10 KiB
[HSF][OC][RST] Advent Signal, Chapter 1: Stern Chase
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Author: u/Sagebrysh Rank 7 Pragmatist*
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URL: http://riordansramblings.tumblr.com/post/132000101422/advent-signal
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Score: 6
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Created: 2015-10-27T04:58:46
Post:
Comments:
u/Sagebrysh [+1] Rank 7 Pragmatist (a minute later)
first chapter of that story I talked about wanting to write. Well I thought wahey, I might as well just write it. I hope you guys like it, and please help me correct any scientific errors in the piece, I'm trying to stay as true to real physics as possible.
u/ArgentStonecutter [+2] Emergency Mustelid Hologram (5 hours later)
Very "first draft". You could do with a re-read to clean up wording.
a long fat tube through with the energies of a star with directed
Also, at half a G difference in acceleration they're going to close that 10km gap in about 100 minutes, but they'll have a relative velocity over 3 km/s just from that hour and a half of thrust.
But you say they've been chasing her for hours already? Then their relative velocities are already dozens of kilometers per second. 10 kilometers means they're zipping past her right now. They need to decelerate, in fact they need to have been decelerating for some time now, if they're going to be going slow enough to engage.
The high G swerve crushed Astrid into the side of her acceleration couch
Given that most of the thrust is directed along the axis of the ship, you're not going to feel much lateral force from a turn. It's not like in an aircraft where you're pushing against the atmosphere.
Okay, okay, the missiles are accelerating at 4 Gs
If the military ships are capable of 10G acceleration, and they're moving at multiple kilometer per second relative velocities (probably hundreds of kilometers per second) missiles only managing 4G would be like fighter jets shooting bottle rockets at each other. You'd need much higher accelerations from the missiles for them to be practical weapons.
But given those figures, at 2G relative acceleration, it's still going to take over an hour for those missiles to reach her. Assuming the military ships had matched velocities close enough for an engagement to be practical in the first place.
Also:
The vessel rode atop a ten kilometer tall pillar of fusion fire;
Why doesn't she just aim her jet at them?
u/Sagebrysh [+1] Rank 7 Pragmatist (9 hours later)
Math is hard. When I ran the numbers on her time to collide with the missiles I did it from the assumption of starting at rest. Which, yeah, is definitely wrong. How should I correct it? I mean plot-wise all that matters is she gets her tranission out, dies when her ship explodes, and takes out the destroyers in the process. The details of how it happens should be due to the cold gods of mathematics.
So increase distances between the ships, increase speed of the missiles, possibly change time to close?
The destroyers wouldn't have started their deceleration burn until she actually stopped. Or, more likely, take her out with nukes and blow past the wreckage at several km/s relative.
Her fusion candle is fairly narrow, and the highly maneuverable destroyers could easily dodge the particle stream. Probably part of regular training for pilots. The problem with practically applying the Kzinti lesson is that everyone learns it and its counters during their first weeks in pilot school.
u/ArgentStonecutter [+2] Emergency Mustelid Hologram (10 hours later)
Nerf the hell out of their drives. Her drive should be generating a fraction of a gee long term, maybe a gee peak, but she can't maintain that for long... I mean minutes, not hours. The military ships can handle 10 gee short term, for minutes, and a gee for a few hours, but long term they should be running a fraction of a gee too. A larger fraction, but still a fraction.
There's no "deceleration burn". They are trying to match her position and velocity. They know her total delta vee, and her course, they can predict where she can be for days ahead with pretty good precision. They'll be burning half way to her predicted position, then decelerating the rest, with the big pushes at the beginning and the end of the journey... because it is more effective, and to allow for maneuvering.
Given the size of the vessel, it can't be carrying much propellant, so the exhaust has to have unghodly velocity. If you're chasing a fusion drive vessel with a high exhaust velocity, there really aren't any good counters. The beam is traveling close to lightspeed, and you're moving at kilometers per second and can barely shift your vector even at ten gees.
They're going to be spread out to cover more predicted vectors. They're not going to be within tens of kilometers of each other.
