Posts by annodomini2 1183 publicly visible posts • joined 24 May 2010
Most Safety Critical systems don't use dynamic memory management.
The MISRA standard specifically forbids it, assuming it's being used.
I'm not saying C/C++ is perfect, far from it.
But to me it does scream "Use this, it's better!" Ignoring the convenient (for them), but convoluted back doors we've put in the code to access your system if we need to.
Fuel and Oxidiser tend to slosh around when subject to loads (i.e. re-entry), there will be design loads on the tank structure for how much propellant can remain in the tanks without damaging the ship on atmospheric re-entry.
They would need to dump to prevent the ship becoming damaged and potentially breaking apart at this point.
You would dump with the engines running as the propellent would separate and move away from the vent port and also hover around the ship until re-entry.
Given on the first launch they had a number of engine failures, it's logical that they would add more propellant to give a greater chance of reaching the target trajectory in these cases.
Also given there was no payload the extra propellant mass will help to simulate one, otherwise the forces experienced during launch will be higher and not a representative test.
Historically with probes, with multi-billion dollar launch costs and programs, combined with no super-heavy launch capability (Saturn V was cancelled remember).
The mass budget available for the landing systems was limited, so there's a trade off between payload for science and payload for landing, given that most of the people designing these missions are scientists, so they want to maximise science. So some risk is there.
With Super-heavy lift of Starship and the intention for them to be manned will require a greater margin of safety in the landing systems to reduce the risk.
Started as a NASA project:
Thorium is no safer than Uranium.
There are reactor designs that are safer than the current stuff, but the fuel has little to do with it.
Also if we can reprocess the existing spent fuel we've enough to power the planet for hundreds if not thousands of years without the need to transition to Thorium.
The problem with a true breeder is proliferation, as it requires removing enriched fuel from the reactor. The concepts use a fertile blanket of material that needs to be replaced periodically.
Fast reactors are intrinsically ISO breeders, which create more fuel from the production of higher actinides e.g. plutonium, which can be burned in the reactor.
This has the downside that the enrichment of the reactor is constantly changing and changes the reactivity, this is part of what makes them harder to control.
Like any engineering decision it's a compromise, harder to control, but doesn't need to be refuelled for 20yrs.
But taking from something like LFTR, where they reprocess and remove fission products from the reactor, automatically during operation, will help with regulating the chemistry of the core and help with control.
The real advantage of fast reactors is they can be run on "spent fuel" from thermal BWR and PWR reactors with minimal reprocessing.
The problem is they're making the same mistake AEA made in the 60's, liquid metal cooling, they're either volatile (sodium, lithium etc) or expensive e.g. Lead + Bismuth. Molten Salts offer a better compromise IMO, but are also not without their risks.
All this is un-proven is the real issue and the major blocker being research investment.
They are DARPA have a few running, being military they'd likely keep it top secret to give themselves a competitive advantage.
Planes, Tanks, smaller ships will relatively "infinite" range (if they can build them that small), would be a serious advantage.
"the light year is probably a difficult unit for Joe Bloggs to relate to"
The Sun is travelling at approximately 828,000km/h
Speed of light (in a Vacuum) is 299 792 458 m/s or 299,792.458 km/s.
A light year is 9,464,615,782,836.48 km
Therefore the Sun takes roughly 1303 years to travel 1 light year.
@Peter2,
It's also not going to have a ~30 meter wing to distribute the weight. It's going to have all of the velocity concentrated upon a meter area like a wrecking ball.
Yes the CSA is smaller, but the mass is much lower ~500-1000kg vs 7000-12000kg for the DC3
Someone would have to do the maths obviously.
It all switched with the regulation changes that allowed users to cancel their mobile contracts at any time.
As the phone was a "freebie" with the contract, you could buy for 1 month and keep the phone, this required the companies to split the contract into the call plan cost and a loan for the device you are purchasing.
When this shift happened, it also conveniently coincided with the prices going up.
"HMRC would label it hypothecated and, on the basis that they don't like hypothecated taxes, would just roll it into the general taxation pot and the intended beneficiaries would get little or nothing out of it."
Treasury would, not HMRC, they seriously don't like having their spending direction dictated to, elected representative or not.
Was about to say the same thing, but for the majority of uses of transistors today (by count) most are used as switches anyway.
The major issue I see with it is the removal of the solid state functionality, just like relays, making the thing reliable over billions if not trillions of actions, in wide environmental conditions is the challenge.
I could only see this being developed if we had room temperature superconductors.
Any data on the switching speed (I respect it's a prototype)?
Red dwarfs emit more radiation because they are physically smaller, i.e. the core is closer to the surface.
It could be that the young Sun was physically smaller for the purposes of starting the reaction and it would take time for the reaction to grow and also heat the outer layers of gas so there could have been more radiation emitted.
"The digital feudal system. They're just replacing local lords (who've been occasionally know to go Robin of Sherwood with corporations, who sometimes do charity, but also very 'charitable' to poor government servants."
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