R-505 in X-plane

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R-505 in X-plane

Postby marko dash » Mon Oct 03, 2011 8:23 am

hello everybody. this will be a long first post, but contains enough airship porn to make up from it. :D

found this place from the link at the bottom of the girl genius comic page. after reading through the fist page of the story several times and putting off reading further due to other stories i was into at the time i finally set aside a few hours over the last three days to read it all the way through.

as it went on i became curious if i could simulate the flying cloud on X-plane, a fairly realistic flight simulator that allows you to build and test fly your own aircraft. these aircraft include airships and i had already created several, two of which you will see later. the only thing stopping me was a lack of data, which was remedied when i found the specifications on the main page that had included information that had been nearly impossible to find when looking for background info for building my other airships. such as empty weight and the amount of lift provided by the hydrogen bags. before i had to calculate the available internal volume and then determine how many and how big the hydrogen cells should be. then i would see if that was enough for my intended weight + cargo, changing the size if needed.

needless to say, this involved a lot of math, which isn't one of my strong suites. however with the data available from that page and from other details still in recent memory from my archive binge of the story i set to it. i think it turned out rather well, certainly one of the best 'looking' airships i've made.

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climbing out of Charleston international on one engine


yes i know it's grey, texturing is something I've never been able do do without making it look worse. if anybody would like to try i'll upload the paint files.

i should probably mention now that X-plane has to 'cheat' slightly when it comes to balloons, blimps, and airships. they are a niche and they're flight operations are different from fixed and rotary winged aircraft. one of these is that there are no mooring masts for them, so i gave R-505 a set of retractable landing gear. the other is the way the buoyancy works, you can't bleed hydrogen or dump ballast to trim yourself out. instead you input an average amount of lift and an adjustment percentage: for example if you put in 100,000lbs of lift an a percentage of 25% you can adjust between 75,000 and 125,000 pounds of lift out of your gas bags. for the flying cloud i used the figure of it's typical gross lift for it's average and a 15% adjustment factor so i could go from 85% full to 100% full, or down to 70%.

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this does not mean however that you can not drop water. the downside is that this feature is set up for fire-bombers, if you hit the button it drops ALL the water you have it carrying. while that may be good for dousing a forest fire it sends an airship from level flight to a 2000 fpm climb. the weight of ballast water wasn't including in the specifications so i guessed.

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in this picture i left the data view up that i use to fly, as i normally fly from 3rd person, to show that after some tweaking to the sleekness of the envelope and turbocharger pressure (and nearly 14 nautical miles to accelerate) i hit 72 knots indicated airspeed. true to the speed trials portion of the story it accelerated from drifting to 64kts quickly, it's that last 8kts that took awhile.

now for some formations! note the A.I. does not know how to work the displacement lever, so most of these are descending despite the A.I. doing what it thinks it should by firewalling the throttle and pulling up which doesn't work so well without wings. these first two i didn't make, you can tell because they've been painted. :P

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you should recognize this little gasbag, she isn't good for much past 30kts and we're doing twice that. :)

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the R-101 managed to not fall out of the sky (probably because her 'average' displacement was high enough to keep her aloft at this altitude), so she got an extra pic.
these next two are mine, the're not very pretty and they don't have R-505's graceful curves. both are modern, purpose built designs.

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this little fellow, trying to stay in the air and failing, is a regional people mover and general utility craft. it can transport up to 80 passengers and their luggage up to 800 miles at 87kts on it's four high efficacy 300hp radial diesels. these engines can swivel from -45 to 120 degrees, allowing for the airship to take off slightly heavy and descend even while light without needing to vent any consumables. this vectoring thrust plus independent control of each engine allows for precision control even in a hover, which lets it preform many of the jobs normally assigned to helicopters at a fraction of the fuel costs and many times the loiter ability.

