SpaceX F9 : CRS SpX-17 : May 4, 2019 - DISCUSSION

[rob2507]

Sorry if this is considered off-topic, but here in the northeast US, the ISS will have a couple of visible passes early Monday morning. Is Dragon visible as it approaches ISS? We've had a lot of cloudy skies here recently, but we should be mostly clear Monday morning, so I'd like to catch it if it's visible.

[flyright]

Sorry if this is considered off-topic, but here in the northeast US, the ISS will have a couple of visible passes early Monday morning. Is Dragon visible as it approaches ISS? We've had a lot of cloudy skies here recently, but we should be mostly clear Monday morning, so I'd like to catch it if it's visible.

I've never had an opportunity to look for Dragon approaching the station, but believe it will be easily visible if the station is visible and the Dragon is also in sunlight.
I have seen the shuttle easily visible when trailing the station by a hundred miles.

[edkyle99]

These numbers are significantly higher than what you present, since you're mixing the development phase failures with the operational phase.

It's a bit like saying that a certain disease kills 30% of the population, whereas in fact it used to kill 50%, then a cure was found, and now it kills 0.1%.  That little bit of extra knowledge completely changes the understanding of the situation.

I just present the totals.  If you try to subdivide them, the division point can always be argued.  Meanwhile, over the very long term, the absolute total percentages are going to likely approach the "operational" results regardless.  I like to see that number, because it certainly told the true tale at the beginning (0 for 3, 2 for 5, etc. or whatever it was) and now it is showing the steady improvement that resulted from all of those trials.  And, by the way, aren't they still in the "development phase", since, for example, they didn't have the right octograbber tool to save B1055, they lost control of B1050, etc?  They've lost 2 of their last 8 landing attempts I think.

 - Ed Kyle 

[meekGee]

These numbers are significantly higher than what you present, since you're mixing the development phase failures with the operational phase.

It's a bit like saying that a certain disease kills 30% of the population, whereas in fact it used to kill 50%, then a cure was found, and now it kills 0.1%.  That little bit of extra knowledge completely changes the understanding of the situation.

I just present the totals.  If you try to subdivide them, the division point can always be argued.  Meanwhile, over the very long term, the absolute total percentages are going to likely approach the "operational" results regardless.  I like to see that number, because it certainly told the true tale at the beginning (0 for 3, 2 for 5, etc. or whatever it was) and now it is showing the steady improvement that resulted from all of those trials.  And, by the way, aren't they still in the "development phase", since, for example, they didn't have the right octograbber tool to save B1055, they lost control of B1050, etc?  They've lost 2 of their last 8 landing attempts I think.

 - Ed Kyle

As the disease example shows, "just presenting totals" is actually more misleading.

The distinction between experimental and operational phase is not something I invented - it was specifically called out by SpaceX.  You are choosing to ignore it.

If you want to let time sort it out, then present yearly statistics.  You'll see horrible numbers in 2016, and then pretty steady numbers starting 2017, and this will teach the trend.

The purpose of statistics is to infer something about the numbers you're studying, otherwise the exercise is pointless.  So it does matter how you take your data sets, or you're introducing bias.

[meekGee]

For example:

Success/Attempts (%)

2015: 1/3 (33%)
2016: 5/8 (62.5%)
2017: 14/14 (100%)
2018: 12/14 (86%)
2019: 7/7 (100%)

This is much more insightful then 38/46 total that you gave.

Flights where a pad or barge landing was not attempted are not counted as either success or failure.

(Still based on the same wikipedia flight history page)

[Lar]

(fan) I agree with meekGee

(mod) this is off topic for this thread, let's have this discussion in a more appropriate thread.

[ugordan]

[Vettedrmr]

That just never gets old!

Thanks for sharing, and have a good one,
Mike

[Jakusb]

Did we ever get a closeup of the core number?

[eeergo]

I happened to find the stills from that video on the same day I saw this APoD:


https://apod.nasa.gov/apod/ap190503.html


And couldn't help but be mesmerized at both, and at their similarity coming from such different phenomena. Truly awe inspiring.

