Author Topic: Ariane 5 VA241-SES-14 (with NASA GOLD payload) Al Yah-3 Jan. 25, 2018-DISCUSSION  (Read 56105 times)

Offline Rik ISS-fan

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We know how reliable Wiki is right  ::) :-[

The result of the VA241 mission can still vary between:
- Succes (with a mayor LOS anomaly)    and
- SES-14 partial Failure and Al Yah-3 compleet failure.
When the orbit tracks are known we will be able to determine the result of this launch.

AFAIK, LOS occurs far more often during Arianespace launches then they like. I'm not knowledgeable enough about there communication system to determine why this is. Each anomaly during the launch proces results in a launch anomaly investigation (those are very common for all launchers).
I think Arianespace will also look at their broadcast of this launch, I agree with the opinion that the LOS should have been called out. But because LOS of one station happens quite often, and most of the times the next station regains communication, I expect Arianespace didn't want to concern viewers to much. But calling AOS events when they don't happen; not mentioning the LOS, and not mentioning that the planned launch script is read out, is wrong (in my opinion).

The complete failure result has been ruled out, because both satellites have AOS. But AFAIK if a satellite can't reach GTO it's still a launch failure. And if it takes much longer and requires more dV (=propellant use) the live expectancy will be compromised, I think this is a partial failure.

Edit: Four weeks later on station is really a short time for a Electric satellite right?
So can we classify SES-14 succesfully launched (in a slightly wrong orbit)?
« Last Edit: 02/01/2018 10:41 AM by Jester »

Offline InfraNut2

The telemetry error might very well not have been an error in the radio systems themselves.

If the rocket 2nd stage under-performed or otherwise was off the nominal trajectory and the ground telemetry stations were tracking to the planned trajectory, the contact might have been lost just because the stage was too far from where the ground stations were tracking.

This obviously depends on how wide a margin the tracking antennas have for off-target radio reception and how far off-trajectory the 2nd stage was.

(The bigger the antenna dish, the smaller the margin; [edit: added:] Other factors such as for example the the relative angle from the tracking station to the planned trajectory are of course also important -- the distance itself not so much, except that it reduces the relative angle error relative to the sideways (as seen from tracking station) component of the position deviation at a given instant).

Just wanted to mention this possibility to make it part of the discussion...
« Last Edit: 01/26/2018 08:39 AM by InfraNut2 »

Offline Ben the Space Brit

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SES-14 owner @SES_Satellites: Off-target dropoff from @ArianeGroup @Arianespace Ariane 5 means all-electric propulsion to take 4 weeks longer than planned to get to GEO. Sat in good health, no other issues. Still awaiting word from @OrbitalATK & @yahsatofficial on Al Yah 3.

Can anyone estimate the dV under-performance of VA241 based on this extra MPS boost requirement on the part of SES-14? How badly will this impact the chemical-fuelled Al Yah-3's on-orbit lifespan?
« Last Edit: 01/26/2018 08:21 AM by Ben the Space Brit »
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Offline FutureSpaceTourist

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Quote
Thread: Attempt at some #Ariane5 #VA241 analysis:
Events:
AOS for Natal tracking station was planned for 06m41sec - Looked Nominal
ESC-A ignition was planned for 09m01sec - Looked Nominal
Natal tracking of ESC-A continued until 09m28sec after which tracking/downlink seemed lost.

https://twitter.com/dutchspace/status/956818025398841344

Quote
This apparent loss is during ESC-A Phase 3 after despin and when it's tilting

https://twitter.com/dutchspace/status/956818027827384320

Edit to add:

Quote
ESC-A tracking seemed lost 27 seconds after ESC-A ignition, which is
around 21.5 seconds into the tilting phase, which lasts 130 seconds

This is around 18.5 seconds before LOX valves are opened

https://twitter.com/dutchspace/status/956843910676078592
« Last Edit: 01/26/2018 10:05 AM by FutureSpaceTourist »

Online woods170

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French news outlets are now reporting that Arianespace has confirmed to the AFP news agency that the satellites were released in an off-target orbit.

http://www.lefigaro.fr/flash-actu/2018/01/26/97001-20180126FILWWW00005-ariane-5-les-deux-satellites-mis-en-orbite-au-mauvais-endroit.php

This indicates towards a serious, but non-catastrophic, failure of the ESC-A/VEB upper composite.

