SpaceX F9 : CRS SpX-18 : July 25, 2019 - DISCUSSION

[intelati]

There are control inversion transitions both as the grid fins go trans-sonic and as soon as the first leg touches the ground.  These are legit engineering reasons for quick control excursions. (Watch the star hopper engine as soon as the first leg touches.) I bet SpaceX can explain the cause of every sharp control input on the video.

I'd love to see a force diagram along the re-entry

[mandrewa]

Wow I didn't realise the $/Kg of the Dragon was 3x that of progress!!! And to be fair the Russian price is excellent - on this graphic (above) - as SX have been so proud of their $62M with discounts for re-usability.... If progress really is $56M including the capsule, SX still have a long way to go! and were clearly not the first to drive down prices.

Hmm...  I did some math and I think the implied prices are rather similar, or arguably taking
everything in to account the Dragon is significantly cheaper.

The main reason is what gongora briefly mentioned, a major part of the Progress payload is
water and other liquids.  These are dense and they don't suffer from what I've been describing
to myself as the "packing problem."

Although the Dragon spacecraft has a smaller ratio of pressurized volume to mass than the
Cygnus, the same can be said for the Progress, and since Progress is the smaller vehicle it
would have an even worse "packing problem" than the Dragon if it were not carrying liquids.

So let's imagine for the moment that the roles were reversed and the Dragon was carrying up some
of the liquids that the ISS needs in addition to the "packing problem" payloads that can fit
within its 11 cubic meter pressurized volume and with yet another payload in its unpressurized trunk. 
That is the Dragon would be full.  All capacities, mass (97%) and volume, pressurized and unpressurized,
would be fully used.  How then would the prices compare?

If we use the $140 million per launch price (see scr00chy above) implicit in the contract that paid
for this launch, and divide that by 5.75 metric tons, then that's $24,346 per kilogram, which is
quite close to the $22,300 per kilogram number that KenigOld gave for the current Progress where
that same Progress is fully used to its capacity.

But if Dragon were carrying the liquids then the Progress couldn't since the ISS needs only so much
liquid per month.  What would the price per kilogram be for the Progress if it were restricted to
carrying only "packing problem" payloads?  I think Progress would be doing very well if it could
reach the 39% mass utilization ratio that this Dragon mission achieved and likely the Progress can
not actually do that, because it doesn't have an unpressurized trunk.  But if we pretended that
the Progress could do that, then its payload would be 1009 kg and the price per kg would be $55,464.

And then there is the fact that the Dragon brings back a payload to Earth.  This payload is arguably
as valuable as the payload taken up.  This is especially true as long as the Dragon is the only path
by which experimental payloads can return to Earth. 

It's going to get harder to assess the value of this once DreamChaser is operational and we have a
second vehicle that can return payload, but for now it seems reasonable to assign half the value
of a Dragon mission to what it returns.

So that gives us four comparisons, with all including the value of the payload returned to Earth:

$30,276 per kg vs. $22,300 per kg (Dragon without liquids vs. Progress with liquids)
$12,173 per kg vs. $22,300 per kg (Dragon with liquids vs. Progress with liquids)
$12,173 per kg vs. $55,464 per kg (Dragon with liquids vs. Progress without liquids)
$30,276 per kg vs. $55,464 per kg (Dragon without liquids vs. Progress without liquids)

To my eyes these are the real price differences between the Dragon and the Progress, but there
are two other factors that might be applied to further adjust these numbers.

First, the price for the Dragon clearly is in part a reflection of the cost of developing the Dragon,
while the development of the Progress has long since been paid for.  This has no impact on what
things actually cost now, but as a measure of technical achievement, I would love to know what the
marginal cost of building a Dragon is versus the marginal cost of building a Progress.

Second, these prices are in part a reflection of the overall state of the US economy versus the
Russian economy.  Since the US economy is doing much better than the Russian economy, anything
being done in the United States faces a penalty versus the same activity in Russia.  Or in other
words Russia wants and needs dollars while the United States doesn't particularly need rubles.
Now we could put a number on this and adjust for it, and although it wouldn't change the real prices,
it would in a sense more accurately reflect the level of achievement of people working within
the space industry in the United States.

