Starship test flight 4. I'm finding it difficult to think of how it could have been much better, given what they intended to test.
The quote they use all the time is, "the payload for this flight is data;" the whole purpose is to examine changes made since the last test with a handful of milestones in mind. They're fond of saying that no matter what they try, only excitement is guaranteed. That said, there were two main objectives for this mission.
For the Super Heavy booster, the objective was to return toward Boca Chica and come to a vertical position above the Gulf of Mexico before splashing down into the gulf. For Starship, the objective was to come through reentry with full attitude control, intact, operational, and do the same sort of landing in the Indian Ocean off the NW coast of Australia. If you remember the first tests with prototype ships launching vertically up to altitudes above commercial air traffic, then falling belly first until a few hundred feet above the ground when the ship would ignite its engines, flip from horizontal to vertical and land. That's what was envisioned for the Starship today.
While I have yet to see video perhaps taken by an aircraft in the targeted area, it looks like both objectives were accomplished.
The only obvious issue in the booster was that one of the 33 Raptor engines shutdown within the first few seconds of flight, unlike Test 3. In the last moments before touching the water in the Gulf, another one of the engines appeared to blow up or RUD (Rapid Unscheduled Disassembly), but the booster appeared to come to zero velocity right at the water surface, although we'll have to wait for SpaceX to tell us if it met all their targets.
A lot of people went gaga over the videos from Starship in IFT-3 and today's were far better. First, the spurious rolling motion and consequent movement of the flaps on the ship were gone. Instead we got what looked like a studio picture on a sound stage - except instead of pink lights shining on the heat tiles, it was plasma at 2500 to 3000 degrees.
Plasma pours over the tiles and control flaps of Starship during reentry high over the Indian Ocean. SpaceX screen capture.
That control flap sticking almost vertically in the frame is at the nose of the ship. Both the white glow close to the flap and the orange-ish glow to its right are plasma. This was the view for minutes, very little movement of the flaps was seen.
As the ship moved into denser parts of the atmosphere and started slowing down more dramatically, they switched cameras pointed at the flap, and we could literally see metal melting off the flap and flying away. It ended up looking more battle-scarred than this view.
Visible damage to one of the flaps on the Starship during reentry. SpaceX screen capture.
Amazingly, with chunks of the stainless steel flap melting and breaking off, the ship maintained its position and continued to fly. Within seconds, the flying molten metal made it difficult to impossible to even see this level of details.
Still a screen capture of a SpaceX video, but relayed by Scott Manley on YouTube
Before this week's test flight, Musk said Starship could fail during reentry with the loss of a single tile in some areas on the vehicle. It wasn't clear where tiles fell away from Starship on Thursday, but Musk posted after the test flight that the favorable outcome "speaks to the incredible resilience of stainless steel at temperature."
With the flaps melting away and showing large holes in them, it's completely reasonable to expect the flap to break off and have Starship lose attitude control. Instead, the control system took the inputs, calculated how to change things to achieve the flip and came to a stop vertically in the Indian Ocean. Before falling over, as it was supposed to.
It's truly some slick engineering. I've come to expect nothing less from this crew.
It's something we've said before, but the next test flight might be rather soon. SpaceX has already test-fired the ship for the next test flight, and the booster could be static fired soon. The FAA might issue a license faster based on the improvements seen in this flight. The mishap investigations were because SpaceX didn't reach their planned destinations. That doesn't apply this time.
"I think we should try to catch the booster with the mechazilla arms next flight!" Musk posted on X, referring to SpaceX's plan to snare a hovering booster with catch arms on the launch pad tower.
Some of the big takeaways from today's launch (besides watching tiles be blown off the flap and metal burning) was that this was basically early prototype versions of both starship and booster.
ReplyDeleteSpaceX is already working on the next generation of heat tiles, of flap designs, of engines and thrusters and controls and, oh, everything.
So, yes, this was all about the data collection. And it was awesome.
Waiting to see how the OLT and other ground equipment faired.
Well... what data collection can protect against deterioration in time?
DeleteHad to watch the whole mission 4 times to reasonably see all the fantastic details, mind blowing video. Really gives you a good understanding just how hot that plasma is. Ever try cutting 304 SST with an oxy-acetelyne torch? Basically you can't. It does not rapidly oxidize at those gas temps, think oxy-acet runs around 2800-3000 depends on your mix. Watching all that structural 304 literally get to molten state and whipped away by the air currents is just mind blowing. But 304 is an excellent high heat alloy. When SpaceX announced they where building their rocket out of 304, to me, it made the rather perfect choice all things considered. They where right. Its such a great balance of properties to it.
ReplyDeleteThe whole event is transformational. Dollars to donuts the folks at SpaceX, their genius and ingenuity, their courage, their faith in what they are doing and are about, if this flight is anything, it just totally changed everything. And to think they are only getting started. Wow.
Looks like the hinge section of the flaps should be moved up further around the circumference if the body, get them up at or past the departure point where the plasma stream leaves the curve of the ship. Or make the section on the body have a lower longer ogive so the plasma isn't ramming it as much. They might have to bury the hinge into the rocket body somewhat. Looked to me the heat is far too intense for anything that protrudes too far into the flow of plasma. The hinge point creates kind of a natural hot spot.