It is confirmed that SES-14 can reach its intented final orbit via its electro propulsion system. Status of Al Yah-3 is still unknown.
« Last Edit: 01/26/2018 09:20 AM by woods170 »

Offline hoku

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SES-14 owner @SES_Satellites: Off-target dropoff from @ArianeGroup @Arianespace Ariane 5 means all-electric propulsion to take 4 weeks longer than planned to get to GEO. Sat in good health, no other issues. Still awaiting word from @OrbitalATK & @yahsatofficial on Al Yah 3.

https://twitter.com/pbdes/status/956810114207543296

Sounds like the orbit is off target, although probably not by much if the extra time to GEO is "only" 4 weeks for an all ion thruster powered satellite.

SES-14 uses PPS-5000 plasma thrusters, which are designed for 200 mN thrust / 3000 s Isp.

How many PPS-5000 thrusters for orbit raising and maintenance are on SES-14? Then one could compute the delta v resulting from a 4 week "burn".

Offline Rik ISS-fan

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If I recall correctly from the launch broadcast; SES-14 was planned to reach GTO location in June or July. Now it's four weeks later. So I don't think it was dropped of very far from it's intended location (intended orbit).
With the two Galileo sattelites launched of VS09 it took months to get them into a circular orbit, that was still lower than intended.
[offtopic] AFAIK Galileo FOC couldn't be reached after the next Ariane 5 quad launch, because many clocks failed, two satellites are is the wrong orbit and one satellite is no longer operational.  :-X[/offtopic]
« Last Edit: 01/26/2018 08:50 AM by Rik ISS-fan »

Offline Kosmos2001

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SES-14 owner @SES_Satellites: Off-target dropoff from @ArianeGroup @Arianespace Ariane 5 means all-electric propulsion to take 4 weeks longer than planned to get to GEO. Sat in good health, no other issues. Still awaiting word from @OrbitalATK & @yahsatofficial on Al Yah 3.

https://twitter.com/pbdes/status/956810114207543296

Sounds like the orbit is off target, although probably not by much if the extra time to GEO is "only" 4 weeks for an all ion thruster powered satellite.

SES-14 uses PPS-5000 plasma thrusters, which are designed for 200 mN thrust / 3000 s Isp.

How many PPS-5000 thrusters for orbit raising and maintenance are on SES-14? Then one could compute the delta v resulting from a 4 week "burn".

For one PPS-5000:
mdot = F/(Isp*g0) = 0.2/(3000*9.80665) = 6.8E-06 kg/s.

4 weeks ~ 2419200 s. Thus, the total propellant mass burn for 1 PPS-5000 in 4 weeks is 16.446 kg.

If SES-14 is 4423 kg at launch according to: http://space.skyrocket.de/doc_sat/astrium_eurostar-3000.htm

Using the formula of delta-v: DV = Isp*g0*ln(m0/m1)

Isp = 3000 s
g0 = 9.80665 s
m0 = 4423 kg
m1 = 4423 - 16.446*#_engines

For 1 to 10 engines:

1   109.6 m/s
2   219.6 m/s
3   330.0 m/s
4   440.9 m/s
5   552.1 m/s
6   663.8 m/s
7   775.9 m/s
8   888.4 m/s
9   1001 m/s
10   1115 m/s

Online Kryten

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 Sounds like the issue isn't that bad, but the lack of telemetry means this is still likely to be a long investigation.

Offline Hankelow8

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I think the question to ask is, were there two separate failures or were they linked?.

