Author Topic: General Falcon and Dragon discussion (Thread 15)  (Read 267545 times)

Online FutureSpaceTourist

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Re: General Falcon and Dragon discussion (Thread 15)
« Reply #40 on: 12/05/2018 02:25 pm »
To bad the story about out-gassing on the Dragon hadn't been known a couple of days earlier.  Would like to have seen the response to questions on this from NASA and SpaceX at the CRS-16 press conference.

There's always the post-launch press conference ...

Online gongora

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Re: General Falcon and Dragon discussion (Thread 15)
« Reply #41 on: 12/05/2018 02:38 pm »
To bad the story about out-gassing on the Dragon hadn't been known a couple of days earlier.  Would like to have seen the response to questions on this from NASA and SpaceX at the CRS-16 press conference.

It's been known for a while, there are probably previous posts somewhere on the site.

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Re: General Falcon and Dragon discussion (Thread 15)
« Reply #42 on: 12/05/2018 02:42 pm »
To bad the story about out-gassing on the Dragon hadn't been known a couple of days earlier.  Would like to have seen the response to questions on this from NASA and SpaceX at the CRS-16 press conference.

It's been known for a while, there are probably previous posts somewhere on the site.

This is in the article:
Quote
After the eleventh Dragon arrived, one contamination-monitoring package’s frequency steadily shifted, according to a presentation posted on September 1 to NASA’s Technical Reports Server, a database of documents created or funded by the agency.

The article has a link to this presentation from September.
https://www.spiedigitallibrary.org/conference-proceedings-of-spie/10748/1074805/Analysis-of-observed-contamination-through-SAGE-IIIs-first-year-on/10.1117/12.2321982.short?SSO=1

Offline GreenShrike

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Re: General Falcon and Dragon discussion (Thread 15)
« Reply #43 on: 12/05/2018 04:16 pm »
ncb, you are assuming a 1.81 mT payload vs. Lou is using a 6mT payload. Which one is it?

I understood that the 1.81t was what FH could send directly to Jupiter via NASA's C3=85 figures, and he wanted to know if a kick stage could boost that payload up to Clipper's mass of 6t.

I think the final 6 in that equation should be a 1.81 (perhaps confused the theoretical c3 of 85 payload with Europa Clipper's nominal mass), payload shouldn't lose mass while second stage is burning. That gives a loss of ~ 878 m/s for a net gain of  ~ 1165 m/s

Yes, exactly -- I reused the equations I'd entered into Google and forgot to mod one of the values from previous. I've edited my post to reflect the update.

To re-answer ncb's question, with a C3=85 payload of 1.81t, adding a STAR 48 should increase payload to around 3.25t.

But I think Jupiter direct is more like a C3 of 80, not 85 (at least if you optimize launch timing for lower C3). Which according to the LSP performance query, Falcon Heavy can do 2195 kg to. That should mean about 3,340 kg with a Star 48 BV stage as that is about where stack delta v without the kick stage and 2195 kg of payload matches with it.

With a 2.195t reference payload, I make a STAR 48BV increasing payload to around 3.5t. I'm guessing the difference is your sub-optimal handing of FH's booster staging (i.e. not throttling FH's center core).

I also get ~3.75t with a STAR 63D -- probably a little less once a TVC is added.

Here's my work:

https://docs.google.com/spreadsheets/d/1wayCq0sx2_lAumbvVD-5iWEun57z7aVSZlulvWH26lw/edit?usp=sharing
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Offline woods170

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Re: General Falcon and Dragon discussion (Thread 15)
« Reply #44 on: 12/06/2018 09:37 am »
To bad the story about out-gassing on the Dragon hadn't been known a couple of days earlier.  Would like to have seen the response to questions on this from NASA and SpaceX at the CRS-16 press conference.

It's been known for a while, there are probably previous posts somewhere on the site.

This is in the article:
Quote
After the eleventh Dragon arrived, one contamination-monitoring package’s frequency steadily shifted, according to a presentation posted on September 1 to NASA’s Technical Reports Server, a database of documents created or funded by the agency.

