Cryogenics depleting when simulating on delay

[Xavienth]

Not exactly sure of the RP1 version, but all mods were up to date in CKAN as of 7 may.

Description: When simulating at a specified time in the future, cryogenics are depleted as if the vessel has existed since the present.

Expected behaviour: Simulate e.g. 16d in the future. Any cryogenics tanks should be at the levels they were at in the VAB when the simulation starts.

Actual behaviour: Simulate e.g. 16d in the future. Any cryogenics are approximately at the level they would be at if the simulation was started at the present and left to sit for 16 days.

Video demonstrates this:

2024-05-07_03-29-55.mp4

Issue occurs whether starting in orbit or on the pad.

[siimav]

You're supposed to use launch clamps.

[Xavienth]

Does not solve the issue.

[siimav]

You attach clamps to your stage; then simulate multiple days in the future; and boiloff still happens with both in orbit and on the pad?

[Xavienth]

Yes, even with ground support clamps attached to the engine, boiloff occurs. I tested orbit only for this case.

Additionally, there are situations where it is not feasible to attach ground support clamps to the stage. For example, cryogenic 2nd stage tested from launch with a simulation delay. Unless ground support clamps on the first stage apply to all stages, in which case disregard this paragraph.

[siimav]

Yes, clamps apply their magic vessel-wide. I would still like to know if this is still an issue for simulating on the pad.

[Xavienth]

I will test to confirm later, but I am reasonably confident I encountered the issue even on the pad with clamps earlier today.

[Xavienth]

I did several tests. Here is a summary of my results:

No clamps

On pad
Time: 0 - tanks full
Time: 7d - tanks depleted
On orbit
Time: 0 - tanks full
Time: 7d - tanks depleted

Clamps

On pad
Time: 0 - tanks full
Time: 7d - tanks start depleted, fill to full.
On orbit
Time: 0 - tanks full
Time: 7d - tanks almost depleted.

The clamps, pad, 7d test was insightful. Sufficient time must be given after the simulation begins to let the cryo tanks refill if not started at time 0.

For the case of a pad simulation, one cannot immediately launch once the simulation starts, to let the cryo tanks refill. For the case of an orbit simulation, the delay parameter must be set to sufficient time (e.g. 10-30s) to let the ground clamps do their magic to refill the cryo tanks before it is placed into orbit.

[siimav]

Weird, clamps are supposed to keep propellants below boiloff temp.