Posts by John Robson

Re: Its a Test

Probably... and this is speculation... because it gave them additional margins to deal with potential issues earlier in the flight.

Re: Its a Test

"The better question is why they didn’t just load a mass dummy instead"

Possibly to give themselves better performance margins throughout the early parts of the flight; the extra propellant would have be used if they had had a number of engine failures.

But you don't want an untested vehicle in space with substantial propellant load, so you dump it.

They don't dump it to reduce acceleration (it has the opposite effect), and they have pretty deep throttling on those raptors - just dump some O2, then some CH4 (rather than have an extra, accidental, rocket engine).

Unfortunately the dumped oxidiser did some oxidation... and it oxidised something important.

Re: Enough with the Elon Musk Snark

No - that was the fondag, and the reinforced foundations - almost no build up at all (because of the wetlands)

They reckoned it would survive one launch, but the ground underneath didn't take the load... which meant that the concrete cracked and at that point it was always going to fail hard.

The "rock tornado" dug a serious crater as a result, but since Elon has described the SH as "the worlds most powerful plasma cutter" that's probably not a huge surprise (once the concrete has failed).

They've since installed a number of deep piles, supporting a stronger platform, with a fairly hefy bit of steel "pancake" on top of that.

And that looks like it survived just fine.

Re: Backwards

"staying true to the Raspberry Pi legacy"

I rather think that's his to determine.

If I recall correctly the intent was to concentrate on low cost machines for education... the massive take up in industry is great, but is funding that original requirement.

Us hobbyists are another group which is great, but not the original requirement.

Re: From what I can recall ....

As I said, you're clearly obsessed with the fossil fuel shills.

Re: From what I can recall ....

So your arguement is that the second hand market for EVs isn't as mature as the second hand market for ICE vehicles?

AT shows a handful of EVs at or around 3k, these are typically ~10 years old, with 40-70k on the clock (i.e. relatively young and low milage)

Putting in "newer than 2011" and "under 60k miles" so that we're comparing the same segment of ICE vehicles to EVs - the prices are ~2k, which is slightly less, but only by ~150 gallons of petrol (substantially less than the typical motorist uses in a year).

Now that's not quite fair, since the EV driver will need to charge - but that's typically ~10% of the cost of fuel... so the first year of fuel savings already make up the difference in purchase cost. (Yes, I know vimes boots apply here)

I looked at my milage for 2023, and calculated based on my previous ICE vehicle's stats what I'd have spent on fuel - the number was more than my entire (four person) household energy usage (that's gas and electricity combined), and that household usage *includes* 99% of my charging.

Re: may be zero carbon

Actually it’s often mentioned - mostly by people who don’t do their research.

The researchers find that the break even point is well under 20k miles….

Re: From what I can recall ....

Science… I don’t expect you to (try to) understand.

Re: From what I can recall ....

"* Over here, cable with BS1363 (a.k.a. 13A) plug, limited to about 3kW, and only intended for emergency use."

They tend to be limited to 10A, i.e. 2.4kW, and there is no reason for them to be "emergency use", you just need to know that your wiring is appropriately sized...

That limit is to give some safety factor for household wiring.

Mine has 32A rated cable from the CU to the socket, then 16A rated to the charger. The (decent quality) socket and plug are also quite happy at 10A, no significant heat output - so the only "weak" point is the fuse - which is quite happy doing 10A all day long.

Re: From what I can recall ....

Ah yes, the "but this mars bar can support one person for an hour, so it must also be able to support 1 million people for a whole year".

Now *that* is hyperbole.

Re: "Cost and maintenance are also an issue"

"it's only a tiny, tiny part of the problem"

Well then let's not do anything ever, because no one thing is a single solution to all man's ills.

It's not a huge rollout, but it's a small piece of a larger puzzle.

I assert that you're overstating the scale of the issue:

RAC data suggests just 30% of households don't have capacity for off road parking - and national statistics show that 20% of households don't have access to a car/van.

I would suggest that there is probably some correlation between houses without access to parking and those without a vehicle. It won't be independent, it also won't be an absolute correlation - If it was independent then we'd be down to 24% of households, and my gut suggests that we're more likely looking at 20%.

Of those we then have to eliminate those who have off road spaces where they consistently park elsewhere - whilst they're at work for instance (workplace, station, nearby car park).

Car parks at places which are regularly visited for 4+ hours should have a decent number of low power (7kW or even 3kW) AC EV chargers - we're only having to cover ~20% of households here, so it's not even like every spot in the car park needs a dedicated charger - spreading them out helps in fact, since you're less likely to be ICED.

