Author Topic: Astronomy/space exploration thread  (Read 100463 times)

Offline Legion

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Re: Astronomy/space exploration thread
« Reply #25 on: November 10, 2006, 03:10:52 AM »
Just send it out into deep space.

So that it crashland onto an alien planet in the future, which in turn will provoke a massive interstellar war with earth?

Haven't you learned anything from watching sci-fi? :D
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Darmok

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Re: Astronomy/space exploration thread
« Reply #26 on: November 10, 2006, 03:18:47 AM »
Just send it out into deep space.

This is an option, but unfortunately, it is difficult. Cassini is in orbit around Saturn and cannot easily escape. A number of intricate maneuvers including Titan flybys would be needed to boost it out of Saturn’s orbit; this would be time-consuming and complex. In addition, even if it were able to be freed, it still may not have enough energy to escape the gravity of the sun. To date, we have only launched five spacecraft total that had sufficient velocity to (eventually) escape; the first of these (launched in the late 70s) is now probing the edge of the solar system.

Offline Stoo

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Re: Astronomy/space exploration thread
« Reply #27 on: November 10, 2006, 03:27:22 AM »
Send it plunging into Saturn, and leave the cameras running for as long as it survives!

[edit]although the space.com article mentions there might be problems with it getting smashed up passing through the rings.
« Last Edit: November 10, 2006, 03:46:55 AM by Stoo »

Offline Da Vinci

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Re: Astronomy/space exploration thread
« Reply #28 on: November 10, 2006, 03:48:18 AM »
Two space.com stories that might be interesting:

Quote
Freak One-Eyed Monster Storm Spotted on Saturn

A freaky storm two-thirds the diameter of Earth and unlike anything ever seen has been spotted on Saturn.

The tempest, some 5,000 miles wide (8,000 kilometers), has an oddly human-looking hurricane-like eye [image]. But it is very different from a terrestrial hurricane, scientists said today.

NASA's Cassini spacecraft photographed the huge storm. It swirls with 350 mph winds at the ringed planet's south pole. It has a remarkably well-defined eye ringed by clouds that soar 20 to 45 miles high (30 to 75 kilometers), or up to five times taller than hurricane clouds on Earth. (...)

(Rest of the story here)
It just looks menacing, reminds me of the eye of Sauron ;D

-----------------------------------------------------------

Quote
Russia, China Discuss Joint Space Projects

MOSCOW (AP) – Russia plans to cooperate with China in robotic missions to the moon and Mars and other space projects, officials said Thursday.

“We have switched from cooperating on technological elements and devices to developing big scientific projects in space research,'' Yuri Nosenko, a deputy head of Russia's Federal Space Agency, told reporters in a televised hookup from Beijing, where he and other officials were attending a Russian national exhibition.

(Rest of the story here)

I'm very curious what those two can come up with.
« Last Edit: November 10, 2006, 03:50:21 AM by Da Vinci »
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Offline nixonshead

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Re: Astronomy/space exploration thread
« Reply #29 on: November 10, 2006, 05:42:23 AM »
I did a review of the Casini mission at Uni back in 1997 (before its launch) and it was always the plan to have it plunge through Saturn's rings as its final act.  It would almost certainly be destroyed, but you'd get a lot of good data before the end.  I don't see why that article says that Casini must be 'decommissioned'.  What's the problem with leving it in orbit of Saturn?  It's not like it's a hazard to navigation or anything!  Plus it could be a tourist attraction in a couple of hundred years  :)

For the Alternate VSE report, yeah I agree the uber-booster seems a bit on the over-large side.  My main concern with the report is that their CEV command module seems a bit on the small side, even for a reduced crew of 2.  Looking at the cutaway on the landing sequence, I can't see where they'd fir in life support, avionics, parachutes, landing airbags, EVA suits, etc, etc.  Problem is, if you increase the cabin size most of their other assumptions go out the window.  So I'll give NASA the benefit of the doubt on their VSE approach...

As for Mars missions, I see no reason to wait for some new propulsion system.  Chemical plus gravity assist via Venus can do the job (for a good portrayal of this type of mission, I recommend Stephen Baxter's novel Voyage).  Sure, it's a long way out for a short time on the surface, but it's quite credible.  If you use In-Situ Resource Utilisation, you can even start a colonisation effort at a modest cost (see Bob Zubrin's The Case For Mars, or check out the Mars Society: http://www.marssociety.org/.  I don't agree with everything they propose, but it's a pretty well thought out engineering approach).

Speaking of Mars, it seems NASA has lost contact with the Mars Global Surveyor. (see SpaceRef at: http://www.spaceref.com/news/viewpr.html?pid=21260)

Quote
Engineers are striving to restore full communications with NASA's Mars Global Surveyor on the 10th anniversary of the spacecraft's Nov. 7, 1996, launch.