[PM3]

SpaceX launch photos by Ben Cooper

This photo nicely shows the different intensities of 1st stage burns. Throttling down before Max-Q, then pretty instantaneously up to full throttle. And the reentry burn begins thin, then gets stronger, and is thin again before cutoff. Thin line = 1 engine, thick line = 3?

[Lars-J]

This photo nicely shows the different intensities of 1st stage burns. Throttling down before Max-Q, then pretty instantaneously up to full throttle.

What you are seeing probably has more to do with atmospheric conditions (cloud and vapor layers) than just throttling.

And the reentry burn begins thin, then gets stronger, and is thin again before cutoff. Thin line = 1 engine, thick line = 3?

That is correct.

[OneSpeed]

This photo nicely shows the different intensities of 1st stage burns. Throttling down before Max-Q, then pretty instantaneously up to full throttle.

I can confirm this impression from the CRS-16 and 17 mission telemetry. CRS-17 is the first time I've seen a Block 5 S1 throttle back up to full thrust out of the bucket. Due to increased propellant flow, it has a correspondingly shorter burn time, and slightly reduced gravity losses. Similarly, at the end of the S2 burn, CRS-17 runs harder for longer, reaching 4gs of acceleration twice. This again reduces the S2 burn time.

It is interesting to see SpaceX incrementally expanding the envelope of Block 5 performance, something that is no doubt made easier by re-use of the S1 cores, giving SpaceX the ability to inspect them after flight.

[photonic]

Sorry if this is considered off-topic, but here in the northeast US, the ISS will have a couple of visible passes early Monday morning. Is Dragon visible as it approaches ISS? We've had a lot of cloudy skies here recently, but we should be mostly clear Monday morning, so I'd like to catch it if it's visible.

By pure luck, I woke up around 5 this morning due to some noise on the street and looked outside. With the sky showing the first signs of dawn, I saw some pretty bright points in the sky. These were not moving, so likely Venus or some landing airplane. Thought immediately that it was a pity that it was not the ISS. Literally 10 seconds later, I saw a much weaker point, which was slowly moving across the sky, with an even weaker point trailing a few seconds behind. This was near Amsterdam circa 5:05 CET. Checked online, to confirm that I indeed saw the ISS and Dragon  . The pass was not immediately overhead, it should have been above Paris by that time. To answer your question: yes, Dragon is easily visible even when not flying overhead, but it might be docked by now.

[Bananas_on_Mars]

Maybe someone can clarify the meaning/context of „Desmo“ or so I kept hearing during communication between MCC and ISS on the capture webcast.

Google search didn‘t help...

Thanks a lot!

[eeergo]

Maybe someone can clarify the meaning/context of „Desmo“ or so I kept hearing during communication between MCC and ISS on the capture webcast.

Google search didn‘t help...

Thanks a lot!

Could you point out the segment where that's heard?

[DaveS]

Maybe someone can clarify the meaning/context of „Desmo“ or so I kept hearing during communication between MCC and ISS on the capture webcast.

Google search didn‘t help...

Thanks a lot!

What you most likely heard was "decimal", not "desmo".

[ValmirGP]

I believe you are referring to "decimal" which is said after certain measurements which have decimal figures on it's values.

[Bananas_on_Mars]

Maybe someone can clarify the meaning/context of „Desmo“ or so I kept hearing during communication between MCC and ISS on the capture webcast.

Google search didn‘t help...

Thanks a lot!

What you most likely heard was "decimal", not "desmo".

Guess that‘s it.

Don‘t know how to link to a certain point in a live stream.

What I hear is:
„Station Houston, you are go for capture sequence.
Perform step 4 in 1 (desmo/decimal) 1 1 0 Dragon capture and begin monitoring the back away cue card“

[Jeff Lerner]

With respect to the cable still attached to Dragon ...no one noticed it missing post launch pad cleanup ?