Didn't see where this had been posted yet.

It may be oversimplifying, but can they have a reserve tank just to turn it back upright, then once it is have the large tank kick in to slow it down?

Do they start the flip so low because of the weight of fuel needed would be too much if they tried higher?

Bondag said:

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It may be oversimplifying, but can they have a reserve tank just to turn it back upright, then once it is have the large tank kick in to slow it down?

Do they start the flip so low because of the weight of fuel needed would be too much if they tried higher?

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That's what the header tanks are for, to kick it upright and ullage. Thw problem SEEMS to be with getting that system going reliably and quickly while in free fall.

Bondag said:

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It may be oversimplifying, but can they have a reserve tank just to turn it back upright, then once it is have the large tank kick in to slow it down?

Do they start the flip so low because of the weight of fuel needed would be too much if they tried higher?

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I think partially, it has to do with too much thrust on the Raptor engines on why they start up so low.

And after watching a few people on YouTube talking about the RUD yesterday and SN8, was that keeping pressure high enough to relight. Could be wrong, but that is what I see most people thinking.

nortex97 said:

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bmks270 said:

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Brad06ag said:

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Ag_of_08 said:

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So odds on how long it takes for the FAA("encouraged" by Boeing and ULA) to declare the test flights to dangerous and stop them entirely?

anyone know what came loose from the rocket about t+6:02

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Well... Couple hours it would seem

https://www.cnn.com/2021/02/02/tech/spacex-starship-sn-9-test-launch-faa-scn/index.html

Quote:

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"The FAA's top priority in regulating commercial space transportation is ensuring that operations are safe, even if there is an anomaly," an agency spokesperson said in a statement, using the industry term for a launch failure. "The FAA will oversee the investigation of today's landing mishap involving the SpaceX Starship SN9 prototype in Boca Chica, Texas. Although this was an uncrewed test flight, the investigation will identify the root cause of today's mishap and possible opportunities to further enhance safety as the program develops."

When asked how the investigation would be carried out, the spokesperson said "we have nothing further to add tonight."

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I was pretty surprised they cleared space X to land a rocket on shore near cap Canaveral. A controls mishap or any failure on the return flight could send the rocket into a building. And if they are going to be doing many launches over years, I just don't think it's reliability is proven yet for landing anywhere but the desert or ocean. Obviously there is even greater risk with these test rockets, what if it came down on their other rocket?

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Boca Chica is a very long way from Cape Canaveral. It's actually incredibly remote (the landing/launch site) from civilization, just a handful of residents in the zone that could get broken windows from the blasts. The videos we see are those using massive zoom lenses from a very safe distance (several miles I believe).

SH is just about ready to begin stacking it sounds like.

https://www.teslarati.com/spacex-first-super-heavy-booster-halfway-complete/

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While Super Heavy is dramatically different from Starship by almost any measure, SpaceX has ensured that hardware commonality is as extensive as possible. Ultimately, with minor tweaks, that means that SpaceX can (in theory) build Super Heavy with the exact same tools and techniques it's used to churn out Starship prototypes.

As of the end of this month, a flurry of public photos from local (and visiting) photographers have confirmed that Super Heavy booster BN1 is effectively halfway to completion and currently stands 18 steel rings tall. Aside from booster-specific layout changes, that 33-meter-tall (~105 ft) barrel section is virtually identical to a Starship's 20-ring barrel section, lacking only conical nose section that caps them off.

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Now, back at Cape Canaveral, there are 2 F9 launches for tomorrow;

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They sometimes land their boosters on a pad on shore at Cape Canaveral .

Not for Starlink launches (although I guess they could in the future), I think they're going for dual droneship recovery tomorrow

Bondag said:

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It may be oversimplifying, but can they have a reserve tank just to turn it back upright, then once it is have the large tank kick in to slow it down?

Do they start the flip so low because of the weight of fuel needed would be too much if they tried higher?

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I think so. As soon as they flip they lose the aerodynamic advantage of the belly flop. So yes it'll take more fuel to overcome the vehicles significantly faster terminal velocity in the vertical position

GCRanger said:

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Do the falcon rockets or startship have an abort detonator to prevent landing on structures if they go wildly off course?


The fail fast, iterative mentality is great to see. I use it all the time as an example of how to work to deliver value more quickly.

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When falcon returns to Cape Canaveral for a RTLS (return to launch site) landing, yes. They aim just offshore and when the rocket likes its trajectory it steers itself over to its landing pad just before the landing burn starts.

You can see this on one of their attempts a couple years ago when a hydraulic fluid issue and the booster began to spiral out of control in the last few thousand feet and landed offshore.

Everyday Astronaut discusses it in a video.

Kenneth_2003 said:

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GCRanger said:

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Do the falcon rockets or startship have an abort detonator to prevent landing on structures if they go wildly off course?


The fail fast, iterative mentality is great to see. I use it all the time as an example of how to work to deliver value more quickly.

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When falcon returns to Cape Canaveral for a RTLS (return to launch site) landing, yes. They aim just offshore and when the rocket likes its trajectory it steers itself over to its landing pad just before the landing burn starts.

You can see this on one of their attempts a couple years ago when a hydraulic fluid issue and the booster began to spiral out of control in the last few thousand feet and landed offshore.

Everyday Astronaut discusses it in a video.

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Quoting myself to add, I don't know if range control has the capability to blow up the rocket. I suspect they might. I know the Saturn 5 could be donated after the crew separated via the escape rockets.

The solid rocket boosters on Challenger continued on their own after the vehicle broke up and were also remotely detonated.

There have been a few pics of the starship stack, posted earlier in this thread, and the suspicion was that detonation packs of C4 were placed in the final steps to prepare for launch, one of the last things done before ground personnel left.

