Commercial Crew - Discussion Thread 3

[DigitalMan]

On a somewhat related note, had not SpaceX already indicated that it was planning to refly the CrewDragon capsules for the Cargo2 contracts once they had them available in the workflow? 

SpaceX statements are the opposite of that. Cargo Services 2 is a different build. No Super Draco’s, for instance.

No. The absence of SuperDracos does not make Cargo Dragon a substantially different build from Crew Dragon. Maybe if it was Boeing, they would have come up with two totally different designs with very little or even nothing in common between them for cargo and crew, but this is Space-X and Elon Musk we are talking about: Everything that CAN be reused/in common between D2 Cargo and D2 Crew WILL be because it is cheaper and faster to design it that way. Thus the absence of SuperDracos on D2 Cargo is merely the absence of an unneeded option and should Space-X need to convert a D2 Cargo to a D2 Crew, they will be able to do so with a minimum of fuss by adding the SuperDracos to the mounts that will already be present but unused on the Cargo D2.

Don't add words to my statement. I never said it was substantially different. SpaceX intentions don't align with yours in regards to converting them.

[yg1968]

On a somewhat related note, had not SpaceX already indicated that it was planning to refly the CrewDragon capsules for the Cargo2 contracts once they had them available in the workflow? 

SpaceX statements are the opposite of that. Cargo Services 2 is a different build. No Super Draco’s, for instance.

IIRC at the Demo-2 post-launch brief, Musk stated that Crew Dragon would not be reused for Crew flights, but would? could? might? be reused for Cargo (sorry do not have reference handy).

As to the differences between Crew and Cargo Dragon 2, see snip below; from Audit of Commercial Resupply Services to the International Space Station, NASA OIG, IG-18-016, 26-Apr-2018.

I believe that there was a press conference with Jessica from SpaceX where she said that they wouldn't be using the crewed Dragon for cargo missions.

[snotis]

On a somewhat related note, had not SpaceX already indicated that it was planning to refly the CrewDragon capsules for the Cargo2 contracts once they had them available in the workflow? 

SpaceX statements are the opposite of that. Cargo Services 2 is a different build. No Super Draco’s, for instance.

IIRC at the Demo-2 post-launch brief, Musk stated that Crew Dragon would not be reused for Crew flights, but would? could? might? be reused for Cargo (sorry do not have reference handy).

As to the differences between Crew and Cargo Dragon 2, see snip below; from Audit of Commercial Resupply Services to the International Space Station, NASA OIG, IG-18-016, 26-Apr-2018.

I believe that there was a press conference with Jessica from SpaceX where she said that they wouldn't be using the crewed Dragon for cargo missions.

Yes - see here (at 40:52 mark):

...As soon as we build the weldment there are slight differences ... while a lot of the sub-systems are the same... they will be different vehicles.  We won't interchange between cargo and crew vehicles.

[FutureSpaceTourist]

https://twitter.com/spcplcyonline/status/1270445134614794240

Bowersox: biggest cost of ISS is transportation.  Cmrcl crew and cargo lowered it compared to shuttle, but not as much as ppl hoped.  Wanted factor of 10 reduction, but only 20-40% based on what I've seen.

Rather surprised by those numbers. Is he including commercial crew development costs too? Or basing it on total payload / something else? Individual crew flights are clearly significantly less than a shuttle flight, although not by an order of magnitude.

[abaddon]

https://twitter.com/spcplcyonline/status/1270445134614794240

Bowersox: biggest cost of ISS is transportation.  Cmrcl crew and cargo lowered it compared to shuttle, but not as much as ppl hoped.  Wanted factor of 10 reduction, but only 20-40% based on what I've seen.

Rather surprised by those numbers. Is he including commercial crew development costs too? Or basing it on total payload / something else? Individual crew flights are clearly significantly less than a shuttle flight, although not by an order of magnitude.

Shuttle took up a LOT of cargo and crew at the same time.  The forced cargo/crew combination was identified as a problem, but that doesn't enter into a pure cost equation.  I'd assume this comparison was also not considering development costs (or amortizing it over flights, which the Shuttle had a lot of) as doing otherwise would cause Shuttle's costs to soar.

