 5m), so presumably loads on the heat shield would be 50% more? (not run the physics on this one)

Basically it's within reasonable bounds of heat loads we dealt with 50 years ago.

John Robson Silver badge

Yes, but that would require production, or planning.

And SLS isn't the best way to get to the moon any more... whether it was ever the best way to get to the moon is questionable.

And it does depend on the modification... and the cost of testing.

Yes, Samsung 'fakes' its smartphone Moon photos – who cares?

John Robson Silver badge

It's one of the most obvious targets for this tech... it's reasonably easy to check that the think looks like the moon, and since the same face is always pointing towards us... you know what it's going to look like. The phone knows the time, the location, the orientation of the phone... and the available high res imagery of the moon at all phases is pretty good.

Got to be one of the easiest AI tasks ever... but it is pretty deceitful in many ways, and it risks the next dataset being trained on what an AI thought the moon should look like...

Don't worry, that system's not actually active – oh, wait …

John Robson Silver badge

Re: pizza is the perfect food

Yep - the safety of a consumer unit (distribution board, fuse box, call it what you will) is, like so many things, a compromise.

I think the requirement not to lose structural integrity under "normal" domestic fire conditions is quite high on the list, but if the monkeys with insulated screwdrivers don't torque the connections decently, and with the cable/busbar in place, then it all counts for naught.

John Robson Silver badge
Pirate

Re: pizza is the perfect food

That's horrifying in so many more ways than I want to think about..

John Robson Silver badge

Re: pizza is the perfect food

Surely you need a label on the shelf "head height"?

Or a box of heads underneath?

John Robson Silver badge

Re: pizza is the perfect food

That's why they are required to have a buttered slice of toast strapped to their backs...

John Robson Silver badge

Re: pizza is the perfect food

More importantly it is likely to increase compliance if the rules are shown to have a reason.

I mean we all know that there is some maximum gap allowed in banister/landing/balcony railings, but it's easy to remember the 10cm rule when you remember that it's that so that an infant's head can't fit through.

John Robson Silver badge

Re: pizza is the perfect food

They'll get replaced over time - given the number of crumbling Bakelite consumer units still installed they really aren't the things to focus on.

John Robson Silver badge

Re: pizza is the perfect food

And some are daft as can be - and some get changed, telling you how daft they were...

Consumer units used to be plastic, now they must be metal.

Turns out that being conductive is only a minor inconvenience compared with the consequences of a consumer unit melting in a fire (particularly the bit around the incoming tails).

The cause of last December's failed satellite launch? Nozzle material, says ESA

John Robson Silver badge

I'm surprised this didn't show up in test firings to be honest...

Even the lunar ascent engine had test firings - not the actual ones used but ones produced the same way, they were strictly one time firings only.

Rolls-Royce, EasyJet fire up first hydrogen-fueled jet engine

John Robson Silver badge

Anyone considering using fluorine as an oxidiser should be required to read Ignition.

And then to explain very, very, carefully why there is no other option...

Used EV car batteries find new life storing solar power in California

John Robson Silver badge

Re: Nonstandard units

Or short term storage options...

John Robson Silver badge

Re: Nonstandard units

Your understanding is woeful then.

8 year warranties are standard, and 200k miles+ is not rare.

Battery replacement simply isn't a thing that people with a EV have to think about, any more than you think about engine repacement

John Robson Silver badge
Coat

Re: There's no denying it: EVs are here, and they're gradually displacing more gas-powered vehicles.

You've nearly got a full house of FUD there.

EV market is currently growing strongly, at the expense of flammable/explosive liquid based vehicles.

Limitations:

- Climate (don't buy ICE, go EV)

- Chargers (not perfect, but getting better each year. Soon you'll be bemoaning the lack of liquid fuel dispensers)

- Cost of electrons, I get about 2p/mile, using current diesel costs (£1.70/l) and my previous vehicle's economy (38mpg, call it 40) that's 20p/miles - literally ten times the price.

Of course I get more expensive electrons on a long journey - say a journey that's fully twice the range of my battery - I pay 2p/mile for the first battery then 65-75p/kWh -> 16-19p/mile for the second (and a little spare) so I pay ~9p/mile for the rare exceptionally long journey, still half the price of liquid fuels.

- Range. You need to stop every so often, but 350+ days a year I don't spend any time charging - not even a "quick" ten minutes at the smelly garage once a week.

- Horrendous accidents aren't actually made any better or worse by EVs - slightly more energy to dissipate, but not all that much.

- I've never actually seen anyone melted by a battery, plenty of images of people self immolating with your choice of "safe" propulsion.

John Robson Silver badge

Re: but, but, but...

Better make sure not to have a gas supply in your house.

LiFePo (more common than plain LiIon) are much more thermally stable, and the charge/discharge cycles are usually not steep (remember these are packs capable of 100kW or more, and likely only being used at 3-5kW in a domestic environment).

John Robson Silver badge

Use the battery in an EV to supply a load (i.e. plug something in, not grid synchronised) or your home (grid synchronised like a portable home battery) or the grid (as V2H, but with grid awareness, so that it can actually arbitrage energy on the grid).

John Robson Silver badge

Re: Nonstandard units

"The other element that is being ignored here is that all these EV car owners have to spend out on a new battery. Makes me want to re-think the economics."

Because after a few hundred thousand miles the engine in your ICE has required no maintenance at all, and is still in pristine condition.

Hubble images photobombed by space hardware on the up

John Robson Silver badge

Re: Doubling of sat streaks

Nope - but it can't track fast enough to be useful looking down.

