I’ve only seen speculation so far on what that might have been, but it seems to have been something from the underside of StarHopper, possibly a pressure vessel, and possibly from the engine vectoring controls. All of the white pressure vessels on top of StarHopper are still there.

Lucky? There’s a saying that luck favors the prepared. They’ve had their failures, and they’ve learned from them. They have an acronym, “RUD”, for “rapid unscheduled disassembly.” This was a test vehicle and a test engine, built for testing. If nothing goes wrong in testing, it only means that you haven’t pushed hard enough.

That makes sense. The yellow was also there early in the launch, and during landing it formed from lower down the exhaust upward.

Shiny saver wrote: “Certainly, the O / F mixing ratio was not changed. Such an approach would be very unusual and probably would not be good for the engine itself.”

Not necessarily. The Saturn V changed mix ratios in order to change performance to get the most out of the rocket.

Shiny saver wrote: “Unit costs of only $ 2 million – for one of the most complex liquid rocket engine that has been built so far are – are in my view, totally unbelievable.”

This price depends upon several things. For instance, it is a target price, not a guaranteed cost of production. Mass production of 500 per year will reduce the fixed costs on a per-engine basis. Additive manufacturing is becoming a mature process, and engineers are finding ways to reduce the number of individual parts that must be assembled.

Additive manufacturing is also reducing the weight used on flanges for bolting pieces together. It is a process that is paying off in several ways.

No matter what, SpaceX is committed to lowering the cost of getting into space, even over rocket performance. They use the less efficient RP1 in the Falcon upper stage in order to reduce the costs associated with using two different types of fuels. This low-cost philosophy is spilling over into the BFR rocket, and attempting to reduce the cost of each engine would be an important goal. Because so many are used in each Super Heavy (SH), reducing the per-engine cost would be a high priority.

As ULA notes, returning a Falcon first stage reduces the mass that can be lifted into space, and ULA’s new design tries to maximize performance while only returning the expensive engines for reuse. ULA is willing to pay the price of building new first stage bodies for each launch in order to keep the performance high, but SpaceX would rather offer a launch for a lower price than maximize its first stage performance.

Why would SpaceX need a dozen SHs a year? Outside of the possibility that sometime in the future there may be a market for using them for lifting masses that require they be thrown away (expensive, but may be necessary), SpaceX may not be able to turn-around each SH as fast as they need them, so they may need multiple SH stages at each launch site.

As Diane Wilson noted, SpaceX wants to go to Mars. They have announced that they want to move a million people there, and that will take a lot of Starships and SHs as well as quite a few tanker versions of Starship.

There is the concept of using Starship for point to point Earth travel. Look at the bottom of this page:
https://www.spacex.com/mars

SpaceX lists eight different routes between ten different cities, so they need at least three (but probably eight) Starships and at least ten Super Heavies. If these routes prove to be popular, then they may need even moire. And if other routes are created, then more of these rockets will be needed.

https://www.youtube.com/watch?time_continue=412&v=lsoS6C0uzGY

Musk has said that he wants to die on Mars, just not on impact. This will get very interesting, very soon.

I do not think that there is a need for 500 Raptor engines a year. That would be about 12 BFR rockets a year. That makes no sense to me, because SpaceX has planned that this space launch system should be fully reused hundreds of times and at that minimal cost per launch. By the way, we should be, in respect to price and cost numbers, which are presented by SpaceX, very careful. I do not trust them. So, we still do not know what cost advantage the reuse of the first stage of the F9 really results. Unit costs of only $ 2 million – for one of the most complex liquid rocket engine that has been built so far are – are in my view, totally unbelievable. I just want to like how this number was generated.

Methane as a fuel for a liquid rocket propellant combination owns advantages and also disadvantages. Its Isp performance is not much larger as that of RP-1 kerosene fuel, in combination with LOX as oxidizer. Its main advantages are its properties as coolant for the combustion chamber’s regenerative cooling system. For example, it does not produce soot as a coolant, which can block cooling passages. However, it is much more hazardous in respect of unwanted ignition of air (oxygen)-methane-mixture, because its ignition energy is very low. In this respect, RP-1 is much less hazardous. And methane is cryogenic. Methane has to vent permanently during propellant loading, parallel to LOX venting, which is not ideal in respect to ignition hazards and environmental impact.

Diane Wilson: You sum this up better with your comment than anyone so far has. I might quote you, and hat tip you if I do.

Congratulations to SpaceX on all counts!

Flying water tank….

I watched this thing live at 1700 CT…. Awsome doesn’t even try to describe the moment……

Congratulations SpaceX!

Seems more like it belongs in this movie.

The Hopper has Landed!