On a pure per-mission basis, on a per seat basis... yeah, this sounds possible to me.  How many CRS/CCS missions in combination does it take to replace a Shuttle flight?  I don't know the answer.  Then again, we didn't retire the Shuttle because it cost too much, we retired it because it wasn't safe enough,  We also can have six-month rotations with CCS where we had 14-day missions with Shuttle.  It's not really an apples-to-apples comparison.  Which makes it all a bit strange if you ask me.

[Coastal Ron]

Bowersox: biggest cost of ISS is transportation.  Cmrcl crew and cargo lowered it compared to shuttle, but not as much as ppl hoped.  Wanted factor of 10 reduction, but only 20-40% based on what I've seen.

Rather surprised by those numbers. Is he including commercial crew development costs too?

He should. We all should actually. Development costs are not "free", as the $40B to develop the SLS and Orion so far show - even if it cost $0 to build and launch each combination of SLS & Orion that would still equal $1B per launch after 40 launches.

So for Commercial Crew, yes, the total invested to get all of the initial contracted flights need to be taken into account.

Individual crew flights are clearly significantly less than a shuttle flight, although not by an order of magnitude.

The average cost for a Shuttle flight at the end of the program in 2011 was $1.5B, including DDT&E. Of course a lot of those costs were amortized over decades of use, so not apples-to-apples with the brand new Commercial Crew vehicles.

Still, $6.8B for up to 12 flights works out to about $567M per flight (and not counting contracts before CCtCap), so not cheap, but considering the Shuttle couldn't keep crew at the ISS, only rotate them, America is getting new capabilities we didn't have before.

Certainly one factor in the total cost for Commercial Crew is that NASA has never done this before, and industry has never been the owner of crewed spacecraft before. Lots of chatter about NASA being TOO involved with Boeing & SpaceX, and maybe they were, but then again both companies had significant problems along the way, so its hard to judge whether NASA was too involved or not involved enough.

I do think that industry will learn a lot from the Commercial Crew program, but the big question is WHAT?

Will they learn that NASA is too involved? Will they learn that there are ways to cut costs?

Not sure we know the answers to these, and many more, questions...

[mandrewa]

https://twitter.com/spcplcyonline/status/1270445134614794240

Bowersox: biggest cost of ISS is transportation.  Cmrcl crew and cargo lowered it compared to shuttle, but not as much as ppl hoped.  Wanted factor of 10 reduction, but only 20-40% based on what I've seen.

Rather surprised by those numbers. Is he including commercial crew development costs too? Or basing it on total payload / something else? Individual crew flights are clearly significantly less than a shuttle flight, although not by an order of magnitude.

Money paid, or that will be paid, to SpaceX by NASA for Commercial Crew.

   CCDev 2     (2011)   $   75 million
   CCiCap      (2012)   $  440 million
   CPC phase 1 (2012)   $   10 million
   CCtCap      (2013)   $ 2600 million
   --------------------------------------
   Total       (2025)   $ 3125 million

But it's important to realize that SpaceX has not received $3.125 billion from NASA. 
CCtCap's $2.6 billion includes a commitment by NASA to buy six commercial crew missions
at a fixed price of $220 million per mission.  But this money is only paid out as
the missions occur (see Wikipedia, Commercial Crew Development, 2020-6-9).

Thus as of today SpaceX has received $1.255 billion from NASA for the development
of its Commercial Crew capability.  The remaining $1.320 billion will be paid out
mission by mission with the last mission and payment in 2025.

In addition to the money that NASA has paid or will be paying to SpaceX there is the
money NASA spent internally to support the effort.  There would be, I would guess,
quite a few people on NASA's payroll that have aided, inspected, supervised, and certified
SpaceX's Commercial Crew program.  To do a true comparison of the cost of Commercial
Crew (SpaceX) to the Space Shuttle program we need to know that number.

We do not need to know what SpaceX spent internally on the program since as a profit-making
enterprise it will eventually recover all of that from what it charges for this service
and thus that amount, whatever it is, is included in the costs already.