The article has a link to this presentation from September.
https://www.spiedigitallibrary.org/conference-proceedings-of-spie/10748/1074805/Analysis-of-observed-contamination-through-SAGE-IIIs-first-year-on/10.1117/12.2321982.short?SSO=1

Also noted in the article:

Quote from: Sarah Scoles
SpaceX, meanwhile, is looking at its ingredients. “SpaceX has scrutinized all external material selections on Dragon and is working with suppliers to custom-develop low outgassing variants of qualified materials to help improve the molecular deposition rate,” says the company, adding that NASA pre-approved all the materials used in the first Dragon design.

Offline niwax

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Re: General Falcon and Dragon discussion (Thread 15)
« Reply #45 on: 12/06/2018 10:09 am »
Also noted in the article:

Quote from: Sarah Scoles
SpaceX, meanwhile, is looking at its ingredients. “SpaceX has scrutinized all external material selections on Dragon and is working with suppliers to custom-develop low outgassing variants of qualified materials to help improve the molecular deposition rate,” says the company, adding that NASA pre-approved all the materials used in the first Dragon design.

Not only that, but the whole article is odd. From the headline you'd think SpaceX was gassing crew members. This feels like someone taking some random safety study from Crew Dragon and claiming "Commercial crew is killing our astronauts!". It's a known issue that is being worked on by NASA, just like about a hundred other small things on the space station. It's not better or worse than other things that are happening and there's no reason to be suddenly very concerned.
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Offline programmerdan

Re: General Falcon and Dragon discussion (Thread 15)
« Reply #46 on: 12/06/2018 01:18 pm »
Also noted in the article:

Quote from: Sarah Scoles
SpaceX, meanwhile, is looking at its ingredients. “SpaceX has scrutinized all external material selections on Dragon and is working with suppliers to custom-develop low outgassing variants of qualified materials to help improve the molecular deposition rate,” says the company, adding that NASA pre-approved all the materials used in the first Dragon design.

Not only that, but the whole article is odd. From the headline you'd think SpaceX was gassing crew members. This feels like someone taking some random safety study from Crew Dragon and claiming "Commercial crew is killing our astronauts!". It's a known issue that is being worked on by NASA, just like about a hundred other small things on the space station. It's not better or worse than other things that are happening and there's no reason to be suddenly very concerned.

The conspiratorial vibe that "We asked questions and NASA pulled the report!!!!" was also not a welcome facet of the article.

Offline eeergo

Re: General Falcon and Dragon discussion (Thread 15)
« Reply #47 on: 12/06/2018 10:53 pm »
Not only that, but the whole article is odd. From the headline you'd think SpaceX was gassing crew members. This feels like someone taking some random safety study from Crew Dragon and claiming "Commercial crew is killing our astronauts!". It's a known issue that is being worked on by NASA, just like about a hundred other small things on the space station. It's not better or worse than other things that are happening and there's no reason to be suddenly very concerned.
.

Outgassing waste deposition of tens of times the allowable limits for the world-class scientific instruments the Station is supposed and mandated to host is no small issue, IMO.
The numbers of how many FOIA requests were denied by NASA and the immediate conclusions the author draws from it aren't negligible either.
-DaviD-

Offline woods170

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Re: General Falcon and Dragon discussion (Thread 15)
« Reply #48 on: 12/07/2018 06:48 am »
Not only that, but the whole article is odd. From the headline you'd think SpaceX was gassing crew members. This feels like someone taking some random safety study from Crew Dragon and claiming "Commercial crew is killing our astronauts!". It's a known issue that is being worked on by NASA, just like about a hundred other small things on the space station. It's not better or worse than other things that are happening and there's no reason to be suddenly very concerned.
.

Outgassing waste deposition of tens of times the allowable limits for the world-class scientific instruments the Station is supposed and mandated to host is no small issue, IMO.
The numbers of how many FOIA requests were denied by NASA and the immediate conclusions the author draws from it aren't negligible either.