[DistantTemple]

snip...
$30,276 per kg vs. $22,300 per kg (Dragon without liquids vs. Progress with liquids)
$12,173 per kg vs. $22,300 per kg (Dragon with liquids vs. Progress with liquids)
$12,173 per kg vs. $55,464 per kg (Dragon with liquids vs. Progress without liquids)
$30,276 per kg vs. $55,464 per kg (Dragon without liquids vs. Progress without liquids)
snip...

Brilliant careful analysis. As they say analysis w/o numbers is opinion. And you have analysed it not just with the numbers, but on a the back of a detailed and justified critical comparison!

And the original leaflet above, had numbers, but they were used to "paint a positive picture" ;-( of the Progress, and imply SX was expensive - by encouraging us to ignore or downplay critical information.... maybe another saying: numbers without analysis ... is ... disinformation.

[eeergo]

And if my grandma had wheels she'd be a bandwagon

It's funny, yet a little disheartening and scary, what level of baroquism some are willing to reach in order to protect preconceived (nationalistic? ideological? sports-fan-like?) ideas, as the last paragraph shows. Note I am not siding with Russian metrics, just noting IMO bad, and shallow, reasoning.

Progress-MS has little to do with the original 7K-TG spacecraft of the 70s. Arguably there are some non-negligible development costs which are quite recent and not amortized (new docking system, new computers, new GN&C, new TPS...).

Furthermore, if we go so deep to dev costs and general economical considerations, shouldn't we also consider other similar (or even not similar, just budget-linked) spacecraft in development by the same entity? Or even the "penalty", to speak with your own terms, that Russia faces considering their economy is worse, has been so for decades (and much worse), and so have their working conditions - yet they manage to launch reliably a core, indispensable system to ISS while introducing upgrades and innovations (2-orbit rendezvous, vehicle upgrades...)?

What about the cost of propellant transfer to the ISS only propulsion system, what value should be assigned to that one compared to return cargo, even if it those return items are not utilization or refurbishment samples, by the way?

And for fast launch-to-(autonomous)-docking capability? Even if it's not really utilized for time-sensitive supplies so far, it theoretically could, as your "liquid-Dragon" concept, how much would that cargo be worth compared to standard one?


Cost estimates are always messy and incomplete, but corrections should be that: corrections, not something that changes completely the value of a previous analysis just by adding qualifiers to it. As for analysis needing numbers: you can punch numbers in the calculator all day, if your underlying concept isn't correct it's worse than opinion - it's undecipherable numerology.

[DistantTemple]

snip...
$30,276 per kg vs. $22,300 per kg (Dragon without liquids vs. Progress with liquids)
$12,173 per kg vs. $22,300 per kg (Dragon with liquids vs. Progress with liquids)
$12,173 per kg vs. $55,464 per kg (Dragon with liquids vs. Progress without liquids)
$30,276 per kg vs. $55,464 per kg (Dragon without liquids vs. Progress without liquids)
snip...

Brilliant careful analysis. As they say analysis w/o numbers is opinion. And you have analysed it not just with the numbers, but on a the back of a detailed and justified critical comparison!

And the original leaflet above, had numbers, but they were used to "paint a positive picture" ;-( of the Progress, and imply SX was expensive - by encouraging us to ignore or downplay critical information.... maybe another saying: numbers without analysis ... is ... disinformation.

eeergo, I am the one at fault here... from your comments it looks as if you read mandrewa's piece thoroughly. He justified his figures sensibly. Now you have added to them, improving the debate.

It was me that made a sweeping generalization about disinformation! However the original graphic was a good "debate starter", and the impression given there is getting picked apart and debated! I was pleasantly surprised that there were arguments that progress is cheaper than Dragon (which I do champion) and of course $60M per seat for Russia launching American crew, is similar to what SX will charge NASA, ignoring development funding I think?
So yes bandwagon... at least somewhat. Careful analysis, truth, and fairness do matter more than shouting for a favourite team.