Naturally just how much the Space Shuttle program cost is a matter of dispute.  But
I will start, perhaps naively, with space.com's estimate of $209 billion for the program
which of course includes the development costs.

At 135 missions that is $1.548 billion per mission.

At 833 crew members that is $251 million per astronaut.

But the Space Shuttle did more than just send people into space, it also had a large
uplift and downmass capability.  To do a fair comparison we need to calculate how
many additional Falcon Heavy, Falcon 9, and Cargo Dragon missions would be needed
to duplicate what the Space Shuttle did.

Unfortunately SpaceX cannot duplicate everything that the Space Shuttle did since
there were times when the Space Shuttle brought back large objects that cannot be
returned on the Cargo Dragon.

It would a time consuming, but perhaps enjoyable, exercise to calculate the optimal mix
of Falcon Heavy, Falcon 9, Cargo Dragon and Crew Dragon missions to replicate most
of what the Space Shuttle accomplished, and then estimate their cost, but skipping that for
now I will crudely estimate that each Space Shuttle mission is the equivalent of
a Falcon Heavy mission plus a Crew Dragon mission.  I will further guess that for NASA
these Falcon Heavy missions would average $150 million apiece.

So at 135 missions that would be $20.3 billion for 135 Falcon Heavy missions.  Subtracting
$20.3 billion from $209 billion leaves $188.7 billon.  Dividing that by 833 crew members
gives a launch cost of $227 million per astronaut.

Since we are assuming additional Falcon Heavy, Falcon 9, and Cargo Dragons to replicate the
capability of the Space Shuttle, we need to add in the money that NASA spent to help finance
those efforts.

Money paid to SpaceX by NASA to aid in the development of Falcon 9 and Cargo Dragon.

   COTS (2006, 2011)   $ 396 million
   
So the new SpaceX total (from NASA's perspective) is $3.52 billion, paid and to be paid,
for the development of Falcon 9, Cargo Dragon, and Crew Dragon plus six full Crew Dragon
missions and including the two demo missions as development costs.

In addition we need to add in the cost of the assistance, inspection, supervision, and
certification provided by NASA employees for both the Crew Dragon and Cargo Dragon programs. 
And again I hesitate to guess what that amount is.

So noting but skipping this, six missions or twenty-six crew members total gives $135 million
per crew member launched.  At $135 million versus $227 million, this would mean the Crew Dragon
plus Falcon Heavy equivalent of the Space Shuttle costs 59 percent, or 41% less, than what
the Space Shuttle cost per crew member. 

But this doesn't seem quite right since the development cost of the SpaceX program is spread out
over only 26 crew members while the Space Shuttle program had 833.  To be fair we should assume
the same number of people launched by both programs.

But then that raises the question of what SpaceX will charge per NASA astronaut in the
future. The current $55 million per astronaut is only for the first six flights.  After
that there will be a new agreement.  What SpaceX will want to charge will no doubt depend
on their costs between now and then.  Since we don't know this yet I will do two price
estimates.  One where the charge per astronaut stays at $55 million and another where
it drops to $40 million.

Two hundred and two Crew Dragon missions at $220 million each (four astronauts at $55 million apiece)
plus $3.52 billion gives $48 billion for 833 astronauts, or $57.6 million per astronaut, or
25 percent of the cost of launching an astronaut on the Space Shuttle.

Two hundred and two Crew Dragon missions at $160 million each (four astronauts at $40 million apiece)
plus $3.52 billion gives $36 billion for 833 astronauts, or $43.0 million per astronaut, or
19 percent of the cost of launching an astronaut on the Space Shuttle.

But the Crew Dragon is designed to carry seven people.  I know that NASA hasn't certified
it for this but let us suppose that after 80 successful missions with four astronauts they
change that certification to allow for seven astronauts while the average mission cost stays
at $160 million.  Note that this would lower the additional up and down cargo mass of the
Crew Dragon but remember we have already assumed in our cost estimates additional Falcon Heavy,
Falcon 9, and Cargo Dragon missions to make up for the greater upmass and downmass of the Space
Shuttle.  In these estimates those missions have already been paid for.

