Interesting comment from Blair Ivey further down that thread:
“It appears from the SpaceX feed that Starship failed to separate at the designated time, and as fuel burned off in SuperHeavy, the center-of-gravity moved forward along the thrust axis until the stack became uncontrollable.”
Lots of analysis will have to be done before the way forward becomes clear.
One of the better Sea Dragon animations (of which there are many):
This won’t buff out:
A brief search for arguments against the Sea Dragon as compared to the Superheavy yielded little in the way of direct comparisons and much in the way of Dunning Kruger regarding the Sea Dragon. One of the more precious Dunning Kruger moments was when an “authority” declared the turbo pump of the Saturn V to be an extremely difficult problem even at far lower flow rates than the Sea Dragon’s fuel flow rates. Truly impressive DK performance given that the Sea Dragon is pressure fed hence has the “optimal turbo pump” being NONE.
Anyway, one argument was that the acoustic assault on sea life would kill everything in the Gulf of Mexico. So I went looking for anything on that topic in the literature and found this study, with this introduction to the dynamics section:
and this acoustics table:
In all, I can see why Musk might have avoided the Sea Dragon:
The environmentalists would have been preemptively all up in his business since we just don’t know what the environmental impact would be given the absence of adequate scientific models and validation thereof that should have started in the early '60s.
Or, as the Canadian bush pilots say, “What you don’t have can’t break.”
When you consider the hoops SpaceX was made to jump through by the environmentalists as part of the FAA licensing process (detailed in the post here on 2022-06-13, “FAA Releases SpaceX Starbase Programmatic Environmental Assessment, Finds ‘No Significant Impact’ ”), one can scarcely imagine how they would have reacted to a proposal to launch Sea Dragon from the Gulf. I’m thinking something like the closing scene of Kingsman.
Also, according to the Wikipedia page on Sea Dragon, “Payload costs, in 1963, were estimated to be between $59 to $600 per kg (roughly $500 to $5,060 per kg in 2020 dollars. TRW (Space Technology Laboratories, Inc.) conducted a program review and validated the design and its expected costs.” Now, that’s a pretty wide range for a cost estimate, but Elon’s goal for Starship is much more ambitious: “Musk has predicted that a Starship orbital launch will eventually cost US$ 1 million (or US$ 10 per kilogram.” Even if he is low by a factor of ten, that’s still one fifth the lowest estimate for Sea Dragon.
Here is Scott Manley’s analysis of the Orbital Test Flight. Note, in particular, the slow motion blow-up of liftoff, where large chunks of concrete can be seen flying to a substantial fraction of the height of the rocket. That makes it plausible that the first three engine failures might have been due to impacts from debris.
That’s quite a bit higher than the impression Truax gave me circa 1990, but then I never bothered to check up on his claim. In any event, I’m pretty sure the “TRW report” is the document I previously linked to. Here is The Money Quote:
To do an apples to apples comparison, we must use the before-amortization cost. Here’s Musk’s quoted target again:
“Musk has predicted that a Starship orbital launch will eventually cost US$ 1 million (or US$ 10 per kilogram.”
That doesn’t look like an amortized cost.
If so, the low end TRW estimate is $(2020)184, which is nearly 20 times Musk’s target.
That said, it still looks to me like Kennedy/von Braun really did a number on the US if not the world by failing to go with prize awards for milestones toward landing a man on the moon using guys like Truax and Hughes rather than a communist style “8 year plan”.
Marcus House has chimed in with his coverage of the flight. He does not go in for speculation about causes of things, but has some video of the launch I hadn’t seen before, including the SpaceX drone shot showing debris landing in the Gulf as the rocket ascends. There are still pictures from Starship showing some missing thermal protection tiles and the stages in the process of breaking up.
Scott Manley is normally an astute observer, but he was probably a bit off in suggesting that the +/-150 feet water depth where the rocket came down is too deep for amateur divers. All SpaceX has to do it get those 4 men & a chick on a rented sailboat who blew up 3 out of 4 NordStream pipelines in significantly deeper water in the Baltic. Those Ukrainians will have the remains on the rocket back on dry land in no time flat!