[ZChris13]

All of the vehicles that have visited or will visit the ISS have brought their own unique and indispensable benefits.
STS had enormous upmass and downmass
Progress fuels the propulsion system
Soyuz is the only current crew capsule and lifeboat
Dragon's upmass and downmass capabilities
I don't know enough about Cygnus to sing their praises, and I'm probably forgetting a few of the other resupply vehicles because I'm not a big ISS fan.
In the future, Starliner and Dragon 2 will provide the same crew up and down capability as STS, but also be capable as lifeboats (I think? I thought they had long duration capabilities) although I don't think the current plan involves these capabilities being used.
I'm sure Dreamchaser does something special beyond the subjective benefits of a lifting body but I am not qualified to sing its praises either.

[mandrewa]

Note I am not siding with Russian metrics, just noting IMO bad, and shallow, reasoning.

How is it bad?  How is it shallow?  Please get specific.

Any comparison between any vehicles produced by different nations is going to be perceived as nationalist by probably the majority of the people that read it.  And that's because people are tribalist.  It's built into our genes.

But this isn't intended to be a nationalist drumbeat.  I'm trying to make an accurate comparison between vehicles and assess where we actually are.

I don't get why you think that last paragraph is a nationalist assertion.  It's just a simple statement of economic reality.  Of course it has a big impact on costs.  You think it doesn't matter that workers in the space industry in the United States get paid twice or three times or whatever more than people in the Russian space industry?  Of course it matters.

And yet I did not even include that in the cost comparison.  I merely pointed out that some people would.

Progress-MS has little to do with the original 7K-TG spacecraft of the 70s. Arguably there are some non-negligible development costs which are quite recent and not amortized (new docking system, new computers, new GN&C, new TPS...).

That's interesting.  Is there any public estimate of the recent development budget for the Progress? 
 

Furthermore, if we go so deep to dev costs and general economical considerations, shouldn't we also consider other similar (or even not similar, just budget-linked) spacecraft in development by the same entity? Or even the "penalty", to speak with your own terms, that Russia faces considering their economy is worse, has been so for decades (and much worse), and so have their working conditions - yet they manage to launch reliably a core, indispensable system to ISS while introducing upgrades and innovations (2-orbit rendezvous, vehicle upgrades...)?

I think it's a remarkable achievement what the Russians have done in rather difficult circumstances.  They deserve a great deal of credit.

You know I almost didn't post this.  I really hesitated because I knew that the Russians would take it as a big criticism.

But at the same time the idea that the Dragon hasn't caught up with or isn't as good as the Progress is, I think, horribly wrong. 

What about the cost of propellant transfer to the ISS only propulsion system, what value should be assigned to that one compared to return cargo, even if it those return items are not utilization or refurbishment samples, by the way?

Yes, I thought about that.  But that's by design.  Propellant can only come up on the Russian side by design.  It's not like it had to be that way.  It's not like that's some virtue in the Progress vehicle.  And remember the context is comparing Progress to Dragon.

And for fast launch-to-(autonomous)-docking capability? Even if it's not really utilized for time-sensitive supplies so far, it theoretically could, as your "liquid-Dragon" concept, how much would that cargo be worth compared to standard one?

And that's by design also.  Because of the orbit of the ISS, the Russians can launch cargo virtually any time day or night and still get there.  And also because of the orbit, there is an opportunity, I think it's about once per day for a "fast launch."  But it's not because NASA is incompetent that they don't do fast launches.  It's because of the orbit.

Cost estimates are always messy and incomplete, but corrections should be that: corrections, not something that changes completely the value of a previous analysis just by adding qualifiers to it. As for analysis needing numbers: you can punch numbers in the calculator all day, if your underlying concept isn't correct it's worse than opinion - it's undecipherable numerology.