So with this second attempt to guess at a plausible future, we have $3.25 billion for the
development of all of this including the first six full missions plus seventy-two $160 million
missions with four astronauts apiece plus seventy-five $160 million missions with seven astronauts
apiece giving a grand total of $26.8 billion for 833 astronauts launched, or $32.1 million per
astronaut, or 14 percent of what it cost to launch an astronaut on the Space Shuttle.

I think this last is a more reasonable estimate of the potential future cost of the Crew Dragon
versus the Space Shuttle.

[jpo234]

But the Crew Dragon is designed to carry seven people.  I know that NASA hasn't certified
it for this but let us suppose that after 80 successful missions with four astronauts they
change that certification to allow for seven astronauts while the average mission cost stays
at $160 million.

If you increase the number of astronauts by a factor of 1.75, you also have to increase the supply flights by the same factor.

[abaddon]

You didn't factor in that Commercial Crew vehicles will be able to achieve a six-month mission for their four astronauts, as opposed to two weeks for Shuttle's seven.  I'm not really sure how to account for that as prorating will underrate the impact, as there are some tasks that would require a longer than two week mission.  You should also not pretend Commerical Crew might carry seven astronauts, because it won't.  But even a straight proration of two weeks to six months will heavily outweigh that correction.

Shuttle had capabilities that CC does not.  CC has capabilities that Shuttle does not.  And none of this considers the fact we didn't retire Shuttle due to cost, we retired it due to safety.  Which seems to be getting lost in this discussion of costs.

[mandrewa]

But the Crew Dragon is designed to carry seven people.  I know that NASA hasn't certified
it for this but let us suppose that after 80 successful missions with four astronauts they
change that certification to allow for seven astronauts while the average mission cost stays
at $160 million.

If you increase the number of astronauts by a factor of 1.75, you also have to increase the supply flights by the same factor.

My first thought was that you are right and that I need to include an estimate of
the additional cargo flights needed to support three more people on the ISS.  My
second thought, which took some time to arrive, was that this is way more complicated
than that and this gets away from the point of this exercise, or in other words
estimating the relative costs of transporting people to the ISS on the Crew Dragon
versus the Space Shuttle.

The Space Shuttle did far more than just transporting people to the ISS.  In addition
to being able to carry large objects up and down, it also, crucially, often carried
a mechanical arm and a crew so that it could assemble large structures in space.

There are several possible ways to accomplish the same thing by different means
but I think that the least expensive and most versatile approach in the longer run
would be to develop a space tug supported by a fuel depot.  If such a system already
existed then rockets like the Falcon Heavy and the Vulcan could launch components
to a target zone and then a space tug would then come to retrieve them and put them
precisely next to other components so that they can self-assemble or if that wouldn't
work and human intervention was needed, the space tug would carry the component to
an occupied space station, such as possibly the ISS, where people could then do
spacewalks, as was the case with the Space Shuttle, and assemble these larger structures.

Now in the estimate I posted above I crudely guessed that it would cost $20 billion
to replicate these additional capacities of the Space Shuttle, that is other than
transporting people into space, with current technology.  If we look at the total
mass and volume lifted by the Space Shuttle it would take considerably less than
135 Falcon Heavy missions to lift the same thing.  What is missing is the ability to
manipulate those masses in space as the Space Shuttle could do.  So really we have
not yet replaced the functionality of the Space Shuttle. 

So a considerable part of the $20 billion estimate is really for developing and
building the first orbital fuel depot and its associated space tugs.

Now this $20 billion is subtracted from the overall cost of the Space Shuttle program
to reflect what it would cost to replace that capability with current technology.
All of the remaining costs of the Space Shuttle are then treated as the cost of
transporting astronauts to space.  Now the question is, is that fair?  No, not
really.  In reality there has been a significant reduction in the cost of doing
the other things that Space Shuttle did beyond transporting people to and from space.