The orbiter is the oldest of five NASA spacecraft currently active at the red planet. Its original mission was to examine Mars for a full Martian year, roughly two Earth years. Once that period elapsed, considering the string of discoveries, NASA extended the mission repeatedly, most recently on Oct. 1 of this year.

The orbiter has operated longer than any other spacecraft ever sent to Mars. It has returned more information about Mars than all earlier missions combined and has succeeded far enough beyond its original mission to see two later NASA orbiters arrive: Mars Odyssey and Mars Reconnaissance Orbiter. Among many important accomplishments so far, Mars Global Surveyor has found many young gullies apparently cut by flowing water, discovered water-related mineral deposits that became a destination for NASA's Opportunity rover, mapped the planet topographically and examined many potential landing sites on Mars.

Gloal Surveyor was one of the first of then-NASA administrator Dan Goldin's "Faster, Better, Cheaper" missions that were exposed to such ridicule after the loss of the Polar Lander and the Mars Climate Orbiter in 1999.  Personally I feel that there was a lot of unjust criticism of the FBC approach - the point was that failures are acceptable with FBC-class missions.  Global Surveyor lasted five times its original design life, and might yet be recovered to give another five years of service.  So who had the last laugh?
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Offline Stoo

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Re: Astronomy/space exploration thread
« Reply #30 on: November 10, 2006, 05:51:05 AM »
  Chemical plus gravity assist via Venus can do the job (for a good portrayal of this type of mission, I recommend Stephen Baxter's novel Voyage).  Sure, it's a long way out for a short time on the surface, but it's quite credible.

Oh, sure, we can try. I'm just skeptical about the chances of of the astronauts coming back alive. I'd rather the priority for the next few decades be moon missions - and taking steps towards a permanent base there. Rather than taking a chance on mars just for the hell of it.
« Last Edit: November 10, 2006, 05:53:41 AM by Stoo »

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Re: Astronomy/space exploration thread
« Reply #31 on: November 11, 2006, 12:36:48 AM »
What's the problem with leving it in orbit of Saturn?  It's not like it's a hazard to navigation or anything!  Plus it could be a tourist attraction in a couple of hundred years  :)

I thought the worry was that it could collide with a satellite and potentially contaminate it with terrestrial life.

Speaking of Mars, it seems NASA has lost contact with the Mars Global Surveyor. (see SpaceRef at: http://www.spaceref.com/news/viewpr.html?pid=21260)

Ah, that sucks! MGS has already accomplished so much; I hope they will be able to restore communications soon.

Edited to correct satellite name.
« Last Edit: November 13, 2006, 10:28:16 PM by Darmok »

Offline Bond, James Bond

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Re: Astronomy/space exploration thread
« Reply #32 on: November 11, 2006, 05:21:55 AM »
Wait wait wait if you kill me, who will bring you unsolicited astronomy news? Not to mention verbose, pompous judgments? Or self-important rants? Or arrogant ramblings?

Right here!  ;D

Bond when he shows back up.

I missed you too, sweetheart.

Darmok

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Re: Astronomy/space exploration thread
« Reply #33 on: November 12, 2006, 12:16:29 AM »
So it looks like the ISS crew may be tossing some trash overboard:

Quote from: [url=http://www.newscientist.com/
New Scientist[/url]]
Astronauts to pitch unwanted gear off space station

22:47 10 November 2006
NewScientist.com news service
Kelly Young


The International Space Station may soon have its first policy allowing crew members to intentionally pitch unneeded gear overboard. This may temporarily increase the amount of space junk orbiting Earth, but scientists say it will pose no extra danger to the crew or other spacecraft.

Tools and other gear have accidentally floated away during spacewalks. But NASA has shied away from intentionally jettisoning gear off the ISS in the past because of the threat of space junk hitting the station or other spacecraft.

(continued)

Offline Da Vinci

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Re: Astronomy/space exploration thread
« Reply #34 on: November 12, 2006, 02:41:24 AM »
They did this before, see for instance SuitSat. (That was basicly a garbage dump disguised as a experiment  ;D)
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Re: Astronomy/space exploration thread
« Reply #35 on: November 13, 2006, 01:26:05 AM »
Hey; I thought SuitSat was a rather nifty idea, albeit one that didn’t work that well…

Offline nixonshead

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Re: Astronomy/space exploration thread
« Reply #36 on: November 13, 2006, 05:45:08 AM »
Following that alternative VSE approach I posted about earlier, news from inside NASA seems to be that the Ares I crew launch rocket (that ungainly shuttle SRB with a hydrogen tank stuck on the top) will not actually be able to launch the Orion CEV.  (See the article at SpaceRef: http://www.spaceref.com/news/viewnews.html?id=1171)

Quote
Sources inside the development of the Ares 1 launch vehicle (aka Crew Launch Vehicle or "The Stick") have reported that the current design is underpowered to the tune of a metric ton or more. As currently designed, Ares 1 would not be able to put the present Orion spacecraft design (Crew Exploration Vehicle) into the orbit NASA desires for missions to the ISS. This issue is more pronounced for CEV missions to the moon.

