Timeline for The Expanse: Sustained Gs during space travel
Current License: CC BY-SA 4.0
29 events
| when toggle format | what | by | license | comment | |
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| Aug 6, 2022 at 5:16 | comment | added | TomTom | Because in reality belters are used to low and zero G environments. That is not bigotry - it is not being ignorant. Facts do not care about your feelings. So, if you have someone living on an asteroid with no gravity, he may be ok with floating - more than a planet dweller. | |
| Aug 5, 2022 at 16:55 | comment | added | Azor Ahai -him- | @TomTom Why are we counting belters out? More inner bigotry smdh. | |
| Aug 5, 2022 at 14:47 | comment | added | TomTom | @AzorAhai-him I would count Millers trip out - was this not a belter style transport? LOW cost and belters are used to low G. | |
| Aug 5, 2022 at 14:46 | comment | added | TomTom | You do not need to go 1.0g - anything from 0.7 possibly down to 0.3 would work without large problems. You can still use normal toilets, eat normally and sleep in a bed. And enjoy a nice glass of wine without too many problems. Also note that the engines in the Expanse may well break physis in terms of fuel efficiency - not sure whether this part is ever discussed outside the "brutally efficient". Expanse is hard SF with some exceptions mostly along the rings... and IIRC also fuel efficiency. Epstein to thank. | |
| Aug 5, 2022 at 6:12 | comment | added | Dale M | @PM2Ring and, of course, that much energy melts everything except unobtainium | |
| Aug 5, 2022 at 2:06 | comment | added | PM 2Ring | FWIW, an ideal deuterium cycle engine converts around 260 kg of fuel to 259 kg of exhaust and 1 kg * c² energy. A ship that's 50% fuel by mass at launch running at 1 g consumes its fuel in just under 21.9 days, reaching a speed of ~0.0618 c. Of course, a real engine will have various losses. | |
| Aug 4, 2022 at 22:55 | comment | added | Azor Ahai -him- | @TomTom I didn't mean to get you so worked up, sorry about that. They do in the books (which is what the question is tagged for), where it is not ridiculously expensive to portray zero-G. If I recall correctly, both Miller's trip to Eros and Amos' trip to Earth have extended parts in the middle "on the float." And by "full," I meant 1G burn, not balls-to-the-wall. | |
| Aug 4, 2022 at 20:53 | history | edited | Dale M | CC BY-SA 4.0 |
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| Aug 4, 2022 at 13:16 | comment | added | Christopher James Huff | In-universe, the Epstein drive uses some kind of "magnetic coil exhaust acceleration" to achieve higher efficiency than a plain fusion torch drive. In reality, the exhaust acceleration system would have power requirements dwarfing what the torch itself puts out...just doubling the exhaust velocity would mean the accelerator is the source of 3/4 of the exhaust power. It would really make more sense if it was just an improved magnetic nozzle. | |
| Aug 4, 2022 at 6:14 | comment | added | Luaan | @Aron Nah, torch ships were always the kind that can accelerate for the whole trip. Even in the Expanse universe, the drive system is unofficially called "the torch" all the time. They also do tea-kettle (using just steam thrusters for close manoeuvring etc.). Epstein is a kind of fusion drive - there were others before it, but they had vastly inferior performance. Some of these old-style drives are still used. | |
| Aug 4, 2022 at 5:48 | history | edited | Dale M | CC BY-SA 4.0 |
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| Aug 4, 2022 at 5:36 | history | edited | Dale M | CC BY-SA 4.0 |
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| Aug 4, 2022 at 5:32 | comment | added | Dale M | @Aron a torch drive requires high thrust and high specific impulse - that means a lot of power which implies either a crap ton of fuel OR a highly efficient power source | |
| Aug 4, 2022 at 5:28 | history | edited | Dale M | CC BY-SA 4.0 |
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| Aug 4, 2022 at 3:58 | comment | added | Aron | If memory serves, torch ships were ships which weren't equiped with the highly efficient (from ISP perspective) Epstein Drives. | |
| Aug 3, 2022 at 20:52 | comment | added | Jason Goemaat | @inorganik - "this type of space travel would cause your speed to increase exponentially" - actually it would cause the speed to increase linearly or logarithmically depending on your frame of reference. At 1G, you would be going roughly 50% the speed of light after 15 days. If you keep accelerating at 1G, it looks to outside observers as if your acceleration is decreasing. 1 second on your ship seems like about 1.155 seconds to an outside observer. So to them your speed will be increasing by about 9.8 meters per 1.155 seconds, slower than 1G. | |