Anybody with knowledge on the subject can tell you that placing world-class scientific instruments on a station, that is regularly being visited by manned and un-manned vehicles, is not the optimal thing to do. NASA found this out early in the shuttle program when some of the instruments flying on Spacelab missions suffered badly from outgassing effects, as well as deposits from RCS bursts.

Why do you think both NASA and ESA originally proposed to have free-flyer platforms, associated with the space station?

They were intented for hosting contamination-sensitive payloads and instrument.

However, the free-flyer platforms fell to the budget axe. So NASA and ESA ended up putting the instruments directly on the ISS structure. That necessitated minimizing outgassing from ISS structures, as well as non-propulsive attitude control of the ISS.

But make no mistake; every time the ISS is visited by a vehicle (be it Shuttle, HTV, Soyuz, Progress, Cygnus or Dragon) the station gets shrouded in a blanket of RCS by-products and outgassing products from said vehicles.
Its not just Dragon polluting the ISS environment. The other craft have that effect too.

Offline eeergo

Re: General Falcon and Dragon discussion (Thread 15)
« Reply #49 on: 12/07/2018 07:13 am »
Sure, I am aware about free-flyers, and there's no question about them being preferable from a disturbances (contamination and other types) point of view. But we're talking order-of-magnitude effects here, not optimal-yet-unrealizable (in the near term, with current platforms) architectures.

Do other VVs regularly pollute sensitive instruments almost 2 orders of magnitude over nominal limits during docked ops?

If so, why is this issue raised as an anomaly for Dragon, and why are the limits so conservative or the mitigation measures so lacking?

If not, what does Dragon do wrong (from the article: paint?), what long-term effects will it have on instruments sensitive to such outgassing if allowed to go on, should the limits be relaxed for certain compounds, should ...?

These issues, if as described in the article (and it appears well-referenced, so no reason to doubt it too much) are hardly like "a hundred other small things" or "not better or worse than any other thing happening", whatever that may mean, as described a few comments above.
-DaviD-

Offline SWGlassPit

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Re: General Falcon and Dragon discussion (Thread 15)
« Reply #50 on: 12/07/2018 03:18 pm »
Also noted in the article:

Quote from: Sarah Scoles
SpaceX, meanwhile, is looking at its ingredients. “SpaceX has scrutinized all external material selections on Dragon and is working with suppliers to custom-develop low outgassing variants of qualified materials to help improve the molecular deposition rate,” says the company, adding that NASA pre-approved all the materials used in the first Dragon design.

Not only that, but the whole article is odd. From the headline you'd think SpaceX was gassing crew members. This feels like someone taking some random safety study from Crew Dragon and claiming "Commercial crew is killing our astronauts!". It's a known issue that is being worked on by NASA, just like about a hundred other small things on the space station. It's not better or worse than other things that are happening and there's no reason to be suddenly very concerned.

The conspiratorial vibe that "We asked questions and NASA pulled the report!!!!" was also not a welcome facet of the article.

Welcome or not, it happened.  It's not even on the non-public NTRS anymore.

Offline Alexphysics

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Re: General Falcon and Dragon discussion (Thread 15)
« Reply #51 on: 12/07/2018 05:28 pm »
Not only that, but the whole article is odd. From the headline you'd think SpaceX was gassing crew members. This feels like someone taking some random safety study from Crew Dragon and claiming "Commercial crew is killing our astronauts!". It's a known issue that is being worked on by NASA, just like about a hundred other small things on the space station. It's not better or worse than other things that are happening and there's no reason to be suddenly very concerned.
.

Outgassing waste deposition of tens of times the allowable limits for the world-class scientific instruments the Station is supposed and mandated to host is no small issue, IMO.
The numbers of how many FOIA requests were denied by NASA and the immediate conclusions the author draws from it aren't negligible either.

