Author Topic: Ariane 5 Flight VA245 - BepiColombo (MPO+MMO) - October 19 (Oct 20 UTC), 2018  (Read 14241 times)

Offline jacqmans

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Offline jacqmans

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Offline lamid

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at 26:47 separation
altitude 1452 km
speed 10.15 km/s
result:
C3 = 1.19 km2 /s2
v_inf=1.09 km/s

according to FLIGHT VA245: ARIANESPACE...pdf :
INFINITE VELOCITY 3.475 km/s
I do not understand that

ratio:
780000 kg rocket / 4241 kg  payload = 184 kg/kg

Offline Steven Pietrobon

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at 26:47 separation
altitude 1452 km
speed 10.15 km/s
result:
C3 = 1.19 km2 /s2
v_inf=1.09 km/s

according to FLIGHT VA245: ARIANESPACE...pdf :
INFINITE VELOCITY 3.475 km/s
I do not understand that

You need to take into account the angle of the flight path. It is not horizontal to the Earth at this point. Also, is the velocity Earth relative or inertial? I'm not sure.
« Last Edit: 10/20/2018 08:31 AM by Steven Pietrobon »
Akin's Laws of Spacecraft Design #1:  Engineering is done with numbers.  Analysis without numbers is only an opinion.

Online Phillip Clark

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I assume that "infinite velocity" is the hyperbolic excess speed.
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Offline jcm

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at 26:47 separation
altitude 1452 km
speed 10.15 km/s
result:
C3 = 1.19 km2 /s2
v_inf=1.09 km/s

according to FLIGHT VA245: ARIANESPACE...pdf :
INFINITE VELOCITY 3.475 km/s
I do not understand that

You need to take into account the angle of the flight path. It is not horizontal to the Earth at this point. Also, is the velocity Earth relative or inertial? I'm not sure.

The 10.15 km/s is Earth-relative.
Using the Horizons trajectory I estimate at 0213:30 UTC we have alt 1463 km, vrel 10.15 km/s vinertial 10.67 km/s, C3 = 12.075,  vinf = 3.475 km/s so all looks consistent to me

edit:  and flight path angle about 24.9 deg Earth-rel, so very far from horizontal
« Last Edit: 10/20/2018 06:45 PM by jcm »
-----------------------------

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Offline zubenelgenubi

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Offline yoichi

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Offline lamid

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Yes.
The stated speed of 10.15 km/s is against Kourou.
The rotation of the Earth gives Kourou 0.463 km / s
If the Ariane VA245 angle is 24.9 , it is 0.419 km / s
And in the altitude 1452 km (+ 6378 = 7830 km) it is 0.515 km/s
10.15 + 0.515 = 10.665 km/s
and C3 = 11.91 km2/s2
v_inf = 3.451 reported 3.475 km/s
that's all right.

And Yes,
horizons
bc_mpo_fcp_00023_20181020_20251102_v01  2018-Oct-20 02:14  2025-Nov-02 08:30
v=10.668674 km/s and distance 7 835.42 km
result
C3=12.055 km2/s2
v_inf = 3.472 km/s

Thanks
« Last Edit: 10/21/2018 04:12 AM by lamid »

Offline lamid

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BepiColombo leaves the Earth.

« Last Edit: 10/21/2018 08:02 AM by lamid »

Offline input~2

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Quote
Jonathan McDowell
‏Verified account
 @planet4589
20 hours ago
Fitting crude orbit to the data on the webcast suggests EPC was in a -580 x +420 km orbit at separation, with about +-50 km on each parameter. Splash around 1500 km S of Cape Verde Is at 0201 UTC?
Correct Jonathan! according to this NOTAM:
A1598/18 NOTAMN Q) GOOO/QWMLW/IV/BO/W/000/999/0404N02229W999 A) GOOO B) 1810200140 C) 1810300300 D) DLY:0140/0300 E) EXISTENCE OF DANGEROUS ZONE DUE TO ROCKET LAUNCHING VA245 DELIMITED AS FOLLOW: ZC/VA245: 0404N02229W - 0230N00739W -0042N00750W  - 0216N02240W F) SFC G) UNL

Offline Jester

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without you know what....
« Last Edit: 10/24/2018 03:17 PM by Jester »

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