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Posted by: GregM Feb 14 2006, 03:21 AM

.

Posted by: BruceMoomaw Feb 14 2006, 07:36 AM

NASA is talking now about allying with the ESA on the Mars sample return -- but "relatively inexpensive" is not a phrase that comes to mind in connection with that one. If this rumor is true (and I'm extremely skeptical): maybe they're planning a multi-nation collaboration on Europa Orbiter, including a lander?

Posted by: djellison Feb 14 2006, 08:01 AM

It all sounds very exciting, but there's no money for it.

I wouldnt call them the 'enemy' in any way shape or form. Certainly not for me anyway.

Doug

Posted by: hendric Feb 14 2006, 03:52 PM

Maybe a Venus lander/blimp? Venus has the advantage of a quick time-to-payoff. Plus, other than the high-temp electronics , it should be a relatively easy planet to land on, ie nice constant atmo, close to Sun, Venus Express will be in orbit (does it have the same relay capability as MEx?), etc.

Posted by: GregM Feb 14 2006, 05:22 PM

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Posted by: tty Feb 14 2006, 07:09 PM

How about a near-earth asteroid orbit modification demonstration mission? If using the "gravity tug" concept it would be relatively cheap, it would be dramatic at first (though rather boring in the long run), and it would have a quite decent scientific payoff as well. A "gravity tug" must be fairly heavy, so it could carry a good science payload, and since it would literally be hanging around in more or less the same place close to the asteroid for years a very close study of it would be possible.

tty

Posted by: AlexBlackwell Feb 14 2006, 07:09 PM

I'm skeptical as well. Not only is it unlikely that, assuming the rumor has any validity, a "huge profile showcase mission being planned" would be simultaneously "inspiring," "relatively inexpensive," though "involv[e] ESA and the Japanese," the only real reason for NASA to bring in international partners to such an endeavor would be to spread the cost and risk. If this rumored mission is so cheap, then that wouldn't really be necessary, would it?

Frankly, this rumor sounds like the buzz that preceded JIMO. Indeed, some of phrasing and locutions used by "Flighstar" are eerily similar (viz., "kept very secret with some guys at the top," "inspiring," "showcase mission," etc.) to what I recall reading when JIMO was unveiled. If that's the mission "Flightstar" is referring to, maybe someone should tell him/her to tell his/her "friend in the industry" that the mission was cancelled.

Having said that, though, I agree that international collaboration is probably the only way to save Europa Orbiter at this juncture.

Posted by: JRehling Feb 14 2006, 08:27 PM

I also seriously wonder if this is an "echo" of the JIMO buzz, although it would speak poorly of the whisper channel that was so far behind the times.

If this rumor has any basis (and most don't), I would say the most-likely-case is some kind of lunar gambit which is perhaps as poorly conceived as JIMO, or is a proposed follow-on to LRO, or is actually based on LRO itself. Some sort of low-orbit or surface base that served as a sort of lunar webcam might be affordable and, in someone's opinion, fit the bill of what was described here.

I can hardly think of a Venus or Mars mission that would fit the bill, with airplanes coming closest.

In any rumor-guessing contest, I would always, though, nominate "no basis in fact whatsoever" as the odds-on favorite.

Posted by: GregM Feb 15 2006, 02:42 AM

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Posted by: BruceMoomaw Feb 15 2006, 05:15 AM

How in the world would they do THAT cheaply -- and who in their right mind would trust them to do it at all?

Posted by: AlexBlackwell Feb 15 2006, 04:07 PM

Okay, since you put it that way, the rumor must be true.

BTW, where were you when I needed to unload some real estate in the Everglades?

Seriously, though, I've seen too many of these "rumors" over the years, so I'll wait for any press conference before getting excited.

Posted by: JRehling Feb 15 2006, 06:30 PM

Bringing an 8km asteroid within 800km of the Earth would produce an object in the sky with the same angular diameter as the Moon. That prospect would have a number of characteristics:

1) It would be breathtaking.
2) It would enable some very good science, as huge telescopes scanned the object in great detail.
3) It would be terrifying and would produce a small but nonzero risk of a species-ending disaster.
4) It would rightly be perceived as a military threat by the enemies of the US, yet would also be part of the spectrum of responses that another nation (like China) could one day bring to bear against the US.
5) Given a long enough lead time, it is perhaps feasible, although not necessarily with an asteroid as large as 8km. Chaos being what it is, a small initial delta-v might produce a large translation of some eventual encounter between Earth and an existing NEO.
6) That would be a flyby, not orbit, if the body were of substantial size. If it is very small, then it would not be a large feature in the sky.
7) Plan B would smash the NEO into the Moon, which would possibly create dangerous secondary impacts on Earth, and might even pollute Earth orbital space with debris rendering many orbital projects permanently ruined.

