Posts by John Robson 4839 publicly visible posts • joined 19 May 2008
Consistency - we have a very good understanding of how hubble works, and what it images. It's a very useful calibration tool for new scopes.
It's also still unique - JWST isn't a replacement, though there is some overlap in observable frequencies.
The Roman scope has a similar diameter mirror but a massively wider fov, it's not looking at the same stuff.
Should have got your boss in earlier...
Had a self proclaimed paper pusher manager at a previous role, and they were brilliant.
They had a great memory for "the team saw something maybe similar seven years ago, here's the first and last couple of emails - does it sound relevant" and was excellent at being a management shield when needed.
I only had one "event" where I ended up on three calls first thing in the morning - the third was meant to be a progress report from the first - but the time between them had been taken up with the other call from a different set of management.
Now both sets of management did need to be updated, and updated properly (and that really meant by me), and the incident wasn't getting any worse (as we were now running correctly and had backups of all the raw incoming data from the event) - it eventually took two full weeks to repair and reprocess the data (which had been sent in the wrong timezone by a handful of systems, there was a nice overlap of timestamps at one end of the data which took more effort to resolve than I care to remember). But the first thing I said on the third call was "no progress, and there never will be if I don't get off these calls now."
So who's going to pay for the new scope?
And what benefits will it bring?
The sensor packages on Hubble have been replaced before, we could replace them again... Hubble isn't nearly as old as the calendar would suggest.
And it's cheaper to send up a new instrument cluster than a whole new telescope.
Can you imagine sending up a mission with a robonaut and some replacement parts, then *leaving* the robonaut attached...
"Hubbles role in deep field observations has largely been supplanted by JWST though."
Different spectrum on each, so not really a replacement.
But the deeper the field the more red shifted the light, so there is some truth in the comment - they have similar resolving power (JWST has a bigger mirror, but detects longer wavelength radiation).
And of course the sheer light gathering capacity of JWST is a significant step forward, allowing deep fields with far less time spent on an observation.
The upgrades have replaced vast amounts of the telescope over the years, but I'm not sure you could reasonably have built several new versions and launched those for less than the maintenance costs.
There were five servicing missions (STS-61,82,103,109,125) - the first being to install COSTAR, and you'd *never* have got the budget for an all new system then.
Could we launch something better and cheaper now?
Well - we could launch something new - the F9 fairing is certainly large enough (other rockets exist and have different fairing sizes, I just picked the most common launch vehicle of the moment).
But how much would it cost to build an all new instrument? It would be substantially more than the cost of replacing a few gyros, batteries, and other items with limited life.
If we really wanted to we could even leave a small thruster unit on the base for orbit maintenance.
JWST launch cost ~200 million, but the spacecraft cost multiple billions.
I know - it was more complex, but that's the kind of thing we'd want to to do improve on Hubble. You can launch an awful lot of maintenance missions, upgrading instruments etc, for the cost of a new bird.
Yes - coincidence.
If it happens again... then I'll revisit that opinion.
Starlink provides services that others can't - it works well, and is clearly generating significant revenue...
There is also a wierd market which they haven't tapped yet - and that's only going to be available once the laser comms come online, the transatlantic latency can be better than oceanic fibre which is important for high frequency traders - and they will pay for it, and potentially pay alot.
Meh - I suspect that the integration will not be the biggest challenge they face.
And each of the launch suppliers will be keen to ensure that integration is done properly.
The chances of the Ariane 6, Vulcan and Glenn rockets all being completely reliable from the get go however... I suspect there is a decent chance they'll lose some to launch issues.
Atlas and Falcon both have good demonstrated reliability.
Switching on the load isn't an issue - and carrying the load tends to be fine for most of those.
The tricky bit is turning off the load, but if you're really determined not to use any intelligence in your charging then you'll almost always be turning off a charger connected to a full car battery, so again, not alot of load being switched.
Ah - yes the "shall I shut down now" popup that allows entry within 5 seconds of appearing, and allows one entry to be sufficient to cause said shutdown rather than two discrete entries.
Sucks to be able to touchtype and be doing so whilst reading a paper doc only to realise that you've just shut down the computer because some stupid popup stole focus... If I've focussed on something it's because I want to be focussed on it - feel free to put a modal box over the top, but leave the focus where it was thank you very much.
How much of your document does the cursor cover?
Heck, mine disappears when I start doing anything in the window, but even without that it's at most covering one character - maybe two, one on each of two consecutive lines.
