Goodie Bag

The time has come to post some links. Some may be useful, others may just be fun. Still others may just be symptomatic of mental illness on my part :).

Rocketry and Spacecraft

The first thing in the Rocketry and Spacecraft department is bad news and related whinging. The NTRS site has been down for quite awhile. Supposedly in response to the recent espionage charges against Bo Jiang. Seems like a lot of the stuff from the sixties, at least, should have been cleared for ITAR a long time ago. I think its more of an opportunity action by people hostile to open government. Hopefully it’ll all be back up on wikileaks pretty soon ;).

Speaking of Wikileaks, they have the full text of Appendix 6 of the NASA Exploration Systems Architectural Study with lots of juicy details on the various launch vehicle alternatives that were looked at in the study. I especially appreciated the, presumably accurate, weights and measurements of the Atlas and Delta evolution phases. It’s a welcome and useful addition to the rest of the report openly published, here. I’m a fan of the nasaspaceflight.com site, and I’d love to get an L2 account if I ever have that kind of money to spare, but I think this is exactly the sort of information that NASA should have been publishing openly on its own…

Pretty clearly, even with greatly disparate propellant densities, tank masses cluster pretty well around the MTank = 10.41 * (VTank)0.75 line(Thanks to http://www.alternatewars.com/).

Pretty clearly, even with greatly disparate propellant densities, tank masses cluster pretty well around the MTank = 10.41 * (VTank)0.75 line(Thanks to http://www.alternatewars.com/). I use Pietrobon’s exponent of 0.848 largely on faith, ’cause I haven’t actually checked his line against this…

Alternate Wars has a nice set of tutorials on the design and modeling of imaginary rockets. The tutorials are intended for modders of the Kerbal Space Program game, but the information on creating 3d rocket models in Blender and figuring out propellant and tank weights is useful to anyone with an interest in this sort of thing. Previously, I used the tank sizing rules from Steven Pietrobon’s Analysis of Propellant Tank Masses(grab that before some Congress-critter decides its a security risk and disappears the thing). One thing I hadn’t been too sure about was how tank masses would vary with propellant density. Pietrobon was looking specifically at hydrolox applications, so I didn’t know how that would vary with kerolox or other propellant combinations. The picture to the left, which I took from Alternate Wars has alleviated my confusion.

In a loosely related vein, this thread has some more pictures of the ‘realistic’ Star dy-100-update_07_sept_06SMTrek DY-100 posted by Winchell Chung(right purdy, those). Samples shown above and to the right. How cool is that? I’m feeling a need to build spaceships! Future post idea!

Stars and Planets

Landon Noll posted a nice table showing stellar parameters by HR  and Luminosity class. I like it. It’s a good expansion upon the similar table in 2300AD. Also like the 2300AD table there’s a clear problem with this kind of chart: try as I might, I can’t find any giant stars with masses similar to Sol. This is kind of an argument in favor of the GURPS Space 4th ed. rules for generating stars that start with mass and age and determine HR spectrum and Luminosity class from that. I still like this kind of chart and I’ll likely be using it frequently. It’s just necessary to use a bit of care when considering the parameters of non- main sequence stars.

Even more useful to me was this page by Larry Bogan. I already had the formulae for determining the luminosity of a star from its temperature and radius(and other combos of those values), but the formulae for Color Index and Bolometric Correction are sure nice.

Electric History

Not that I haven’t had algorithmic simulation of social attributes swimming around in the back of my mind since long before I was inspired to make this post, by a post on Sword vs Dagger about population distribution, but it has been bubbling up a lot lately. Back in the ’80s I played a game on my Amiga called Balance of Power. This was a game about playing power politics without immolating the Earth in nuclear fire! I usually failed on both counts… In spite of that, I was fascinated by the idea of simulating global politics on a computer. I’ve been wanting to do something like GDWs Great Game(Check out the map) for two centuries now.

The way things in life seems to focus on an idea makes me believe in synchronicity. Although, as I’ve said, this idea has been at the back of my head for a long time, but just lately it seems to have come to a head. So I was trawling Atomic Rockets(Winchell Chung again…) looking for stuff on interstellar colonization. This leads me on into his history stuff: Future History, Alternate History and (especially)Modeling History. In the last, Chung brings up Balance of Power and a book detailing something about the internal algorithms of the game. Well after a bit of digging I find a copy of that book right here on the internet. Posted by the author no less.

In another tab, I’m looking at SFRPG forum, mostly to see if Constantine Thomas has anything new going on. There I find a thread on Taxonomies of Governments. I think it’s about time to get my thoughts together and write a post on this particular subject…

GIS, Terrain Generation and Visualization

Another field that needs a bit of love lately. I haven’t done much in this area, but I did run across a couple of good bits. Genesis 4 is a terrain visualization tool that I had a good deal of interest in awhile back, but not enough to loosen the clawlike grip I maintain on my not terribly heavy wallet. Now it’s altogether free. Just look for the registration name, key and validation on the linked page. I’ve messed around a bit with Landformer, but this is nice to see. On the down side, it probably doesn’t bode well for the financial health of the producer or the programs future updatage. Always a cloud…

Next time I boot up Windows, I’ll also try out Nem’s Mega 3D Terrain Generator. Should be good for a lark at least.

Thank you for reading,
The Astrographer

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2 Responses to Goodie Bag

  1. jjaquinta says:

    Let me know if you find any terrain generators that produce spherical terrain. The next step in the ChView is from inferring stars to inferring planets. The data is there, but I want to do 3D renderings. I’ve got some of my own generators based on a HEALPix projection. It’s handy because it decomposes a sphere into 12 squares. So all the algorithms for rectangular based generation can be used. I’m happy with it for terrestrial planets, but it falls short for planets whose primary terrain feature is craters. I’ve got one based on some 1966 paper about simulating the crater densities observed in the old Ranger probes. But the results are not terribly compelling. The other major surface type is gas giants. I just need a decent fluid simulator. Unfortunately the best one out there is patented. 😦 The search goes on…

    • Astrographer says:

      As to terrain generators that produce spherical terrain, any 3D perlin noise will do fine. I’m loosely associated with the planetGenesis project(I know, sourceforge… sorry). That also includes the somewhat improved perlin simplex noise as an option(I’m still kind of proud of that).

      Pretty much any automated generator with the exception of physical process-based simulators like tectonic plate simulations will tend to fall flat in realism, especially across a global scale. Perlin generators probably aren’t much good except to generate continental outlines with threshold(mask in pG), and even that will take a bit of node-jiggering and have some serious deficiencies. Visual forgeries of reality aren’t too hard, but fooling a geomorphologist? That requires an artist.

      Can you share the 1966 paper? Probably not much I could do with it and it would surely remain less uncompelling, but I collect that kind of thing and it might even set my little grey cells into motion.

      It ain’t just gas giants. Generating a decent cloud cover map for an earthlike planet is a nightmare at best and very few are even good as visual forgeries. I’ll let you know if I ever find a decent free fluid sim. Blender might be okay if you can get it going and figure out how to export it in a useful format.

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