Unaffordable and Unsustainable, NASA’s failing Earth-to-orbit Transportation Strategy |
Unaffordable and Unsustainable, NASA’s failing Earth-to-orbit Transportation Strategy |
Aug 5 2006, 06:57 PM
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#61
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Member Group: Members Posts: 688 Joined: 20-April 05 From: Sweden Member No.: 273 |
Some of these effects are more important than others. At sea level on the equator, you get a tangential velocity of 0.464 km/sec from the Earth's rotation. If you started on a mountain 8 kilometers high, you would only get 0.5 m/sec more velocity. So altitude is irrelevant. Also, google reveals that Sangay is a very active volcano, which I think we would catagorize as a "logistic concern". :-) I was not considering the extra rotation speed which is indeed minimal. However the take-off altitude is not at all irrelevant, for a number of reasons: 1. You save the energy needed to lift the vehicle those x kilometers 2. Air resistance is much less 3. Rocket engine efficiency is better in thinner air 4. Max Q will be appreciably lower, permitting a lighter structure As a matter of fact I'm a bit surprised that nobody has ever built a high altitude launch site. The reason is probably mostly logistic, and also due to the problem with discarded stages impacting potentially inhabited areas. Still, the Cinese don't seem to worry about this. tty |
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Aug 5 2006, 07:56 PM
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#62
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Senior Member Group: Members Posts: 1636 Joined: 9-May 05 From: Lima, Peru Member No.: 385 |
I was not considering the extra rotation speed which is indeed minimal. However the take-off altitude is not at all irrelevant, for a number of reasons: 1. You save the energy needed to lift the vehicle those x kilometers 2. Air resistance is much less 3. Rocket engine efficiency is better in thinner air 4. Max Q will be appreciably lower, permitting a lighter structure As a matter of fact I'm a bit surprised that nobody has ever built a high altitude launch site. The reason is probably mostly logistic, and also due to the problem with discarded stages impacting potentially inhabited areas. Still, the Cinese don't seem to worry about this. tty What about does with less gravity per kilometer of altitude as Doug has said previously influence the velocity escape? The gravity is around 9.8 m/sec˛ at the sea level but I don't know about what would be the acceleration if the launch platform is on the highland of equadoran Andean territory (above than 3,000 msnm). The Earth gravity variation effect up to 13,000 msnm (airplane intercontinental flights) would be very subttle or not? Rodolfo |
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Guest_DonPMitchell_* |
Aug 5 2006, 08:41 PM
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#63
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Guests |
Ah, right you are tty, lower air pressure is an advantage.
The Chinese don't seem to worry about impacting their territory, nor do they seem to worry about using horribly toxic non-cryogenic fuel. The controversy about using NDMH and N2O4 goes back to the old feuds between Korolev and Glushko. When the second M-69 launch exploded near the launchpad, a kiloton of this toxic mixture went off -- the yield of a tactical nuclear weapon! When people saw the poisonous orange cloud, there was pandemonium as they rushed to their cars to escape. I'm amazed that anyone would use this for manned launches. Oh dear, this thread is really meandering. But I think the original white-paper discussion was beaten to death. |
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Aug 5 2006, 08:57 PM
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#64
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Senior Member Group: Members Posts: 2492 Joined: 15-January 05 From: center Italy Member No.: 150 |
The Earth gravity variation effect up to 13,000 msnm (airplane intercontinental flights) would be very subttle or not? Rodolfo, 13000m is a 0.2% distance variation from Earth center; due to inverse square dependency of gravity force from distance, the acceleration reduction at this height is 0.4% or 4cm/s2. The reduction on top of a (virtual) mountain with the same heght is lower, due to gravity ot the mountain itself... -------------------- I always think before posting! - Marco -
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Aug 6 2006, 12:02 PM
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#65
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Senior Member Group: Members Posts: 3419 Joined: 9-February 04 From: Minneapolis, MN, USA Member No.: 15 |
Ah, right you are tty, lower air pressure is an advantage. The Chinese don't seem to worry about impacting their territory, nor do they seem to worry about using horribly toxic non-cryogenic fuel. The controversy about using NDMH and N2O4 goes back to the old feuds between Korolev and Glushko. When the second M-69 launch exploded near the launchpad, a kiloton of this toxic mixture went off -- the yield of a tactical nuclear weapon! When people saw the poisonous orange cloud, there was pandemonium as they rushed to their cars to escape. I'm amazed that anyone would use this for manned launches. Oh dear, this thread is really meandering. But I think the original white-paper discussion was beaten to death. Well, Don, the U.S. of A. used those horribly toxic fuels to launch 10 manned Gemini capsules on the Titan II booster. And, of course, every lunar orbit insertion, every lunar descent and ascent, and every trans-Earth injection performed during Apollo used these fuels. And, IIRC, the Shuttle uses these fuels for its reaction control system and its orbital maneuvering system. And, oh yes, the CEV and LSAM are now planned to use these fuels. I agree, they're horribly toxic, hard to handle, and even small leaks can have catastrophic effects. But the specific impulse of these fuels, along with their (relatively) easy storage over the course of a long mission, make them still the best choice for many applications... -the other Doug -------------------- “The trouble ain't that there is too many fools, but that the lightning ain't distributed right.” -Mark Twain
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Aug 6 2006, 04:21 PM
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#66
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Member Group: Members Posts: 624 Joined: 10-August 05 Member No.: 460 |
"Toxic" fuels do not necessarily yield highly toxic reaction products. Hydrazine reduces to nitrogen and ammonia. The sodium azide burned in early air bags yielded almost pure nitrogen.