Whereas if you don't have focus follows cursor then you can't pop up a reference document and type into your actual work window whilst still having the reference doc open, because your working document just needs focus, and to "peek out" from below the reference doc, which is only going to be there for a few minutes.
It's something you get used to very quickly, and it's much more natural - your focus is just where you (tell the computer you) are looking.
focus doesn't require interaction, and it certainly doesn't require the *whole* window to take priority
"That's not saying much"
Have you managed it yet, on a rocket this powerful?
Demonstrating hot staging is a significant acheivement.
We do know that the booster survived for quite a while, and SpaceX have much more data than we do, they're not relying on random youtube streamer's equipment (impressive though much of it was)
I'm surprised they aren't building a "catch only" tower half a mile or so away from the launch site... I know there is seriously limited space available since it's a nature reserve...
I'd have thought that the oil rigs would have made a good starting point for this kind of platform
It was a success - but it wasn't as much of a success as it potentially could have been.
They've demonstrated hot staging - deceleration is generally bad for fuel staying in the pumps, but that's a relatively trivial fix, just don't throttle those three engines down as far and you don't end up decelerating... the booster is important to reuse, but also it's never the primary mission.
We still don't know what actually went wrong on the ship, but the booster demonstrated the IFT system worked as well (which is a significant improvement on last time).
There are a few bits of hardware very close to ready to test, and stage zero looks in remarkably good condition.
"With Starship, there's the need to open up the top in a mechanically sound way (a single hinge point on a round tube isn't going to cut it)"
Well for their first payloads there will be a slot door and what is effectively a pallet loader will spit the birds out individually, or in pairs.
There have been previous spacecraft with a recloseable fairing (the shuttle is just one) although they are all much smaller (but then that's hardly a surprise, starship/superheavy is the largest and most powerful rocket to fly
I've heard it said that is (at least part of) the reason for the sequenced engine shutdowns on the booster. It reduces the "shock" on the entire system, especially the hydraulic shock on the fuel tanks and pumps/pipes etc going from very high acceleration to almost none over a longer time period.
It's not the jerk* thats the issue, it's the flow rate - each engine is pulling about 650kg of propellant each second down the plumbing. That's a very significant amount of fluid momentum (relative to the rocket) to abruptly stop...
"As was the shutdown sequence of the booster engines. Very pretty. Will this become a trademark "SpaceX Star", like the "Korolev Cross"?"
I doubt it - it's not really visible for long enough, or without the benefit of the telemetry.
* jerk - rate of change of acceleration
"In many ways the N1 is a more elegant design than the Saturn V, but elegance must sometimes take a back seat to efficacy and the brute force of the F-1 turned out to be the correct play over the NK-15 back when the race was on.*"
There were serious issues with the F1 - combustion instability was seriously threatened the whole Apollo program.
I'd be interested to see a source on that - I haven't seen anything on the knees which looks like it might be the cause, but no-one else seems to comment on it, so I have almost certainly missed something.
If they were a leak I suppose it would likely get *worse* during deluge, which doesn't appear to be the case.
There was no loss above and beyond what was intended for the flight, in what way could that possibly be considered pyrrhic?
The aim here is fully, and rapidly, reusable - but this was always a test with the hardware being discarded in pieces at the bottom of the ocean.
for both a very successful test and a great show for those watching.
I'm still concerned at the amount of leakage from the "knee" of the water deluge system every time it fires - but there's quite alot of water taking a right angle bend in a pipe which isn't well supported by concrete... I am surprised it's such a sharp corner, rather than a more gentle curve.
It's five seconds between ignition start (which is sequential, so not an instant thing) and lift off (which is scheduled for t+2).
Memory tells me it was ten seconds last time (quite happy to be wrong).
I don't think the final sequence will be sub 3 seconds, but I do expect it to be substantially less time "settling" at full power - of course what I didn't think about is that "full power" is more than IFT2 power. (payload and requirement to minimise gravity losses)
Not ripping up the pad would be good, although again the launch is going to be slower (and therefore more damaging) than a "regular" launch, so some damage might well be sustained.
Having the fire suppression system work better in the engine bay will almost certainly let them get to stage separation.
Everything after clearing the tower will be considered a bonus - getting through stage separation, and potentially to (just) sub orbital would be a major achievement.
If that thing survives re-entry then there will be more than one or two beers consumed I imagine.
The Register 
Biting the hand that feeds IT
Copyright. All rights reserved © 1998–2023