But on the other hand, the human angle is the reason for the majority of the cost
of the Space Shuttle.  Having people on the Space Shuttle made it very costly to
change or improve or lower the cost of these other functionalities.  So although
it is a bit misleading as to where the cost savings are actually coming from, and
in particular the costs being assigned to sending astronauts to space on the Space
Shuttle are a bit high, still the overall story, the comparison of the combination
of the cost of these two things is correct.

Now the primary virtue of the Crew Dragon versus the Space Shuttle is the lower
cost and, we expect and hope, greater safety.  But the Crew Dragon can also stay
at the ISS for six months at a time.  The longest Space Shuttle mission was 17 days,
although it could have been 28 days with a second Extended Duration Orbital Pallet.
This means that as long as we mandate that there has to be a way for the crew of
the ISS to get back if something goes wrong then the Space Shuttle could not be
used to support more astonauts on six-month missions beyond the three (plus three
Russian) allowed for in the ISS as it was actually implemented.

It's a worthwhile question of what it will cost for each astronaut maintained on
the ISS but this is a separate question from what it costs to get them there.

This scenario,

So with this second attempt to guess at a plausible future, we have $3.25 billion for the
development of all of this including the first six full missions plus seventy-two $160 million
missions with four astronauts apiece plus seventy-five $160 million missions with seven astronauts
apiece giving a grand total of $26.8 billion for 833 astronauts launched, or $32.1 million per
astronaut, or 14 percent of what it cost to launch an astronaut on the Space Shuttle.

doesn't include the cost of cargo flights to supply the additional food and consumables
that three more astronauts would need, nor does it include the additional demand for
scientific payload that they would probably imply, but I don't think these costs should
be assigned to the transportation budget.  These astronauts wouldn't be sent up just
for the heck of it.  They would be there for a purpose and presumably it is that purpose that
is paying for them being there -- including the cost of their transportation -- but also
these other things.

Having said all of that -- my third take on this -- is that it is still a very interesting
question to compare the relative cost of using the Space Shuttle to maintain an astronaut
on a six-month mission to the ISS versus the Crew Dragon plus Cargo Dragon.  To answer that
question we need to include the cost of the Cargo Dragon missions.  But I will save that for
another comment.

[ncb1397]

You are making this too complicated. Commercial crew is $220 million per flight not counting development(specifically the crew dragon which is the cheaper of the two vehicles). You need two of these to replace a space shuttle flight(yes, we could go through the hoops of hypothetically suggesting 7 crew per flight, but we could also imagine putting significantly more people on Shuttle than the nominal 7 (in fact it did fly with 8 people on occasion). You also need 2-3 cargo vehicles to replace its logistics capability when paired with a MPLM. Those cargo vehicles tend to cost about $200 million per flight (it varies based on vehicle and CRS-2 prices are more opaque than CRS-1 prices). So, the Shuttle replacement cost is probably on the order of $840-$1040 million dollars. Shuttle costs were somewhat higher than that counting development, but Ken Bowersox's estimate of 20%-40% isn't terribly inaccurate (it indeed is in the ballpark, not surprising coming from the acting HEOMD AA). There are decent savings, but the savings are often exaggerated.

[MattMason]

But the Crew Dragon is designed to carry seven people.  I know that NASA hasn't certified
it for this but let us suppose that after 80 successful missions with four astronauts they
change that certification to allow for seven astronauts while the average mission cost stays
at $160 million.

Crew Dragon, by SpaceX design, could carry up to seven people.

But NASA's specific Commercial Crew specifications. with Crew Dragon used by this sole customer thus far, revised this so that no more than 4 astronauts are possible in the Dragons built for NASA. For seven astronauts, SpaceX would need to re-customize the interiors.

This article notes that NASA's change to swivel the seats and add other modifications meant that the NASA-built Crew Dragons will only support 4 people.

After SpaceX had already designed the interior layout of the Crew Dragon spacecraft, NASA decided to change the specification for the angle of the ship’s seats due to concerns about the g-forces crew members might experience during splashdown.

The change meant SpaceX had to do away with the company’s original seven-seat design for the Crew Dragon.