| Aug 3, 2022 at 1:47 | comment | added | StephenS | @inorganik It’s not troubling; speed is the entire point. Who wants to spend 9 months traveling, including carrying all the food you’d need for that, when you can (at the ideal time) get there in just two days? | |
| Aug 3, 2022 at 0:32 | comment | added | Lexible | @inorganik "this type of space travel would cause your speed to increase exponentially." Remember that space is big. | |
| Aug 2, 2022 at 22:29 | comment | added | Peter Cordes | @Hypnosifl - you eventually run into problems from the diffuse dust / gas causing drag (and radiation) for a ship moving at relativistic speeds wrt. to it. The faster you're moving, the more atoms you plow into per unit time, and the more energy each collision has. I haven't watched The Expanse yet, but it seems these aren't ramscoop ships, so at least they're not creating drag over a large area/volume swept by a magnetic field. But for high relativistic speeds you'd want some kind of particle screening, not to mention dealing with rare micrometeoroids (e.g. via laser) in a solar system. | |
| Aug 2, 2022 at 20:16 | comment | added | Michael | @hypnosifl Oh, absolutely. As I understood the original comment, the concern was for indefinite increase in velocity relative to the rest frame or the departure point. | |
| Aug 2, 2022 at 20:08 | comment | added | Hypnosifl | @Michael ultimately relativistic effects kick in and acceleration drops Yes, if you're talking about coordinate acceleration as measured by observers in some fixed inertial frame, like the Sun's rest frame. Though note there is a separate notion of proper acceleration in relativity, which can remain constant indefinitely, and it's the proper acceleration that determines the G force felt on board the ship. See relativistic rockets for figures on constant proper acc. | |
| Aug 2, 2022 at 16:44 | comment | added | TomTom | "Well, military ships in The Expanse tend to do full-acceleration/full-deceleration" - no, they do not. They go with a comfortable acceleration UNLESS OTHERWISE NEEDED. As you can see in ANY military craft in the series where people walk around normally during normal operation. "Non-military ships float for the middle part of the journey, both for comfort of civilian passengers " - this makes ZERO sense. They ALSO use constant acceleration normally because especially civilian passengers ARE NOT USED TO ZERO G and need to strap in then. Unless they are collecting ice or doing something similar. | |
| Aug 2, 2022 at 16:13 | comment | added | Michael | Non-military ships don't do high-g burns, but from memory still go for continuous acceleration. Zero-g is as inconvenient as high-g for civilians not used to it. | |
| Aug 2, 2022 at 15:29 | comment | added | Azor Ahai -him- | Well, military ships in The Expanse tend to do full-acceleration/full-deceleration. Non-military ships float for the middle part of the journey, both for comfort of civilian passengers not used to high-G burns, and economic reasons (lack of juice, fuel, etc.) | |
| Aug 2, 2022 at 13:26 | comment | added | reciprocal lettuce | a constant acceleration does not increase your speed exponentially, but linearly. and if you burn at 1g for 1 day you reach about 850km/s - that's not insanely fast | |
| Aug 2, 2022 at 13:20 | comment | added | Michael | Up to a point - ultimately relativistic effects kick in and acceleration drops. In reality, for travel within the solar system as 1g of constant thrust, you're looking at peak velocities probably <1% speed of light, and travel times of days to months. Collision avoidance and armour is important, but not out of the question especially given the relative lack of matter once you're out of planetary orbit. | |
| Aug 2, 2022 at 13:06 | comment | added | inorganik | I think this must have been what the authors intended, but I still find it... troubling in the practical sense, because this type of space travel would cause your speed to increase exponentially. If plotted on a graph, it would look like a hockey stick. Over long periods of time a ship could not maneuver out of the way of anything if it was off course because the speed would be too great | |
| Aug 2, 2022 at 12:45 | vote | accept | inorganik | ||
| Aug 2, 2022 at 7:36 | history | answered | Dale M | CC BY-SA 4.0 |