If this is your first visit, be sure to check out the FAQ by clicking the link above. You may have to register before you can post: click the register link above to proceed. To start viewing messages, select the forum that you want to visit from the selection below. |
|
|
Thread Tools | Display Modes |
#111
|
|||
|
|||
"Tim Ward" wrote in message ...
"pacplyer" wrote in message om... SSS - Space Sling Shot feasibility wags using a ONE INCH line: (devil's advocates get one free beer for each correction substantiated by some sort of rough data. Nanotube rope discoverer gets free Johnny Walker Blue - 60year old Scotch) I. Subsonic Line Operation FL750. Vectran towrope Assumptions: Length: 10sm's long or 52,800 ft Dia: One in or 24mm Avrg. Tensile strength: 200,000 lbs? Cd 1.0 1" Line Drag at.82M: 143,333lbs (D = 50,000*1.0/12*34.4*1.0=143.333) Deployed 10sm Wt: 54.4lbs/100ft. +28,723lbs (52,800/100(54.4)= 28,723) Total tension on the 1" line: 172,056? (line sees its wt plus drag wt?) Allowable Space Vehicle Drag: 27,944 (derived from 200,000 limit) Thrust Assumptions: 6 GE C90s: Thrust at S.L: 110,000 lbs * 6 engs = 660,000 total thrust at S.L. Thrust at FL500 (1/4 of S.L va.): 165,000 lbs Thrust at dismount: 165,000 Line Drag at Mach .82 -143,333 Residual thrust available for vehicles 21,667 Thrust needed for 747 only -40,000 (whoops shortfall of 20k here!) Available for OrbitOne vehicle none: (I think we need 747 SRB's) snip supersonic stuff Note: Towship is a stripped-down 747-132SF. These supersonic line calcs are for 10-15 seconds only in 30 degree towship bank. You may have noticed I had to hang six GE C90 engines on this thing. (maybe we'll have to call the Russians on this, they built one right?) Conclusion: This Vectran Boat Rope just isn't going to cut it. To overcome 10sm drag at Mach numbers I feel like we can not exceed a half inch line. The one inch line weighs about 28,000lbs on the glider assymbly and produces 143,333 lbs of drag in M.82 flight *just for the line*. Richard Lamb was right: "He's dead Jim, dead Jim, dead." So I guess we would have augered in with a stock 747-200. As Clint Eastwood used to say: "A man's just gotta-know his limitations." pacplyer It may not be as bad as we think. On page 138 of Warner and Johnston's "Aviation Handbook" I came across a graph of "Effect of inclining wires into wind". And so I did a little more sophisticated drag analysis by pulling numbers from that place which such numbers are usually pulled from. I divided the line into 8 sections, and decided arbitrarily, that the first line section was at 10 degrees, the 2nd at 20 degrees, and so on, up to the eighth, which was at 80 degrees. The graph shows the percentage of the maximum drag for the wire vs the wire inclination So, 10 .05 20 .1 30 .2 40 .35 50 .5 60 .7 70 .85 80 .9 Sum 3.46 Now, each of those segments is only 1/8 of the total line drag, so divide that total by 8, and the drag is only about .46 of the previously calculated "worst case". That lowers the drag for the one inch cable down to 66000 pounds. There being no free lunch, with this particular sag schedule, we only get about 65% of the line length as altitude, so the towed vehicle is only about 34000 feet higher than the towplane. That's 84,000 ft at "Slingshot" maneuver. I'll take it! That's a free cold one for you for this fine bit of cocktail napkin work. With yet more sophisticated analysis, the drag might get better yet. The high drag parts of the line are up where the air is a little thinner. Tim Ward Good post Tim. I didn't want to half to hang six: ten million dollar motors on the tugplane anyway! Four is do-able. Six means major headaches with new pylon engineering... ugghh. Talked to my NASA friend last night. She's heavy into a project at work right now, but says she'll get me some answers on max altitude for the Shuttle transport and hopefully some drag figures. Gotta remember that NASA doen't like the latest turn of manned flying events. SS1 made em' look kinda bad! pac |
#112
|
|||
|
|||
|
Thread Tools | |
Display Modes | |
|
|
Similar Threads | ||||
Thread | Thread Starter | Forum | Replies | Last Post |
SoCal hangar space? | nauga | Home Built | 1 | May 6th 04 07:13 AM |
Steven F. Udvar-Hazy Air and Space Museum | Errol Groff | Home Built | 1 | February 26th 04 06:01 AM |
Xprize and tethered space station | Ray Toews | Home Built | 18 | December 16th 03 06:52 PM |
Rounded elevator counterbalance leading edges | Ed Wischmeyer | Home Built | 3 | October 16th 03 12:40 PM |
Air and Space Museum | Home Built | 1 | July 7th 03 06:58 PM |