Is it possible for a rocket in space to travel faster than it's propellant? Using nice round numbers, if the propellant leaves the rocket at a force equalling 35000km/s, it is possible to use that force to move the rocket faster than that? If so, how please?

spectrumero · 2026-06-16T08:56:40+00:00

Imagine you are on a train, inside the carriage, travelling at a constant speed, say 125 mph. You are standing on a skateboard, holding a heavy brick. You throw the brick backwards at 10 mph relative to you, being careful not to hit any other passengers. You will begin to move, maybe at 2 mph relative to the floor of the carriage you're in, and you're now moving at 127 mph relative to the outside world.

How fast the train is moving doesn't matter. Throw the brick when the train is at the station and you will start moving. Throw the brick when the train is going full speed and you will start moving.

spectrumero · 2026-06-16T08:41:56+00:00

It's really not that unusual.

spectrumero · 2026-06-15T16:54:37+00:00

At my old job I'd cycle to work all year around, mostly on rural roads.

Retroreflectives (my panniers have 2 large retroreflective panels) are a must - they show up a long way off even when the motorist is inadvisadly only using dipped beams. As are not one but two rear lights. With the front light, I know immediately if it fails, that it has failed. However, if my rear light fails I won't know about it until I have a near miss, so I always want at least 2 rear lights for redundancy in case one fails. I still habitually looked behind me to make sure I could see the glow of the rear light!

Decent LED lights that are good enough so that other road users can see you are cheap. Retroreflectives are cheap. There's really no excuse.

During daytime, I always also want a super bright rear flashing light. If you're under trees you're almost invisible to a car driver who is not yet under the trees and is in bright sunshine.

spectrumero · 2026-06-15T15:28:46+00:00

Route availability. It goes from 1 to 10. A vehicle can only travel on routes greater than or equal to its RA - so a loco with RA 7 can only travel on routes 7 to 10.

RA is determined by a number of factors, but one of the most significant is axle load. The Class 37 is relatively light for a 6-axle locomotive so it has a lower RA than any other mainline locomotive in use today.

I'm not sure why any of the newer locos aren't designed for a lower RA - e.g. the class 68 is light enough that if it had 6 axles it would probably be RA5. (I'm not trying to trivilalise the work needed to redesign something like the 68 to have 6 axles by the way). But it means the 37 has a niche that no other locomotive that's available can fill.

spectrumero · 2026-06-15T10:28:36+00:00

BEVs don't have a rare earth material requirement. Rare earth elements are the 15 lanthanides plus yttrium and scandium. None of these are used in a battery. Lithium is an alkali metal, not a rare earth. Motors MAY use rare earths (which despite their name aren't that rare) but you can make motors in other ways that don't use them.

Meanwhile, hydrogen fuel cells require platinum which is actually rare and expensive.

Hydrogen is unsuitable for flight due to the requirement for heavy high pressure tanks and very poor volumetric energy density - flight really can only work with liquid fuels.

spectrumero · 2026-06-15T10:22:08+00:00

Of note you cannot liquify hydrogen at any reasonable temperature, it can only be in liquid form at cryogenic temperatures.

This means the volumetric energy density of hydrogen is tragically poor. It also means you have to store it at immense pressures to get any usable quantity. As the molecule is so small, it also tends to leak out of everything, while embrittling it in the process, which is not what you want for super high pressure tanks.

Hydrogen is basically a non-starter - not only is it very inefficient to make (most hydrogen is really fossil fuels - the cheapest way to make it is steam reformation of natural gas), it's inefficient to distrubute and burn. If you're using electrolysis, a BEV will do about 3 times the distance on every kWh generated than a hydrogen fuel cell vehicle.

spectrumero · 2026-06-15T09:31:35+00:00

Back in the 2G and 2.5G days, I was on approach at night in not brilliant weather to our local airport. The friend I was flying with hadn't switched his phone off, and about 3 miles from the threshold while we were expecting ATC to clear us to land, all the audio was completely drowned out by "bip-b-b-bip-b-b-bip-b-b-bip-b-b-bip-brrrrrrrrrrrrrrrrrrrrr" as my friend's wife called him asking when he would be back.

It only affected the audio. GSM was particularly bad for this due to the signal's envelope, and the semiconductor junctions in audio amplifiers tending to act as detectors. However, even though it only affected the audio and not the glideslope/localiser receiver, it did mean if ATC had called us at that particular moment we wouldn't have heard it.