Given the situation, the only way I can see to make it work is for her to convincingly fake running out of fuel and surrendering, and blowing her drive when they come close. If she's actively resisting, they're going to stand off and nuke her from orbit.
u/Sagebrysh [+1] Rank 7 Pragmatist (11 hours later)
- Nerf the hell out of their drives. Her drive should be generating a fraction of a gee long term, maybe a gee peak, but she can't maintain that for long... I mean minutes, not hours. The military ships can handle 10 gee short term, for minutes, and a gee for a few hours, but long term they should be running a fraction of a gee too. A larger fraction, but still a fraction.
I wanted to go for high efficiency 1 G standard torch drives. They fly in brachistone transfers doing 1 G halfway, then flip, then 1 G deceleration to destination. No long periods on the float for the most part, just regular 1 G burns. Obviously that's a 'normal' situation, not a military one, but I rather wanted to have 1 G constant acceleration to be the standard.
- There's no "deceleration burn". They are trying to match her position and velocity. They know her total delta vee, and her course, they can predict where she can be for days ahead with pretty good precision. They'll be burning half way to her predicted position, then decelerating the rest, with the big pushes at the beginning and the end of the journey... because it is more effective, and to allow for maneuvering.
That only works if she's flying in a straight line, she's not. Every time they try to position themselves to match course and get 'ahead' of her, she changes course. She's also constantly accelerating with no particular destination in mind and has a head start. If they match course and velocity with her and cut their engines to coast towards intercept...well she keeps accelerating and pulls away. Instead they just keep accelerating at a slightly highly rate then her, and slowly close the gap. Given that she's actively maneuvering to avoid capture, going for a hard burn, coasting, then another hard burn to match velocity isn't going to work as well. Maybe hard burn so their solar velocity is much higher then hers, then going for a lower acceleration, then hard deceleration to match velocity?
3.Given the size of the vessel, it can't be carrying much propellant, so the exhaust has to have unghodly velocity. If you're chasing a fusion drive vessel with a high exhaust velocity, there really aren't any good counters. The beam is traveling close to lightspeed, and you're moving at kilometers per second and can barely shift your vector even at ten gees.
But you're also really far away for the most part. Though yeah, they should have cut acceleration and started maneuvering as soon as she came about.
- They're going to be spread out to cover more predicted vectors. They're not going to be within tens of kilometers of each other.
Also true. Need to get over my classic soft sci-fi 'ships flying in close formation' mentality.
Given the situation, the only way I can see to make it work is for her to convincingly fake running out of fuel and surrendering, and blowing her drive when they come close. If she's actively resisting, they're going to stand off and nuke her from orbit.
I think I can work with that, mind re-reading after I edit and letting me know how it looks?
u/ArgentStonecutter [+2] Emergency Mustelid Hologram (12 hours later)
I wanted to go for high efficiency 1 G standard torch drives.
And I suspect that you probably can't get there with a 70 meter pile of junk thrown together by a hacker. Niven's "Singleships" were pretty good hard-ish SF in 1972, but if you're going to do the math I'm not sure you can do it with fusion.
That only works if she's flying in a straight line, she's not.
It works if you know the total delta vee she has and you know her initial orbit. Even with "standard torch drives" there's a limited solution space, and it gets more and more limited as she uses up her propellant. Remember, interplanetary velocities are high. You can't do a right turn in space except by interacting with a gravity well.
Maybe hard burn so their solar velocity is much higher then hers, then going for a lower acceleration, then hard deceleration to match velocity?
I think that's another way of putting the same thing. ^^
u/Sagebrysh [+1] Rank 7 Pragmatist (13 hours later)
And I suspect that you probably can't get there with a 70 meter pile of junk thrown together by a hacker.
Its actually a decent engine and fusion core. The junk part of it is the rebuilt crew quarters she duct taped onto the top of the drive assembly. I imagine the original assembly came off a larger ship and she just welded the crew quarters on top.
made some changes that hopefully lead to less abuse of physics. Check the link for the updated version and let me know how it is.