Posted by: ljk4-1 Feb 15 2006, 06:40 PM

It would need to be mined right away to start our space infrastructure, which would
also reduce its size and therefore its danger to Earth.

I also had this crazy thought of someone using this space rock as the ultimate
(though suicidal) threat. Ever read Robert Forward's Martian Rainbow?

Posted by: helvick Feb 15 2006, 07:20 PM

Ignoring all other problems, and there are many.

Taking a 1500kg/m^3 density as a pure guess and for the sake of argument assume that this would be an 8kmx2km approximately cylindrical rock pile. It would have a mass of around 37,500 million tons.

To impart a delta v of 1m/sec to that requires the equivalent of 10 kilotons of TNT, or 6700 first stage Saturn 5 engines in parallel.

With a typical current Ion drive, Isp ~ 30kN s/kg, we would need ~1.2million tons of fuel. VASIMR designs if proven in flight should get Isp ~300kn s/kg and would reduce that to around 120 thousand tons.

And that's just for a total 1m/sec delta v.

How exactly would that be done cheaply?

Posted by: Bob Shaw Feb 15 2006, 07:40 PM

Using a gravitational tractor to gently nudge a threatening NEO into a non-Earth-intersecting (at least for a while) path is one thing; braking it into orbit is quite another. If it's a matter of saving the earth, then budgets might become available, but...

...just don't send any squid!

Bob Shaw

Posted by: JRehling Feb 15 2006, 07:55 PM

If the goal were to alter the translational position of The Rock at some point in the far future, then you could get away with a much lower delta-v. Let's say it were Halley's Comet, and we were trying to alter, near perihelion, where it would eventually intersect Neptune's orbit. The outer leg would take decades. Let's say 30 years = 1 billion seconds. 1 m/s (the high bar you set) would change the intercept at Neptune distance by 1 billion meters = 1 million km.

But if you have A Rock that is going to pass near Earth in the first place, you could obtain a much larger sensitivity. Let's say asteroid 2004 MN4, which is going to pass within ~40,000 km in 2029. The question is if a delta-v much, much lower than 1 m/s could create an enormous translational difference for some point after 2029. And 2004 MN4 is much smaller than 8 km. I could see a single Saturn 5 fitting the bill, but the devil is in the nonlinear details.

Posted by: helvick Feb 15 2006, 08:48 PM

You are right of course, I was just using the extreme example to point out how much energy is needed to move something really large. And given enough time even a very small delta-v can make a very big difference.

There are quite a few NEO's that could be experimented with that are substantially less massive than 8x2km. Apophis\2004MN4 is around 46 million tons and would require ~820 times less energy to move. A delta v change of 0.05 m/s could bring it's closest approach down to just grazing the atmosphere which would be really spectacular. That would only need about a third of a Saturn 5 or a VASIMR with about 7.3 tons of fuel. Now that should be possible. Does anyone have an opinion on whether we could actually do this with the precision that would be needed?

Bob's point about setting up an orbital capture is worth repeating - setting up a close flyby is one thing but there is no way we could arrange for a new moon to be captured, that would require quite a couple of km/sec delta v and then we're back to needing 6000+ Saturn 5 boosters.

Posted by: ljk4-1 Feb 15 2006, 09:05 PM

Is this rumor really about the plans of the B612 Foundation to move
a planetoid by 2015 as a test for preventing NEO impacts?

http://www.b612foundation.org/

And/or the plan to use a gravitational tractor spacecraft to tug a planetoid?

Lots of online references here:

http://www.b612foundation.org/press/press.html

Thread in this forum:

http://www.unmannedspaceflight.com/index.php?s=&showtopic=1446&view=findpost&p=21361

Posted by: tty Feb 15 2006, 10:10 PM

The only conceivable way of braking an asteroid into orbit would be by a moon gravity assist. It would however be extremely dangerous since a very small miscalculation might put it on a collision course with Earth which there would be no time to correct.

However as I've said in an earlier post, demonstrating changing the orbit of a small near-earth asteroid would be possible, and not too expensive today. The maximum distance the orbit would ever need to be moved to avoid a collision is 6500 km, and it would in most cases be a lot less. Over a 20 year period, which is a reasonable warning period, this equals a velocity change of 1 cms-1.

