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35 comments

Taking bets... (4, Funny)

Gothic_Walrus (692125) | about 10 years ago | (#8682870)

How long before "Ten weeks != Two Years" is posted by some moron?

Remember, kiddies: Earth isn't the only planet that orbits the Sun!

Re:Taking bets... (4, Funny)

Neil Blender (555885) | about 10 years ago | (#8683828)

How long before "Ten weeks != Two Years" is posted by some moron?

But don't 10 metric weeks equal 2 Imperial years?

Re:Taking bets... (2, Funny)

freuddot (162409) | about 10 years ago | (#8684590)

Maybe "Ten weeks != Two Years", but according to the article :

Unable to meet that schedule, the mission will use its backup window that begins July 30 and extends 15 days.

[...]

Launch on July 30 will occur during a 12-second window opening at 2:17:44 a.m. EDT (0617:44 GMT) from pad 17B at Cape Canaveral Air Force Station

So, it still looks like a 12 second == 15 days. ;-)

Does I then qualify as "some moron" ?

Re:Taking bets... (2, Informative)

Gothic_Walrus (692125) | about 10 years ago | (#8685085)

I was actually referring to the delays...the launch window has been moved back ten weeks, and the new ETA to Mercury is two years later than the original one.

And since I'm in a good mood...no, you're not a moron. :)

Ironic: Slow Boat to the Fleet-Footed (4, Funny)

G4from128k (686170) | about 10 years ago | (#8682981)

Its ironic that a mission to the fleet-footed god of messages should take so long. I guess its revenge by those ancient Roman gods.

I'm just glad that the mission was not scrubbed.

An Understandable Shame (5, Insightful)

Embedded Geek (532893) | about 10 years ago | (#8683161)

I think it's a shame they'll miss the better window, but giving more time to check out the on board diagnostics seems like a dang fine reason. I'd hate to see the thing get all the way to Mercury and then go dead. If the program mangers want this breathing space (and you can be sure they'd only consider this if they were getting a lot of warnings from within the ranks), they'd be fools not to take it. Still, the extra Venus flyby would have been nice (2 vs. 3).

I'm kinda concerned about the budget hit, though. Maintaining an engineering infrastructure on the ground for an additional two years, even one in "standby," is going to be costly. Sure, they can loan out personell to other projects during the interim, but you're going to see two more years of attrition and then retraining costs to catch up. A boom or bust in the tech cycle will simply agravate the situation (boom=more people leaving, bust=fewer new engineers to fill vacated slots).

The delay is probably acceptable, but let's hope the added budget doesn't hurt another probe.

Re:An Understandable Shame (0, Funny)

xoran99 (745620) | about 10 years ago | (#8683688)

Wow. That's really insightful. I'm glad someone around here knows enough about these things to post insightful comments.

*can't think of anything insightful to say, so plays UT2004 instead.*

At least the n00bs respect me...

Re:An Understandable Shame (4, Insightful)

Ahotasu (206241) | about 10 years ago | (#8686898)

I bet the budget hit won't be significant --at least not due to engineering infrastructure. As an interplanetary mission (with some tricky orbital mechanics to boot), things have already been very thoroughly documented to mitigate the risk of losing knowledge about the system as time progresses. Engineering staff will (still) be busy in the first month or two following launch, then will move off onto other projects. Thus, a boom or a bust in the industry will have little to no effect on the engineering costs associated with this slip.

There's simply not enough work to keep the engineers busy while the bird flys to Mercury--automated data processing as well as monitoring by Operatins staff will take over the job of monitoring health and safety. If problems occur, then the engineers are brought back only long enough to deal with the problems. This has doubtlessly been the plan all along.

Where the cost really goes up, though, is in Mission Operations. Antenna time, operations staff, etc will eat some of the budget. I bet that's fairly trivial, though, compared to your scenario of a 'marching army'. I wonder how MESSENGER's doing in terms of budget reserves (these 'little' dollar signs NASA forces you to hedge)...

The extra time could be bad (1)

Xolotl (675282) | about 10 years ago | (#8690835)

There is another worry though - the extra two years in space also significantly increases the risk of the probe or its instruments being damaged by solar flares (as happened to Mars Odyssey [bbc.co.uk] , radiation, temperature changes and debris.

