Neptune Orbiter, Another proposed mission |
Neptune Orbiter, Another proposed mission |
Nov 10 2005, 03:51 PM
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Member Group: Members Posts: 509 Joined: 2-July 05 From: Calgary, Alberta Member No.: 426 |
This seems like a good place to start off the Uranus and Neptune forum: with the next ice-giants mission.
I will admit to not knowing a whole lot about the Neptune Orbiter With Probes (NOWP), other than the fact that it's in the planning stages, and a few other details I've gathered from Wikipedia and various other Internet sources. Anyone care to get this one going with a bit more information? |
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Dec 5 2005, 07:35 AM
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#2
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Senior Member Group: Members Posts: 3419 Joined: 9-February 04 From: Minneapolis, MN, USA Member No.: 15 |
Does Triton *really* have enough of an atmosphere to allow for efficient aerobraking? At least, without a gazillion passes before you're significantly slowed down?
-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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Dec 5 2005, 08:34 AM
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#3
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Member Group: Members Posts: 648 Joined: 9-May 05 From: Subotica Member No.: 384 |
QUOTE (dvandorn @ Dec 5 2005, 10:35 AM) Does Triton *really* have enough of an atmosphere to allow for efficient aerobraking? At least, without a gazillion passes before you're significantly slowed down? -the other Doug NO IT DOES NOT! The atmospheric pressure at Triton's surface is about 15 microbars , 0.000015 times the sea-level surface pressure on Earth...that's not enough for any kind of aerobraking... Mars has average presure of 7 milibars, that is why MRO will have to spend many months aerobraking and don't forget that it uses only upper parts of atmosphere where presure is much less than that... The average pressure on the Earth surface (sea level) is 1000 millibars.... In order to use that little atmosphere on Triton for aerobraking our unlucky spaceprobe would have to fly verry,verry,verry dangerously close to surface... Edit: Some approximate calculatins based on these facts: Mars atmosphere is 143 times less efficient in aerobraking then atmosphere of Earth is... Triton atmosphere is 467 times worst then Mars... So it would take gazillon passes through it to slow down significantly... Solution : USE ROCKET ENGINES!!! -------------------- The scientist does not study nature because it is useful; he studies it because he delights in it, and he delights in it because it is beautiful.
Jules H. Poincare My "Astrophotos" gallery on flickr... |
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Dec 5 2005, 10:49 AM
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Member Group: Members Posts: 255 Joined: 4-January 05 Member No.: 135 |
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Dec 5 2005, 11:42 AM
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Member Group: Members Posts: 648 Joined: 9-May 05 From: Subotica Member No.: 384 |
QUOTE (chris @ Dec 5 2005, 01:49 PM) What did you meen by "exiting" ? What's exiting about landing on a patch of nitrogen or methane ice? Edit: Also what does it have to do with rocket engines? -------------------- The scientist does not study nature because it is useful; he studies it because he delights in it, and he delights in it because it is beautiful.
Jules H. Poincare My "Astrophotos" gallery on flickr... |
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Dec 5 2005, 12:52 PM
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#6
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Member Group: Members Posts: 255 Joined: 4-January 05 Member No.: 135 |
QUOTE (Toma B @ Dec 5 2005, 11:42 AM) What did you meen by "exiting" ? What's exiting about landing on a patch of nitrogen or methane ice? Edit: Also what does it have to do with rocket engines? If you land on a patch of such ice, and the rocket exhaust is hot enough to vaporise the ice, then you might get an explosive release of gas, which would be dangerous to the lander. The surface of Triton, at -235 Centrigrade, is only 20 degress lower than the freezing point for nitrogen, so it wouldn't be that hard. Chris |
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Dec 5 2005, 01:27 PM
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#7
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Member Group: Members Posts: 648 Joined: 9-May 05 From: Subotica Member No.: 384 |
QUOTE (chris @ Dec 5 2005, 03:52 PM) If you land on a patch of such ice, and the rocket exhaust is hot enough to vaporise the ice, then you might get an explosive release of gas, which would be dangerous to the lander. The surface of Triton, at -235 Centrigrade, is only 20 degress lower than the freezing point for nitrogen, so it wouldn't be that hard. Question: Will methane explode without oxygen? NO IT WILL NOT !!! ...there's not much oxygen on Triton isn't it? About Nitrogen... How long would rocket engine work when verry close to surface...2-3 seconds perhaps? Without any atmospheric presure there might be some sublimation but I'm sure nothing exiting.... Here's a deal: Why don't we make a bet and we will see when NASA send that probe in the next 20 to 150 years... -------------------- The scientist does not study nature because it is useful; he studies it because he delights in it, and he delights in it because it is beautiful.
Jules H. Poincare My "Astrophotos" gallery on flickr... |
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Dec 5 2005, 03:07 PM
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Member Group: Members Posts: 255 Joined: 4-January 05 Member No.: 135 |
QUOTE (Toma B @ Dec 5 2005, 01:27 PM) Question: Will methane explode without oxygen? NO IT WILL NOT !!! ...there's not much oxygen on Triton isn't it? About Nitrogen... How long would rocket engine work when verry close to surface...2-3 seconds perhaps? Without any atmospheric presure there might be some sublimation but I'm sure nothing exiting.... Toma, I wasn't talking about combustion. The explosion I am postulating would be purely mechanical, driven by gas pressure. Imagine if the exhaust warmed some water ice with pockets of nitrogen gas in it. Secondly, remember the geysers on triton - small in temperature lead to some pretty dramatic effects - from Wikipedia: "It is thought that the surface of Triton probably consists of a semi-transparent layer of frozen nitrogen, which creates a kind of greenhouse effect, heating the frozen material beneath it until it breaks the surface in an eruption. A temperature increase of just 4 K above the ambient surface temperature of 38 K could drive eruptions to the heights observed." (That height being 8Km!) Chris Edit: added Wikipedia info |
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