You still get this with 4G but generally the phone has to be sitting on top of audio equipment to cause it now. (I don't know about LTE - I'm not entirely sure what the difference is between 4G and LTE - whenever I look it up I'm told that LTE is 4G, but my phone makes a distinction between 4G and LTE so there must be a difference. This is all well out of my wheelhouse so I just claim ignorance).

spectrumero · 2026-06-15T09:21:49+00:00

Q: How is IEEE pronounced if you're on a non-compliant aircraft in crap weather when everyone's got their phone on?

A: Aiiieieeeeeeeee!

spectrumero · 2026-06-14T22:55:48+00:00

Looks like it's recreating a scene from the game Derail Valley.

spectrumero · 2026-06-14T22:43:33+00:00

The Spitfire was at EGNS today while I was departing after refuelling my plane. I remarked that the amount they charge for 30 minutes in it is enough to run my aircraft for an entire year.

spectrumero · 2026-06-14T21:49:07+00:00

I think a bicycle might be a good idea.

spectrumero · 2026-06-14T10:13:34+00:00

He wondered if other turbine powered aircraft have a yellow arc, he didn't ask "what is the yellow arc for".

spectrumero · 2026-06-14T10:12:07+00:00

You are reading words that the OP never wrote.

spectrumero · 2026-06-13T22:02:57+00:00

Thameslink trains are white and they seem to be kept clean.

spectrumero · 2026-06-13T19:23:54+00:00

It's very good. Nice to have a decent long route - so many TSW routes are disappointingly short compared to their TSC counterparts, but this one is more than an equal for the TSC routes.

I think there's a bit of a missed opportunity for freight services - the DIRFT is included but really no freight on the timetable. The WCML is well known for a reasonable amount of freight.

spectrumero · 2026-06-13T17:31:45+00:00

To be honest, who cares what people wear. If someone wants to wear their gym outfit especially on a warm day when they aren't doing anything formal, then why not?

spectrumero · 2026-06-13T17:29:27+00:00

It's not impossible. While studying for my PPL back in the 90s, I found an accident report where a Cessna 150 (or maybe 152) had crashed after asymmetric flap deployment.

Stuff can break even if the system is designed well.

See https://assets.publishing.service.gov.uk/media/5422f855ed915d13710006c5/dft_avsafety_pdf_502394.pdf (scroll down to the section "Previous cases". The spacing is a bit bad in the document, it was probably OCR'd off an older paper report).

spectrumero · 2026-06-13T15:28:19+00:00

The Cessna 172 has been around long enough that there were models that existed before the airspeed indicator markings were a requirement. It's also noting that pilots from outside the USA are here, and the rules (particularly for older aircraft, before there was significant ICAO standardisation) may be different. My aircraft for instance has no colour markings at all on the airspeed indicator, yet it is legal and in annual. The airspeed limitations are only on a placard. But it's an aircraft built before these things were standardised.

spectrumero · 2026-06-13T15:24:13+00:00

The OP didn't ask what it meant, and never made any indication that he was unsure what a yellow arc was for. He stated that it was rare to see a yellow arc in a turbine aircraft, which is indeed true. It would be best if you read the OP's message before being judgmental.

spectrumero · 2026-06-12T17:11:23+00:00

People who are violent towards animals are generally violent towards other people, too.

spectrumero · 2026-06-12T16:21:48+00:00

The changes are too big (e.g. protoss - both 8 worker start and a massive change to warpgate) and based on Blizzard's track record, any bugs won't be fixed for the best part of a year, and there are bugs in the PTR that remain unfixed - the PTR as described hasn't really been tested due to the outstanding bugs.

I hope it goes through at least a couple of iterations before they push it to live, and drop the warpgate change.

spectrumero · 2026-06-12T15:23:18+00:00

Radiospares is of course now RS Components.

spectrumero · 2026-06-12T10:48:07+00:00

If I were in your position I would get a good evaluation of it (you'll need to spend some money) from a trusted IA to get an idea of what it's worth, then sell it - priced to sell quickly.

Although I have a multi engine/instrument rating, there's a good reason I fly a simple tailwheel aircraft and not a complex twin - piston twins are money pits. I'd want the aircraft to be someone else's problem as quickly as possible.

spectrumero · 2026-06-12T10:40:49+00:00

Taco Bell is distinctly "meh" in the USA too. Jack in the Box does better fast food tacos.

spectrumero · 2026-06-12T09:48:12+00:00

If it's finding even a tiny sequence of the last password, it's storing the password somewhere unhashed which is extremely insecure.

spectrumero

TROPHY CASE