If they were not linked but two separate failures it could be difficult for Arianespace to find the cause of stage failure as the telemetry was down.

Being a super-synchronous orbit the satellites will have a better chance of achieving orbit using their own propulsion.

Whatever the outcome we are in for big delay in Arianespace's next launch.

Online woods170

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I am so laughing it this turns out to be faulty antenna.  ;D

That would have been a highly unlikely scenario.
The last 30 minutes of the mission pass over no less than 4 ground tracking stations. All of those would have had to have an antenna malfunction to not receive telemetry.

If the antenna failure was on the vehicle side it would have to be a multiple failure given that the telemetry sub-system consists of:
- 2 separate central processing units
- 2 separate telemetry transmitters
- 2 separate antennae

What bothers me is the strange nature of this failure: orbital targeting was off AND no telemetry YET successful deployment sequence of the payload.

All three elements are controlled from the VEB. And all equipment in the VEB is redundant.

So:
For no telemetry both telemetry sub-systems would have to be off-line.
For successful payload deployment at least one sequencer sub-system (and the associated electrical sub-system) would have to be on-line.
For the incorrect target orbit both inertial unit sub-systems AND/OR both GNC sub-systems would have to off-line OR the propulsion system on the ESC-A upper stage had to have failed.

I for one will be very interested in what explanation the investigation will eventually come up with.
« Last Edit: 01/26/2018 11:08 AM by woods170 »

Offline GWR64

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...

SES-14 uses PPS-5000 plasma thrusters, which are designed for 200 mN thrust / 3000 s Isp.

How many PPS-5000 thrusters for orbit raising and maintenance are on SES-14? Then one could compute the delta v resulting from a 4 week "burn".

Hi,
I found: SES 12, SES 14 and SES 17 uses SPT-140 thrusters.
( Fakel Kaliningrad, Russia )

http://epic-src.eu/wp-content/uploads/14_EPICWorkshop2017_SES_EPIC-Workshop-2017-SES-Presentation.pdf

Online Elthiryel

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https://twitter.com/pbdes/status/956839344379252736
Quote
Peter B. de Selding‏ @pbdes

Al Yah 3 owner @yahsatofficial says satellite is making its way to GEO orbit, but co is silent on orbital position & fuel budget. @OrbitalATK sat uses chemical propellant to get to GEO, then electric prop for stationkeeping during 15-yr life.
GO for launch, GO for age of reflight

Online kevinof

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A telemetry failure would not make the stage end up in the wrong orbit (if I understand how these things work). From the reports I've seen, the sats are most likely in the wrong place and that implies a failure of the stage, and not just the telemetry side of things.

I am so laughing it this turns out to be faulty antenna.  ;D

That would have been a highly unlikely scenario.
The last 30 minutes of the mission pass over no less than 4 ground tracking stations. All of those would have had to have an antenna malfunction to not receive telemetry.

If the antenna failure was on the vehicle side it would have to a multiple failure given that the telemetry sub-system consists of:
- 2 separate central processing units
- 2 separate telemetry transmitters
- 2 separate antennae

What bothers me is the strange nature of this failure: orbital targeting was off AND no telemetry YET successful deployment sequence of the payload.

All three elements are controlled from the VEB. And all equipment in the VEB is redundant.

So:
For no telemetry both telemetry sub-systems would have to be off-line.
For successful payload deployment at least one sequencer sub-system (and the associated electrical sub-system) would have to be on-line.
For the incorrect target orbit both inertial unit sub-systems AND/OR both GNC sub-systems would have to off-line OR the propulsion system on the ESC-A upper stage had to have failed.

I for one will be very interested in what explanation the investigation will eventually come up with.

