For various launch vehicles it usually it occurs at altitude around 110-120 km range but for inaugural launch of Vega C flight VV21 payload fairing jettison altitude seems too high, why is it so?
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Interesting question!
The excellent answer to this question How strong and "hot" is the wind on the payload after the fairing is deployed at ~110km? tells us that most boosters jettison the fairing when the heat flux drops to < 1135 W/m2.
However, the Vega C User's Guide states
2.3 Aerothermal flux at fairing jettisoning
Jettisoning of the payload fairing can take place at different times depending on the passengers aerothermal flux requirements. Typically, for SSO missions, the fairing separation takes place 5s after Z9 ignition around 270 seconds from lift-off and the aerothermal flux is lower than 300 W/m2 .
(emphasis mine)
So this booster is waiting for a lower value of the heat flux to jettison the fairing, compared to the other boosters.
Why that is, I do not know.
answered Jul 13, 2022 at 16:41
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1$\begingroup$ The lower heat flux after fairing separation may allow payloads with less heat protection. So some weight may be used for electronics, propellants or solar panels instead of heat protection. $\endgroup$– UweCommented Jul 13, 2022 at 22:50