I'm not sure about the Falcon. My suspicion would be, likely probable... Or probably likely.

Falcon and starship both have termination abilities. As stated in a previous post, they actually detonated the in flight abort booster.

That's right. Don't know why that slipped my mind as I typed.

Given the massive amounts of information they've provided over the last few years, sometimes I'm just glad when the rocket doesn't go boom, much less remember details lol.

Is crazy how much things have changed, and how many people have gone to from "rockets go woosh" to having at least a somewhat educated opinion on the subject.

Whats crazier is how much a stupid game like kerbal space program, and a company being willing to be open and honest have driven a lot of it!

KSP is amazing for learning basics of space flight characteristics.

Honestly I attribute most of my interest in all this stuff to KSP.

Is kerbal space program like roller coaster tycoon, or sim city, for rockets?

I'm sure they've thought of many ideas for slowing the rocket and ended up where they are as the best compromise.

I'm surprised they don't add larger drag devices to expand on the way down.

Yes except actual rocket scientists play it too.

My biggest accomplishment was landing on the moon and returning safely to earth.

KSP is an awesome program

Here's a few of my toys

TexAgs91 said:

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KSP is an awesome program

Here's a few of my toys

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You need procedural part and/or spacey heavy in your life lol.


And for the person who asked: ksp is more.... flight simulator type play. There are campaigns, but mainly it's you in control of the design/building of the vehicles.

Then you get into real solar system and realism overhaul, and it becomes challenging on a whole new level. I've known a couple of aerospace people that started and rp-0 plathrough, and finally had to walk away from frustration.... too much like work lol!

When Elon is in a mood, and a little salty, he says some hilarious crap to people trying to be too serious!

LOL, just this weekend Elon had tweeted he was going to be off of twitter for a while. I imagine he was not real happy with that outcome.

Really, the first one 'almost' landed but this one didn't really even get close.

SLS vs. Starship SH comparison that is pretty fare from space.com.

My geologist brain says that although the two Starship landing attempts at first appeared to fail quite differently, with the first ship almost landing and the second not coming close, the root causes are probably quite similar in nature. At least I believe this to be true at the high level. My guess is they are still having fuel flow and pressurization, and perhaps flow stability, issues in the turbo pumps.

The G-loads and accelerations the vehicle is under are very unique as it goes from belly flop to vertical, and perhaps even with the header tanks, they're still getting entrained vapor bubbles in the fuel system. I wonder if they would benefit from adding draco, or super draco, thruster packs to perform the flop to vertical rotation and provide ullage before reigniting the raptors for landing.

I don't know what a lot of that is but I agree that even though the tests looked like different results - they were basically the same.

PJYoung said:

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I do think MadOverlord is right on this. There's two points of failure. When the falcons are recovered you don't need redundancy... It's not manned. The Starship will be. You must have redundancy.

Ok, let me put it this way... Lots of sloshing in the fuel tanks leads to poor fuel flow to the fuel pumps in the engines. The header tanks, separate fuel tanks for the landing sequence were supposed to alleviate this but it appears that they have not. Ullage is the process of accelerating the vehicle in a desired direction to intentionally slosh the fuel towards the fuel lines. Apollo would do it with their attitude control thrusters for burns during thier journey to and from the moon.

The draco or super draco thrusters burn gaseous fuels rather than liquid fuels so sloshing isn't a problem. These are the names of the systems SpaceX already uses for maneuvering their Dragon capsule in space and as the escape system should they need to get away from a booster.

These are hypergolic fuels, so as soon as they touch they go boom. No ignition system required. Think dropping metallic sodium in water or baking soda and vinegar vs needing a spark plug in your car.

To me, its not so much using 2 Raptors but that the flip is really close to the ground to start with. Any failure at that point and you dont have time and distance to recover. They are killing a lot of velocity, flipping 90 degrees and doing it with no room to spare.

I'm kinda thinking it might have been an issue with the Raptor itself this time. Fuel pressure was good enough that engine #1 fired right up. I obviously don't have a piping diagram in front of me, but the Raptors are probably piped in parallel (getting fuel from a common feed). If fuel pressure was an issue, I think #1 wouldn't have fired up and maintained mach diamonds as well as it did. It probably would have looked similar to SN8, where you had the green flames.

To your point, however, you are putting a radical loading scheme on the turbopumps, and I do have to wonder if anyone has really done the analysis on the bearings there. These pumps are screaming at ridiculous speeds (for instance, the high pressure fuel turbopump on the Shuttle's main engines ran at 35,000 RPM). At that kind of speed, there's going to be a gyroscopic effect that resists motion, and if you try to force it and the bearings touch off....you're going to have a bad time...

Won't the operational Starship be running 6 Raptors? I think they're just using 3 for these hops. No cargo and minimal fuel load so the total weight is comparatively low right now.

Kenneth_2003 said:

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Won't the operational Starship be running 6 Raptors? I think they're just using 3 for these hops. No cargo and minimal fuel load so the total weight is comparatively low right now.

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3 atmospheric raptors and 3 vacuum raptors. Different beasts.

So you're saying it's all ball bearings these days.

Gracias.

Unless I'm wrong (totally possible), they pretty much have to run journal bearings at those speeds and power ratings. Probably product lubricated, which makes life a lot more complicated.

Maximus_Meridius said:

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Unless I'm wrong (totally possible), they pretty much have to run journal bearings at those speeds and power ratings. Probably product lubricated, which makes life a lot more complicated.

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There are roller bearings suitable for those speeds and loads. The SSME turbo pumps used one cylindrical roller bearing plus one ball bearing on the LH2 side and one cylindrical and two ball bearings on the LOX side. I can't think of any flying turbo machinery that uses journal bearings. Journal bearings are typically used on industrial machinery only.