I totally agree that the concept has to be sound.  I introduced two concepts into the comparison of Dragon and Progress.  One concept is to point out that that Dragon returns payload and that this of great value.  I can see an argument about just exactly how much it is worth.  But I don't understand an assertion that it is not of great value and that we should ignore it.

The second concept is even more important and as it happens I've been thinking about it a lot lately in the context of getting cargo to NRHO and comparing the virtue of different systems for doing that.  And as it happens this comparison, Dragon to Progress, is a wonderful example of the same general problem.

It's relatively easy to design a vehicle to efficiently carry dense fluids to NRHO because you don't have a packing problem.  It's harder to assess and compare different vehicles that will be transporting things that do have a packing problem to NRHO because you don't really know what the mix of things is going to be.  Dragon kind of provides an estimate of what the actual ratio of payload to theoretical capacity will likely be, as in this case where only 39% of the mass capacity of the Dragon is used.

Progress doesn't have that problem because, by design, it carries liquids in addition to its other cargo, and therefore it always goes up almost 100% full.  Dragon, by design, does have the packing problem because Progress is already taking the liquids, and most of the cargo that the ISS needs is stuff that goes through the packing problem bottleneck.

Anyway, in my opinion, if you compare these two vehicles, and ignore this issue, then you're ignoring half of what's going on.

[gongora]

How is it bad?  How is it shallow?  Please get specific.

You're taking payloads off of Progress that it was specifically designed to carry and then saying that it no longer compares favorably with another vehicle that you magically increased the payload on.  Progress has the fuel transfer equipment instead of one of the pressurized modules that is on Soyuz.  The fuel is also delivered to a part of the station that Dragon doesn't interact with.

[mandrewa]

How is it bad?  How is it shallow?  Please get specific.

You're taking payloads off of Progress that it was specifically designed to carry and then saying that it no longer compares favorably with another vehicle that you magically increased the payload on.  Progress has the fuel transfer equipment instead of one of the pressurized modules that is on Soyuz.  The fuel is also delivered to a part of the station that Dragon doesn't interact with.

Yes, but that's part of the point.  Progress carries liquids because it's designed to.  Vehicles that go up with 97% of their mass capacity are generally going to do quite good on a cost per kilogram basis compared with vehicles that carry only 39% of their mass capacity.

But the whole reason Progress gets 97% mass capacity is because of the liquids it transports.

And further we could reinterpret the numbers I gave as an estimate of how much of the difference in cost is due to the nature of the cargo.

[eeergo]

It is shallow because it just considers disproportionate corrections for one side, ignoring equivalent obvious ones for the other, and using broad-sweep generalities (macroeconomic conditions) to fill in gaps. It is bad because the initial well-researched post, while undoubtedly subject to discussion, only aimed at establishing a face-value comparison between the two most-used vehicles in the ISS program, using publicly-available and quantifiable data, including some of your caveats like downmass or unpressurized open cargo, not a complete history of which development was more "worthy". Your corrections were hand-waved in magnitude and seemed to aim to a foregone conclusion. It is nationalistic (which is definitely NOT something in our genes) because it's baselessly and unnecessarily talking about "accurately reflecting achievements" of a (your) side based on a shallow contextualization that ignores the other.

Of course salaries matter. Of course sanctions matter. Of course working conditions and brain drain matter. Of course industrial power and leverage matter. Of course accumulated knowledge matters. But if you're gonna use those many profound considerations, you have to do it at least coherently, or you'll reach any "result" and come across as pursuing a partisan picture.

Anyway, first you say that you intend to make the comparison more accurate. A couple of paragraphs later you assert some of the unique capabilities of Progress I mentioned are not to be considered because they are "by design" (??) - ignoring that Russian propulsion is "by design" precisely because Roscosmos is the only one in the ISS consortium who has a proven, working propellant transfer system. Dragon doesn't have it also "by design", even though STS could (and did) reboost the Station, and a back-up or primary ISS thruster system could be developed for the USOS. It just wasn't.

