dhanson865
Well-Known Member
If the seas are calm you'll get drone footage at a minimum, no way you can keep looky loos from sightseeing a known location and the view range on a clear day above the ocean is quite far.
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From that maps posted above, are the blue regions the exclusion regions for the booster path?. Which means the booster is expected to splash mid gulf coast? Will we get some live video?
Airborne assets like WB-57 and ships w drones likely.
Hawaii has marine hazard zone, will likely be enforced by coast guard. Only 20x20nm ish though, so can get in range with good lens.
Blue is booster/stack path if intact. Doesn't mean they are planning to land midgulf, just that ballistics could carry it there. Blue zone at Hawaii is landing zone.
Larger zones are RUD or FTS debris areas.
Just in case the issue of whether or not the upcoming Starship launch profile is an “orbital” or “suborbital” trajectory, this diagram posted by @theradicalmoderate on ars technica provides an explanation.
Heck, even with same apogee, the difference between a multiorbit trajectory and a not quite one-and-done is only a few meters per second.
Given the amount of stuff in the minimum orbit + 150km range, I sort of expect a lower orbit. Especially with Elon referencing Starship's L/D performance which (I think) supports a shallower re-entry.
Yeah, this flight is likely free return. Normally, it would need a deorbit burn.
Now that we are possibly just weeks away from the first orbital launch attempt, I re-watched this year-old Scott Manley video about Starship heat shield tiles. Worth a viewing if you’ve never seen it.
Not sure why Scott thinks heat shield damage is most likely at launch approaching Max Q. That would only be the case if the damage mechanism is aero pressure related. Static fires have already seen damage occurring - not sure if this is due to structural distortion, plume impingement, poor quality fixing or vibration. Presumably this sort of damage is most likely at launch and then at start-up of the ship engines after stage 1 separation.
Damage due to aero loadings at Max Q would be surprising as Max Q occurs close to Mach 1 and the flow mechanisms in this flow regime are well known and hence pressure distributions are amenable to calculation.
The models for the hypersonic flows and the heat transfer mechanisms which will be experienced during the transition from space to upper atmosphere and how these evolve as the atmosphere thickens (and Knudsen number changes) around a complex (but essentially blunt) body with dynamic geometry (as the control surfaces move) are just models at present and will only be validated by flight data. I seem to remember reading some time ago that NASA are paying SpaceX for the data from these flights, presumably so that they can improve the NASA flow models. Thus there is a lot of uncertainty about the conditions which will actually be experienced and hence the SpaceX guys may be designing for conditions that are different to actual flight.
I would guess that the failure mechanisms in these regimes will not be aero pressure but tile structural failure due to thermal degradation, aero induced vibration or dynamic loadings as the shock waves fluctuate.
Mostly views from 30 years ago.
petit_bateau
Active Member
Are you including the acoustics in the "vibration" you describe ? I've read/discussed with folk that the post-ignition / pre-launch (i.e. before clamp release) acoustic conditions - i.e. mechanical forces transmitted via gas pressure fluctuations - can be one of the greatest challenges for heat shield damage etc. (and for payloads and similar)
This is the moment when the noise emission is greatest; it reflects off the pad & tower etc; the static atmospheric pressure is greatest (which is the transmission pathway); and the ship is sitting there not moving, i.e. not fleeing the scene.
And how much of that is due to lack of a flame trench? just wondering.
petit_bateau
Active Member
My own personal understanding (which may be wrong) is that the deluge system is the main attenuation for the acoustics.
It's lucky that getting off Mars doesn't require a booster.
B7 got a full prop load test today, LOX detanking now underway, CH4 tank still full.
Either side of the speed of sound, likely. However, the transonic zone where the airflow starts separating seems more like it would be more chaotic. Sort of like flow separation in an overexpanded engine bell.
One point to keep in mind is that all Starship tests to this point have been on a much shorter test pad. For launch, it will be an extra 70+ meters above the ground with a few million tons of liquid below it which seems it would have some level of damping. Were any SN24 static fire tests fully fueled?
Good points. That extra elevation should make a difference. And I think they were all just partially fueled.
Wow, you and @mongo are asking me hard questions now!
Re acoustic forces at launch I had not not considered them acting directly on the ship tiles due to the height of the booster and the deluge system being below the ship. However indirectly the acoustic loading will add to the 'vibration' being transmitted up the booster to the ship.
Re transonic flows, these can be a little chaotic but the point I am trying to make is that the flows and loads that will be seen will not be dissimilar to those on other rockets and hence SpaceX should be fairly confident of their prediction accuracy (lots of analysis codes have been developed for combat aircraft which have more complex geometries and where test data has been available to validate the correlations used). So while the design work needs to be done the answers should be close to reality.
The upper atmosphere flow and heat transfer (convective and radiative) modelling just seems to have far more uncertainty to me. The first flight should remove a lot of that uncertainty.
Yeah... but...
Rockets are 'just' pressurized metal tubes. Dragon capsules have a basically monolithic PICA heat sheild. Only the shuttle had a similar tile system and that was fully glued vs air gapped on three pins. Plus, its tiles primarily faced the external tank and were out of the shock front.
Cool photos:https://ntrs.nasa.gov/api/citations/20110007108/downloads/20110007108.pdf
Not saying they will fail, just that launch survival isn't a given.
S24 rollout and OLM preparations. B7 grid fins were tested. There has been some speculation online that SpaceX will not attempt a soft landing of the booster in the Gulf. I have always been of the opinion that they will attempt that; why waste the opportunity? Seeing the grid fins being tested indicates to me that they plan to use them. Of course the fins serve to guide the booster to the desired landing location, they do little to reduce velocity; that requires an entry burn and then a landing burn. But why not try?
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