“With this change and the angle of the seats, we could not get seven anymore,” [Gwynne] Shotwell said. “So now we only have four seats. That was kind of a big change for us.”

https://spaceflightnow.com/2019/12/07/after-redesigns-the-finish-line-is-in-sight-for-spacexs-crew-dragon/

[Brovane]

You didn't factor in that Commercial Crew vehicles will be able to achieve a six-month mission for their four astronauts, as opposed to two weeks for Shuttle's seven.  I'm not really sure how to account for that as prorating will underrate the impact, as there are some tasks that would require a longer than two week mission.  You should also not pretend Commerical Crew might carry seven astronauts, because it won't.  But even a straight proration of two weeks to six months will heavily outweigh that correction.

Shuttle had capabilities that CC does not.  CC has capabilities that Shuttle does not.  And none of this considers the fact we didn't retire Shuttle due to cost, we retired it due to safety.  Which seems to be getting lost in this discussion of costs.

The CC also has a redundancy that the Shuttle could never had in that you will have two separate crew spacecrafts and launch vehicles. 

[Brovane]

Having said all of that -- my third take on this -- is that it is still a very interesting
question to compare the relative cost of using the Space Shuttle to maintain an astronaut
on a six-month mission to the ISS versus the Crew Dragon plus Cargo Dragon.  To answer that
question we need to include the cost of the Cargo Dragon missions.  But I will save that for
another comment.

I wanted to share this study with you in-case you had not seen it.

"An Assessment of Cost Improvements in the NASA COTS/CRS programs and implications for future NASA missions." Edgar Zapata

https://ntrs.nasa.gov/search.jsp?R=20170008895

[niwax]

You are making this too complicated. Commercial crew is $220 million per flight not counting development(specifically the crew dragon which is the cheaper of the two vehicles). You need two of these to replace a space shuttle flight(yes, we could go through the hoops of hypothetically suggesting 7 crew per flight, but we could also imagine putting significantly more people on Shuttle than the nominal 7 (in fact it did fly with 8 people on occasion). You also need 2-3 cargo vehicles to replace its logistics capability when paired with a MPLM. Those cargo vehicles tend to cost about $200 million per flight (it varies based on vehicle and CRS-2 prices are more opaque than CRS-1 prices). So, the Shuttle replacement cost is probably on the order of $840-$1040 million dollars. Shuttle costs were somewhat higher than that counting development, but Ken Bowersox's estimate of 20%-40% isn't terribly inaccurate (it indeed is in the ballpark, not surprising coming from the acting HEOMD AA). There are decent savings, but the savings are often exaggerated.

You can explore that rabbit hole in any way you want and come up with number anywhere from 1/10th to the same. If shuttle is only used to send up a new toilet seat, then it still transports many astronauts and tons of equipment. That doesn't mean it's the equivalent of four capsules. In fact, the ISS crew was never large enough that all those seats on a shutte were actually used for resupply purposes. Launching seven people to drop one off and bring one back is a fraction of the value of a docked capsule. We see the same now, a Dragon could launch 6t of cargo, but after 20 flights they've only done someting like 40t total.

[abaddon]

You are making this too complicated. Commercial crew is $220 million per flight not counting development(specifically the crew dragon which is the cheaper of the two vehicles). You need two of these to replace a space shuttle flight

Conversely, you need 12.8 shuttle flights for the 14 day duration to replace the 180 day (six month) duration.  (With the note that anything that requires a longer than two week stay is impossible).  You also have to magically walk back that Shuttle was retired for being unfixably unsafe.

[ncb1397]

You are making this too complicated. Commercial crew is $220 million per flight not counting development(specifically the crew dragon which is the cheaper of the two vehicles). You need two of these to replace a space shuttle flight

Conversely, you need 12.8 shuttle flights for the 14 day duration to replace the 180 day (six month) duration.  (With the note that anything that requires a longer than two week stay is impossible).  You also have to magically walk back that Shuttle was retired for being unfixably unsafe.

You don't know that. There were a myriad of changes introduced after Challenger and that specific issue never reoccured. There was also a myriad of changes post Columbia(all factored into Shuttle operational costs) including changes to the ET, on orbit repair and inspection and keeping shuttles on standby in the event a Shuttle was disabled on orbit or couldn't return and needed to be rescued. A lot of that is above and beyond what is being done on the follow on program.

