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back to article No chance now to save Phobos-Grunt Mars mission

The window to contact the stranded Phobos-Grunt and send it on its mission to the Martian moon has now closed. The craft could still fly by the Red Planet, but it will no longer be able to complete its exploration of the Martian moon Phobos and return to Earth, space industry sources told Russian state news agency RIA Novosti. …

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Silver badge

Eh?

'Failing that, just getting the craft to land on Earth instead of crashing through the atmosphere could allow the agency to recover equipment from the ship and even readings from its instruments.'

Fobos-Grunt isn't equipped with a heat shield - how is that meant to happen?

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Part of it (I don't know how large a part) was intended to return to Earth with samples from Phobos.

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Silver badge

Just part of it?

It was due to collect samples from Phobos and return to Earth so I assume there is a small part that is built to make it back through the atmosphere. If they could get that to separate from the rest and make a controlled re-entry that bit could be recovered while the rest burns up (they hope).

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Just what I was pondering...

I assume they wouldn't try to get the whole craft back. It might well be possible to return interesting parts - the Mars transfer stage would have more than enough juice to bring the craft speed way down. At that point, a heat shield isn't so important as the craft would be going "slowly" and would just fall into the atmosphere "down". It would hardly heat up at all - a mere few hundred degrees. Still, doesn't solve the minor problem of plummeting towards the ground with no effective parachute. I wonder how many interesting parts would survive the bounce. A landing would be stretching it a bit...

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The spacecraft contains an amount of fuel to provide it with a Delta-V (change of velocity) sufficient to reach escape velocity plus a bit more.

The craft currently has an orbital velocity of about 28000 kph. It needs about 40000 to attain escape velocity. If it were possible to use the engines in a braking maneuver instead (it isn't) then the most it could reduce velocity is to a mere 12000 kph. Reentry would then take place at *only* around mach 10 or so (instead of mach 25). Not enough to turn it into plasma but far more than enough to melt most of the components and shred it into confetti before it explodes. It has the aerodynamic qualities of a bird's nest attached to a brick of C4..

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Bronze badge
Windows

I'm always confused by this "escape velocity" mularkey.

Rockets:

Look, if the bloody thing can get off the ground (where gravity is highest), why can't the damn thing simply keep going? If I can throw a ball slowly into the air, why can't it be slowly sent to the moon?

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Andus, it is possible to escape the earth's gravity without reaching escape velocity, going "slowly" as you say. However, this would be much less fuel efficient, since most of the fuel would be spent on the hovering portion instead of propelling the craft further from earth. Moreover, since more fuel would have to be burnt at higher altitude in order to keep the craft hovering, that same fuel would have to be carried along, requiring even more fuel to be carried through the lower altitudes. Below a certain speed, this would become impossible with conventional rockets, as the thrust of the rockets would be unable to lift the amount of fuel required from the ground. So, yes with a yet-to-be-invented light anti-gravity device with near infinite energy, you could slowly rise into orbit. Until then, we need to boost the rocket to escape velocity as low down as possible, burn up almost all the fuel (except that required later for maneuvering) and jettison the spent engine for additional weight loss.

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Flame

Tracking the Satellite

This website has a real-time orbit track, fly-over predictions, and if you click the link in the upper left, details of the current orbit (high and low points):

http://www.n2yo.com/?s=37872

Because the Earth's atmosphere density is exponential, each 10 km the orbit decays doubles the drag. So the time it takes to fall 10 km times two roughly gives the time to re-entry. Around 120 km is re-entry altitude. At that point drag is so high it will not finish another orbit and heating from atmospheric friction will start to melt parts.

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Mushroom

descending a pace!

Thanks to Dani's post I;ve just watch it get 1 mile closer to the earth in 40 seconds!

It's now only 140 mile up.

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Facepalm

Eliptical orbit

Its in an elliptical orbit, so it's height varies as it goes round.

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Unhappy

That's OK...

Just send up a Space Shuttle on a recovery mission and... Oh wait... Forgot about them canceling that program.

Maybe the military can use a space based target for their High Energy Weapons Tests.

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There's nothing the Shuttle could have done in any event. Unless a launch was imminent, there wouldn't have been time to arrange one at such short notice. And there would have been many problem to solve. P-G wasn't designed to be grabbed by the Shuttle's robot arm. A housing to hold P-G would have to be designed and built. Astronauts to be trained for the mission. And all to retrieve something that cost less than a Shuttle launch.

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Bronze badge

Nothing

that Michael Bay couldn't solve.

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Black Helicopters

What was that fancy robotic cross range CIA space craft that stays up for months?

X73-B ?

Maybe the advanced tech has been snatched by this craft? And a small Bigelow inflatable left in place to fool radar?

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No surprise there. I used to drive a Lada (company car). The engine of that thing frequently failed to start as well.

If world war III had started on a cold winter's morning, I reckon most Russian rockets wouldn't have got out of their silos :/

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The fuel on board should give it enough delta V to be able to slow it down enough that it doesn't need a heat shield. After all it's enough to get it to Mars and get into orbit there.

But doing a soft landing - at least soft enough that parts can be reused - seems a bit optimistic, especially as the reason it's stuck here is that they can't control the motors.

It's a shame.

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Silver badge
Pirate

From Russia with Love

You might like to think that Mother Russia has stolen a long march on a much more lucrative and accommodating space with missions and master pilots that deliver Earthly treasure, in out of this world measure ....... http://www.ur2die4.com/?p=1030

And quite a perfect fit for an exceptionally fit for purpose intelligence regime and chiefs with nothing to prove and more time on their hands to share and show what they know about Cyber Control with Command of IT.

Deny it if you will, but who do you fool if not just yourself.

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Anonymous Coward

SO...

Why are they not using the space station to contact the probe? If the issue is line of sight from the ground, the station would have a much better vantage point.

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LDS
Silver badge

Or why didn't they ask help from the NASA space network?

NASA has a far better space communication coverage than Russia. Why didn't they ask for help? Or NASA does not allow it? Or Putin's Russia still prefers the "we are able to do mistakes by ourselves"?

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FAIL

I don't know if the Russians have asked NASA for help -

I rather suspect they have - but as this ESA blog (http://www.esa.int/esaCP/SEM4NEZW5VG_index_0.html) makes clear, aid was requested from ESA within a day after the launch of Fobos-Grunt and now, after nearly two weeks of work, the spacecraft has finally been traced. Perhaps, LDS, your snide comments about «Putin's Russia» were a tad premature ?...

Henri

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Mushroom

Just face the facts

I think the Russians are in denial. It's been weeks, they still haven't heard a peep from the damn thing and here they are wasting time on all these alternate plans when - in reality - they should only be worried about one thing: when/where is this bad boy going to come down?

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Bronze badge

What they need is some sort of reusable craft that could fly up into space, synchronise orbits with it and maybe grapple it into some sort of cargo hold to effect repairs. Now if only somebody had thought of something like that...

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RIP Buran

According to the Wikipedia, Buran died in a hangar collapse :(

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