The Ares 1 SRR (System Requirements Review) was held last week at MSFC. Mike Griffin was in attendance. Others participated off-site via webex.com.

It is widely known that both Mike Griffin and Scott Horowitz are reluctant (to say the least) about abandoning their current launch vehicle concept. Alternate approaches such as using EELVs are not welcome solutions by either Griffin or Horowitz.

One possible solution to the Stick's current design problems is to add side-mounted solid rocket motors. Many inside the program are not so sure that this solution is worth the effort. Others suggest that starting from a clean sheet of paper may be the only prudent course of action.

Why are NASA still pushing this design?  My suspicion is that the main reason was to keep Thiokel (who maunfacture the SRBs) in business - especially as NASA want to use SRBs on the Ares V heavy lifter - if Thiokel go under or have to sack half their experienced workforce before Ares V production starts, then that would leave VSE in a sticky situation.  However, the Ares I "Stick" has now been re-designed so extensively and is so far from being an optimum launcher that I really don't think it's worth persevering with.  It'd probably be cheaper for NASA to buy Delta or Atlas EELVs for the Crew Launch Vehicle and just give Thiokel free money to send their engineers on sabatical until they're needed for Ares V!

@Stoo:  I agree with you that the biggest unknown for a Mars mission is the crew.  Life support on a long mission, and especially the radiation concerns, are not easy.  However, compared to what terrestrial explorers like Scott put up with, Mars-bound astronauts wouldn't be too badly off.  (Then again, Scott died - maybe I should have said Shakleton  :) )

@Darmok, I wouldn't expect planetary contamination concerns to be a major issue with Casini's destruction.  It's been irradiated in deep space for the past decade, and the chances of any microbes surviving to 'Andromeda strain' a moon are as close to zero as makes no odds.  I think NASA already worries far too much about this sort of thing - playing to the media.  If bugs could have survived on Casini and then thrive on some moon after ramming it at a dozen kilometres per second, then good luck to them.  Tonnes of extraterrestrial material is entering Earth's atmosphere every year, but I'm not going to start worringing about Rigellian Fever.
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Offline Da Vinci

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Re: Astronomy/space exploration thread
« Reply #37 on: November 13, 2006, 07:54:03 AM »
That's seriously bad news, a metric ton isn't nothing. I still don't understand why they don't use a modular system comparable to the Saturn 1b and Saturn V, as they currently stand Ares I and Ares V have little in common. Add to that the virtual absence of reuse of current shuttle hardware (which was the point of these rockets in the first place), they're probably indeed much better of making the current EELV's manrated than to continue with this dead horse. Don't you just love company politics?
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fowlerbryan

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Re: Astronomy/space exploration thread
« Reply #38 on: November 13, 2006, 12:16:27 PM »
Quote
NASA Loses Contact With Mars Global Surveyor
By Ker Than
Staff Writer
posted: 10 November 2006
11:24 am ET

NASA's Mars Global Surveyor (MGS) spacecraft has failed to check in with Earth for the fifth straight day in a row, after losing contact during a routine adjustment of its solar array.

If contact is not reestablished by Saturday, NASA might try to have another Mars-orbiting spacecraft take pictures of MGS to assess its condition.

On Nov. 2, MGS mangers sent commands for the spacecraft to adjust the position of one of its solar power arrays to better track the sun. Returning data indicated a problem with the motor that moves the array, so a backup motor and control circuitry were switched on.

No signal was received on Nov. 3 and 4, but a weak signal was received on Nov. 5, suggesting the spacecraft had switched to a safe mode and was awaiting further instructions from Earth. The signal cut out completely later that day and nothing has been heard since.


http://www.space.com/news/061110_mgs_missing.html

It's interesting and sad to see one experiment/satellite go badly while others that go quite well. Hopefully they will ascertain that the satellite is just in "safe mode" or whatever. I hate to see a NASA project fail like this...

fowlerbryan

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Re: Astronomy/space exploration thread
« Reply #39 on: November 13, 2006, 12:22:09 PM »
Quote
Shuttle Discovery Treks to Launch Pad for Next Mission
By Tariq Malik
Staff Writer
posted: 9 November 2006
11:12 a.m. ET
 

This story was updated at 4:00 p.m. EST.