ReplyDeleteBut it sure was a trip seeing it in action in real time, what a feat of technology in itself having real time visuals, all on its own merit never mind the total stunning success of the whole vehicle.
A comment on X mentioned moving the hinge points up so they would not get as much direct impingement. There certainly does appear to be an area of stagnant flow to leeward where the hinges would be somewhat protected.
DeleteFWIW, the first screenshot is the port aft fin viewed from the front, the little- fin-that-could is the starboard forward fin.
As Old Surfer said, next iteration of Starship will move the forward fins further away from the centerline of the ship. And will have a slightly different fin and shroud design.
DeleteGood points. Just my layman's observations, FWTAW. Indeed, its what test flights are run for, figure these things out and as they say, rapid iteration, R&D on the fly, for sure.
DeleteWhat really bakes my noodle, they will eventually figure out how to make this vehicle passenger jet reliable, WEW! What a feat. Think about it, here is this big tin can, coming in at 17,000mph, and close to 24-25 thousand,(i think, remember from Apollo days), if its re-entering from a moon trajectory. To be able to repeatedly safely reliably and cost effectively accomplish such a feat of engineering and manufacturing. One tiny leak past heat shielding eats its way thru the skin into the LOX tank, its all she wrote.
I mean how do you even do this? It has to be close to or even at fail safe levels of reliability. Its an astonishing proposition no matter how its looked at.
Excellent screen captures! Saving those babies for the aerospace pic archive. Might never see it's like again cause those folks at SpaceX are sure to have a mod for dealing with the plasma damages on this flight. What a fantastic tool it must be having live visuals to work with like this.
ReplyDeleteOne overlooked item about this launch was the use of Starlink to downlink the video, and I'm guessing the flight data, too. If this works reliably, then they won't need to rent transponder time on the TDRSS birds.
ReplyDeleteWatching the telemetry on Starship as its entering, it kind of appears they were "dipping their Spaceship toes into the upper atmosphere, seeing how steep a re-entry curve they could get away with. Note how they kept the ship really steady on a number of streatches, just barely bleeding off velocity, it was amazing, trying to think like a test engineer, imagine they are going back and forth to the telemetry guys, "Yeah, drop us down another quarter mile, watch the increase in plasma, see whats eroding too quickly." Looks exactly like destructive testing I'm personally once involved in on the RL10 rocket engine. How modification components where slowly pressure tested till they fail, you get just this crazy scale level of data, but to be able to give it the old hairy eyeball in real time, because of the robust capabilities of StarLink, (did they use direct link up laser coms i wonder? Is that how to defeat the blockage of radio frequency wave lengths, normally associated with such a plasma cloud enveloping the ship?) Coherent light cutting thru plasma field, sounds right to me. Maybe thats why a 20 minute black-out, how they where getting alignment figured out, they'd have to have a laser target first to create the link, then match the re-entry curve which is constantly changing, like wild crazy deflection angles, to create a steady alignment, man thats like total upper cutting edge tech, state of the art in action, snd we get a front row seat to boot. Awesomeness.
ReplyDeleteThe plasma doesn't completely envelope the ship. It's only on the "hot side", which is facing Earth.It will block ground based radio signals completely at times. BUT....the Starlink satellites are in a higher orbit. They see the "cool side" of the ship, where this little to no plasma. Put the Starlink antennas on the cool side, and transfer data like crazy.
DeleteReason why I thought it might be laser comms, its a lot of data to provide such high grade video, and who can say how much data from telemetry of the onboard systems, and they have cameras mounted inside the tanks, probably engine cams too, think about it really, lot of data, and using light you can transfer it at far higher bit rates using laser light, similar effect as fiber optic cable.
DeleteWe pretty much know the Starlink antennas are on the space-facing side of the ship, and that at least some of the satellites have the capability of millimeter wave radios. Pretty sure it was V-band, around 70 or 80 GHz. As for which gets through any plasma better, V-band or laser, I haven't worked with either kind enough to guess.
DeleteIt was remarkable to see the video as steady and reliable as it was. I'm sure some of that was "build it and try it" just like Starship itself.
Got a kick out of the SpaceX crew oohing and awing, their reactions as the re-entry progressed, aside from the fun factor, it was rather informative in its way, as these are the folks who built it with their own hands, having a larger idea of criticality of so many aspects and potentials. Like a kind of analog gauge on your car's dashboard.
ReplyDeleteI was surprised at how low they were for such speed.
ReplyDeleteI think they were trading speed for altitude off and on. The altitude would Stay constant while the speed decreased rapidly. The ship can be flown as a lifting body and I'll bet they play with altitude and speed to optimise the re-entry.
DeleteI thought the same thing. They weren't quite "skipping" in and out of the atmosphere. but they were using the times of no descent rate to let the tiles cool, or at least lessen the energy being put into them.
DeleteLike they kept it right at or just in the fringe, of the line where atmospheric density increases considerably. Is that the Kharmin Line they talk about, edge of space?
DeleteI'd be concerned about catching it on the next flight, but it's not my toy, and I don't own SpaceX. Otherwise, bravo!
ReplyDelete