Anybody with knowledge on the subject can tell you that placing world-class scientific instruments on a station, that is regularly being visited by manned and un-manned vehicles, is not the optimal thing to do. NASA found this out early in the shuttle program when some of the instruments flying on Spacelab missions suffered badly from outgassing effects, as well as deposits from RCS bursts.

Why do you think both NASA and ESA originally proposed to have free-flyer platforms, associated with the space station?

They were intented for hosting contamination-sensitive payloads and instrument.

However, the free-flyer platforms fell to the budget axe. So NASA and ESA ended up putting the instruments directly on the ISS structure. That necessitated minimizing outgassing from ISS structures, as well as non-propulsive attitude control of the ISS.

But make no mistake; every time the ISS is visited by a vehicle (be it Shuttle, HTV, Soyuz, Progress, Cygnus or Dragon) the station gets shrouded in a blanket of RCS by-products and outgassing products from said vehicles.
Its not just Dragon polluting the ISS environment. The other craft have that effect too.

Although I'm with you on the first part and it's true that Soyuz and the rest of the other vehicles create some of the contamination, Dragon is by far the one that contaminates the most with high rates right at the times when a Dragon is on station while when other vehicles go and stay there the contamination rises only a bit. However... it's true this is not a big issue and can be corrected so that Dragon stays on the same levels as the other vehicles, this is totally normal to happen in this industry, there are always unknowns even when more than 10 dragons have flown into space and back, we just have to wait and see what they do and what can be done, I'm confident they'll get it right :)

Offline programmerdan

Re: General Falcon and Dragon discussion (Thread 15)
« Reply #52 on: 12/07/2018 05:33 pm »
Also noted in the article:

Quote from: Sarah Scoles
SpaceX, meanwhile, is looking at its ingredients. “SpaceX has scrutinized all external material selections on Dragon and is working with suppliers to custom-develop low outgassing variants of qualified materials to help improve the molecular deposition rate,” says the company, adding that NASA pre-approved all the materials used in the first Dragon design.

Not only that, but the whole article is odd. From the headline you'd think SpaceX was gassing crew members. This feels like someone taking some random safety study from Crew Dragon and claiming "Commercial crew is killing our astronauts!". It's a known issue that is being worked on by NASA, just like about a hundred other small things on the space station. It's not better or worse than other things that are happening and there's no reason to be suddenly very concerned.

The conspiratorial vibe that "We asked questions and NASA pulled the report!!!!" was also not a welcome facet of the article.

Welcome or not, it happened.  It's not even on the non-public NTRS anymore.

It appears to still be here: https://www.spiedigitallibrary.org/conference-proceedings-of-spie/10748/1074805/Analysis-of-observed-contamination-through-SAGE-IIIs-first-year-on/10.1117/12.2321982.short?SSO=1

The paywall sucks, but probably could just email the principles for a copy. Horrible optics for NASA to pull it, totally agree.

Offline ncb1397

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Re: General Falcon and Dragon discussion (Thread 15)
« Reply #53 on: 12/07/2018 06:35 pm »

If not, what does Dragon do wrong (from the article: paint?), what long-term effects will it have on instruments sensitive to such outgassing if allowed to go on, should the limits be relaxed for certain compounds, should ...?

My guess is they aren't properly baking everything out.

This video goes into how it is done for Mars 2020:


From what I can tell from the graph posted above, there is a spike after docking but it flattens out in the period prior to release. This suggests it is simply a matter of duration of simulating the space environment on the ground during the baking process prior to launch to reduce the affect substantially. This is assuming contaminants aren't re-absorbed in the launch process afterwards though.
« Last Edit: 12/07/2018 07:13 pm by ncb1397 »

Offline Wolfram66

Re: General Falcon and Dragon discussion (Thread 15)
« Reply #54 on: 12/07/2018 10:04 pm »
Quote
Although I'm with you on the first part and it's true that Soyuz and the rest of the other vehicles create some of the contamination, Dragon is by far the one that contaminates the most with high rates right at the times when a Dragon is on station while when other vehicles go and stay there the contamination rises only a bit. However... it's true this is not a big issue and can be corrected so that Dragon stays on the same levels as the other vehicles, this is totally normal to happen in this industry, there are always unknowns even when more than 10 dragons have flown into space and back, we just have to wait and see what they do and what can be done, I'm confident they'll get it right :)

One question is there a difference between a New Dragon and a recently refurbished Dragon? Are the procedures to re-paint, re-PICA-X and re-SPAM not baking out the VOC's effectively or does the heat of re-entry affect the process. someone will need to pull which the offending Dragons and correlate..

