-
#440
by
Michael J
on 23 Nov, 2011 23:33
-
-
#441
by
Chris Bergin
on 23 Nov, 2011 23:41
-
Yeah, which is why I'm asking so many questions, as this is a bit of a minefield with the conflicting reports - but it looks solid on the success of comment to the transmitter, followed by the success of gaining abbreviated telementy later.
What we don't know for sure is the health of the spacecraft, be it for some level of a mission or an ability for a controlled re-entry.
-
#442
by
pm1823
on 23 Nov, 2011 23:43
-
From the English version Ria Novosti.
http://en.ria.ru/science/20111124/168984266.html
I've noticed that there is a difference of what is reported in the Russian version versus the English version.
b'coz posting time difference is more than an hour.
-
#443
by
mr. mark
on 23 Nov, 2011 23:46
-
Interesting Mars mission may be over but, they may aim the craft at a near earth asteroid. Sounds like a precursor for a manned mission. Maybe fate has a way of working itself out? If it does happen that way, talk about snatching itself from defeat into the arms of victory.
-
#444
by
alk3997
on 23 Nov, 2011 23:55
-
Interesting Mars mission may be over but, they may aim the craft at a near earth asteroid. Sounds like a precursor for a manned mission. Maybe fate has a way of working itself out?
Let's talk about this supposed asteroid mission. First it costs money. Remember FG is insured. If you're having to pay out the insurance and Roscosmos starts using the spacecraft, aren't you going to want to deduct some of the payout? If you ever want an FG II, then that doesn't seem like a good idea.
If you decide to go forward with the asteroid mission, what is your target? Despite Star Wars and early NASA animation, there isn't a continous stream of asteroids coming past Earth. Finding one that is worth the money for mission operations, narrows the field further. Then you have to account for the PG spacecraft mass and engine (assuming it is working), and that will narrow it further. I guess they could jettison unused mass (like the Chinese satellite) to gain more delta V but that has its own political raminifcations.
Finally and most importantly - we don't know if the spacecraft is healthy, let alone the main engine.
So randomly asking for an asteroid mission is right now like saying how about we send FG to Venus or the asteroid that is in Earth's solar orbit or we randomly explore deep space with it or send it to L1 or explore geostationary orbit or countless other potential targets that aren't really available due to delta-V or spacecraft capabilities or even if the targets are worthwhile...It's way too early to start picking targets when you don't know the health of the spacecraft and what capabilities are available and what funding is available.
Andy
-
#445
by
Lee Jay
on 23 Nov, 2011 23:57
-
Regarding the conflicting reports/opinions as to whether or not they can still get to Mars, what if some are assuming the delta-V available is equal to that required by the originally planned trajectory, while others are assuming more than that, either through some arbitrary margin (i.e. 10%) or through knowledge of exactly how much delta-V the spacecraft was capable of at LEO insertion?
-
#446
by
hop
on 24 Nov, 2011 00:01
-
Interesting Mars mission may be over but, they may aim the craft at a near earth asteroid. Sounds like a precursor for a manned mission.
Only through the lens of HSF-centric fantasy. In reality, it would just be an attempt to get something out of the spacecraft. As Mr. Zakharov says, landing on Phobos is similar to landing on an asteroid, so it would be the next best use of the spacecraft and instruments. Not so much for poor Yinghuo-1, but at least they'd get some deep space experience.
Whether there are any NEOs PG could actually reach is an open question, but it's certainly worth looking at if the Mars window closes with the spacecraft in operable condition.
-
#447
by
pm1823
on 24 Nov, 2011 00:03
-
they only had about 160-180 m/s for two corrections after automatic TMI maneuver. It was needed b'coz of engine performance and control system uncertainties or errors.
-
#448
by
Chris Bergin
on 24 Nov, 2011 00:05
-
-
#449
by
savuporo
on 24 Nov, 2011 00:07
-
they only had about 160-180 m/s for two corrections after automatic TMI maneuver.
Wonder if they could regain some delta-v by getting rid of some baggage ( *cough* poor Yinghuo-1 indeed *cough* )
EDIT: that was intended tongue in cheek. It does not appear that early jettisoning of YH would be possible.
-
#450
by
kevin-rf
on 24 Nov, 2011 00:08
-
Wonder if they could regain some delta-v by getting rid of some baggage ( *cough* poor Yinghuo-1 indeed *cough* )
Doesn't the probe have to break apart to do that and jetison the cruise stage with all that precious fuel?
