Gwynne Shotwell Interview - June 22, 2017 on The Space Show

[Jim]

Current fairing is 5.2m. You can safely assume that at least 5.2m dia second stage is okay.

No, you can't.  The current fairing halves are road transportable.

[gospacex]

Current fairing is 5.2m. You can safely assume that at least 5.2m dia second stage is okay.

No, you can't.  The current fairing halves are road transportable.

The question was "What is the largest diameter of US that could feasibly fit atop an F9/FH?"

[RotoSequence]

Current fairing is 5.2m. You can safely assume that at least 5.2m dia second stage is okay.

No, you can't.  The current fairing halves are road transportable.

The question was "What is the largest diameter of US that could feasibly fit atop an F9/FH?"

Depends if SpaceX decides to start shipping the Falcon 9 to the cape in two halves or not. 

[guckyfan]

It is a well known fact that stages can be transported by other means than road.

[Jim]

It is a well known fact that stages can be transported by other means than road.

Not Spacex stages

[Jim]

Current fairing is 5.2m. You can safely assume that at least 5.2m dia second stage is okay.

No, you can't.  The current fairing halves are road transportable.

The question was "What is the largest diameter of US that could feasibly fit atop an F9/FH?"

If it can't get to the launch site by the current means or use the existing TEL, then 5.2m does not fit "feasibly".

[guckyfan]

It is a well known fact that stages can be transported by other means than road.

Not Spacex stages

How are potential future SpaceX stages different from stages of other launch service providers that it is physically impossible to transport them by other means than road?

[MP99]

Some thoughts:

1) If they go this route, (implement Raptor on essentially the existing Falcon line), they could do so in an evolutionary rather than revolutionary way.  They could start with development of the Raptor US that would work with an existing F9 (or FH) 1st stage.  All the while continuing with flights with their existing rockets/pads.  Then introduce the new US on a test flight.  When confident, slowly transition from existing US to new US.  With multiple pads (and perhaps a new pad as someone suggested) available, they could pretty easily modify pads serially to accommodate Methane for the new US.  Following this, they could repeat this process with development of a 'Raptor 9' 1st stage.  So all in all, they could transition the existing Falcon line to be Raptor based with little or no impact to their existing flow.

OK, so here's a weird / Frankenstein thought...

Imagine an existing F9US. It has a certain LOX volume. Methalox would require a larger fuel volume than RP1. Add two cylindrical side tanks to the upper stage which add fuel volume so that it matches the requirements for the mixture ratio for Raptor.

These could be sized and positioned so that the u/s can operate with the existing TEL mechanically. This would require the side tanks to be positioned at 90 degrees to the TEL, and with a height which doesn't interfere with the existing grabber mechanism. Of course, there would still be issues with umbilicals for the new prop type, and aerodynamic charges.

One possibility is that the stage would reach orbit using just the fuel in the core tank, and then the side tanks would replenish the core tank before the GTI burn. Early runs might go through GTI in that config, with later runs dropping the side tanks before GTI to improve dry mass and increase payload.

OTOH, a reusable stage might use the additional area of the side tanks to improve the ballistic coefficient during reentry to make the thermal loads a little easier.

Cheers, Martin

[Jim]

How are potential future SpaceX stages different from stages of other launch service providers that it is physically impossible to transport them by other means than road?

SpaceX MO is road transportable stages.  That is why the first stage is so long whereas a wider diameter would be better.   Anything related to Falcon 9 is road transportable.  The vehicle and system (factory, test site and launch site) are based on road transportable.

McGegor has no substantial airport or water access.

And BFR stages are going to built at the launch site per Elon.  This eliminates the need for transport.

[meekGee]

ISTM,

The downsides to a 5.x meter RUS are 1) loss of road transportability and 2) it may need a new fairing - unless they go with a wasp-waisted connection.

Downsides to a 2m stage stretch are 1) increasing fineness and 2) TEL mods.

EITHER needs other GSE & plumbing mods.

Which is easier/cheaper?

If second stages are reusable, road transportability is a much lesser issue.  Especially if launch cadence from CA increases - you can helicopter them to Vandy, and always collect them at the cape...

