Launch vehicle, Atlas V |
Launch vehicle, Atlas V |
Jun 3 2006, 01:19 PM
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#1
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Member Group: Members Posts: 134 Joined: 13-March 05 Member No.: 191 |
NASA has decided to use the Atlas V, with 4 strap-on solid rocket boosters to launch MSL. This is the same rocket that launched MRO (no solids) and New Horizons (5 solids).
Cost: $194.7 million, less than half the price of the Titan IV which would have been needed a few years ago. Rocky Mountain News article NASA press release |
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Guest_DonPMitchell_* |
Jun 4 2006, 06:20 PM
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#2
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Guests |
Let's look at some numbers. Here are some figures for vacuum and sea-level specific impulse, which measures engine efficiency (and thrust in metric tonnes). The F-1 was the biggest engine ever built, but it was based on an old-fashion gas-generator cycle:
F-1 (Saturn V) - 304 265 (790 tons) YF-20B (Long March) - 289 259 (83 tons) Staged compustion is the current state of the art, and this gives you significantly more thrust per kilogram of fuel. The Proton managed 316 sec. even using less efficient fuels (N2O4 + Dimethylhydrozine). At the time of the F-1, only the Russians had mastered staged combustion design: RD-253 (Proton) - 316 285 (178 tons) NK-15 (N-1) - 318 297 (157 tons) RD-180 (Atlas V) - 338 311 (423 tons) RD-701 (MAKS) - 415 330 (408 tons) Today we see the benefits of both staged combustion and liquid hydrogen. The SSME was the groundbreaking technology here, the starting point for all the other cryogenic staged-combustion engines. In the RD-0120, the Russians made some improvements to the SSME which NASA has been studying. It is a simpler design, and is able to achieve combustion stability without complex anti-oscillation dampening chambers. The RS 68 is also a fine engine, designed to be cheap simple and disposable. RS 68 (Delta IV) - 420 365 (338 tons) Vulcain (Ariane) - 434 318 (110 tons) SSME (Shuttle) - 453 363 (232 tons) RD-0120 (Buran) - 455 359 (200 tons) For orbital vehicles, it is better to look at the LEO payload, because that depends on the thrust of all the stages and how their sizes have been balanced against one another. Super-heavy: Saturn V: 118 tons N-1: 95 tons (if it had worked) Energiya: 88 tons Heavy: Shuttle: 27.5 tons Delta 4-H: 25.8 tons Proton: 21.0 tons Atlas V: 20 tons (551 config.) Titan 4: 17.8 tons Ariane V: 16.0 tons Atlas V: 12.5 (401 config.) Long March 2E: 9.2 tons Soyuz: 7.4 tons |
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Jun 4 2006, 06:46 PM
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#3
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Senior Member Group: Members Posts: 3648 Joined: 1-October 05 From: Croatia Member No.: 523 |
You're forgetting the engine RD-180 was derived from -- the RD-170 from the Energia strap-on boosters. With twice the thrust of an RD-180, it beats even the mighty F-1 at 800 tons of thrust. Its variant (RD-171) is being used on the Zenit rocket.
IIRC, the F-1 were actually closer to 700 tons of thrust than 800. -------------------- |
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Guest_DonPMitchell_* |
Jun 4 2006, 07:04 PM
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#4
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Guests |
You're forgetting the engine RD-180 was derived from -- the RD-170 from the Energia strap-on boosters. With twice the thrust of an RD-180, it beats even the mighty F-1 at 800 tons of thrust. Its variant (RD-171) is being used on the Zenit rocket. IIRC, the F-1 were actually closer to 700 tons of thrust than 800. The RD-180 and RD-170 are clusters of 2 and 4 engines, respectively. The RD-701 is a dual engine. But nevertheless they are powerful and well designed. [attachment=6054:attachment] |
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Jun 4 2006, 07:12 PM
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#5
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Senior Member Group: Members Posts: 2488 Joined: 17-April 05 From: Glasgow, Scotland, UK Member No.: 239 |
The RD-180 and RD-170 are clusters of 2 and 4 engines, respectively. The RD-701 is a dual engine. But nevertheless they are powerful and well designed. Don: I'd always thought that one of the particularly Soviet design threads was the way that they saw grouped nozzles as only part of a single engine, particularly when they shared turbopumps and other plumbing. The US designers would see four engines, but the Russian just one. Isn't this descriptive dichotomy what we're seeng with the RD-180 and RD-170? Bob Shaw -------------------- Remember: Time Flies like the wind - but Fruit Flies like bananas!
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Guest_DonPMitchell_* |
Jun 4 2006, 07:23 PM
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#6
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Guests |
Don: I'd always thought that one of the particularly Soviet design threads was the way that they saw grouped nozzles as only part of a single engine, particularly when they shared turbopumps and other plumbing. The US designers would see four engines, but the Russian just one. Isn't this descriptive dichotomy what we're seeng with the RD-180 and RD-170? Bob Shaw Exactly, and the RD-108 on the Soyuz was also such a grouped design. The issue is combustion stability, an extremely difficult problem. Today the Russians are the masters, but in the 1960s, they just couldn't build large chambers. The N-1 had 30 1st-stage engines, at which point the increased probability of failure is a problem. I doubt anyone would ever attempt to build such a large single-chamber engine like the F-1 today, but it was an impressive engineering feat. The Russians also like to simplify the pumping system, typically with a single-shaft multi-turbine design (like their RD-0120 vs. the multi-pump SSME). |
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