Althouse: "Is that normal?"

August 5, 2020

"Is that normal?"

Is that normal?: pic.twitter.com/BR85nHbRmv
— Javier Navarro (@Javier_NavarroM) August 5, 2020

45 comments:

MountainMan said...: Fantastic, and successful, test by Spacex.; 8/5/20, 5:37 AM
Rusty said...: It looks like something burning off rather than a leak. Cool stuff though. I wonder how much of that rocket motor is 3D printed.; 8/5/20, 5:50 AM
Big Mike said...: Probably not a good thing, but might be “the new normal.”; 8/5/20, 6:09 AM
Howard said...: Liquor fuel rocket engines are hard. Problems during testing is normal. There's no spell check for hot rodding.; 8/5/20, 6:09 AM
born01930 said...: Is it normal? No, but it is minor. It is a methane leak which will need to be found and corrected. This is only the second flight test of a raptor engine. Test stands don't subject the engine to the same stresses of flight so they will find stuff like this as the program progresses. The engine is exposed to very high stresses and temperatures, that relatively cool flame from the small methane leak won't cause damage directly but should the methane accumulate somewhere, you have a potential for RUD.; 8/5/20, 6:38 AM
Larry J said...: I work for a company that makes, among other things, rocket engines. I took a class on rocket design and we discussed the first test firings of SpaceX's Raptor engine, the same type used in this flight. Liquid fuel rocket engines are normally powered by turbopumps and there are different cycles. Most cycles run either propellant rich or oxidizer rich. SpaceX is using the most efficient, but most challenging, type of cycle. When it first fired up on those early tests, the flame was green. My instructor said that means the engine was running "metal rich" (eating itself). What we're seeing in this video is not normal nor is it desirable, but it is fixable.; 8/5/20, 6:40 AM
stevew said...: It may not be normal but it was not catastrophic so it must be minor.

Rocket science question: with the propulsion coming from underneath the rocket, and therefore the majority of the mass and weight above, does the weight need to be balanced across the rocket (parallel to the earth) to a fine degree to prevent the rocket from veering off course?; 8/5/20, 6:57 AM
MikeR said...: "does the weight need to be balanced across the rocket (parallel to the earth) to a fine degree to prevent the rocket from veering off course?" If it's not balanced there will be torque on the rocket - it will try to twist. Maybe you can correct that with some other system (SpaceX uses nitrogen thrusters to correct the booster's direction during landing) but you don't want to need to do that.; 8/5/20, 7:08 AM
Crimso said...: "Rocket science question: with the propulsion coming from underneath the rocket, and therefore the majority of the mass and weight above, does the weight need to be balanced across the rocket (parallel to the earth) to a fine degree to prevent the rocket from veering off course?"

Not a rocket scientist, but this prototype has an engine that is slightly offset, which would (by itself) make the vehicle extremely difficult to control. The engine is gimbaled, meaning they can direct its thrust to compensate for deviation between center of lift and center of mass. In addition, this vehicle has a reaction control system (RCS) for additional help in controlling its flight.; 8/5/20, 7:15 AM
MikeR said...: Yeah - SpaceX has already blown up a few of these on the test stand. This is a good time to smoke out issues. And this was a successful flight. As SpaceX has already done a few times, Starship will revolutionize space flight. It is slated to carry way more mass to orbit than anything that flies, and to be completely reusable: the payload is released and the whole Starship comes back down. (Unlike the current iterations where the booster is saved but the second stage and usually the fairings are lost.) If it works right - eventually - the main cost will be the fuel. That means the cost per flight drops from tens of millions of dollars to like a million dollars. That means you can use Starship for under-an-hour flights from Texas to Australia. Or, that means that two Starships can handle a trip to the moon, with a landing, and a return, for less than the cost of any other company putting a satellite in orbit.
New world.; 8/5/20, 7:16 AM
MikeR said...: You know, I worked for Bellcore back in the late '80s; we were just finishing DSL (we called it ISDN) and about to roll it out. We were worried - who is going to buy this? How much demand is there for data over phone lines? Some people said, just put it out there; others will figure out uses for it.
Well, we couldn't have imagined what happened after that. The availability of cheap data transmission, and the world just exploded around it.
Space travel may be like that too. Bring the price way down and the world will find a thousand uses for it that we can't even imagine.; 8/5/20, 7:19 AM
rehajm said...: I like the idea of letting all the lefties climb on that thing to head for Mars.; 8/5/20, 7:20 AM
stlcdr said...: This is a test. Obviously, there are things that go wrong, which get corrected in a later revision. You don't just suddenly create a fully functioning light bulb.; 8/5/20, 7:26 AM
Unknown said...: Looks like there are a lot of places for an Alien to hide!; 8/5/20, 7:33 AM
Marco the Lab said...: Since I am not a rocket scientist, I'd guess that was the pilot light in case the big flame went out.; 8/5/20, 7:53 AM
mandrewa said...: Yes, I noticed the same thing. That's not normal. It looks like the engine got damaged during lift-off.