-
#451
by
hop
on 24 Nov, 2011 00:08
-
If you're having to pay out the insurance and Roscosmos starts using the spacecraft, aren't you going to want to deduct some of the payout? If you ever want an FG II, then that doesn't seem like a good idea.
I would expect that salvaging some science out of the mission would be better for the careers of those involved than collecting insurance.
I guess they could jettison unused mass (like the Chinese satellite) to gain more delta V but that has its own political raminifcations.
Can't jettison that until the cruise stage (MDU/modified Frigate) is used up, YH-1 is contained in a truss between the stage and spacecraft. The cruise stage was responsible for MOI. Jettisoning the return capsule should be possible.
-
#452
by
Mark Max Q
on 24 Nov, 2011 00:10
-
-
#453
by
mmeijeri
on 24 Nov, 2011 00:12
-
How about turning it into Deimos Grunt to save some delta-v if necessary?
-
#454
by
pm1823
on 24 Nov, 2011 00:15
-
How about turning it into Deimos Grunt to save some delta-v if necessary?
as I remember, it's very small saving or none. Braking and closing ops&landing for any small body near Mars will be almost same.
-
#455
by
iamlucky13
on 24 Nov, 2011 00:16
-
I guess they could jettison unused mass (like the Chinese satellite) to gain more delta V but that has its own political raminifcations.
Unfortunately, this is almost certainly not an option. Referring back to the construction of F-G, note that the YH-1 orbiter is sandwiched between the Fregat-derived (MDU) stage and the cruise/descent stage.
http://www.russianspaceweb.com/phobos_grunt_design.htmlSo it appears impossible to separate the YH-1 until the MDU separates, which if I remember right, is after Mars Orbit Insertion, which is when YH-1 nominally separates anyways.
Possibly as an alternative they could use the cruise/descent stage to complete Mars Orbit Insertion, but that eliminates the possibility of landing on Phobos.
Also, I don't think anyone is calling for F-G to be sent to an asteroid. However, there is a possibility it is functional, but now unable to reach Mars. If that is the case, it's only logical to consider whether there might alternative targets.
-
#456
by
mmeijeri
on 24 Nov, 2011 00:21
-
as I remember, it's very small saving or none.
The old
delta-v budget chart from Jim's favourite aerospace source suggests the difference may be ~100m/s.
-
#457
by
Michael J
on 24 Nov, 2011 00:21
-
I guess they could jettison unused mass (like the Chinese satellite) to gain more delta V but that has its own political raminifcations.
Unfortunately, this is almost certainly not an option. Referring back to the construction of F-G, note that the YH-1 orbiter is sandwiched between the Fregat-derived (MDU) stage and the cruise/descent stage.
http://www.russianspaceweb.com/phobos_grunt_design.html
So it appears impossible to separate the YH-1 until the MDU separates, which if I remember right, is after Mars Orbit Insertion, which is when YH-1 nominally separates anyways.
Possibly as an alternative they could use the cruise/descent stage to complete Mars Orbit Insertion, but that eliminates the possibility of landing on Phobos.
Also, I don't think anyone is calling for F-G to be sent to an asteroid. However, there is a possibility it is functional, but now unable to reach Mars. If that is the case, it's only logical to consider whether there might alternative targets.
Not to mention China wouldn't be too thrilled about having their spacecraft discarded as excess baggage.
-
#458
by
pm1823
on 24 Nov, 2011 00:33
-
The old delta-v budget chart from Jim's favourite aerospace source suggests the difference may be ~100m/s.
that's what I remember, for more I need to look in old NPOL publications
on Deimos.
-
#459
by
iamlucky13
on 24 Nov, 2011 00:35
-
From what I've read, the first one only got the carrier wave/signal, while the second contained abbreviated telemetry data.
Matches Anatoly Zaks account here http://www.russianspaceweb.com/phobos_grunt_launch.html#11_23
3 Watts from a 1.3 meter dish versus several hundred Watts (?) from a 15 meter dish. That's quite a difference.
Aside from the naturally wider beam from the smaller dish, there was some commentary about modifications to further widen the beam.
So the communications issues may indeed have been related to spacecraft tracking all along. I will keep an eye out for possible confirmation of that. Consider it speculation for the moment.
And now the main article for baselining updates on the successes of the previous 24 hours or so:
http://www.nasaspaceflight.com/2011/11/live-fobos-grunt-recovery-efforts-underway/
I see you're commenting on the same factor.
As a minor note, your diagram of the spacecraft is labeled slightly differently than Anatoly Zak's. Neither are misleading, but since his information is being widely quoted and has been generally excellent, consistency might be worthwhile.