EDIT: https://en.wikipedia.org/wiki/SpaceX_Dragon

The following are CRS missions using Re-flown Dragons
CRS-11
CRS-13
CRS-14
CRS-15
CRS-16
« Last Edit: 12/07/2018 10:08 pm by Wolfram66 »

Offline deruch

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Re: General Falcon and Dragon discussion (Thread 15)
« Reply #55 on: 12/08/2018 10:19 pm »
Quote
Although I'm with you on the first part and it's true that Soyuz and the rest of the other vehicles create some of the contamination, Dragon is by far the one that contaminates the most with high rates right at the times when a Dragon is on station while when other vehicles go and stay there the contamination rises only a bit. However... it's true this is not a big issue and can be corrected so that Dragon stays on the same levels as the other vehicles, this is totally normal to happen in this industry, there are always unknowns even when more than 10 dragons have flown into space and back, we just have to wait and see what they do and what can be done, I'm confident they'll get it right :)

One question is there a difference between a New Dragon and a recently refurbished Dragon? Are the procedures to re-paint, re-PICA-X and re-SPAM not baking out the VOC's effectively or does the heat of re-entry affect the process. someone will need to pull which the offending Dragons and correlate..

EDIT: https://en.wikipedia.org/wiki/SpaceX_Dragon

The following are CRS missions using Re-flown Dragons
CRS-11
CRS-13
CRS-14
CRS-15
CRS-16

The original Wired article, paraphrasing the SAGE III presentation, said that CRS-11 showed 21x over the contamination limits and CRS-12 at 32x over.  So, it's clearly not an issue limited to only the first flights of Dragons.  I don't believe that the currently public information is sufficient to determine whether the difference in outgassing between "new" and "reflown" vehicles is statistically significant.
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Offline Comga

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Re: General Falcon and Dragon discussion (Thread 15)
« Reply #56 on: 12/08/2018 11:34 pm »
Statement:
I have direct knowledge of this instrument and measurements and am not throwing things against the wall to see what sticks.  This is within my professional wheelhouse.

I have access to and have downloaded the SPIE (Society for Optical Engineering) article which contains the technical discussion on which this discussion is based and from which the half-hidden graph was pulled.

There are quite large pulses of contamination in the ram direction (looking "forward" against the velocity and against the flow of the exosphere through which the ISS flies) for some, but not all, of the Dragon visits.  The first visit, which may have been CRS-11, was not accompanied by a clearly resolved spike in condensable volities.  The other two were.

Also contained in the article is a graph of the transmission on the SAGE-III contamination door/window at specific wavelengths including 290 nm, the UV wavelength of the high altitude Ozone measurements.  While there is a decrease of transmission of (edit: up to 2%), the transmission returns to the baseline in a few weeks.  This is quite transient deposition if the surface is not cooled like the TQCM contamination monitors.  The effect decreases as the wavelength increases, becoming minuscule beyond the visible spectrum. (SAGE-III has SWIR channels to 1050 nm plus one at 1550 nm.)  Given the way SAGE-III operates, it does not significantly degrade the Ozone measurements, or any others.  If this outgassed material deposits elsewhere on ISS hardware, it probably dissipates rapidly from there, too.

The measurements of SAGE-III-ISS on, of course, the ISS, can be contrasted to those of it's twin, SAGE-III-M3 which flew on the Russian meteorological satellite Meteor-3M.  My understanding, although I have not seen the data, is that it's UV channel was rendered useless by contamination within the first year of operations. Those who extol the virtue of free-fliers can take note.   