Of course, it might be difficult for SpaceX to get in touch with those wiley Ukrainians. No-one else seems to be able to find them.
The water cooling of the steel plate will be open loop rather than closed loop. This begs the question of the discharged water. It would have to be steam, which will probably be classified as a pollutant by the EPA.
Perhaps musk can come up with a way to deflect ice falling from the rocket to help aid in the process.
The methane heat of combustion flow of just one Raptor is >7GW or ~250GW per Superheavy.
I’ve heard stuff like “as much power as the entire US electrical grid” associated with big rockets so – ok – about a quarter terawatt must be cooled by the water flow. Sheesh… ok… so that’s, what water mass flow rate?
'Zat rite?
(See, Calchemy still comes in handy 25 years after doing all those thermal calculations for the ultracentrifugal rocket engine!)
*Note this assumes steam is the output which must be carefully weighed against the fact that the thermal transfer properties of steam are far less favorable than liquid water. You really have to be careful about hot spots forming if you are relying on the total heat of vaporization. Things can get out of hand. You like to keep things liquid. It’s like, a really big deal at these areal powers.
The existing water deluge systems for SLS, Falcon 9/Heavy, and Atlas all emit huge clouds of steam into the atmosphere and nobody seems to bother about it. Of course, this is clown world where CO₂ has been classified as a “pollutant”, so you never know….
For comparison, the NASA water deluge system used for SLS launches, called the Ignition Overpressure Protection and Sound Suppression (IOP/SS) system is said to release 450,000 gallons of water over a period of 60 seconds. Here is a test of the system without the mobile launcher in place. As NASA noted at the time,
A geyser occurred because the mobile launcher was not present at the pad. When the mobile launcher is sitting on its pad surface mount mechanisms, the rest of the IOP/SS system is connected to the pad supply headers and the water will flow through supply piping and exit through the nozzles.
From this, Units Calculator says:
((450000 gallon) * waterdensity) / 60 seconds = 28.39 tonne/second
Given that Super Heavy has around twice the liftoff thrust of SLS, this seems consistent with your estimate of 100 tonnes/second.
Here is a comparison of Starship, Space Shuttle orbiter, and Cargo Dragon (original version) to scale.
If, as I surmise might well be the case, cooling steel plate must avoid phase transition to vapor in order to avoid hotspots, the output could be 100C liquid water (or thereabouts). One can minimize the amount of liquid water dumped into the environment by keeping things under enough pressure during contact with the steel plate that upon contact with atmospheric pressure, it immediately vaporizes. In that event the pressurized liquid water in contact with the steel plate should go well above 100C. The pressurizing pumps for this would need to be pretty powerful. I don’t have a handle on how powerful. I encourage the use of Calchemy for this kind of stuff:
PS: The copyright holders of Calchemy finally gave up supporting it because no one but me was using it. That’s why I salvaged a copy for my own use. This calculator really deserves a better home than I can give.
Were there not videos circulating showing an elevatable work platform under the launch structure? Used to help crews install/replace engines. Wonder what happened to that?
Since the intent is eventually for Starship to have a high launch cadence, it looks like one of the key lessons of this first flight will be the need for a very effective flame/exhaust diversion system. Maybe a complete redesign of the launch/retrieval tower?
Regarding the steel plate as a combustion chamber wall is kind of interesting. The “chamber” pressure is less than 200psi even if all pressure is projected to the circle directly under the rocket.
Does this mean the cooling channels could do film cooling into the chamber?
Depending on the mix (kinetic vs thermal) of the energy to be diverted this would increase the pressure on the chamber from all that superheated steam on the flame side of the chamber. And if your cooling channels weren’t at a high-enough pressure over the chamber, you could get “chugging” instability that could, in turn, destroy the system including pumps.
Here is video from the launch taken by rocket photographer Trevor Mahlmann. This video is notable in being a single take that shows the rocket from launch to destruction, capturing the experience of an observer nearby. The sound is superb, with the low frequency rumbling and rarefaction to vacuum crackling not heard since the last launch of a Saturn V in 1973. The flares as “events” occur during the ascent are particularly obvious in this view.