Offline calapine

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I am so laughing it this turns out to be faulty antenna.  ;D

That would have been a highly unlikely scenario. < SNIP >

I am aware of all of that. By that time of the mission, to paraphrase Shakespeare, 'the wish was father the thought'

That aside, we have an update for Al Yah3 via PBDES:

Quote
Al Yah 3 owner @yahsatofficial says satellite is making its way to GEO orbit, but co is silent on orbital position & fuel budget. @OrbitalATK sat uses chemical propellant to get to GEO, then electric prop for stationkeeping during 15-yr life.

https://twitter.com/pbdes/status/956839344379252736
« Last Edit: 01/26/2018 10:03 AM by calapine »

Offline kevin-rf

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I would argue the telemetry failure could be related. If the anomaly was the stage attitude was wrong, and the stage antenna was no longer oriented to be visible to the tracking station(s).
« Last Edit: 01/26/2018 10:29 AM by kevin-rf »
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Offline hoku

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...

SES-14 uses PPS-5000 plasma thrusters, which are designed for 200 mN thrust / 3000 s Isp.

How many PPS-5000 thrusters for orbit raising and maintenance are on SES-14? Then one could compute the delta v resulting from a 4 week "burn".

Hi,
I found: SES 12, SES 14 and SES 17 uses SPT-140 thrusters.
( Fakel Kaliningrad, Russia )

http://epic-src.eu/wp-content/uploads/14_EPICWorkshop2017_SES_EPIC-Workshop-2017-SES-Presentation.pdf
Thanks. SPT-140 seems to have a 40% higher maximum thrust, and about 40% lower Isp than PPS-5000. Thus the order of magnitude of delta v computed by Kosmos2001 should still be applicable, i.e. most likely a few 100m/s additional delta v required for SES 14 to reach GEO.
« Last Edit: 01/26/2018 10:33 AM by hoku »

Offline pippin

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I am so laughing it this turns out to be faulty antenna. 

That would have been a highly unlikely scenario.
The last 30 minutes of the mission pass over no less than 4 ground tracking stations. All of those would have had to have an antenna malfunction to not receive telemetry.

If the antenna failure was on the vehicle side it would have to a multiple failure given that the telemetry sub-system consists of:
- 2 separate central processing units
- 2 separate telemetry transmitters
- 2 separate antennae

What bothers me is the strange nature of this failure: orbital targeting was off AND no telemetry YET successful deployment sequence of the payload.

All three elements are controlled from the VEB. And all equipment in the VEB is redundant.

So:
For no telemetry both telemetry sub-systems would have to be off-line.
For successful payload deployment at least one sequencer sub-system (and the associated electrical sub-system) would have to be on-line.
For the incorrect target orbit both inertial unit sub-systems AND/OR both GNC sub-systems would have to off-line OR the propulsion system on the ESC-A upper stage had to have failed.

I for one will be very interested in what explanation the investigation will eventually come up with.
My money is on software.
They did something wrong implementing the new (to them) supersynchronous orbit ascent profile which resulted in the wrong orbit and because the position was wrong communication didn’t work (position different than expected or wrong attitude ).

But we’ll probably know that soon because if this is true there would have to be a deviation of the ascent profile even before the LOS and they will probably have data then.
« Last Edit: 01/26/2018 10:33 AM by pippin »

Offline mlindner

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NASA had a station in Ascension until 1999, at which point ESA took over.

My Dad worked on Ascension in the mid 70s. At the time they tracked Apollo-Soyuz and Russian ICBMs.
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Online woods170

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I would argue the telemetry failure could be related. If the anomaly was the stage attitude was wrong, and the stage antenna was no longer oriented to be visible to the tracking station(s).
Unlikely. The Ariane 5 VEB is equipped with TWO telemetry antennae, on opposite sides of the VEB. Regardless of attitude of the stage, at least one antennae is always visible from the ground.
Normal attitude control of the ESC-A is such that BOTH telemetry antennae are visible from the ground.
So, for your fault scenario there would have to be two separate failures:
- Off-nominal attitude of the ESC-A stage
- The one telemetry antennae still pointing to Earth is defective.

Granted, it is not impossible, but it is unlikely.

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