That leaves a relatively small number of people who don't have regular access to fixed charging, though again, a decent spread of maybe 11kW, or even 22kW capable AC (though few cars will take 22kW AC) at places like supermarkets or other "frequently visited for more than thirty minutes" destinations - and they will also be covered.

And then you need the 50+kW (with 150+ being much nicer, and 350kW being almost overpowered) chargers on (or near) the trunk roads to support long journeys.

Re: From what I can recall ....

What's this "full charge" you talk of?

If you replenish each day the range you used, then you never do a full charge. And you never do a full charge with an EV.

Twenty miles a day is the average distance a car does in the UK, and it's about the same in the US as well.

That's ~5kWh - which is 500W over 10 hours.

"Of course it would be ideal if there is an infrastructure capable of delivering 50kW+ to every parking spot on a street,"

Completely unnecessary - in the same way we don't see the petrol equivalent of a milkman going around refilling each ICE vehicle on a street every day (60 litres each of course).

50kW+ Charging (and the plus is key really) is used on long journeys, it's trunk road technology, not daily use.

Re: From what I can recall ....

No - let's not forget the particulates.

Tyre particulates are equivalent between ICE and EV (evidenced by the fact that EV tyres don't last any less distance than ICE tyres), but EVs emit far less brake dust (partly through not using their brakes much, but also increasingly through using drum brakes, which capture the pad dust).

"it's the one measure by which EVs are only slightly better than ICE ones."

I can't think of any meaningful measure by which an ICE is better than an EV. I'm never going back.

Re: From what I can recall ....

"If 'just' 30% of people are affected thats still some 15+ million outside the M25 ring."

Indeed it is. But some proportion of those households won't have a vehicle (22% nationally, though whilst this includes London, which I suspect boosts the ratio, it's also probably more likely in places without off road parking available). Many of the rest will have off street parking elsewhere that they regularly use (at work for example)

And the whole point about using "slow" AC chargers is that they don't cost a fortune to install, and therefore you don't need to charge obscene energy rates to cover the financial outlay of installing a single high powered charger.

You can install a handful, and then add a few more next year, and the year after - and soon you'll have a car park full of them. Yes they'll need to have a decent power supply to handle all of them at once, but one "high speed" charger connection can supply 50 "normal" AC chargers at full speed, so you could reasonably install 75 or so for a relatively sane additional grid connection (since they can throttle how much power they deliver based on the number of vehicles actually charging.

And since 70% of people won't need them since they'll charge at home instead...

Average commute is 20 miles, in an 8 hour working day you need to average substantially under a kW to never need to charge elsewhere (since you'll be full by the end of the week, which will carry you through the weekend, and then top up through the week again). And you can shape that demand to the morning, rather than having it evenly spread.

Re: From what I can recall ....

You tend to have 220v, split phase so that you get two 110v systems

But that is, by definition slow charging... so they all use the slow charging you just said that they never used.

The real crime is the lack of cost for dumping noxious gasses into the atmosphere over there - but you know - fossil fuel subsidies keep the politicians fed with campaign funds...

Re: Slow charging at any public charging point is so stupid

Wow - you really have no idea how charging works do you... The cables lock in place - they can't be unplugged without unlocking the vehicle first.

Re: From what I can recall ....

Because EVs are not ICE vehicles - you don't need to stand over them whilst pumping flammable liquid.

You plug them in and then go into the office for your working day, or home to bed.

Ubiquitous AC chargers effectively remove the need for DC charging except on trunk roads (i.e. long journeys still need a rapid charge).

Are BT claiming this will supply the whole country with enough charging? No - they are quite reasonably expecting to provide one or two spots where they already have kit installed.

It's things like this that cater to the *minority* of people with neither off street parking nor an office with off street parking (RAC figures suggest just 30% outside London, but some proportion of those won't have a car at all).

ABC - always be charging, rock up to the office/shop/cinema/theatre/climbing wall/library/home/whatever, plug in, then by the time you come out you've topped up by more than the usage to whatever it is you just did. Doesn't need an expensive charger, just an AC connection.

95+% of my charging is done at <3kW.

Re: From what I can recall ....

"It'll all be slow chargers as well. Which no-one really wants."

Except everyone with an EV.

Re: Some data is better than nothing

Not only do they use the same engines on both stages of both the F9 and the upcoming SS/SH stack (with some nozzle extensions) - they build them, they know them, they can scale production as per their needs.

ULA are reliant on suppliers who have other customers, and on varying suppliers for each of the three engine types they use.

The US military really needs two viable launch providers - if BO can get something to orbit themselves, and can start to reuse part of, or all of, that stack... then ULA will be in a more difficult position to support - the military will pay what they need to pay to have two providers, but they don't need to feed three.