Shuttle propellant is not very toxic, although there is evidence exposure to one of the main ingredients (perchlorates) can cantribute to thyroid problems. Shuttle exhaust fumes do contain hydrochloric acid, although direct contact with the exhaust, after it has cooled, will usually only be slightly irritating, unless inhaled. |
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Guest_DonPMitchell_* |
Aug 7 2006, 03:53 AM
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#67
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[attachment=6929:attachment]
UDMH is both toxic and carcinogenic. It's been a big concern in Kazakhstan for some time now, and Russia is developing the Kerosene/LOX Angara first stage as a replacement for the Proton. When spent rocket stages from Baikonur fall to Earth, the local residents rush out and begin cutting them up to sell the titanium scrap metal. Children play in the wreckage, herds of farm animals die mysteriously. You also get considerable contamination around the launch site, because combustion is not perfect during startup. [attachment=6930:attachment] [attachment=6931:attachment] Titan II was an ICBM developed in 1959, and hastily pressed into service as a manned launcher when the space race first began. The Ariane 1 also used this fuel, but it was developed with extensive Soviet assistance -- they even supplied UDMH to France. But for a country to use this technology for manned flight in 2006 is not very advanced. |
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Guest_DonPMitchell_* |
Aug 19 2006, 08:30 PM
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#68
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Looks like NASA has decided to put some serious money into COTS, the program to boost new private-sector space efforts.
MSNBC It's a gamble, but I would like to see SpaceX succeed with the Falcon series. In interesting feature of Kistler is that they are using Russian engines designed for the N-1 moon rocket -- LOX/Kerosine staged-combustion engines. |
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Feb 5 2007, 07:22 PM
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#69
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Member Group: Members Posts: 153 Joined: 14-August 06 Member No.: 1041 |
http://www.spaceref.com/news/viewsr.nl.html?pid=23230
NASA OIG Report: NASA's Plan for Space Shuttle Transition Could Be Improved by Following Project Management Guidelines QUOTE Our evaluation of NASA's "Human Space Flight Transition Plan" found that it did not comprehensively address certain elements that we believe are essential to management and high-level oversight of an activity of the transition's scope and importance. Specifically, the transition plan did not comprehensively address the following elements: A work breakdown structure that divides the transition activities into manageable segments. Detailed cost estimates to support the budget preparation process and facilitate cost control. Metrics for measuring transition progress and success. Periodic milestone reviews. Internal and external communication plans to facilitate an efficient flow of information to the stakeholders. Asset end-state requirements and security provisions for Space Shuttle Program property. A centralized data management system to document transition-related recommendations and decisions. Clearly defined responsibilities for the components of the transition governance structure and designation of the component responsible for post-2010 decisions. Two comments: 1) It is surprising that this project-level planning is not in place. 2) This assessment is buzzword loaded, and could have been written by any audit of any type of enterprise anywhere. Perhaps technical expertise is not required in the OIG; or they may be taking a first-things-first approach. |
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Sep 27 2007, 05:09 PM
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#70
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Member Group: Members Posts: 568 Joined: 20-April 05 From: Silesia Member No.: 299 |
NASA has decided to end its use of the Boeing Delta II rocket.
Delta II will be retired In my opinion it's very bad decision, Delta II is so cheap and reliable launch vehicle. What you think about this decision ? -------------------- Free software for planetary science (including Cassini Image Viewer).
http://members.tripod.com/petermasek/marinerall.html |
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Sep 27 2007, 05:21 PM
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#71
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Founder Group: Chairman Posts: 14431 Joined: 8-February 04 Member No.: 1 |
http://www.unmannedspaceflight.com/index.php?showtopic=4626 is a discussion on that issue
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