George Bush (-1, Troll)

Tuxinatorium (463682) | about 10 years ago | (#8683163)

george bush touched my junk liberally. he strapped me in to his georgebushmobile and he couldnt keep his offensive hands off of me. he was performing many red flag touches. i couldnt believe what the fuck was going on. i told georgebush the city would not approve of a millionaire touching an underage kid for free. can you believe it? georgebush did all this. he picked me off the street, strapped my arms and legs down in the georgebushmobile's passenger seat, and just wouldn't stop fondling my cock'n'balls. they definately were red flag touches. the goddamn referee he had in the back seat kept on raising up this red flag every time he touched my junk but did georgebush care? NO WAY! he just kept on doing it. I couldn't believe what the fuck was going on, indeed. I pleaded with georgebush but to no avail. I told him the city would not approve of such a wealthy man touching an underage kid like me (at the time I was 13) without at least compensating me for the trauma and the use of my body as his own personal plaything. this got to him, worrying about his image. he continued to fondle me, all the while ignoring the referee's red flags. then he drove the georgebushmobile to my house and ejected the seat i was in! it was amazing. but surprisingly, after I woke up the next morning, my bank account had $150k in it!!! Can you believe it??

Why 2 years? (1)

tjmsquared (702422) | about 10 years ago | (#8683668)

Mercury goes around the sun in 87 days. Assuming that the orbits are circles (they're pretty close) it should never be more than 86 days for the planet to be in an optimal position to launch a probe. So, why would it be off by two years? What am I missing here?

Re:Why 2 years? (5, Informative)

Neil Blender (555885) | about 10 years ago | (#8683720)

Mercury goes around the sun in 87 days. Assuming that the orbits are circles (they're pretty close) it should never be more than 86 days for the planet to be in an optimal position to launch a probe. So, why would it be off by two years? What am I missing here?

Uh, maybe an in depth knowledge of how the gravity of all the planets affects trajectories?

Re:Why 2 years? (1)

Curtman (556920) | about 10 years ago | (#8683952)

Why not install Celestia [shatters.net] plug in the dates, and take a look. :)

Re:Why 2 years? (1)

lommer (566164) | about 10 years ago | (#8701066)

do you have a Celestia update file for messenger (either its planned trajectory, or this revised one)? I'd be interested in getting that if you do

Re:Why 2 years? (5, Funny)

Anonymous Coward | about 10 years ago | (#8684153)

What am I missing here?


a degree in astrophysics.


Re:Why 2 years? (3, Informative)

CXI (46706) | about 10 years ago | (#8684329)

Because they're planning to swing around Venus to get there, and more than once.

Re:Why 2 years? (5, Informative)

CheshireCatCO (185193) | about 10 years ago | (#8684996)

The links already posted answer the question, but the short, simple answer is "angular momentum". Specifically, the need to dump a lot of it (and, equivelently, a lot of energy). The energy changed needed to get to Mercury is actually greater than that needed to reach Pluto. This means that it's better to use the inner planets (Earth, Venus, and/or Mercury) in gravitational slingshots (but backwards of how we usually use them) to save fuel. In theory, if you jacked up NASA's budget, you could go straight there once a synodic (not sideral: it doesn't matter how often Mercury orbits, but how long it takes to get back to the same relative arrange with Earth) period. But NASA, alas, has a finite budget for this sort of thing, so slow and cheap is the way to go.

Re:Why 2 years? (2, Informative)

joggle (594025) | about 10 years ago | (#8685454)

You're correct. It needs to loose about 62% of its angular momentum, which is a pretty significant amount of energy. This is in addition to the amount of energy needed to reach earth's escape velocity in the first place and to insert into an orbit around Mercury.

Re:Why 2 years? (1, Funny)

Anonymous Coward | about 10 years ago | (#8689239)

"Loose" needs to lose about 50% of its "o"s, which is a pretty significant amount of "o"s.

Re:Why 2 years? (0)

Anonymous Coward | about 10 years ago | (#8691388)

Angular momentum refers to the probe spinning on itself.

What you want is to compare the energy (kinetic + potential gravitational) between Earth's and Mercury's neighborhood.

How can we trust your "62%" figure if you can't get this straight?

Re:Why 2 years? (1)

lommer (566164) | about 10 years ago | (#8701014)

Um, no, and no.

Angular momentum refers to the linear momentum of the probe times the radius from the sun at which it is orbiting.

As for the energy, It's actually pretty tricky to lose KE + PE in space - you either have to use engines (with expensive-to-launch fuel) or sophisticated aerobraking techniques and whatnot by making close passes to other planets. In fact, when this probe gets to Mercury, if i'm not mistaken, it will still have nearly the same energy (in terms of KE and PE).

Five braking flybys, 3 of them @200km (1)

leonbrooks (8043) | about 10 years ago | (#8688445)

...which does seem pretty camel-through-eye-of-needle at ranges of tens of millions of km. Venus gets two flybys @3000km and 300km.

This is needed because Earth orbit is about 3x as energetic as Mercury orbit. Messenger needs to dump the other 2/3 of its momentum, and slingshot flybys are far and away the cheapest method for that. This requires eveything to be lined up just so.

