Author Topic: H-IIA F39 - IGS Radar-6 - June 12, 2018 (04:20 UTC)  (Read 7115 times)

Offline ChrisC

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Re: H-IIA F39 - IGS Radar-6 - June 12, 2018 (04:20 UTC)
« Reply #60 on: 06/12/2018 04:15 PM »
Max-Q condensation shocks hi-res pictures in this tweet.

Chris #1 tweeted this out, so it's worth clarifying that these condensation clouds are NOT necessarily indicating Max Q.  A vapor cone typically occurs as the vehicle approaches transonic speeds, which MAY happen to coincide with maximum dynamic pressure, but not necessarily.  In fact, in orbital rocket launches, Max Q normally occurs in the low supersonic regime, right? (It depends on the acceleration profile, which depends on the thrust to weight ratio.)  So Max Q is more like a dozen seconds or so after the transonic regime in which a vapor cone is seen.

These kinds of condensation clouds can be observed on humid days on regular airliner wings or engine nacelles as they approach or depart an airport.  And those are hardly transonic or even Max Q scenarios.

This kind of image is also sometimes mislabeled as "breaking the sound barrier".  Nope, not that either, but typically close in time, as per above.
« Last Edit: 06/12/2018 05:44 PM by ChrisC »
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Offline eeergo

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Re: H-IIA F39 - IGS Radar-6 - June 12, 2018 (04:20 UTC)
« Reply #61 on: 06/12/2018 11:15 PM »
Chris #1 tweeted this out, so it's worth clarifying that these condensation clouds are NOT necessarily indicating Max Q.  A vapor cone typically occurs as the vehicle approaches transonic speeds, which MAY happen to coincide with maximum dynamic pressure, but not necessarily.  In fact, in orbital rocket launches, Max Q normally occurs in the low supersonic regime, right? (It depends on the acceleration profile, which depends on the thrust to weight ratio.)  So Max Q is more like a dozen seconds or so after the transonic regime in which a vapor cone is seen.

These kinds of condensation clouds can be observed on humid days on regular airliner wings or engine nacelles as they approach or depart an airport.  And those are hardly transonic or even Max Q scenarios.

This kind of image is also sometimes mislabeled as "breaking the sound barrier".  Nope, not that either, but typically close in time, as per above.

All very true, thank you for the clarification. in fact, the condensation clouds in the Prandtl-Glauert singularities in these cases follow the shockwave airflow, and they roughly coincide with parts of the vehicle accelerating the flow to past supersonic speeds, while the vehicle itself may be subsonic. Thus the sound "barrier" nickname (since they usually occur in rockets when the "singularity" is approached at Mach 1), or the Max-Q language since it roughly coincides with when pressures are becoming the highest. Even though, as you say, the clouds may coincide with neither single event.
-DaviD-

Offline Lewis007

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Re: H-IIA F39 - IGS Radar-6 - June 12, 2018 (04:20 UTC)
« Reply #62 on: 06/13/2018 05:50 AM »

Offline zubenelgenubi

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Re: H-IIA F39 - IGS Radar-6 - June 12, 2018 (04:20-04:33 UTC)
« Reply #63 on: 06/13/2018 11:49 PM »
Many thanks Steven!
My thanks as well--I couldn't stay up to watch the launch live; so I'm thankful for this thread!
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Offline jcm

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Re: H-IIA F39 - IGS Radar-6 - June 12, 2018 (04:20 UTC)
« Reply #64 on: 06/23/2018 04:37 AM »
Object C now cataloged. Most of the IGS Radar series have had such a debris object associated with them,
possibly related to radar deployment hardware?
-----------------------------

Jonathan McDowell
http://planet4589.org

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