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this half mile long monstrosity has few places on land able to receive it, which it why it normally makes a soft landing in lakes and harbors to offload it's four million pounds of cargo. it looks more like a sky going submarine air an airship, and shares many features with them. it's aluminum skin which is fairly thick at the nose is balanced by a pair of huge electric motors driving two sets of counter rotating props with blades close to the size of those found on wind turbines. it's enormous size and extreme loadlifting allow it to do what the NB-36 and X-6 could not... carry, and properly shield, the two lightweight 3MW reactors nestled in it's belly. these two provide not only the electrical power to the massive engines but also allows it to crack water which is ether stored or collected from moisture on the hull for replacement hydrogen. it's hardened nose lets it cruise at over 160kts and the reactors provide for feasibly unlimited range, it needs only land to transfer cargo and crews.
Some say the sky is the limit. but to those who love aviation, the sky is home.
marko dash
 
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Re: R-505 in X-plane

Postby PaulGazis » Wed Oct 05, 2011 11:44 am

Hi Marko, those ships look awesome! And it's interesting to see how your speed trials came out. Those are quite close to the figures I estimated based on Nevil Shute's fabulous essays about the R-101 and some physics calculations on pencil and paper. You handled the ballast/lift issue the way I would have. Since Everett and his crew would be extremely reluctant to let their hydrogen volume drop below 65%, that 70-100% range looks good. The big question is how X-plane deals with the pressure height issue -- assuming it deals with it at all. If it doesn't, I can imagine some work-arounds, but I have yet to determine how well they'd work in practice.

I've been meaning to get a copy of X-plane for quite some time to build an R505 model (as well as an R87 model, R212 model, L137 model, Mysterious Cruiser model, etc.). This should get me off what MacKiernan might trenchantly refer to as my 'duff' :) I'm sure other readers have X-plane as well, so we'll have to prevail upon you to post a link to your design files!

That nuclear-powered ship looks intriguing. I was putting together figures for something similar for an entirely different series of stories. I ultimately dropped the technology level for that particular culture back to the late 1930s after determining that the economic base couldn't support something more sophisticated, but I still have a spiral binder full of notes somewhere. I'll have to dig it out and see how they compare with your ship. Will those other stories ever see publication? This will be a test of my powers of persuasion and the imagination of literary agents...

Now, can you model the Blimp Race in Episode 114? :)
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Re: R-505 in X-plane

Postby marko dash » Wed Oct 05, 2011 1:32 pm

if you can put out some stats and maybe a 2 or 3 view for the airships i could probably do it. X-plane should be able to handle most airships, as you can have up to eight engines. although not being able to have more has stopped me from making some of the larger ones featured in crimson skies, and is why extremely large ones like my nuclear powered 'ship have huge fixed engines when i'd prefer more, smaller engines so that i can have more control at low speed. as it is the nuclear airship, having such a large surface area is at the mercy of the winds until it hits about 30kts, even weighing as much as it does.

i won't really be able to race them however, i could set the average displacement up enough that it will stay up under A.I. control but the A.I. will go wherever is pleases. X-plane does have a aftermarket plugin for multiplayer which you can bring your own aircraft into, but I've never had the patience to get it working.

it took a few tries to get the flying cloud up to 72kts mostly just tweaks to the drag on the gondola and envelope. i also set the props to maintain a constant tip mach, this is probably to advanced for the 20s, i had them set to manual control but it was difficult to keep in the optimal rpm band along with throttle and displacement. you can justify that as having the engines tend to by another crew member. i think i have to adjust the engines a little, on that run i had them turbocharged up to 6,000ft but that led to them producing more than 800hp at sea level. what altitude was the trials held at? i also need to change to sfc values for the engines, the default is set up for engines running on avgas or turboshafts on jet-a. the diesels would sip fuel a little better.

as to pressure height, it doesn't account for it at all. you will continue to climb until the air thins out enough for you to be heavier than it again, during the test flights i got high enough that the engines shut down due to the thin air. you could set it up to get a warning buzzer when you get within 500 ft of 6,000ft this is normally set up as a ground alert however, changing the settings will lose that.

what is the state of development regarding bow planes? IIRC didn't quite a few crashes happen due to the tail striking the ground/water when trying to pull up at low altitude due to a storm or a microburst?

as to getting the sim, you may want to hold a bit, versen 10.0 is coming shortly witch will include a fairly extensive graphics improvement. it will also make the price for 9.0 go down.

if you just want to build and test you can download the demo here, or browse the forums here. the demo only allows for 10min of control input per startup but includes the programs for the planemaker and airfoil creator if i remember right.

the learning curve for using the planemaker isn't steep, it's mostly about putting realistic data for the size aircraft your trying to make. most of my early attempts at it didn't go so well because i didn't know what scale i was making everything at and what it should weigh, so i had four engined jets the size of a small single engined prop weighing as much as a loaded F-15E. that's most of the reason i was so pleased about the specifications for the R-505 as it included most of what i needed, the rest was getting the shape of the envelope, control car, and engine pods right. i remember you said somewhere on here how many sides the envelope had, how many was it?
Some say the sky is the limit. but to those who love aviation, the sky is home.
marko dash
 