But that's the point of a test like this, you are looking for issues.

But I'm not entirely surprised that this would happen. The issue behind this issue is that SpaceX has not spent a billion dollars and years building a launch pad for this.

For contrast here is the Ariane 6 launch pad which the European Union is currently building at a cost of how many billions and that was begun in 2016 and is still not done.

Not being a government SpaceX can not spend this kind of money and neither do they have five years to spare either. Instead they are trying to get away with a launch pad they took a few months to build.

I hope SpaceX can find an affordable way to do this. So much hangs on it, because if Starship is successful, this will be like an order of magnitude or two order of magnitude improvement. Or in other words between ten and a hundred times better than other rockets (dollars per pound to orbit).; 8/5/20, 8:09 AM
chuck said...: "does the weight need to be balanced across the rocket (parallel to the earth) to a fine degree to prevent the rocket from veering off course?"

Weight distribution is important, think of balancing an upright pole on your palm. It is easier to do if the weight is concentrated at the high end.; 8/5/20, 8:24 AM
Kirk Parker said...: MikeR,

ISDN and DSL are two entirely different things.; 8/5/20, 8:29 AM
mandrewa said...: Now should say I don't know really what's behind the flame. I'm imagining something knocked off the launch mount by that extremely powerful engine and hitting those lines on the engine during launch, which caused the leak, which produced the flames.

This Starship prototype, SN5, and this is like the seventh prototype SpaceX has built depending on how you count them, was launched on a steel frame launch mount and it isn't really that far off the ground given the energies involved.

But this is just me speculating as to what is going on and what is causing it. But hopefully it is a different issue that will be easier to remedy.; 8/5/20, 8:34 AM
What's emanating from your penumbra said...: Looks like a pilot light to me. It's fine.; 8/5/20, 8:47 AM
PB said...: Who said methane? The Merlin engine runs on kerosene and liquid oxygen.; 8/5/20, 8:53 AM
MikeR said...: @Kirk "ISDN and DSL are two entirely different things." Explain? That was what we called it then. It seems like DSL is what we have today. It took us a decade to develop. But why, "entirely different things"?; 8/5/20, 9:15 AM
Tom T. said...: Some of you are being so cavalier. That could have killed everyone on board!; 8/5/20, 9:19 AM
PB said...: Someone asked about balancing fuel. There are 2 pressurized tanks required for combustion (kerosene as fuel and liquid oxygen as oxidizer), plus a third helium tank that pressurizes the 2 main tanks and maintains that pressure as the fuel and oxidizer are depleted. Gravity balances the liquid at takeoff and when accelerating to achieve orbital speed the acquired G-forces performs the same task, always perpendicular to the long axis of the rocket.

In zero g, it's tricky. you can't rely on gravity to ensure the fuel is at the bottom of the tank so other techniques are required, a bladder for the pressurized gas forcing the fuel to the bottom of the tank, spinning the rocket to force the fuel the the sides of of the tank along with multiple drain points, or interior surface features to wick the fuel to the drain point. The Saturn 5 3rd state designers used the trick of maintaining a slight continuous venting to maintain just enough G forces to force the fuel to the bottom of the tank.; 8/5/20, 9:22 AM
MikeR said...: @Kirk - I see you are right about DSL: a different technology. It doesn't change my point, though.; 8/5/20, 9:33 AM
Crimso said...: "The Merlin engine runs on kerosene and liquid oxygen."

Indeed, but that engine is a Raptor. Methalox.; 8/5/20, 9:49 AM
mandrewa said...: "Who said methane? The Merlin engine runs on kerosene and liquid oxygen."

This is a Raptor. It runs on liquid methane and liquid oxygen.

