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su37
路人甲乙丙
Taiwan
1337 Posts |
 Posted - 09/18/2008 : 02:26:44
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最近看完惑星奇航的動畫,
開始上網找有關目前太空科技的資料,
有個東西的性能數據小弟搞不太懂,希望有大大可以指教:
有關美國太空梭的主引擎(SSME)的推力數據,
目前找到兩個衝突的數據,
在http://forum.dtmonline.com/cgi-bin/topic.cgi?forum=48&topic=52這篇文章中,提到每具SSME在真空中所產生的推力約為21150kg,
如果沒記錯的話,一架太空梭上應該裝了3具SSME吧?
那21150kgX3=63450kg
可是,小弟查維基百科發現不一樣的數字
在百分之百的出力狀況下,
SSME的海平面推力有375000磅,約為170096kg
而且這似乎指單一具SSME便有將近十八萬公斤推力
約為上篇文章數據的九倍,
到底是怎麼回事? |
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ewings
路人甲乙丙
943 Posts |
Posted - 09/18/2008 : 02:30:10
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關鍵字
"真空中"
"海平面"
*****************************
當你看到我在版上發的文章越來越多時，也代表我拿到博士學位的時間會越來越晚
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toga
版主
Tajikistan
12781 Posts |
Posted - 09/18/2008 : 02:37:42
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http://en.wikipedia.org/wiki/Space_shuttle_main_engine
SSME thrust (or power level) can be throttled between 67 to 109% of rated thrust. Current launches use 104.5%, with 106 or 109% available for abort contingencies. Thrust can be specified as sea level or vacuum thrust. Vacuum thrust will be higher due to the absence of atmospheric effects.
100% thrust (sea level / vacuum): 1670 kN / 2090 kN (375,000 lbf / 470,000 lbf)
104.5% thrust (sea level / vacuum): 1750 kN / 2170 kN (393,800 lbf / 488,800 lbf)
109% thrust (sea level / vacuum): 1860 kN / 2280 kN (417,300 lbf / 513,250 lbf)
Specifying power levels over 100% may seem confusing, but there is a logic behind it. The 100% level does not mean the maximum physical power level attainable. Rather it is a specification, decided on early during SSME development, for the "normal" rated power level. Later studies indicated the engine could operate safely at levels above 100%, which is now the norm. Maintaining the original relationship of power level to physical thrust helps reduce confusion. It creates an unvarying fixed relationship, so that test data, or operational data from past or future missions can be easily compared. If each time the power level was increased, that value was made 100%, then all previous data and documentation would either require changing, or cross-checking against what physical thrust corresponded to 100% power level on that date.
SSME power level affects engine reliability. Studies indicate the probability of an engine failure increases rapidly with power levels over 104.5%, which is why those are retained for contingency use only.
Toga, 宅男三十一根草
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su37
路人甲乙丙
Taiwan
1337 Posts |
Posted - 09/18/2008 : 02:40:20
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quote:
Originally posted by ewings
關鍵字
"真空中"
"海平面"
維基上的資料顯示,
在百分之百的出力狀況下,
SSME在海平面的推力為375,000磅 ,在真空中為470,000磅
不管是哪個數字都比上面文章的數字大很多啊-___-...
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berkut
新手上路
215 Posts |
Posted - 09/18/2008 : 07:53:12
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quote:
Originally posted by su37
維基上的資料顯示,
在百分之百的出力狀況下,
SSME在海平面的推力為375,000磅 ,在真空中為470,000磅
不管是哪個數字都比上面文章的數字大很多啊-___-...
你有看完全文嗎? |
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