Nov10
What a name. Anyway, I have an article about it up over at Popular Mechanics.
[Update a while later]
Here’s some more info. According to that piece, it’s dropping in altitude a little over a mile per orbit, but that will accelerate as it gets lower in the coming weeks, if they can’t get it on its way.
[Update a few minutes later]
Emily Lakdawalla has the latest. It’s not looking good, according to sources in Russia.
America’s first success with Mars was the Mariner 4 flyby in 1964.
That is, was launched 11/28/1964 — flew past Mars 7/14/1965.
I’m watching this very closely, and hope they can get it on its way for multiple reasons. One of the biggies for me is that an ongoing complaint against propellant depots is that once a spacecraft is in orbit, it only has one opportunity to fly to a beyond Earth orbit target without huge delta-v penalties. The argument didn’t make sense to me, but I haven’t been able to refute it due to a lack of time/computer software. If Phobos-Grunt (bad PR name, I know, but apparently Grunt is a translation for dirt) can get on its way days or weeks after launch using the same propellant load it was launched with, it will deflate that argument against depots.
Hmm. I have an orbit calculator I wrote a long time back; if I wrote it correctly and if I still remember how to use it the difference in delta V from a direct launch and from a launch to orbit and then boost out of orbit doesn’t look that significant.
The opinion that my counter-arguer holds is that 1 orbit after the optimal burn time (assuming a botched first attempt), the geometry between the departure orbit and the necessary transfer orbit has changed so the required delta-v goes up. The amount of delta-v increases the further you get away from your optimal departure. I see his point, but just haven’t been able to prove the existence of other non-optimal, but do-able trajectories given the propellant margines allowed assuming a depot. If P-G can do it with the propellant it has, it goes a long way towards proving my point, but given Emily’s summary it looks like they’ll be lucky to just get a command in.
He is assuming that the departure will be from LEO. It will most likely be from EML-1.
If the plane of your earth orbit was the same as the plane of the target planet’s orbit, then you would return to your departure point every 90 minutes (for LEO). That point would very slowly change as the target planet’s orbit took it on around the sun, relative to Earth. But that just means you start your departure burn a little earlier or later in your orbit, perhaps by a few seconds per orbit you’ve delayed, and the only fuel penalty would be due to the slow change in the launch window as you depart from an ideal Hohmann or other transfer orbit.
But if your initial orbit was not in plane with the target planet’s orbit (as if you’re on your porch throwing a tomato overhand at a car driving past your house), then tracking the target planet’s motion requires at plane change, and those cost a lot fuel, worsening as the target planet moves until it’s no longer possible to make the trip.
This should be the same reason that the ISS is considered a horrible orbit for launching interplanetary missions. The plane is not at all aligned with the solar system, and is instead set up to maximize payload from Baikonur.
At least that’s what I think is going on.
I think the bigger problem is recession of the line of nodes. If you’re in a non-equatorial LEO, the Earth’s equatorial bulge causes your orbit plane to rotate. Miss your window by a few orbits, and it either gets expensive, or you wait a long time for the next window. The alternative is to boost into a loosely bound orbit, do a cheap plane change at altitude, and come back for the trans-Mars burn at low altitude.
“What a name.”
You’re telling me. I laugh every time I hear it.
“Phobos”…HA HA HA!!!
The Martians are getting trigger-happy. They didn’t use to shoot down Phobos probes (“That’s not a moon…”) until they were well into Martian space; now they’re taking them out in Low Earth Orbit. Has someone warned the Russians to be on the watch for strange Tripods in the vicinity of Baikonur?
Actually, they sabotaged quite a few before they even got to orbit, especially back in the sixties.
Rand,
A correction for the Popular Mechnics article …. The Zenit is a Ukrainian-built rocket from the Yuzhnoye SDO in Dnipropetrovsk. It isn’t a Russian launcher.
And the Zenit performed very well …
John,
Tripods or triffids, we can’t win for losing.
What a name.
It should either be Fobos – Grunt, a straight transliteration, or Phobos – Ground or Phobos – Soil, a straight translation. Or maybe Phobos Sample Return for a less literal translation that is more in the line with the sorts of names NASA would use.
What a name.
Pronounce the ‘u’ in “Grunt” as the “oo” in “too,” like the Russians do, and it doesn’t sound so bad.
Isn’t that turning it into a Star Wars name? “Meet with Phobos Groont you must. Made the trip here in 5 parsecs, he did.”
I wonder if they will do the equivalent of an “Operation Burnt Frost” to ensure the fuel burns up in the atmosphere?