NASA’s shuttle Discovery made the slow journey to its Florida launch pad early Thursday as engineers prepare the spacecraft for a December flight to the International Space Station (ISS).

The shuttle settled onto Launch Pad 39B [image] at NASA’s Kennedy Space Center (KSC) in Cape Canaveral, Florida at about 9:03 a.m. EST (1402 GMT), more than eight hours after rolling out [image] of the Vehicle Assembly Building at 12:29 a.m. EST (0529 GMT), KSC officials said.

Discovery is poised to launch towards the ISS with its STS-116 astronaut crew on Dec. 7 at 9:35:42 p.m. EST (0235:42 Dec. 8 GMT), the agency’s first night flight in four years. Discovery’s STS-116 mission managers decided today not to push Discovery’s planned launch ahead one day to Dec. 6, NASA spokesperson Kyle Herring, at the Johnson Space Center in Houston, told SPACE.com.


http://www.space.com/missionlaunches/061109_sts116_rollout.html

Quote
Shuttle Computers Find No End to 2006
Author Tariq Malik
One year might as well be an eternity for NASA’s space shuttles, which – it turns out – have no automatic reset once the calendar hits Jan. 1, 2007.

“The interesting thing about the shuttle computers and the ground computers that support the shuttle is that they were never envisioned to fly through a year-end changeover,” says NASA’s shuttle chief Wayne Hale here at the agency’s Johnson Space Center. “So the shuttle computers actually keep counting and they believe that it is Day 366 instead of Day 1 of the New Year.”


http://www.livescience.com/blogs/2006/11/07/shuttle-computers-find-no-end-to-2006/

A couple of related stories. I didn't know about the year rollover issue with the shuttle computer. However, it does make a little bit of sense, looking at the computers of the era. I had no idea that they hadn't switched out some of the computer components in the recent years and upgrade schedules...

Offline Torlek

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Re: Astronomy/space exploration thread
« Reply #40 on: November 13, 2006, 06:12:18 PM »
Quote
NASA Loses Contact With Mars Global Surveyor
By Ker Than
Staff Writer
posted: 10 November 2006
11:24 am ET

NASA's Mars Global Surveyor (MGS) spacecraft has failed to check in with Earth for the fifth straight day in a row, after losing contact during a routine adjustment of its solar array.

If contact is not reestablished by Saturday, NASA might try to have another Mars-orbiting spacecraft take pictures of MGS to assess its condition.

On Nov. 2, MGS mangers sent commands for the spacecraft to adjust the position of one of its solar power arrays to better track the sun. Returning data indicated a problem with the motor that moves the array, so a backup motor and control circuitry were switched on.

No signal was received on Nov. 3 and 4, but a weak signal was received on Nov. 5, suggesting the spacecraft had switched to a safe mode and was awaiting further instructions from Earth. The signal cut out completely later that day and nothing has been heard since.


http://www.space.com/news/061110_mgs_missing.html

It's interesting and sad to see one experiment/satellite go badly while others that go quite well. Hopefully they will ascertain that the satellite is just in "safe mode" or whatever. I hate to see a NASA project fail like this...
It sounds like you might be confusing MGS with the Mars Reconnisance Orbiter (the CIA spy satellite that got sent to Mars ;D), MGS has been in orbit for 8 years and is well past its initial life.
« Last Edit: November 13, 2006, 06:35:57 PM by Torlek »
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Re: Astronomy/space exploration thread
« Reply #41 on: November 13, 2006, 10:38:27 PM »

@Darmok, I wouldn't expect planetary contamination concerns to be a major issue with Casini's destruction.  It's been irradiated in deep space for the past decade, and the chances of any microbes surviving to 'Andromeda strain' a moon are as close to zero as makes no odds.  I think NASA already worries far too much about this sort of thing - playing to the media.  If bugs could have survived on Casini and then thrive on some moon after ramming it at a dozen kilometres per second, then good luck to them.  Tonnes of extraterrestrial material is entering Earth's atmosphere every year, but I'm not going to start worringing about Rigellian Fever.

