delta V

Darkness Within (9): Miscalculation

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MET 186-23+4

So I’ve been running some numbers.

At a best guess from the nav data available, Gutpunch had 18.5 hours1 to run at standard cruising acceleration, 9.6 standard gravities effective2. That in turn implies that I need something approaching six million m/s of delta V effective to make zero-zero with the Kerjejic stargate.

These are not happy numbers.

Actually, let me rephrase that: these numbers represent a six-species clusterfuck at a Clajdíän clambake.

The candle plan will not work, obviously, hope and head injuries notwithstanding. Samildán could bring his traveling Heaven alongside and hand me a dreadnought-sized fusion torch with all the trimmings, and I couldn’t squeeze 6e6 out of it. That’s why we had to learn to cheat in the first place.

I need a vector-control core. So let’s hope Kirchev parked the cutter facing aft the last time out.

MET 187-4-32

Well, damn.

I have half a cutter. Snapped in two at the shear line, clean as you like. Not, however, the half with the core in it.

I also have two racked tactical observation platforms, neither of which has a core, along with some spare parts racks, tools, and plenty of debris. Everything I could need to build a candle, if that would help.

I need a new plan.

  1. 20 of your Earth hours, for anyone who wants to check my numbers.3
  2. 9 of your Earth gravities.
  3. I always wanted to use one of your Earth “of your Earth”s.

Hohmann Transfer Delta-V Approximator

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Speaking of handy little Mathcad tools, this one is a generic delta-v approximator for planet-to-planet Hohmann transfers, based on the same mathematics as this Stack Overflow answer:

http://space.stackexchange.com/questions/1380/how-to-calculate-delta-v-required-for-a-planet-to-planet-hohmann-transfer

As mentioned there, it makes various assumptions, including that the bodies’ orbits around their sun are within delta of circular and coplanar (which works reasonably well for Sol), and that you aren’t using low-thrust drives and as such it can get away with treating burns as instantaneous. The further you wander away from these, the more approximate the approximation gets, belike. Caveat calculator!

Anyway, here it is:

https://onedrive.live.com/redir?resid=8B53BC30DA65DCAA!90356&authkey=!AAMfSsixhk7pGRI&ithint=file%2cmcdx

Enjoy!

Basic Delta-V Worksheet

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So, as those who follow my Google+ account will know, I use PTC Mathcad to do the various calculations behind the scenes to reality-check my work, starship designs, orbital parameters, etc., etc. And being the kind and generous soul that I am, I thought I might clean up and share my tools for the benefit of, well, everyone who wants to do this kind of thing.

Here, then, is the first of those cleaned-up sheets – a basic calculator that does the ground-to-orbit-or-escape delta-v calculation, as illustrated by Atomic Rockets here.

Here’s what it looks like (printed as XPS); and here’s the live version for those of you who have PTC Mathcad (requires only the free-for-life Express version).

Run Silent, Run Drunk

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Deep recon and forward scouting is the job of the recon destroyers. And contrary to “Running Cold”, it’s not a particularly stealthy job. For all the boffins dream about stealth starships and talk airily about basement universes and domain walls and dimensional transcendence, I’ve never seen one. And no, that’s not a joke.

The aim is not to avoid being seen. They can see you, bright, hot, and clear. (It’s not all bad – this also means that you can see them.) The aim is to be seen sailing through the target area fast and high and out of the way – beyond intercept range and outside their engagement envelope – so they can’t touch you. Except for exchanging the usual bluster.

Not that that stops people from taking a pot-shot or two at you anyway on general principles. So you jink, jink, jink and trust to light-lag! But all that drunkwalking cuts deep into your delta-v reserve for evading and running, which is why they give you a whole library of variable-power drunkwalk algorithms, from a pro-forma wobble on the reaction wheels up through the affectionately named Torpedo Tango, Missile Minuet, Warhead Waltz, Firing Solution Foxtrot, and so forth, right on up to the good old Hellfire Hop. Choose carefully, ‘cause you might need whatever you burn now later. And if you’re really worried, you can fire up the kinetic barriers to military power – if you wouldn’t rather keep that energy to go into thrust, and if you don’t mind being provocative by shining the EM signature of a battle-ready warship all over the system. Any misjudgment at this point may result in a salvo or two of unanticipated k-slugs ripping big holes in your ‘can.

This is why every recon captain I ever served under had an ulcer and the temperament of a grouchy bear.

– Senior Chief Viviré Galicios, Imperial Navy (unpublished memoir)