Propellant isn't carried just as if it was Tang bags. It requires a safe and robust pressurization, distribution and purging system that also takes away cargo capacity. How much more "dry" cargo could Progress carry if this system wasn't in place? Of course, it's a rhetorical question since that would make a different vehicle and we could also ask what if we strip Dragon of something else, or add a propellant transfer system to it? That's why a face-value comparison is useful, while using only partial corrections becomes dicey and misleading.

Concerning fast-track docking... please have a look again at how it works. Launches from Florida have no handicap with respect to Kazakhstan or any other point in latitudes within ISS' orbital inclination, quite the contrary upmass-wise. Of course Russia cannot launch to ISS at any time of the day/night! US VVs could minimize launch-to-docking times as much as they wanted too if the relevant choreographies were developed, and window flexibility impacts accepted.

A "corrected" version of price per kg like you're pursuing will also strongly depend on the programatic needs in a given period: downmass is valuable only if there's something worthwhile to carry down. Clearly not the same to use that capability for souvenirs, trash or high-school experiments than biological samples or EMUs to repair. OTOH, destructive disposal of trash may be very valuable too (STS used to carry down large amounts!). Propellant is only valuable if the orbit needs to be changed (in STS times it was quite lower, so reboosts were more frequent, and major construction operations meant more fuel was needed to desaturate the CMGs after frequent attitude changes). Etc.

Sorry if this comes across as terse, but I keep seeing how the pluralistic, insightful and respectful views this forum used to boast are being dragged down in most threads to endless simplistic, pushy narratives always aimed in the same direction.

[abaddon]

You're taking payloads off of Progress that it was specifically designed to carry and then saying that it no longer compares favorably with another vehicle that you magically increased the payload on.  Progress has the fuel transfer equipment instead of one of the pressurized modules that is on Soyuz.  The fuel is also delivered to a part of the station that Dragon doesn't interact with.

The default was the opposite, though.  Dragon was never given an opportunity to carry those Progress payloads and is being dinged because of it.  I think @mandrewa's pointing that out is totally valid.  Their assessment isn't "right" but it points out an inherent built-in bias that Progress "enjoys" in this comparison, and that's completely valid.

Comparisons like these are very difficult because they are apples to oranges.  The original assessment did a very simplistic comparison and was very misleading as a result.

All of that said... perhaps this should be in a different thread...

[mandrewa]

eeergo, I'm not going to continue with this argument.  I think I've said all I wanted to say. 

But if you wanted to put numbers as these various factors that you don't feel I'm taking proper account of and that should be considered in this comparison well then I would like to hear that.  I realize it's not stuff you can just look up; it would have to be estimates.  But as far as I'm concerned estimates are just fine.

And also I like your point about the mass of the system for manipulating the fluids, the "safe and robust pressurization, distribution and purging."   That's a good point and I hadn't considering it.

And also would it be possible to give a rough estimate of how much that system masses?  Is that public information?

[leetdan]

Aside from upmass, it's a lynchpin of ISS operations, full stop.  ATV alone shared this capability, and it only flew five times.

4700kg prop upmass for ATV, up to 1950kg for Progress according to Wikipedia.

[eeergo]

eeergo, I'm not going to continue with this argument.  I think I've said all I wanted to say. 

But if you wanted to put numbers as these various factors that you don't feel I'm taking proper account of and that should be considered in this comparison well then I would like to hear that.  I realize it's not stuff you can just look up; it would have to be estimates.  But as far as I'm concerned estimates are just fine.

And also I like your point about the mass of the system for manipulating the fluids, the "safe and robust pressurization, distribution and purging."   That's a good point and I hadn't considering it.

And also would it be possible to give a rough estimate of how much that system masses?  Is that public information?

Sure, I would also love to see an assessment that went from KenigOld's comparison of *two particular missions* (SpX-18 and Progress-MS 11), and then move on to a more general face-value comparison between systems, to one that took into account objective balanced corrections for each vehicle to reach a more comprehensive picture. Unfortunately, I think it requires an amount of time and expertise in researching elusive information archives I do not possess. As for estimates, I think the error bars they'd add would be more significant than the contribution they'd make.