I too am not very concerned about planetary contamination; I believe that fear of contaminating one of Saturn’s moons is the concern. It is true that radiation causes genetic damage usually sufficient to kill cells, but it also promotes mutations, and bacteria with their short reproductive cycles are quite fast at evolving. And it’s not as if we don’t already have bacteria that are relatively resistant to radiation (for instance, Deinococcus radiodurans) on Earth. I suppose we have different philosophies. You wish good luck to terrestrial bacteria growing on one of the satellites, but I do not feel this would be a good thing. I want the satellites to stay free of Earthly contamination so that 1) we may search of life that may have developed there and 2) we don’t interfere with the prospect of future life developing there. Your converse situation is not a good analogy; any extraterrestrial organisms arriving from space would be poorly adapted to Earth’s environment; it is quite unlikely that they would be infectious to humans and they probably wouldn’t even be able to survive in the face of competition from our native organisms.

It's interesting and sad to see one experiment/satellite go badly while others that go quite well. Hopefully they will ascertain that the satellite is just in "safe mode" or whatever. I hate to see a NASA project fail like this...

I’m with Torlek on this one; while it’s always sad when satellites cease working, it must eventually happen, and I would not certainly not categorize MGS as a project that failed!
« Last Edit: November 13, 2006, 10:46:27 PM by Darmok »

Offline nixonshead

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Re: Astronomy/space exploration thread
« Reply #42 on: November 14, 2006, 01:24:22 AM »
I too am not very concerned about planetary contamination; I believe that fear of contaminating one of Saturn’s moons is the concern.

Sorry, I was counting moon contamination as planetary contamination.

It is true that radiation causes genetic damage usually sufficient to kill cells, but it also promotes mutations, and bacteria with their short reproductive cycles are quite fast at evolving.

Quite right - bacteria with short reproductive cycles evolve fast.  However, what is the reproductive cycle of a bacteria in a vacuum without a supply of nutrients?  F-all, is the answer.  It's just possible that bacteria could survive on a spacecraft in a dormant state and revive when conditions improve (when it has a supply of nutrients and a cosy environment - this apparently happened with bacteria from the Ranger moon landers), but bacteria are NOT reproducing in-transit on Casini. 

Your converse situation is not a good analogy; any extraterrestrial organisms arriving from space would be poorly adapted to Earth’s environment; it is quite unlikely that they would be infectious to humans and they probably wouldn’t even be able to survive in the face of competition from our native organisms.

So how come you think Earthly bacteria would have more luck on Titan or wherever than space bacteria would have on Earth?  Earth bacteria are not adapted for living at temperatures of -150 celsius with no food supply, and any existing life-forms that are already there would surely be able to compete with our shivering micoscopic cousins. 

I agree that contamination from Earth bacteria can be a problem if we're looking for native life - the decontamination procedures for the Viking landers were pretty lax by today's standards, at that may have contributed to their abiguous results.  But the odds of life from Earth surviving and wiping out (hypothetical) species on some other body in the Solar System are so absurdly remote that I see no reason to waste propellant decomissioning Casini in some suicide run at Saturn.  And anyway, what of life in Saturn's atmosphere?

As for concerns over possible future life, I think it's all getting a bit philosophical.  Do the rights of currently non-existing potential life supercede those of currently existing bacterial life?  And if by some miricle bugs from Casini started a thriving ecosystem out round Saturn, would that be worse than leaving it barren and empty for the foreseeable future?

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Re: Astronomy/space exploration thread
« Reply #43 on: November 14, 2006, 01:50:15 AM »
Quite right - bacteria with short reproductive cycles evolve fast.  However, what is the reproductive cycle of a bacteria in a vacuum without a supply of nutrients?  F-all, is the answer.  It's just possible that bacteria could survive on a spacecraft in a dormant state and revive when conditions improve (when it has a supply of nutrients and a cosy environment - this apparently happened with bacteria from the Ranger moon landers), but bacteria are NOT reproducing in-transit on Casini.

You are right, of course; I was referring to the evolution of the bacteria upon reaching a more suitable environment, not in transit.

So how come you think Earthly bacteria would have more luck on Titan or wherever than space bacteria would have on Earth?  Earth bacteria are not adapted for living at temperatures of -150 celsius with no food supply, and any existing life-forms that are already there would surely be able to compete with our shivering micoscopic cousins. 

I agree that contamination from Earth bacteria can be a problem if we're looking for native life - the decontamination procedures for the Viking landers were pretty lax by today's standards, at that may have contributed to their abiguous results.  But the odds of life from Earth surviving and wiping out (hypothetical) species on some other body in the Solar System are so absurdly remote that I see no reason to waste propellant decomissioning Casini in some suicide run at Saturn.  And anyway, what of life in Saturn's atmosphere?

I believe they would have more luck since they would not have a native population with whom to compete. Interference with a native population was not one of the scenarios I mentioned. Cassini’s propellant is not recoverable and will be wasted no matter what. Saturn’s atmosphere is quite different from the environment on Titan, but yes, I would prefer Cassini not impact a celestial body at all.