...plus a third helium tank that pressurizes the 2 main tanks and maintains that pressure as the fuel and oxidizer are depleted.

This prototype, SN5, uses helium to pressurize the tanks, but they are hoping to do it without helium (ie. self-pressurizing tanks). As Elon Musk points out, the helium costs more than the methane and oxygen combined.; 8/5/20, 9:58 AM
Joe Smith said...: That Musk guy can be kind of a prick sometimes but he gets shit done.

As goofy as he is, if he keeps it up he will go down in history along with Einstein and Galileo.

This is the kind of foreigner we need more of.; 8/5/20, 10:01 AM
CP said...: It uses the Raptor engine. Methane is the fuel, liquid oxygen is the oxidizer.
No this leakage/flame is not normal and if the SpaceX test engineers saw this in real time they would have been terrified. The only place you want to see flame during an engine test is out the nozzle. Trust me on this because I’ve experienced this type of failure first hand.; 8/5/20, 10:10 AM
MikeR said...: @Tom "Some of you are being so cavalier. That could have killed everyone on board!" It was a test flight. That's what they're for. The previous three or so blew up and shattered the rocket into smithereens. Also part of the system. Eventually they'll get good at it; that's what they did with Falcon, which by now is almost routine. The first few of those failed too.; 8/5/20, 10:26 AM
Nichevo said...: plus a third helium tank

Why not nitrogen? Cheaper and more abundant.; 8/5/20, 10:48 AM
gilbar said...: It is easier to do if the weight is concentrated at the high end.
get out much?; 8/5/20, 11:08 AM
PM said...: That pretty much depicts my ideal space flight.; 8/5/20, 11:18 AM
Gospace said...: Not normal. Something wasn't torqued correctly or a proper seal wasn't installed. I have stories about seals and oxygen leaks and seals and high pressure oil leaks- - which didn't involve catastrophes or I wouldn't be around to tell them...

There's a whole lot of knowledge about "O" rings, gaskets, and other seals that has built up over the years- some from actual science, some empirical knowledge from trying things out and saying "Hey, this works!" And it;s truly amazing how many people working with them have no clue and simply use what they have... which is usually, but not always, good enough.; 8/5/20, 11:21 AM
Gospace said...: Nichevo said...
plus a third helium tank

Why not nitrogen? Cheaper and more abundant.

And heavier.; 8/5/20, 11:46 AM
SensibleCitizen said...: Looks like a corn silo. Aerodynamic much Spacex?; 8/5/20, 1:11 PM
mandrewa said...: Scott Manley does his usual great job of explaining things and in this video he does talk about the issue of the flames on the side of the engine:

Scott Manley: Starship SN5 150 meter hop; 8/5/20, 2:00 PM
Gahrie said...: It looks to me like the pad was damaged at ignition, and something flew up and hit the engine causing the damage. It's kind of surprising that it was successful.; 8/5/20, 2:24 PM
Nichevo said...: Why not nitrogen? Cheaper and more abundant.

And heavier.

8/5/20, 11:46 AM

Yes, certainly, but enough to make the difference?; 8/5/20, 2:34 PM
eddie willers said...: This is the kind of foreigner we need more of.

Indeed. And since he became a naturalized citizen, he is a TRUE African-American.; 8/5/20, 3:07 PM
Unknown said...: Note that for an open cycle engine, the second flame IS expected. You can see it on all the Merlin engines (and it's much bigger with a lot of smoke). It is the burning exhaust from the turbines.

The Raptor is full cycle, so it is not expected here.; 8/5/20, 3:25 PM
Big Mike said...: But let’s not overlook the lovely color and shape of the exhaust.; 8/5/20, 5:41 PM
Nichevo said...: Well we're all smarter than Elon Musk and SpaceX, so maybe somebody should write them an email about the inappropriate looking flame and see what they have to say about it. Probably they haven't even noticed yet.; 8/5/20, 10:35 PM
Nichevo said...: Since I'm the one last to flap my gums, at least there is this thread on Reddit which appears to not be too concerned:

https://www.reddit.com/r/SpaceXLounge/comments/i42f5y/any_idea_why_the_raptor_is_on_fire_during_sn5_hop/; 8/6/20, 7:13 PM
Kirk Parker said...: Mike,

True enough about your point, as long as it's about DSL. ISDN never made it out of niche mode.; 8/7/20, 9:00 AM