[hplan]

You are making this too complicated. Commercial crew is $220 million per flight not counting development(specifically the crew dragon which is the cheaper of the two vehicles). You need two of these to replace a space shuttle flight

Conversely, you need 12.8 shuttle flights for the 14 day duration to replace the 180 day (six month) duration.  (With the note that anything that requires a longer than two week stay is impossible).  You also have to magically walk back that Shuttle was retired for being unfixably unsafe.

You don't know that. There were a myriad of changes introduced after Challenger and that specific issue never reoccured. There was also a myriad of changes post Columbia(all factored into Shuttle operational costs) including changes to the ET, on orbit repair and inspection and keeping shuttles on standby in the event a Shuttle was disabled on orbit or couldn't return and needed to be rescued. A lot of that is above and beyond what is being done on the follow on program.

Are you suggesting that in order to get up to the level of safety of the Space Shuttle SpaceX and Boeing ought to have heat shield repair kits for use in orbit and a spare shuttle on standby?

[abaddon]

You are making this too complicated. Commercial crew is $220 million per flight not counting development(specifically the crew dragon which is the cheaper of the two vehicles). You need two of these to replace a space shuttle flight

Conversely, you need 12.8 shuttle flights for the 14 day duration to replace the 180 day (six month) duration.  (With the note that anything that requires a longer than two week stay is impossible).  You also have to magically walk back that Shuttle was retired for being unfixably unsafe.

You don't know that. There were a myriad of changes introduced after Challenger and that specific issue never reoccured. There was also a myriad of changes post Columbia(all factored into Shuttle operational costs) including changes to the ET, on orbit repair and inspection and keeping shuttles on standby in the event a Shuttle was disabled on orbit or couldn't return and needed to be rescued. A lot of that is above and beyond what is being done on the follow on program.

You should go back in time and let everyone who shut the program down know that they were wrong.  As well as all of the folks who calculated the projected LOM/LOC at 1 in 90 at the time of the end of the program.  I am sure they will all be fascinated to hear that you think they're wrong.

[ncb1397]

You are making this too complicated. Commercial crew is $220 million per flight not counting development(specifically the crew dragon which is the cheaper of the two vehicles). You need two of these to replace a space shuttle flight

Conversely, you need 12.8 shuttle flights for the 14 day duration to replace the 180 day (six month) duration.  (With the note that anything that requires a longer than two week stay is impossible).  You also have to magically walk back that Shuttle was retired for being unfixably unsafe.

You don't know that. There were a myriad of changes introduced after Challenger and that specific issue never reoccured. There was also a myriad of changes post Columbia(all factored into Shuttle operational costs) including changes to the ET, on orbit repair and inspection and keeping shuttles on standby in the event a Shuttle was disabled on orbit or couldn't return and needed to be rescued. A lot of that is above and beyond what is being done on the follow on program.

You should go back in time and let everyone who shut the program down know that they were wrong.  As well as all of the folks who calculated the projected LOM/LOC at 1 in 90 at the time of the end of the program.  I am sure they will all be fascinated to hear that you think they're wrong.

It was more aimed at the issues being unfixable. According to one of the later probabilistic risk assessments, the 4 greatest risks to the orbiter and crew in order of severity were...

1. MMOD debris risk (1 in 277)
2. SSME failure (1 in 652)
3. ascent debris (1 in 840)
4. crew error on entry (1 in 1220)
https://ntrs.nasa.gov/archive/nasa/casi.ntrs.nasa.gov/20100005659.pdf

The ascent debris is traditionally the only thing that was looked upon as intractable due to the side mount configuration. The increased MMOD risk due to the size of the vehicle would apply to almost anything of large size, but was hardly an intractable problem (better tracking for instance would reduce risks). In fact, the current crew vehicle(s) will only operate in an environment with improved tracking - given the air force(space force?) only deemed the space fence operational in March 2020 (prior to the first crewed Commercial Crew flight).