Posts by John Robson

using != taking

Rooftop solar takes alot of land, but by definition it's land that already has buildings on it...

Re: Fuel usage

They did look at an emergency ascent solution - which was completely batshit crazy, basically a platform they'd stand on in their eva suits and steer by leaning...

Re: Why the Moon?

There is always no data to start with...

That's why I wouldn't advise it until we have some better understanding of the long term effects of low gravtiy on growth...

Early data (https://www.cell.com/iscience/fulltext/S2589-0042%2823%2902254-X) suggests that mammalian embryos can develop in microgravity, which is likely far more challenging than merely low gravity

Re: Why the Moon?

Would you consider the ISS a permanent base in LEO?

Because they contend with even less (effective) gravity...

No idea why bearing children would be particularly scary, I mean it's not something that I'd advise until we have some better understanding of the long term effects on growth overall...

Re: Tintin

"The reason Lunar Orbit Rendezvous was chosen: immensely more fuel efficient, this cheaper."

And it's not actually cheaper if you consider the possibility of complete reuse of the vehicle by not dropping stages all over the earth moon system.

We got back ~5.5t of the saturn 5 stack, throwing away 200t (and fuel).

If instead you launch using starships then you get back *all* of the spacecraft, just using fuel.

Ok, you use more fuel - but you also have more mass to the lunar surface...

HLS is looking at ~100t payload to the surface, the uncrewed version of Apollo was looking at 5t - so that's twenty times more payload.

Assume 12 launches needed then that's 4,800t each, and 1200 extra in "payload" fuel to refuel the lander in orbit - that's 58kt

Apollo used about 2.5kt of fuel, multiply that by twenty to get the same delivered mass is 50kt, slightly less, but you just threw away twenty full stacks of SaturnV.

I'm actually surprised how close it is - the basic "bigger rocket is more efficient" comes quite close to wiping out the "six stages" efficiency of the apollo scheme.

And the reusability plays a larger role than you might think in the total cost. Fuel for the SpaceX stack is about a million dollars, but they have 39 raptors, which SpaceX are aiming to bring the cost down to a quarter of a million dollars - if the *smash* that goal and bring it down to $100k then they'll still have $4m of engines alone on each stack... ignoring everything else which makes up the rocket. Being twenty percent less fuel efficient is clearly cheaper than throwing away the engines.

"Please define 'waste of energy'. How about we ban all motor racing, NASCAR and F1, surely the gas/petrol used in those is a 'waste'; no - unless you can convince me of the benefit to humanity of allowing it."

Well there are some benefits, though how much they actually benefit us is questionable.

Certainly there are some efficiency gains which have been passed down from sports like F1, as well as such innovations as ABS, and materials engineering research enabling much larger carbon fibre structures.

If we didn't have ABS then there is a good chance the people would simply have to drive a little more carefully, but since risk homeostasis exists... we can't have both :(

Re: Why the Moon?

"Hence noi mrrors on the Moon!!"

Except the mirrors which the apollo program took there, and are still in use to this day?

"So why go?"

Because people can still do things robots can't, and because developing the technology for this enables other missions as well.

One could argue the world would be a better place if Columbus had sailed back and noone had returned from Europe to the American continent, but going to the moon is a stepping stone, or a pathfinder.

Of course if you do set up a permanent moon base then you don't need to keep earth levels of bone density, just not needed - and in all likelihood early bases would be subterranean (sublunarian?), even if that's only partly underground, and partly with rocks and dust overlaid.

"The Monn is an awful place to live or work:"

So was your office in the jurassic period... in fact it probably wasn't a great place to work a hundred years ago.

Re: Tintin

It's a staged descent from LEO, and an ascent only to LLO.

The 33 engines on the first stage acheived a full duration burn - in what way is that a failure "similar to the N1"?

And suggesting that starship is "destroying the Earth's resources" is somewhat hyperbolic don't you think?

Yes, there is some material scrappage going on at the moment, but the intent is explicitly not to waste resources, they're aiming to reuse the thing - repeatedly.

And when they use in in an interplanetary setting they intend to refuel it from local resources...

Re: With apologies to Mr. Lehrer

And you should apologise for so brutally ruining a perfectly good verse.

Note of course that Elon intends Starship to land on the bloody launch tower, whilst every other operator intentionally throws away every launch vehicle after one use.

And yes I know it was meant as a joke... meant is doing alot of heavy lifting in that sentence though.

Re: 150 tonnes of fuel and oxygen combined

I suspect you've just remembered the amount of RP-1:

Badly written sentence in the first google hit splitting the masses.

