7 ms·
> Aftershock II reached a velocity of 5283 ft/s and Mach 5.5. The comparatively lightweight rocket amounted to 330 pounds, at a height of 13 ft and 8” diameter.
by tromp 2y ago
> Aftershock II reached a velocity of 5283 ft/s and Mach 5.5. The comparatively lightweight rocket amounted to 330 pounds, at a height of 13 ft and 8” diameter.
For the imperially challenged, that's a velocity of 1.6 km/s, weight of 150kg, height of 4m and 20cm diameter.
- brudgers 2y agoOr 7.662481e-14 parsec/sec, 1467.9126 Newtons, and 4.4041166e-16 light years. Because space.
- deleted 2y ago[deleted]
- 7734128 2y agoYou can't turn mass into force, especially not in space.
- brudgers 2y agoFor the metrically challenged, pounds are a unit of force not mass.
- littlestymaar 2y agoWikipedia disagrees with you[1], and if pounds were a unit of weight that'd be very unpractical from a legal PoV to have things being labeled in pounds since the same object have a different weight in Puerto Rico (close to the Equator) and Fairbanks (close to the North Pole). [1]: https://en.wikipedia.org/wiki/Pound_(mass) https://en.wikipedia.org/wiki/Pound_(mass)
- two_handfuls 2y agoI distinctly remember reading how I would weigh a different amount on the moon. This only makes sense if the pound is a unit of force.
- stouset 2y agoYou would weigh a different amount on the moon, but that is completely independent of how we label our units of measurement. The pound a unit of force. It is also a unit of mass. Both units share the same name.
- two_handfuls 2y agoIt's not independent because if I'm 80kg here, I'm still 80kg on the moon. Because gravity does not affect mass. If I weigh 160lb on earth I'm told that I would weigh 26lb on the moon. That makes sense if lb measures force because gravity affects force. In short, this commonly shared "fact" is consistent with pounds being a unit of force, not of mass. Or, I suppose, of lb at least sometimes being a unit of force.
- stouset 2y agoIf you weigh 160lb on the Earth, you also have 160lb of mass. You would weigh 26lb on the moon and still have 160lb of mass. I don’t know how to make the point any clearer that there are two units of measurement, both with the same name. https://en.m.wikipedia.org/wiki/Pound_(force) https://en.m.wikipedia.org/wiki/Pound_(force) https://en.m.wikipedia.org/wiki/Pound_(mass) https://en.m.wikipedia.org/wiki/Pound_(mass)
- two_handfuls 2y agoSo how do I know which is meant in a given sentence?
- M3L0NM4N 2y agoI think it's used as both. Foot-pounds is used as a unit of work, so it's a force in that context.
- delta_p_delta_x 2y agoTo be very pedantic, the pound is a unit of both force and mass, and it's because the unit evolved before the Newtonian understanding of weight versus mass. That's why there exists the pound-mass, and the pound-force. Of course, in SI this is very straightforward: the unit of mass is the kilogram and the unit of force is the newton, which is the force acting on a mass of one kilogram experiencing an acceleration of one metre per second per second in an inertial frame of reference.
- brudgers 2y agoYour comment is ambiguated. https://en.wikipedia.org/wiki/Pound https://en.wikipedia.org/wiki/Pound
- beAbU 2y agoIn case you didn't understand the other reply, you can't use newtons in this context. Kilograms is perfectly fine here. The thrust of the engine can (and should) be measured in newtons though. Also, 4 decimal points of precision is completely overkill. Maybe one decimal point at most would be more than enough, but most wouldn't even bother with that.
- brudgers 2y agoThe force of a rocket engine can be measured in pounds. And pressure in PSI and torque in foot-lbs because pounds are a unit of weight (i.e. force) not mass.
- nordsieck 2y ago> The thrust of the engine can (and should) be measured in newtons though. It's very common to measure engine thrust in ton-force because it makes it easy to compare the thrust to the weight of the rocket, which is a critical metric.
- foxglacier 2y agoThe problem is the 8 significant figures, not 4 decimal places - 0.3300 kip and 1467.9126 N both have 4 decimal places but one is much worse than the other. Even if 330 lb was exact, all those digits in 1467.9126 N aren't even correct. It should be 1467.9131 N using standard gravity. It looks like brudgers used 1 lbf = 4.44822 N which is what Google says but is only rounded to 6 s.f. so can't be used to generate an 8 s.f result.
- deleted 2y ago[deleted]
- merek 2y ago> For the imperially challenged You mean everyone in the world expect for the Americans, Liberians and Burmese? :)
- foooorsyth 2y agoMaking this joke falls flat in the comments section of a rocket science article about Americans continuing to dominate space.
- lionkor 2y agoNot sure if I would necessarily say that the reason the US is pretty good at space stuff is imperial measurements. Its probably imperialism, instead.
- etiennebausson 2y agoIt's mostly because the US was the only nation to survive WW2 with its infrastructure intact. Same story as computing, really.
