That said, it was always intended that this thread focus on discussing the impact of reuse on SpaceX and not on the industry in general (via launch prices, except as a secondary effect because lower costs allow a provider to remain profitable at lower prices).
The fact remains there is a cost for reusability progress and its in the failure rate of the vehicle. As long as there are people who feel the risk is not worth the lower price, and when they can choose which LV they use they will go with something with a longer continuous list of successful launches.
I don't understand that reasoning.If anything the first use of something has the potential for "infant mortality", whereas the longer something is used the more dependable it's use is. I found this chart on Wikipedia that addresses this:No doubt SpaceX has to understand when things will wear out, both for moving machinery and for structures, but they have done a lot of that work already.
The fact remains you can have an F9 (15+ flights from RTF) or an Ariane 5 (78+ flights from RTF). All we can really say (statistically) is that one has a < 1 in 78 chance of going bang and one has a < 1 in 15 chance of going bang.
Quote from: Coastal Ron on 11/02/2017 10:58 pmI don't understand that reasoning.If anything the first use of something has the potential for "infant mortality", whereas the longer something is used the more dependable it's use is. I found this chart on Wikipedia that addresses this:No doubt SpaceX has to understand when things will wear out, both for moving machinery and for structures, but they have done a lot of that work already. All we can really say (statistically) is that one has a < 1 in 78 chance of going bang and one has a < 1 in 15 chance of going bang.
Seems fatuous to claim that. We can say previous builds of it had a 1 in 8 (roughly) failure rate. This says nothing at all about the most current, and still less the Block 5 build.
Quote from: tdperk on 11/03/2017 07:51 pmSeems fatuous to claim that. We can say previous builds of it had a 1 in 8 (roughly) failure rate. This says nothing at all about the most current, and still less the Block 5 build.I'm merely pointing out that empirically that is what has happened. Yes being able to inspect and measure actual damage (and conversely what parts are over built for their task) should improve reliability. We will see in the long term if it does, as we all hope it will.
I think this thread was always mis-named as customers don't pay "costs" they pay "prices" and while they have cut the "floor price" for medium launch it doesn't look like they are going to go on cutting it. That's their choice, but it's prices that matter to customers, not costs.
Quote from: john smith 19 on 11/03/2017 06:28 amThe fact remains you can have an F9 (15+ flights from RTF) or an Ariane 5 (78+ flights from RTF). All we can really say (statistically) is that one has a < 1 in 78 chance of going bang and one has a < 1 in 15 chance of going bang. Absent inclusion of confidence levels, I'm not sure that's a statistically valid statement.
The only F9 failure that occurred on the first stage is the loss of a Merlin 1C engine. That flight made orbit and the 1C engine is now out of service. From the point of view of the first stage, success rate for (primary) payloads is 100% and the first stage is 44/44. (I'm giving the first stage CRS-7).So from the view of the booster, Ariane is 78+ from RTF, F9 S1 is 44+ from first flight.
And both second stages that failed were brand new, so I fail to see how their failures hurt the case for booster reuse.
You said "reflown boosters should be more reliable but that hasn't happened yet". Yet it is the reusable part that hasn't caused loss of mission, while the expendable part has, twice. Whatever the true reliability of reuse is, it's performing better than expendable right now.
Given the craven misuse of statistics above, I'm going to join in and go with reflown boosters being 100% reliable. Which is absolutely and incontrovertible true. According to the latest data....
No. Reuse is likely to reduce failure rate.
Being able to inspect your boosters after flight is a gigantic advantage to SpaceX that I do not think gets enough credit here. It allows your to retire low probability failure modes before they happen.With an expendable booster, if you had a low probability (say 0.1%) failure mode that can't show up in tests, the only way to find it is to wait for it to happen. If you can inspect your boosters you are likely able to find the weak areas before they fail and fix the problem beforehand.
Re-usability will also increase cadence, which is a pathway to improved reliability itself. Part of the reason air travel is so safe is because we have thousands of flights a day, so even 1 in a million failure modes become visible in reasonable timeframes. That previously mentioned 0.1% failure mode on an expendable LV may never show up in a ~100 launch lifetime, but it's still there lurking under the surface... Nobody would fly an airplane with a 0.1% failure probability.
Quote from: Norm38 on 11/12/2017 11:34 pmYou said "reflown boosters should be more reliable but that hasn't happened yet". Yet it is the reusable part that hasn't caused loss of mission, while the expendable part has, twice. Whatever the true reliability of reuse is, it's performing better than expendable right now.Which should come as no surprise. The Shuttle never failed in the orbiter. The failures in the mfg and/or design of the expendable parts destroyed them, the second failure being due to the "minor" redesign of the ET's spray on foam insulation being (in fact) not so minor. The question is at what point does a semi reusable design become stable enough that the benefits of reuse in terms of reliability start to show themselves? Empirically the answer is "not yet."
The Shuttle never had a LOM failure in the orbiter, but parts of the orbiter failed rather frequently. Some of them came pretty close to causing LOM.