Not to mention helicopter it to any boat in the LA harbor, and be in the cape a couple of weeks later.

Really a non-issue.

[meekGee]

One thing that's striking about the last few months of SpaceX ITS info/rumors is the degree to which these two things are happening simultaneously:
1) accelerating in timescale, with lots of actual work being done and
2) significantly in flux. All sorts of things which we thought or were told were true are now up in the air.

It really seems to me we're much closer to SpaceX being able to land people on Mars, including the hardware needed to do so, while also having much LESS of a firm plan than we did in September.

Grand plans are over-rated. Execution and dynamic flexibility are much better.

This is a very deep observation.

balancing reliability, launch rate, innovation, and flexibility - that's unprecedented.

[Jim]

If second stages are reusable, road transportability is a much lesser issue.  Especially if launch cadence from CA increases - you can helicopter them to Vandy, and always collect them at the cape...

Not to mention helicopter it to any boat in the LA harbor, and be in the cape a couple of weeks later.

That is not happening.  Show me a large load that regularly helicoptered over a large urban area, or any where for that matter.

[Jim]

balancing reliability, launch rate, innovation, and flexibility - that's unprecedented.

Yes, because  they have yet to achieve all of them

[Jim]

It really seems to me we're much closer to SpaceX being able to land people on Mars, including the hardware needed to do so, while also having much LESS of a firm plan than we did in September.

Actually, it is further away.

[SoulWager]

I don't see raptor replacing merlin any time soon. I think you might be able to reduce long term costs by doing it, but that would be a very long term prospect, likely another 10 years of development and certification before Merlin could be phased out in a f9 class booster.

If it does happen, I think it will be a 5 engine core, maybe 7, will be fully reusable, and will be substantially cheaper to fly than F9(can get rid of all the RP-1 and helium infrastructure). It may or may not have as big a payload capability as F9.

[punder]

Great interview, make time to hear the whole thing.

Sounds like they definitely weren't happy with the CF tank test. Imho.

She didn't say tourist, she said private customers.

Very confusing about Red Dragon. Lots of interest outside the company, but she never sounded very committed. Again imho. Tea leaves, Kremlinology etc. She certainly seems to know when to answer a question directly, and when to talk around it!

I wish David had followed up on the Raptor/F9 thing.

[punder]

It really seems to me we're much closer to SpaceX being able to land people on Mars, including the hardware needed to do so, while also having much LESS of a firm plan than we did in September.

Actually, it is further away.

Would you please elaborate on why you think so?   

[meekGee]

If second stages are reusable, road transportability is a much lesser issue.  Especially if launch cadence from CA increases - you can helicopter them to Vandy, and always collect them at the cape...

Not to mention helicopter it to any boat in the LA harbor, and be in the cape a couple of weeks later.

That is not happening.  Show me a large load that regularly helicoptered over a large urban area, or any where for that matter.

It's 5.5 miles to the ocean, and only 1.5 of that is residential. 

If you're willing to do a road-block on Hwy 105 for 5 minutes, then you have a clear path without overflying anything other than pavement.

If the stages are reusable, you only have to do it occasionally - maybe once a month or less.

A non-issue.

[neoforce]

Sounds like they definitely weren't happy with the CF tank test. Imho.

Can you give a time stamp when she said that?  I listened live and had it drop out for a few min, so I might have missed something. But I thought I did hear her talk about carbon fiber and the test tank and I didn't take away that they weren't happy. I thought she was just avoiding definitive statements about how testing has gone, that more work was required, but that they still would work toward CF tanks.

[gospacex]

Current fairing is 5.2m. You can safely assume that at least 5.2m dia second stage is okay.

No, you can't.  The current fairing halves are road transportable.

The question was "What is the largest diameter of US that could feasibly fit atop an F9/FH?"

If it can't get to the launch site by the current means or use the existing TEL, then 5.2m does not fit "feasibly".

I interpreted the question as asking about aero loads and the like. For 5.2m US, aero loads don't change at all. So 5.2m US is feasible in that sense.

You are right that 5.2m is not road transportable, I did not imply it is. I agree that moving 5.2m out of Hawthorne factory is very difficult bordering on impossible, and if SpaceX would want to make them, it will do it elsewhere.