The comparisons to the Soyuz and Progress dockings are direct, but somewhat disingenuous.  Those craft approach and dock to the Russian "back half" segment of the ISS.  Emitted volitiles are swept away from the American "front half" segment.  SAGE-III-ISS is mounted close behind, and just off to the starboard side of the ISS, from where the Dragons are berthed, a great spot to collect emitted material from them.  The solar panels, which were hypothesized as being potentially contaminated, are far to the sides, so less likely to collect condensables, and likely to quickly shed them as they warm in the sunlight.     

As of this week there have been three more Dragons berthed to the ISS.  It would be very interesting to see the data from this doubling of the number of visits.
« Last Edit: 12/11/2018 05:06 am by Comga »
What kind of wastrels would dump a perfectly good booster in the ocean after just one use?

Offline niwax

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Re: General Falcon and Dragon discussion (Thread 15)
« Reply #57 on: 12/09/2018 12:31 am »
Quote
Although I'm with you on the first part and it's true that Soyuz and the rest of the other vehicles create some of the contamination, Dragon is by far the one that contaminates the most with high rates right at the times when a Dragon is on station while when other vehicles go and stay there the contamination rises only a bit. However... it's true this is not a big issue and can be corrected so that Dragon stays on the same levels as the other vehicles, this is totally normal to happen in this industry, there are always unknowns even when more than 10 dragons have flown into space and back, we just have to wait and see what they do and what can be done, I'm confident they'll get it right :)

One question is there a difference between a New Dragon and a recently refurbished Dragon? Are the procedures to re-paint, re-PICA-X and re-SPAM not baking out the VOC's effectively or does the heat of re-entry affect the process. someone will need to pull which the offending Dragons and correlate..

EDIT: https://en.wikipedia.org/wiki/SpaceX_Dragon

The following are CRS missions using Re-flown Dragons
CRS-11
CRS-13
CRS-14
CRS-15
CRS-16

The original Wired article, paraphrasing the SAGE III presentation, said that CRS-11 showed 21x over the contamination limits and CRS-12 at 32x over.  So, it's clearly not an issue limited to only the first flights of Dragons.  I don't believe that the currently public information is sufficient to determine whether the difference in outgassing between "new" and "reflown" vehicles is statistically significant.

I believe Dragon are largely rebuilt, they are being reused mainly to shut down pressure vessel production. The paint or even the entire outer hull is likely reapplied before every flight, so reuse should not make a difference.
Which booster has the most soot? SpaceX booster launch history! (discussion)

Offline Okie_Steve

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Re: General Falcon and Dragon discussion (Thread 15)
« Reply #58 on: 12/10/2018 04:55 am »
I remember Elon once commented that an F9 booster could more or less do SSTO just not with any payload. Using two stages made much more sense. So, my question is,  what could an F9 stack with no payload do? Would lunar free return be a possibility? That could make one heck of a TPS test.

Offline HMXHMX

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Re: General Falcon and Dragon discussion (Thread 15)
« Reply #59 on: 12/10/2018 10:58 pm »
I remember Elon once commented that an F9 booster could more or less do SSTO just not with any payload. Using two stages made much more sense. So, my question is,  what could an F9 stack with no payload do? Would lunar free return be a possibility? That could make one heck of a TPS test.

Heck, the Titan II first stage could do expendable SSTO, and with a 1400 lb. payload – it is just that the burnout Gs would be intolerable, given lack of throttle on the engines.  I'm pretty sure that a 0.96 PMF F9 S1 could provide a 40 or 50:1 growth factor (ratio of GLOW to PL) easily enough, and without the Titan II Gs problem, since F9 engines can be shut off in pairs, down to the central single one, which itself can slightly throttle as well.

It'd be amusing for someone to run OTIS or POST on such an option.
« Last Edit: 12/11/2018 04:18 am by HMXHMX »

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