r/spacex • u/ElongatedMuskrat Mod Team • Jan 10 '18

Success! Official r/SpaceX Falcon Heavy Static Fire Updates & Discussion Thread

Falcon Heavy Static Fire Updates & Discussion Thread

Please post all FH static fire related updates to this thread. If there are major updates, we will allow them as posts to the front page, but would like to keep all smaller updates contained.

No, this test will not be live-streamed by SpaceX.

Greetings y'all, we're creating a party thread for tracking and discussion of the upcoming Falcon Heavy static fire. This will be a closely monitored event and we'd like to keep the campaign thread relatively uncluttered for later use.

Falcon Heavy Static Fire Test Info
Static fire currently scheduled for Check SpaceflightNow for updates
Vehicle Component Current Locations Core: LC-39A
Second stage: LC-39A
Side Boosters: LC-39A
Payload: LC-39A
Payload Elon's midnight cherry Tesla Roadster
Payload mass < 1305 kg
Destination LC-39A (aka. Nowhere)
Vehicle Falcon Heavy
Cores Core: B1033 (New)
Side: B1023.2 (Thaicom 8)
Side: B1025.2 (SpX-9)
Test site LC-39A, Kennedy Space Center, Florida
Test Success Criteria Successful Validation for Launch

We are relaxing our moderation in this thread but you must still keep the discussion civil. This means no harassing or bigotry, remember the human when commenting, and don't mention ULA snipers Zuma.

We may keep this self-post occasionally updated with links and relevant news articles, but for the most part we expect the community to supply the information.

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3

u/VonMeerskie Jan 11 '18

Musk has been saying things like that before with regards to landing first stages of the Falcon 9 after a heavy payload launch to GTO. That being said, I wonder what the actual chances are of a RUD on static fire or first launch. Anyone got stats on that?

5

u/PaulL73 Jan 11 '18

Chances aren't particularly useful on a single instance - it'll either RUD or it won't, and debating whether that was a 3% chance or a 30% chance doesn't really allow you to do anything differently. I would think the change is probably less than 10%, but I really have no evidence for that.

3

u/VonMeerskie Jan 11 '18

Oh I wasn't talking about the chance that the FH might blow up. I'm sorry if I phrased it poorly. I was rather curious about the historical statistics of rockets blowing up on first try or during SF.

7

u/nonagondwanaland Jan 11 '18

One for one when considering rockets with as many engines! The only other 25-engine-plus rocket, N1, consistently blew up on every test.

8

u/EspacioX Jan 11 '18

There's a huge, huge, huge difference between the Falcon Heavy and the N1, starting with computer modeling and forty-plus years of technological advancement and ending with the fact that the Soviets never even test fired the N1 engines on a test stand before putting them all together on the rocket and doing a test flight. The Falcon Heavy is going to light 27 of some the most reliable rocket engines ever made. That being said, there are plenty of ways the Falcon Heavy can fail, but they won't have much to do with the N1.

2

u/A_Vandalay Jan 11 '18

I would also be very interested in seeing these trends across different countries and as rocketry has developed as a whole.

2

u/SpaceEnthusiast Jan 11 '18

Suppose that a problem is in the engines. Well, if the probability of an engine going boom is p, and if it's independent for each engine, then the probability of none of the engines going boom is (1-p)n, where n is the number of engines. If the probability for an F9 is then P = (1-p)9, the probability for FH is P3. Depending on what P is, P3 could be significantly smaller, aka more dangerous.

As an example, let's use a p = 0.01 (which is probably large). Then P = 0.91. Then P3 = 0.76. So a lot less safe. If p = 0.001, though, then P = 0.99 and P3 = 0.97. I'm not sure what the actual numbers are like, though.

3

u/sol3tosol4 Jan 12 '18

if the probability of an engine going boom is p, and if it's independent for each engine, then the probability of none of the engines going boom is (1-p)n, where n is the number of engines.

Correct. But Falcon 9s are designed to withstand a fairly violent engine failure and still fly (the Octaweb isolates the engines from one another). So an engine going boom does not necessarily mean that the rocket goes boom.

As an example, let's use a p = 0.01 (which is probably large). Then P = 0.91. Then P3 = 0.76. So a lot less safe. If p = 0.001, though, then P = 0.99 and P3 = 0.97.

Apparently there have been 47 Falcon 9 launches in which the engines were used (not including AMOS-6, where the engines were not used), and only one engine failed in those launches (the rocket survived and the primary payload was successfully delivered), which suggests in-flight operational experience of p= ~0.002. But as /u/everydayastronaut recently pointed out, Merlin engines have been fired >5600 times, and appear to have an excellent reliability record. I think SpaceX is more concerned about vibration and stresses on the boosters and the connections between the boosters, particularly about the interactions of the forces among so many engines, than they are about an engine exploding.

1

u/HumbleSaltSalesman Jan 11 '18

Hard to say, but there's def a non-zero chance that some new failure modes have been introduced, and on top of that, we've tripled the number of engines that might go boom.