It's a pity, really, because I suspect Mercury of harbouring numerous hermeological surprises [nasa.gov] (as surprising as Valles Marineris [nasa.gov] on Mars, a 3000km gouge up to 10km deep which was not formed by water, wind or tectonics), and a bugger-the-cost lets-burn-many-tonnes-of-propellant (much to meet Mercury, a little more to kick the probe into orbit around it) approach would get a probe there in only a few months.

We don't have many pictures of it [nasa.gov] yet, and the aforementioned surprises should stimulate significant scientific progress, most likely by killing off a large percentage of current solar system formation theories.

At least there will still be a probe. With Dubya at the reins, it could have been worse.

Re:Why 2 years? (1)

adeyadey (678765) | about 10 years ago | (#8694817)

What am I missing here?

Orbital mechanics is a weird game - especially with old-fashioned rockets with limited fuel/thrust, so you have to use various tricks like gravitational boosts/brakes by flying by other planets, in a sort of celestial game of pool. Sure, you could fly straight to mercury, if you use a big enough rocket - but then you would be flying by at such a huge speed you would need an even bigger rocket to carry fuel to allow you to slow down enough to make orbit. Mercury does not have a huge gravity, so to make orbit and get into its small gravity-well requires a huge amount of thrust.

The ESA bepi-columbo mission to mercury will use ion drives, which makes a lot of sense when you see how much free power would be available to a solar craft near mercury.. We are probably seeing the last of the old fashioned rocket-only planetary missions, ion drives will take over more and more in the future.

Who comes up with these? (1)

Tree131 (643930) | about 10 years ago | (#8684582)

I wonder who comes up with these names/acronym mixes? There must be a job at NASA to name all these missions, like
MeSSEnGeR or NOAA or ECHO or SOHO (which stands for many things, including the solar observatory).

http://www.acronymfinder.com/ [acronymfinder.com]

Re:Who comes up with these? (1)

CheshireCatCO (185193) | about 10 years ago | (#8685081)

Actually, probably the team that proposed the mission in the first place. That's usually where they come from these days. Mercury is a Discovery-class mission, which means that it was proposed out of house, rather than created and designed within NASA.
I don't recongize the ECHO acronymn, but NOAA isn't part of NASA at all (it comes in under the Dept. of Commerce, I believe) and SOHO is jointly run with the European space agency, not a pure NASA endevor.

Coming up with forced acronymns and impressively useless code-names for things isn't only a NASA activity, of course.

Re:Who comes up with these? (4, Funny)

irokitt (663593) | about 10 years ago | (#8685320)

MeSSEnGeR or NOAA or ECHO or SOHO

So how long until we see names like M3553n93R or N044 or 3(H0 or 50|-|0?

Relativistic effects on the craft & orbit (3, Interesting)

RobertB-DC (622190) | about 10 years ago | (#8685265)

To what extent does the "warping" of space near an object as massive as the sun affect this little spacecraft's orbital calculations? I know (but don't fully understand) that there are relativistic effects on Mercury's orbit [ucr.edu] that aren't described by pure Newtonian physics.

To what extent do the mission planners have to account for this effect? Can they even know for sure until they see what happens as they pass by Mercury those three times before orbital insertion? Or will the effect be negligible compared to the solar wind and other "normal" forces? The link above notes that Newton is only off by 43 arcseconds out of 5600, but it seems like even 0.77% could add up pretty quick.

Re:Relativistic effects on the craft & orbit (3, Insightful)

egomaniac (105476) | about 10 years ago | (#8685488)

To what extent do the mission planners have to account for this effect? Can they even know for sure until they see what happens as they pass by Mercury those three times before orbital insertion?

Of course they can. We know the speed of the Sun and planets relative to us, and we know all of their masses. That's everything you need to do full relativistic calculations.

And yes, these are astrophysicists we're talking about. Of course they take this into account.

Re:Relativistic effects on the craft & orbit (1)

MrIrwin (761231) | about 10 years ago | (#8697494)

We know the speed of the Sun and planets relative to us, and we know all of their masses. That's everything you need to do full relativistic calculations.

I believe you also need to know how to convert between imperial and metric units.

Job Security (-1, Troll)

Anonymous Coward | about 10 years ago | (#8685435)

It's not surprising. In this crappy economy and with the current president and Congress driving it into the ground, I'd add two years to my project if I could get away with it.

Hmm. (1)

Trejkaz (615352) | about 10 years ago | (#8700311)

The best thing about this name is that if NASA ever develop teleportation technology, they can integrate it into the next version and call it "Instant MESSENGER."

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