- kortilla 2y agoNope, that’s a lazy excuse. The US space industry was dead in the early 2000s. Astronauts went to the ISS on Soyuz.
- conductr 2y agoIt was more of an exploration lull and not much industry had came out of it quite yet as privatization was being implemented and so it’s the case the industry was actually just being born.
- mrguyorama 2y agoYou are simply wrong for anything other than human rated flight. They didn't have the kind of PR that NASA and Space X have, and they were never human rated, but private satellites never stopped flying on Atlas, Delta, and Titan programs that variously went from the 1960s all the way up until the 2020s. All three of those rocket programs are direct descendants of ICBM programs. https://en.wikipedia.org/wiki/Comparison_of_orbital_launcher_families#List_of_retired_launcher_families https://en.wikipedia.org/wiki/Comparison_of_orbital_launcher... I disagree with the premise that it was lack of bombing of US infrastructure related though. Space programs are very simply the public output of ICBM programs. Most of the modern day is simply a direct descendant of ICBM programs. You like distributed and reliable communication networks like the internet? Built so ICBM silos could command each other even if certain hubs were nuked. You like the miniaturization of solid state electronics? That capability was paid for entirely by the US Air Force who wanted powerful computers under 100 pounds for advanced planes and precision ICBMs. Satellite navigation was also explicitly invented for nuclear missiles fired out of submarines to have an accurate fix for guidance purposes. Basically the entirety of the modern world exists because the US of the cold war pumped trillions of dollars into producing ICBMs and planes that were genuinely "next gen" while every single private business takes the credit for stuff they never paid for. Computer and telecommunications companies would never have built this stuff on their own: They were fine with computers taking up an entire facility that they could rent out (cf modern clouds) and fully switched networks that were reliant on a big company to manage. None of them needed to sell you a "personal computer". None of them wanted a distributed, uncontrolled network like the Internet.
- dragonwriter 2y ago> For the imperially challenged, US customary units are a distinct system from imperial units (some of the individual units overlap, and several others have the same names but different definitions.)
- soneca 2y agoI dont know if you were downvoted for being pedantic or for being wrong. But I’d love to know if this is true. And if so, I will upvote your pedantry
- variaga 2y agoIt is true: https://en.wikipedia.org/wiki/Comparison_of_the_imperial_and_US_customary_measurement_systems https://en.wikipedia.org/wiki/Comparison_of_the_imperial_and...
- analog31 2y agoIt's interesting that I'm perfectly fluent in both US and metric units, yet I don't have a personal frame of reference for the magnitude of many of the numbers given in the article, in either unit system. For instance, how they compare to rockets that are actually in practical use.
- daemonologist 2y agoCompare to New Shepard (Blue Origin suborbital passenger vehicle): 1 km/s top speed, 100-120 km max altitude. Of course it also carries a payload of six passengers and (the rocket part) lands propulsively. Compare to orbital rockets: (low earth) orbital velocity is 7.8 km/s, the ISS orbits at about 400 km, the lowest satellites are at about 200 km.
- jjmarr 2y agoAltitudes for aircraft use feet worldwide, to be fair.
- dj_gitmo 2y agoTV screens and monitors are also measured in inches. ¯\_(ツ)_/¯
- delta_p_delta_x 2y agoThey are decidedly not. They are marketed in inches of the diagonal (a supremely brain-dead decision, if you ask me), but they are engineered, manufactured, and even programmed only in SI units. If you look at your display's EDID output, the diagonal doesn't even factor in; what you do have are vertical, horizontal, and per-pixel dimensions; all in millimetres. This is what all panel manufacturers (LG, AUO, Samsung, Innolux, BOE, TCL, and so on) do.
- Tepix 2y agoIn Germany you have to always mention the metric size. Luckily.
- delta_p_delta_x 2y ago> use feet worldwide, to be fair Many CIS countries and China use metre flight levels[1] and kilometres per hour for indicated speed reporting. Additionally, the ICAO has recommended transiting to metre flight levels since 1979[2]. More additionally, the Airbus A300 had flight levels initially set up to be metric (obviously, since it was an effort spearheaded by the French), but to appeal to American airlines the Airbus consortium switched to feet. Although I am positive that Airbus engineers work exclusively in SI. METARs worldwide except in North America use SI units for reporting weather. [1]: https://en.wikipedia.org/wiki/Flight_level#Metre_flight_levels https://en.wikipedia.org/wiki/Flight_level#Metre_flight_leve... [2]: https://en.wikipedia.org/wiki/International_Civil_Aviation_Organization#International_System_of_Units https://en.wikipedia.org/wiki/International_Civil_Aviation_O...
- Tepix 2y agoNo, and this is not an aircraft, is it?
- HPsquared 2y agoImperial units fit nicely here: 1.00 mile/sec.
- tw04 2y agoCan I get that in stone and hands please?