As for concerns over possible future life, I think it's all getting a bit philosophical.  Do the rights of currently non-existing potential life supercede those of currently existing bacterial life?  And if by some miricle bugs from Casini started a thriving ecosystem out round Saturn, would that be worse than leaving it barren and empty for the foreseeable future?

Yes, it is philosophical, as you have stated it. My personal views tend to be match those expressed by the Federation: they do not terraform worlds that have the prospect of life developing.

But in this case, no such abstract notions need be debated. My interest in this is scientific. Since all life we currently know of has descended from the same primordial cell, the field of biology is at an enormous disadvantage. The scientific benefits of having a second form of life to study are enormous, and I would greatly prefer not to interfere with that.

Darmok

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Re: Astronomy/space exploration thread
« Reply #44 on: November 14, 2006, 03:16:42 AM »
So it looks like NASA is going to use the Mars Reconnaissance Orbiter Friday to take a look at the malfunctioning Mars Global Surveyor, and possibly even try to enlist the rovers to help.

Quote from: [url=http://www.cnn.com/
CNN[/url]]
Orbiter may be last chance to rescue Mars probe


This week, engineers are preparing for what may be their last chance to salvage the spacecraft.

NASA plans to use the newly arrived Mars Reconnaissance Orbiter, or MRO, to take a picture of Global Surveyor to see how the failed craft is oriented relative to the sun for power and to Earth for communications.

The picture will be taken Friday when the satellites are about 93 miles apart. MRO’s high-powered camera should be able to image details of Global Surveyor as small as about 10 centimeters, said Tom Thorpe, the spacecraft project manager.

“We have a good chance of recovering it still,” Thorpe said in an interview.

Flight controllers also plan to try to get Global Surveyor to contact one or both of NASA’s roving geology stations, Spirit and Opportunity, which are located on opposite sides of Mars’ equator.

The rovers would not be able to relay the spacecraft’s science data but engineers would at least get an idea of its general position. The linkup also could show if Global Surveyor still has power.



Offline nixonshead

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Re: Astronomy/space exploration thread
« Reply #45 on: November 14, 2006, 06:25:20 AM »
Okay, I'm now very confused about your concerns on the planetary protection thing...

Quote
Quote
Quote from: nixonshead on Today at 01:24:22 AM
Quite right - bacteria with short reproductive cycles evolve fast.  However, what is the reproductive cycle of a bacteria in a vacuum without a supply of nutrients?  F-all, is the answer.  It's just possible that bacteria could survive on a spacecraft in a dormant state and revive when conditions improve (when it has a supply of nutrients and a cosy environment - this apparently happened with bacteria from the Ranger moon landers), but bacteria are NOT reproducing in-transit on Casini.

You are right, of course; I was referring to the evolution of the bacteria upon reaching a more suitable environment, not in transit.

My original point here was that there is likely no viable bacteria on Cassini because of the radiation exposure.  You're counter was that radiation can be good for evolution, and my comment above was stating that I don't believe that applies in this case.  So are you saying that you think that it is likely that there are currently viable (though maybe dormant) bacteria on Casini or not?

(Incidentally, I made an error - the dormant bacteria I referred to were recovered from a Surveyor probe, not Ranger, by the Apollo 15 mission IIRC).

Quote
I believe they would have more luck since they would not have a native population with whom to compete. Interference with a native population was not one of the scenarios I mentioned.

So the concern is bringing life to another world where it doesn't currently exist? 

Quote
Cassini’s propellant is not recoverable and will be wasted no matter what. Saturn’s atmosphere is quite different from the environment on Titan, but yes, I would prefer Cassini not impact a celestial body at all.

It's not a question of recovering the propellant, it's a question of making the best use of it.  Adding a final suicide plunge to the mission means you will have a lower propellant budget for the science mission, and will probably have to terminate the mission sooner - and means that any Earth bacteria on Cassini that survived the crash would be introduced to an alien environment, which is what I understand your concern to be.  My original notion of just leaving Cassini in orbit would be the best way to avoid contaminating impacts with other worlds.  Of course, with such a complex gravitational system, it's possible that an impact will occur sometime in the next few thousand years, or maybe just centuries, but the only way to avoid an impact is to send Cassini on a Saturn escape trajectory - preferably a solar-system escape orbit - and it doesn't have fuel for that anyway.

Forgive me, but the logic of your arguments seems to be suggesting that you are against the colonisation (or even the robotic exploration) of space.  Is this really the case?  Because you can bet your life that human activity, plumbing, waste disposal, etc from some colony will release a hell of a lot more bugs than an irradiated probe making a high-speed collision.  Plus the fact that humans are not now present on other worlds, so following through the logic they shouldn't be introduced there.