JWST can't turn around, that five layers tennis court sized sun shield isn't just for show.

John Robson Silver badge

Re: Doubling of sat streaks

One would hope that hubble spends most of it's time not looking down, so there's an awful lot of space that isn't going to have any starlink sats in view... in fact it's only really looking in either polar direction that you'd expect starlink to be an issue at all... of course there are many more geostationary sats as well...

Warning on SolarWinds-like supply-chain attacks: 'They're just getting bigger'

John Robson Silver badge

I was going to say citation needed but:

https://www.theregister.com/2020/12/16/solarwinds_github_password/

Who writes Linux and open source software?

John Robson Silver badge

Re: I knew this would end in tears.

I did indeed - but it's a hell of an allegation without any basis, particularly given that such evidence should be pretty easy to find - it's not like the kernel is closed source.

John Robson Silver badge

Re: I knew this would end in tears.

"Linux kernel is now a worse piece of spyware than Windows"

citation needed.

Japanese balloon startup wants to 'democratize space' – with $180,000 ticket price

John Robson Silver badge

Re: Progress

You can view the curvature of the earth for much less than that...

https://www.youtube.com/watch?v=xpUcZXiKtfU

Biden: I want standard EV chargers made in America by 2024 – get on it

John Robson Silver badge

Re: Of course chargers must be standard

Except that in Japan ChaDeMo is still common, in the EU Type2 is the standard, and in China they do their own thing as well.

It's not like it's difficult to provide different options on the same car, heck Tesla already does it.

John Robson Silver badge

Re: CCS DC cables are awful

I think you misread the comment - there is no such thing as having to bring your own cable to a DC charger in Europe.

John Robson Silver badge

Re: What about a converter?

Car doesn't need to keep a card number - just need to be able to send an invoice based on the VIN/registration.

John Robson Silver badge

Re: 3-Phase?

So it's probably a wash in the US... Type2 can do three phase, and there are a number of cars (not as many as there maybe should be) which can use three phase AC for substantially faster charging without the expense of a DC charger.

It's not all that useful at home (relatively few domestic properties have three phase supplies), but would be really good for many destination chargers - particularly for relatively short stay destinations - making it three times more useful to plug in whilst shopping for example.

John Robson Silver badge

Re: Good

Indeed - it's still an obvious miss from the CCS standards (and the Type1/2 AC standards as well)

They've minimised the data transfer to make it "simple", ignoring the massive benefit from having an integrated system.

John Robson Silver badge

Re: 3-Phase?

But the connector is the same as their AC charger connector... they are dual use pins.

And they can only do single phase AC, since there are only two pins.

John Robson Silver badge

Re: CCS DC cables are awful

Nope - they are using metric with a bunch of conversion factors now... all their measurements are now defined in terms of the metre/kilogram (stupidest SI unit ever)/etc

John Robson Silver badge

Re: Good

Well the US currently has two standards for DC charging (Tesla and CCS1), and two for AC charging (Tesla and Type1).

Tesla ship a dongle to allow their vehicles to use CCS1... so it should be easy enough to add CCS1 cables to tesla stations.

You only need to bring your own cable to a destination (low power) charger, this prevents cables clogging up pavements and getting damaged when not in use. All DC chargers come with a tethered cable, some of which are even liquid cooled. This is because they operate at a much higher voltage and current, and are therefore pretty rugged, and reasonably heavy.

The car already does the "what speed can I charge at" bit - the DC "charger" is really only the power delivery half of a charger, the brains are in the car already.

The AC charger is literally a supply (single or three phase) with a bit of communication to say "don't pull more than my circuit can handle" to the charger on the car.

Automatic billing is such an obvious miss - you only need to have the VIN or registration as an ID, and billing can happen easily based on that (generally by login, but if not paid inside 24 hours then via the DVLA or local equivalent).

Most charge stations have multiple connectors available, with one or more "chargers" having a ChaDeMo and a CCS cable attached, just pick a unit with your connector and charge. Much like petrol pumps have both diesel and petrol heads - and one of those won't fit in the other (though you can get it wrong the other way round)

John Robson Silver badge

Re: Of course chargers must be standard

ChaDeMo isn't all bad... it has long supported bidirectional charging, which is a key technology moving forward.

John Robson Silver badge

Re: Of course chargers must be standard

Yep - but someone had to do the first charging standard... and Tesla had wide rollout before any other standard was, well, standard.

I quite like the tesla connector in some ways, having dual use pins isn't a bad idea - but it doesn't allow for three phase charging as far as I am aware (not that many cars avail themselves of three phase anyway)

John Robson Silver badge

Re: CCS DC cables are awful

To be fair CCS1 is pretty widespread in the US - basically for everything other than Tesla.

Tesla use CCS2 in the EU, so it shouldn't be too hard to use CCS1 in the US - just add an extra cable to the charger (they already sell a dongle for existing vehicles).

John Robson Silver badge

Re: CCS DC cables are awful

AC "chargers" are just suuplies

DC chargers are half a charger, with the brains still in the car, but the voltage conversions and current regulation are all done off board.

Could 2023 be the year SpaceX's Starship finally reaches orbit?

John Robson Silver badge

Re: Gwynne Shotwell

"my money is on a RUD on re-entry....."

So long as any RUD is far enough away from the ground that stage zero isn't damaged by a RUD (it will likely need some work after the launch anyway) then we can all be happy.

They'll get useful data - I'm at this point assuming that their telemetry will be good up to failure as well.

John Robson Silver badge

Re: Starship?

And very early on Big Falcon Rocket (not that anyone used the Falcon designation)...