Need Writing help on Technical Details...

[seawasp]

I'm working on Threshold, the sequel to Boundary. With Boundary, I basically only had to do one or two orbital calculations, and as they were Earth-Mars, I could steal most of that info from a couple of sources.

In Threshold, I've got a number of trips between Earth and Mars, and I need to schedule them as quickly together as possible (with a very small number of ships), and then I have plot reasons to go to (or at least have ships heading for) no less than three other astronomical bodies.

I am, unfortunately, NOT a rocket scientist. I know the technologies which will be available to the characters (several, including one Very Cool Neato drive approach). I know where I want these people to get to, and I know other events I want to have happen, but I am stopped at the point where I actually have to assign numbers to things like "how long will this take" and "what stuff do they need to take with them".

A couple of people on Baen's Bar pointed me towards some software that was supposed to do this, but I cannot seem to get it to work (and other packages are of course Windows, while I'm running on a Mac) and, speaking honestly, I don't know enough to even know what I don't know, if you know what I mean. I know more about the physics of space travel than most laymen do, but it's not nearly enough.

If I can tell you where I want to go, for what reason, and what technology I use to get there (and, I suppose, some of the dramatic reasons why and how), can someone help me achieve the following:

1) Reasonable (if AWFULLY TIGHT) schedules to get people from point A to B
2) Any special requirements (e.g., extra throwaway fuel tanks, etc) needed to get where they're going
3) particular times I'd have to be "hitting" in order to get the particular planetary alignments I'd need
4) Any special maneuvers (slingshots, etc.) which would be used in getting there or stopping there.

Note that I reserve the right to BEND physics to serve dramatic necessity, but I don't want to BREAK physics in any areas where I'm using known tech. I don't mind people saying "Ooooh, jeez, that's an awfully optimistic set of assumptions"; I do mind them saying "Not One Chance In All The Hells of Space".

I really do need technical advice on this one. I can handle a lot (sensor tech, etc.) but there's about eight major sciences involved in Threshold that I want to avoid bobbling too badly.

Anyone interested can either email me by replying to this message, or you can join up with my Livejournal community for betareaders of my stuff, rykspoor_beta.

For this assistance you would get a "thank you" acknowledgement in the front of the book (similar to the one for Phil Moynihan in Boundary) and, if you liked, a cameo/redshirting/Tuckerization.

Comments

[ckd]

The immediate first question I can think of is whether you have constant boost with a turnover at midpoint, or whether you're coasting most of the way. (Note, however, that I am not a rocket scientist; I'm in NE30, Space Propulsion Lab is in 37.)

Constant boost is easy to do the math for.

I have...

[seawasp]

... NERVA rockets (like the NIKE from Boundary, although you could have a larger vessel or disposable tanks), electric/ion drives (lower thrust, much better ISP) and one relatively constant boost drive (think lightsailish, though not exactly).

Re: I have...

[ross-teneyck.livejournal.com]

What kind of acceleration are we talking about? My impression is that if you can do constant thrust in the 1g range, then you can largely ignore orbital effects and treat the solar system as more or less flat.

Of course, last time I looked, the numbers on doing constant 1g thrust were depressing, even if you assumed magically efficient drives.

[aardy.livejournal.com]

I don't actually know any of this (never took physics, myself), I'm just a librarian with some searching skills. :)

The Hohmann transfer orbit (which before slingshotting was the only method and is still used to get satellites into place) takes approximately 1/2 the orbital period of the outer orbit to get from one orbit to another. See Wikipedia for the actual math involved. (I couldn't find the fastest possible turnaround time in 5 minutes or less, though.)

The bi-elliptical orbit is a variant on the Hohmann transfer orbit, but takes more time than the standard Hohmann method. If going to a significantly outer orbit (by a factor of 12, if I read the numbers correctly), it may be more energy-efficient, though. There's a link in the above Wikipedia article about this one if you want to read more.

The gravitational slingshot approach takes "less" time, and the math is here. I couldn't quickly find any actual statements of comparison, or comments on possible turnaround time, though the celestial map showing Cassini's travels and the dates it reached each planet may help some with that.

There are also some interesting equations about the possible thrust of various alternative rocket types (such as ion engines), especially as compared to current standard rocket propellant here.

NASA has a paper comparing fusion & antimatter propulsion here, and mention in the abstract that magnetic fusion rockets could theoretically do a round trip from Earth to Jupiter in a year, and that inertial fusion rockets could do a round trip from Earth to Pluto in 2 years, if that helps any with the context.

None of that helps do the tough math for you, unfortunately, but I hope it's helpful anyway.

[elainegrey.livejournal.com]

What's the mac software you can't get to run, and what's the version of the OS you attempted? Unless someone's helped you on that score....

Regrettably, my mechanics training was pretty trivial compared to those requirements....

obital mechanics

[(Anonymous)]

Ryk,

your orbit transfer times are dependent on three things.

1) Relative positions of the planets when you start
2) Total delta V of the ship
3) maximum sustainable acceleration

That is, a ship with a total delta V of 1 million meters per second, with a maximum acceleration of 0.01g will take a very different path than a 1 million meter per second ship with a maximum acceleration of 1g

never-the-less, if your acceleration is very low (0.01g range) and/or if your delta V is in the < 100,000 m/s range then you're looking at transfer times on the close order of half-the-orbital-period of the outer body.

if your "semi constant boost ship" has a substantially higher acceleration, then times drop.

Do what Eric does, post it the other way around. Which planets, and how long does the story need for it to take? "is this possible" is much easier than the open ended question you asked.

-_ Rick Boatright

[k-kinnison.livejournal.com]

obviosuly if would help upon arrival to mars when Mars and earth are near perihelic opposition, that would cut the distance down to at least 55 million KM (not sure the exact distance)

Since we are making time the limiting factor IPS (interplanetary Superhighway) type low thrust routes would be unfeasable. But almsot all Earth to mars journies use the Hohmann Transfer Orbit

I know in Boundary you dismissed the idea of Aerobraking for the Nike, but the risks might be worthwhile for a craft that is more spartan and can take the punishment of Aerobraking, maybe even using inflatable ballons made out of heat resistant fabric mylar coated fabric similar to what we saw in the movie 2010, this would allow for less time in deceleration. Then again, I dont know the physics invovled and wether it is feasable with the thin martian atmosphere.

here is some info on Hohmann Transfer Orbit: http://www-spof.gsfc.nasa.gov/stargaze/Smars2.htm

Maybe you should contact the local University, and thier Astronomy department with your Thrust information.

You might need to also ask WHEN they are leaving compared to the other methods if it becomes some sort of Race. There are some Optimal times to leave for a least time Earth to Mars transpher, but if time was of the essance things could get interesting

Btw, any type of Moon-Earth-Mars slingshot would be unfeasable due to the Escape velocity needed from the moon, and the gains by the gravity assist from the earth.

[quantumseriph.livejournal.com]

You can quite easily set up your mac to duel boot between windows and OSX (I write this on a mac that does just that). For a very small diskspace sacrifice and some other dues of sata. . . I mean microsoft of course.

Maybe...

[seawasp]

... on some of the newer Macs which use Intel chips. None of the ones I use qualify on that. I can set up VirtualPC on mine but that severely impacts system performance.

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