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Re: R-505 in X-plane

Postby Mutabilis » Sun Oct 09, 2011 7:37 pm

flightgear has a purpose written physics engine for lighter-than-air-vehicles. it's used in various balloons, and a fairly accurate model of the zeppelin NT.
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Re: R-505 in X-plane

Postby marko dash » Mon Oct 24, 2011 5:01 am

i've left the model of the 'flying cloud' alone for now, i do have a version with adjusted ballast for AI formation flying, but i haven't tweaked it anymore. i have however been on a bit of an airship binge lately (guess the cause of that :P ), more specifically the 20-40s era. i'm having problems finding information, could to shed some light on various engines used at the time? i'm also try to arm a few of them, what armament does the R-505 carry and where? the only thing i recall is a 40mm gun in a drop down platform, but surly there must be a few MG mounts? and what about the cruiser that splashed the 'flying lady', would it be giving too much away to get some info on her size, engine fit, and weapons load out?

i'm also trying to do a 'fighter' type airship, a small 1-3 man airship with forward facing armament (maybe a belly turret), and a single high performance engine, with just enough volume in the gas bag to lift it all. it would fit with the universe but it seems like a fixed wing aircraft, even a early WWI era one, would do the job much better.

what is the state of development of aircraft in captain Everett's world? because even the earliest fighters world be a dangerous threat to an airship.
Some say the sky is the limit. but to those who love aviation, the sky is home.
marko dash
 
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Location: Summerville, S.C., United States

Re: R-505 in X-plane

Postby PaulGazis » Tue Oct 25, 2011 1:16 am

If you can find manage to track down a copy of Zeppelin, by Peter Brooks, grab it immediately! It's long out of print, and used copies cost a fair penny, but it has detailed specifications for every ship that ever flew. Douglas Robinson's The Zeppelin in Combat is a good reference for German ships -- that's where I got the hypothetical 'L137' -- and his Up Ship contains pretty much all the information one could ever need about the US Navy's magnificent but ill-fated program. Another neat book, which discusses the bottom end of the size range, is John McPhee's The Deltoid Pumpkin Seed. I've been tempted to slip one of those aircraft into the world of the Flying Cloud.

I hadn't thought of posting specifications for other ships, but now that you've suggested it, these may appear on the Extras or About pages. It takes time to edit the text and tables and straighten out the graphics, so bear with me. If you want to get a head start on the Mysterious Cruiser, it's pretty close in size and statistics to the US Navy's Akron and Macon, as I'm sure you've already guessed from the graphics. After spending many years at NASA's Ames Research Center, riding my Suzuki past Moffett Field's Hanger One every morning, I have a soft spot for those two ships :)

I've got a notebook full of numbers for engines... somewhere. This was part of the research for... cue suspenseful music...The Novel. I'll dig it out when I can. As far as machine guns go, the Flying Cloud would carry single .30 cal machine guns in the upper lookout and stern stations, with more fitted elsewhere as the mission might require. Since the arms companies in Everett's world haven't quite figured out recoilless rifles yet (the idea of all that backblast next to several million cubic feet of hydrogen does give one pause), the biggest cannon the Mysterious Cruiser could carry is probably a '75'... but this does not exhaust the limits of aerial weaponry in Captain Everett's world.
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Re: R-505 in X-plane

Postby marko dash » Thu Oct 27, 2011 3:07 am

no dice so far on buying that particular book as i'm unemployed and broke. it seems to be rare enough that none of the online library's have it, though it seems there's a copy at the library in Columbia. if i'm unable to find information by other means i'll see if they can ship it to the local branch. However google has quite a few ebooks on the subject, some of them free, including "British airships, past, present & future" By George Whale.

ive also started on the blimp used in the airship race. going off the description on the page before the race i've been able to find the SS class scout blimp and the engine mentioned on Wikipedia. so i'll use the figures there for size, weight, and envelope capacity. just have to alter engine placement and maybe extend the control car.
Some say the sky is the limit. but to those who love aviation, the sky is home.
marko dash
 
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Joined: Mon Oct 03, 2011 5:33 am
Location: Summerville, S.C., United States


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