"Both stages of SpaceX’s workhorse Falcon 9 rocket guzzle about 312,200kg of LOX and 186,006kg of RP-1 throughout a flight."

That's about 37% RP-1, so 146t of 393t - that's close enough to 150t

~160 seconds to do all but a few tens of tons of propellant...

If that's ~65 tons burnt then it's 32TJ, or 200GW, *way* more than the UK grid ever pulls....

Those raptors are seriously powerful ~ 650kg/s mass flow, of which ~140kg/s is Methane, so that's ~7GW each... two and half times the largest power station in the UK (https://electricityproduction.uk/plant/)

And there are 33 of them... which would add up 231 GW - so that matches the initial estimate closely enough.

Re: ablative surfaces

From: https://www.nasa.gov/humans-in-space/after-15-years-1000-tests-orions-heat-shield-ready-to-take-the-heat/

"The Apollo crew module’s heat shield relied on a material called Avcoat to beat the heat. It’s an ablator, meaning it burns off in a controlled fashion during re-entry, transferring heat away from the spacecraft. "

"Following the Artemis I mission, the Ames team will also harvest samples of the charred Avcoat tiles to analyze how the material ablated."

Ablated - i.e. shed bits to carry away some of the energy of reentry

The shuttle however had a Thermal Protection System, consisting of High/Low Temperature Reusable Surface Insulation tiles - note the lack of the word ablative, because it wasn't an ablative system.

Space Explored has a useful paragraph:

"An ablative heat shield, as SpaceX uses on Dragon’s primary heat shield, works by heating part of the material itself into gas and burning away, thus moving the heat buildup away from the capsule. By comparison, a thermal soak heat shield – as was used on the Space Shuttle – is designed to absorb the heat and radiate it, without the material burning away."

Let's ignore active cooling etc, since AFAIK noone uses it yet.

It only needs to be strong enough to do it's job - it's not a structural element when it's open, and strengthening it would add mass that isn't needed.

Fuel efficient?

AtlasV takes 305 tons of propellant (first and second stage, no boosters) for a 12 tons to LEO

Soyuz takes 4*40+96+22 = ~280 tons of propellant for ~7 tons to LEO

Falcon9 takes 400 + 92 tons for ~22 tons to LEO, or 18.5 tons when the booster is recovered.

Those are mass factors of 25, 40, and 22 (26 with recovery).

Starship is 3400t+1200t, with a payload capacity of 150t (250t if expended)

That's a ratio of 18.5 (better than any of the above) when expended, and 31 when fully reused (middle of the pack, but without disposing of all the engineering every time).

Re: Space station video

Then look at a weather sat - geostationary and with a good view:

e.g. https://dmn-dallas-news-prod.cdn.arcpublishing.com/resizer/v2/V6JEJGVAORHKFG5X5OMYFEK6JQ.gif

(Article at https://www.dallasnews.com/news/weather/2024/04/08/after-the-total-solar-eclipse-these-satellite-images-from-space-show-path-of-totality/)

Re: Space station video

You need a significantly higher viewpoint than the ISS then...

Are you browsing using links?

Re: Is it just me...

Well yes, I can't imagine how a car would work if the app didn't know what the battery SOC was...

Oh, no wait a second the only thing that wouldn't work is the app, the car would be fine.

Re: off peak power

Absolutely - though it's pretty simple to argue that a system that delays that analysis to overnight wouldn't adversely affect outcomes.

I mean the AI result needs to be checked by a specialist human anyway...

"In the US, preexisting conditions are covered if the patient was insured for them (by someone else) at the time the condition was noted/diagnosed."

As they are by BUPA in the UK... 35 years on and they're still covering, despite me being off book for several periods when my (varied) employers used different providers.

No insurance company will cover you for something that's already happened.

Oh my house burned down, can I have some house insurance please, yes I'd like fire coverage.

Re: "is trying to lock future governments into"

No he hasn't ruled out reclaiming money lost to fraud.

And as for the not raising taxes... he doesn't need to, the tories have already raised them massively, he just needs to cut out some of the tax breaks which mean that the ultra wealthy don't actually pay their fair share.

What he does need to do is win the election.

Re: "is trying to lock future governments into"

What are you smoking?

Re: Anticipating grid failure is more like it..

"Yet 'renewables' were supposed to reduce our energy costs, and yet they haven't. Why is this, I wonder?"

They have - you can tell because the price is pretty much inversely correlated with the proportion of renewables on the grid - more renewables = lower price.