You can never eliminate the risk that we will do something that in a billion years time will mean something beautiful doesn't happen.  So we've got to live with it.  As the late-great Mr Adams might say: "Those who study the cosmic forces of cause and effect in the Universe say that this sort of thing happens all the time, but we are powerless to prevent it.  'It's just life'"

So anyway, I still think Cassini should just be left in whatever orbit it finishes its science mission in.  Life in the universe can take its chances.  I'm certain that we are going to take bacteria to other worlds - but not on Cassini.

And it's increasingly looking like a case of "RIP MGS".  :(
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Tim Bisley: Good for you.
Bilbo Bagshot: Yeah, thanks. But that's not the point, Tim. The point is I was defending the fantasy genre with terminal intensity, when what I should have said was "Dad, you're right, but let's give Krull a try and we'll discuss it later."

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Offline Stoo

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Re: Astronomy/space exploration thread
« Reply #46 on: November 14, 2006, 06:58:30 AM »
Aw come on, suicidal plunge into Saturn! It could be an opportunity for some pretty fantastic pictures, seeing the planet far closer-up than before. Okay it would probably break up pretty fast once it hit the atmosphere, but even low-orbital kind of distances would be worthwhile.

[edit]I was wondering why they didn't do that with Galileo's death-plunge, looks like the camera was broken by that point. Shame.   :(
« Last Edit: November 14, 2006, 07:04:31 AM by Stoo »

Offline Bond, James Bond

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Re: Astronomy/space exploration thread
« Reply #47 on: November 14, 2006, 12:22:03 PM »
Space elevators: 'First floor, deadly radiation!'

18:10 13 November 2006
NewScientist.com news service
Kelly Young
 
Space elevators will face deadly doses of radiation in the Van Allen belts around Earth (Image: Liftport)Space elevators are touted as a novel and cheap way to get cargo, and possibly people, into space one day. So far, they have barely left the drawing board, but ultimately robots could climb a cable stretching 100,000 kilometres from Earth's surface into space.

But there is a hitch: humans might not survive thanks to the whopping dose of ionising radiation they would receive travelling through the core of the Van Allen radiation belts around Earth. These are two concentric rings of charged particles trapped by Earth's magnetic fields.

"They would die on the way through the radiation belts if they were unshielded," says Anders Jorgensen, author of a new study on the subject and a technical staff member at Los Alamos National Laboratory, New Mexico, US.

Space elevators had been planned to be anchored on an ocean platform near the equator, with the other end tied to a counterweight in space.

At the equator, the most dangerous part of the radiation belts extends from about 1000 to 20,000 kilometres in altitude. The region did not hurt the Apollo astronauts in the 1960s and 1970s because their rockets delivered them swiftly through it.

For a space elevator travelling at the current proposed speed of 200 kilometres per hour, however, passengers might spend half a week in the belts. That would hit them with 200 times the radiation experienced by the Apollo astronauts.

Centrifugal forces
There are several possibilities for dealing with the radiation – all of which come with drawbacks. One option would be to move the elevator off the equator. By shifting the elevator north or south, the most intense part of the radiation belts could be avoided.

"Basically what we found was that by moving off the equator by the largest amount you can, you reduce the radiation by a small factor – but probably not enough," says study co-author Blaise Gassend of MIT in the US.

In addition, if the elevator was located at a latitude of 45° north, roughly the same latitude as MIT, the cable would veer south, pulled towards the equator by centrifugal forces. So it would run nearly horizontally through Earth's atmosphere for thousands of kilometres, putting weather-related stresses on the cable that could weaken it.

Another option would be to have some sort of radiation shield stationed along the cable so the elevator could pick it up when it is about to reach the belts. But such a shield would weigh down the whole apparatus, disrupting the natural motion of the cable.

Heavy lifters
"Most of us are agreeing we don't want permanent weights on the ribbon," says Michael Laine, founder of LiftPort Group, a space elevator company in Bremerton, Washington, US. "It starts dampening out the ribbon's motion in ways we don't think we want."

Generating magnetic fields around the climber could shield the habitat module from the radiation as it climbs through space. But it may be difficult to beam enough power to the climber to generate such a shield.

Finally, space elevator builders could simply increase the overall mass of the elevator "car", or lifter – which will require more energy to heave it into space. LiftPort Group, which plans to take up as many as 20 people per trip, will pursue this strategy with a 100-tonne lifter. That is significantly heavier than the 20-tonne lifter planned by Brad Edwards, who devised the current conception of a space elevator.

"I'm confident that we can solve it," Jorgensen says of the radiation problem, "but it's going to make things a little more complicated and a little more expensive."