This would be quite feasible with one of the smaller earth-crossers. In most cases it would also be possible to use solar sails instead of or together with a ion drive for a gravity tug, though the sails should probably canted a bit to avoid reflecting the sunlight onto the asteroid.

tty

Posted by: BruceMoomaw Feb 15 2006, 11:52 PM

It ain't crazy at all -- intelligent SF writers are now using this idea regularly. (Greg Bear and Joe Haldeman are just two of them.) For all the current blather about how Humans Need to Develop Space Technology to Deflect Asteroids that would Endanger Life on Our Planet, Mother Nature provides those only every few tens of millions of years -- whereas, if humanity does develop the technology to start deflecting asteroids, it's a pretty safe bet that at some point within the next few THOUSAND years some political faction will aim one at Earth as a weapon.

As for the Great Rumor: my theory is that it's some relatively modest scheme for international space cooperation (Europa Orbiter?) that's been blown up out of proportion by the standard processes of rumor.

Posted by: ElkGroveDan Feb 16 2006, 12:38 AM

No worries about annoying things like operating in a near-vacuum or mind-numbing cold temperatures that the MER rovers are facing. It should be a piece of cake.

Now that I think of it, there would be no need for high-tech testing facilities. The engineering team cold bring the components home to spend the night in their kitchens' self-cleaning ovens.

Posted by: DFinfrock Feb 16 2006, 01:59 AM

Are they possibly referring to the THOR mission?
See: http://www.universetoday.com/am/publish/thor_mars_mission.html?1322006

Or is that proposal too much in the open to be considered a secret new proposal?

David

Posted by: BruceMoomaw Feb 16 2006, 02:11 AM

"Thor" is a relatively small Mars Scout proposal run entirely by an American team. I still don't know what this could be, but I'm willing to bet that the rumor is blowing the actual event (if any) all out of proportion.

Posted by: DFinfrock Feb 16 2006, 04:35 AM

But THOR would qualify as a relatively "inexpensive" mission. And wouldn't it be interesting if it was timed to arrive together with the ESA Exomars mission. If EXOMARS landed nearby, wouldn't it be fascinating to see from the surface what THOR unearths? This could be a very interesting collaboration, without adding huge costs to already planned missions.

David

Posted by: Phil Stooke Feb 16 2006, 05:21 PM

The question about whether an asteroid could be deflected to hit earth as a weapon was discussed in Carl Sagan's Pale Blue Dot. Well worth a read if you have not done so already. Pale Blue Dot is my [insert holy book title of your choice].

Phil

Posted by: ljk4-1 Feb 16 2006, 06:16 PM

Some relevant excerpts from Carl Sagan's Pale Blue Dot (1994) are written here:

http://www.spaext.com/info/sagan/index.html

"Their eventual choice, as ours, is spaceflight or extinction."

Posted by: AlexBlackwell Feb 17 2006, 07:50 PM

While reading the Feburary 13, 2006, issue of Aviation Week & Space Technology, I noticed the excerpt below. I wonder if this could be related to (or the basis of) "the rumor"? Certainly, all of the "players" are mentioned (e.g., Russia, France [Europe], Japan, etc.).

World News & Analysis
NASA Budget Mollifies Partners; Lunar Talks Begin
Aviation Week & Space Technology
02/13/2006, page 40

Frank Morring, Jr.
Washington

[...]

"MOST FUNDS ORIGINALLY targeted for the old Project Prometheus space nuclear power effort were redirected to the new human exploration programs, and to pay closeout costs on the Jupiter Icy Moons Orbiter program that would have used nuclear-electric propulsion to reach Europa and other Jovian moons.

"In keeping with the push for international cooperation in exploration, Griffin said NASA 'will seek to leverage the work of other nations which have developed small nuclear reactors that could be applied to space.' While no talks have been held, he said, potential partners include France, Russia, whose engineers have built nuclear-powered spacecraft, and Japan, where researchers are conducting generic design studies on small plutonium-fueled, sodium-cooled fast-neutron reactors."

Posted by: tedstryk Feb 18 2006, 02:44 PM

Well, perhaps you can, if you are thinking of some type of SCIM - like proposal.

Posted by: blairf Feb 19 2006, 12:38 PM

Over on space.com message boards one of the Japanese posters mentioned this...

http://uplink.space.com/showflat.php?Cat=&Board=missions&Number=430845&page=0&view=collapsed&sb=5&o=0&fpart=

It includes missions/proposals I'd never even heard of that seem to fit the bill, especially...

Solar sail mission to Jupiter including a probe?