What do you think the operational cost is for a solar farm or a wind turbine? What's the delivery cost for wind/light, I bet even Amazon can't beat that price.

Re: Anticipating grid failure is more like it..

So you don't understand the energy market, climate change, international trade, physics...

Anything I missed - I'm pretty sure you just got a bingo card of deliberate ignorance.

"Intermittent 'renewables' increased the dependency and demand for gas, so gas power could make up for all the times when the windmills weren't spinning"

So if it weren't for those renewables the gas turbines wouldn't be needed at all?

I really don't know why I bother... you're clearly not capable of critical thought.

Re: Anticipating grid failure is more like it..

You've never actually worked in the electricity supply industry then.

Very little inertia is actually required, and yes - buying electricity when there is a surplus and selling it back when there is a deficit is part of the picture now, it has been for many decades.

Renewables don't "create instability", they provide clean energy in a predictable fashion throughout the year. That prediction might only be out a few days for the highly accurate models, but it's enough to provide a very substantial portion of the energy we use. The larger, and more distributed, the renewable generation the better.

Inflation was not being caused by the wind becoming more expensive, that was actually gas - you know, that non intermittent, completely stable, resource you profess your love for. Of course it's only stable if you can get it, and it's availability is massively at the whims of foreign powers. It's also completely fucking the planet we live on, to the extent that we won't live on it for all that much longer if we carry on using it.

The world has changed since the start of the industrial revolution, do try to keep up.

Re: Anticipating grid failure is more like it..

So you build your offshore farm with an onshore module, which is the anti-curtailment module.

It is used to store energy that can't be sold, and then to sell it when it can be sold.

That could use batteries, or hydrogen, or some other form of energy storage.

Re: Anticipating grid failure is more like it..

No - I'm old enough to remember a government that wasn't only concerned about internal squabbles, and actually had a legislative program.

Besides which you already don't need a sleeving contract, as mentioned.

Re: Anticipating grid failure is more like it..

You know what's great about legislation - you can change it. The laws of physics, not so much, but contract limitations - absolutely.

Of course you can also do direct PPA, colocate the generation of electricity and hydrogen, or colocate them enough to have a dedicated cable.

Re: Anticipating grid failure is more like it..

"Something that seems to get overlooked with 'ideas' like using wind to make H2 etc."

Not overlooked at all.

There are plenty of issues with hydrogen as long term storage, but "currently you can't sell electricity direct" isn't one of them.

Re: "Those would be big no-nos under US law"

So you have a choice between earning a "barely scraping by, with help from friends" job or no job at all...

No - minimum wages need to be enforced; it's clear from round the world and all across history that the minimum wage needs a boost.

Hell most people who claim universal credit in the UK are in work, just not work that pays enough to live... i.e. the government is subsidising the profits of exploitative companies.

Re: Open Source developers

Open source != amateur.

Whilst you can release code that you write as an amateur as open source, if it becomes popular then you're going to need to spend more and more time on it, and being paid for that time isn't an unreasonable expectation... particularly when others are making substantial profits using the fruits of your labour. And for many of these larger projects it's not just one person coding them on a couple of hours in the evening in their back room.

The alternative is that the demands of users take up too much of your time and you just drop it...

Re: Perspective

"Yes, but you could calculate what it is exactly, for your desired parameters. For instance how long it can be open before temperature drops by one degree."

Hardly takes a phone - an ESP8622 is perfectly capable of reading a DS18B20 to determine the outside temperature, which is all you need to make that calculation - not that it's a calculation it's a simple lookup.

"It is certainly being less wasted than doing nothing in the landfill..."

So recycle it instead. The article headline is very misleading, as illustrated by the first sentence contradicting it directly.

We're generating e-waster faster than we *are* recycling it... not faster than we *can* recycle it.

62 Mt of waste - 14 was recycled through documented operations, 16 through developed waste management, 18 through low quality recycling (probably releasing some of the less nice chemicals) and 14 to landfill.

We don't actually need to increase recycling capacity by that much to do alot better.

Re: Perspective

That memory/cpu is completely wasted on something like a door openner...

I know you were exaggerating somewhat, but there are real cases where the phone could be a reasonable thing to reuse (currently using two old iPhones as roving NDI cameras for a streaming setup for instance).

Calculating how long the door should be open is easy - it should always be open for the shortest possible time.

Re: Perspective

To be fair it's trivial to control a garage door with an ESP8266 or similar, certainly no need to have the guts of a phone.

The phone is already a decent form factor, all we really need is unlocked boot loaders, and some binary support for the soc.

Re: Hmm

No - it's just what we're used to over the last 14 years