Journal reference: Acta Astronautica (doi: 10.1016/j.actaastro.2006.07.014)


http://space.newscientist.com/article/dn10520-space-elevators-first-floor-deadly-radiation.html

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Re: Astronomy/space exploration thread
« Reply #48 on: November 14, 2006, 11:16:16 PM »
Okay, I'm now very confused about your concerns on the planetary protection thing...

It’s all right, but I don’t really have the interest to explain it anymore. You bring up some good points.

Offline nixonshead

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Re: Astronomy/space exploration thread
« Reply #49 on: November 16, 2006, 05:55:21 AM »
Interesting article on the Space Elevator, Bond (Nice to have you back, BTW  :)).  I can't really see that shielding would be too much hassel for a system that gives you effectively no limits on the mass you lift - just double the car's mass with radiation shielding and double the number of motors hauling it up the cable.  Problem solved.

Regarding the much-maligned Ares I booster, the program manager at NASA has come out fighting (from SpaceRef: http://www.spaceref.com/news/viewsr.html?pid=22553):

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From: Hanley, Jeffrey M. (JSC-ZA)
Sent: Monday, November 13, 2006 3:54 PM
Subject: FW: NASA Encounters Problems With Ares 1 Launch Vehicle Design

All, between articles like this one (see below) and the wave of 'better ideas' for architecture that have waded into recent notoriety, I thought it was time to level set folks on where things stand - and - dispel these rumors and hearsay surrounding the "issue" of the Ares 1 performance and overall implications to the architecture.

In summary, many who carp from the sidelines do not seem to understand the systems engineering process. They instead want to sensationalize any issue to whatever end or preferred outcome they wish. So be it, that is the world we live in.

So where are we today, specifically on the issue of what the launch vehicle can lift and what the Orion is allowed to weigh?

First, the latest set of analyses indicate that the Ares I can lift 58 klbm to the program-specified injection point of -30 x 100 nmi. This number PROTECTS worst case propulsion performance on the first and second stage.

This compares favorably to the requirement that we specified for the Ares I to inject 52.1 klbm.

The Orion team is working to a control mass of NGT 48.4 klbm. They in turn carry margin within that allocation ranging between approximately 10-20% for mass growth as the design process proceeds.

Further, we have been fairly conservative on the amount of propellant we will load in the Orion Service Module for the lunar missions.

<snip>

Architecturally speaking, we have improved our performance projections over the past year for the amount of mass we can launch to TLI on a Lunar mission by more than 2 mT. We have a highly synergistic launch vehicle approach for Ares I and Ares V that gains high leverage off of our early investments in the 5-segment motor and J2X engine. Our selection of the RS68 engine for the Ares V core stage reduced our outyear costs by billions. And most significantly, our strategy is within our budgetary means for developing the associated launch infrastructure - something that most 'alternative' architectures largely ignore.

We will continue to get these faux expressions of concern from those who wish to see us fail.

They will be disappointed.

Jeff Hanley
Program Manager
Constellation Program Office Houston, Texas 77058

So he's sounding confident that "The Stick" will do the job.  Good for him, and I hope he's right.  However, the way he glowingly describes the changes to a 5-segment SRB, J2X and RS68 does seem a little strange given that the systems they replaced (4-segment SRB and Space Shuttle Main Engine, as well as the issue of re-sizing the External Tank which he doesn't mention) were touted as the main reason (re-use of shuttle technology) for developing new boosters rather than use EELV...

In other news, it seems our local galactic neighbourhood is more crowded that we thought (http://www.spaceref.com/news/viewpr.html?pid=21285):

Quote
Astronomers have identified 20 new stellar systems in our local solar neighborhood, including the twenty-third and twenty-fourth closest stars to the Sun. When added to eight other systems announced by this team and six by other groups since 2000, the known population of the Milky Way galaxy within 33 light-years (10 parsecs) of Earth has grown by 16 percent in just the past six years.

<snip>

The 20 newly reported objects are all red dwarf stars, which now comprise 239 of the 348 known objects beyond our Solar System within the 10-parsec boundary of the RECONS survey. Thus, red dwarfs likely account for at least 69 percent of the Milky Way's residents.

So, lots more candidate worlds that Archer could have gotten to at Warp 5 in the course of 4 seasons  :)
Bilbo Bagshot: I once punched a guy out for saying that "Hawk the Slayer" was rubbish.
Tim Bisley: Good for you.
Bilbo Bagshot: Yeah, thanks. But that's not the point, Tim. The point is I was defending the fantasy genre with terminal intensity, when what I should have said was "Dad, you're right, but let's give Krull a try and we'll discuss it later."

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