Re: Some data is better than nothing

"It didn't even take 12 tanker flights for it to send a payload to the moon"

Nothing like comparing apples with concrete is there.

Do you want a 90 kg payload delivered or a 100 ton payload? Launch a thousand of these and then compare that with the <20 starship launches it would take.

Of course you're also "forgetting" that SpaceX have already sent a similar sized mission to the moon on an F9, not even a heavy, and recovered and reused the first stage of that stack.

Not taking anything away from the team at ULA and their suppliers, including BO. The rocket performed well, just a shame to see no attempt to reuse anything.

Re: They don't have a clue

Yes lots of it was...

The best estimate I've found is ~50%

So if you subtract all of that that from SpaceX (which is a little unfair), then they end up with 30% of the global mass to orbit.

Starlink becomes number 1 with 50%, SpaceX (other) is number 2 with 30%.

It's a little hard to put together the rest, I keep getting quarterly results and lack the time/inclination to sum them all.

But looking at Q3 - CASC lifted 25 tons, SpaceX lifted 381 tons, out of a total of ~450 tons

Even if 225 tons (50%) was starlink, SpaceX (other) still has 150+ tons of commercial lift, substantially more than CASC (and we ought to discount their internal programs as well?)

Q3 might not be representative...

Re: They don't have a clue

Then spaceX make a loss... that's not NASA's problem.

I don't think reentry is going to be impossible though, it's just the biggest remaining "completely untested" thing.

Re: You don't have a clue

Not jsut the efficiency - if the thrust increases then they can stretch the stack (which they are already planning to do) and therefore carry both more fuel and more "payload" fuel.

Re: Deadlines

There are a couple of routes to the moon.

If we assume SpaceX manage to get SS/SH working... and that's not an unreasonable assumption, even if the timescale is still under question, then even without SLS the US could still have lunar capability.

Launch (and refuel) the Lunar Lander SS.

Launch a Dragon, rendezvous and dock with the HLS.

Take both craft to lunar orbit.

Drop the Dragon off (potentially with a little extra cargo, see later) in orbit.

Land, do science, return to the Dragon.

This is where we need a little extra deltaV, probably taking some of the HLS payload capacity for a dragon TEI stage - but the dragon was originally designed for a Lunar return, so kick it back into a return trajectory, leaving HLS in LLO as a potential bonus item for later.

As for a Chinese *woman* being next... I'm not sure they're that fussed about getting that particular first, so it's probably a 50/50 shot (assuming that the US don't get there in a reasonable time frame)

Re: They don't have a clue

If you look at the graphic at 29:57 in Destin's video it's pretty clear that it's starship launches all the way down.

I'm pretty sure that the only refueling is for the starship lander, which will all be starship tankers.

Orion and SLS are one shot disposable devices.

Re: They don't have a clue

"It seems that for some, SpaceX can do no wrong..."

They can - as their HR fiascos clearly show.

When it comes to rocket engineering, they do seem to produce results.

Even when they get something wrong ("We think the fondag will survive one launch") they work to repair the damage and improve systems far faster than most people would guess.

Yes, I know they nearly went under with the F1, but the F9 has given them a ridiculous share of the market (80% of mass to orbit in 2023, after ~50% in 2022Q4), and they are applying many of the same lessons to SS/SH.

They really don't look all that far away from orbit... reentry is clearly an unknown at this point, but that's not technically required for Artemis - though they'll clearly be wanting to emulate their F9 success.

Re: They don't have a clue

It's a significant number of launches, but it's also not unreasonable.

The whole design ethos of the SS/SH stack has been rapid reuse. Heck they want to literally land the booster on the launch pad so it's ready to go* again a few minutes after launch.

Have a look at the F9 recovery success - the last time they failed to land a booster was back in February 2021 (flight 108), and other than two flights with no attempt made we're past flight 288 with a 100% record, that's 180 F9 flight as well as a handful of FH flights with successful landings of the side boosters (one flight had no attempt, and none of them tried the land the core).

I'm sure SS/SH will take a few losses early on, but I wouldn't bet on many failures after they start launching regularly.

* And by 'go' I mean: be restacked and then refuelled, not ready to launch in a few minutes.

Re: No need to rush

Agreed - although for unmanned tests etc, I'm quite happy for ready to be a "we've got some hardware, let's see what breaks"

Re: Standardized

"If someone would come up with an open-source standard"

Then we'd have three more standards than we already do...

https://m.xkcd.com/927/

Re: Which Led Zep Album?

"Not sure if I am making some kind of translation error, as I live in a Nordic country."

The 'error' is merely that there is no possible heat pump which will satisfy some people.