No idea how much the propellant transfer system weighs, but I do know its tanks occupy the middle section of the craft (where Soyuz has the re-entry capsule), together with the water and gas transfer system - it's called the "refueling module": spaceflight101.net/progress-spacecraft-information.html / russianspaceweb.com/progress.html. I actually like to consider the gases and propellant as "unpressurized cargo", since they're not inside the crew-accessible pressure vessel: the refueling module is an unpressurized truss covered with light MMOD, and the tanks are exposed to vacuum. Of course, it's confusing to call a pressurized gas an unpressurized payload

Anyway, I think this is the point of cooperation vs "my team/country should lead and be best in everything": provide dissimilar redundancy, fresh viewpoints, backup options and complementary capabilities.

[...] I'm probably forgetting a few of the other resupply vehicles because I'm not a big ISS fan.[...]

I think you'd find it surprisingly rewarding and uplifting to delve deeper into the ISS program and learn more about its history and capabilities, in spite of the some shortfalls it has This forum certainly has quite some material to enjoy!

[CorvusCorax]

So, long story short, comparing Progress to Dragon will always be comparing apples to oranges.

-One primarily transports consumables and fuel, while the other primarily transports science payloads.
20k $ per kg is much compared to the commodity value of fuel, while 70k $ per kg might be quite insignificant compared to the price of one-of-a-kind scientific experiments/instruments
-One has downmass, the other doesn't
-One is mass, the other volume constrained
-The economies of production are not comparable
-The financing structure is not comparable (SpaceX uses CRS missions to in part amortise R&D of F9, Reusability, Dragon1, Dragon2 Raptor and Starship dev, I have no clue what Russia is using the progress launch money for)
( Not even opening the whole price vs cost can of worms )
-ISS needs both, not one XOR the other, so they are not competing vehicles in the first place.

Edit: mostly typos

[mandrewa]

That's a pretty good summation, CorusCorax.  I like that way of looking at things.

There should be some mention of the Dragon's unpressurized trunk which makes it possible to add elements to the structure of the space station, as with this mission.  But even there usually the elements being added are science experiments.

[envy887]

Dragon's ability to carry large amounts of downmass greatly affects every other aspect of it's performance and cost, so there is no good way to compare it to a vehicle that cannot transport downmass at all. The only other vehicle to visit ISS that could do this was the Shuttle, which was even more expensive per cargo kg.

[tleski]

I just wanted to point out that the comparisons of which country is better (has better technology etc..) which triggered such a strong condemnation by @eeergo was not really started by @mandrewa. The original infographic posted by @KenigOld contains the US and Russian flags on balances indicating that we are comparing capabilities (or pricing)  offered by two competing countries. I am not surprised that it could make some people unhappy.

And yes, this discussion should probably be moved to one of the general Dragon threads.

[mn]

https://twitter.com/Space_Station/status/1166343146734850048

To accommodate better lighting conditions today, the @SpaceX #Dragon cargo craft is now scheduled to leave the station at 10:59am ET today. #AskNASA | https://www.nasa.gov

So they change the departure time for better lighting conditions? Like they couldn't predict the lighting conditions at this date and time years in advance? Did the sun suddenly change orbit?

Just curious how such a thing gets scheduled and then changed for things that are known well in advance.

[Ken the Bin]

https://twitter.com/Space_Station/status/1166343146734850048

To accommodate better lighting conditions today, the @SpaceX #Dragon cargo craft is now scheduled to leave the station at 10:59am ET today. #AskNASA | https://www.nasa.gov

So they change the departure time for better lighting conditions? Like they couldn't predict the lighting conditions at this date and time years in advance? Did the sun suddenly change orbit?

Just curious how such a thing gets scheduled and then changed for things that are known well in advance.

The sun doesn't change orbit, but the ISS does.  In fact it may have changed because of being in free drift last night for the MS-14 docking.  (I don't have enough technical knowledge to know if that specific thing would cause a significant change in orbit, but there are other things that definitely do, such as orbit raising burns.)