Second Stage Stretch

[Lars-J]

Instead of stretching the 2nd stage or introducing the Raptor Vac.

Can a new composite 2nd stage of 5.2 meter diameter with a Merlin Vac and the same length as the current stage make sense for the Falcon Heavy in the future?

No because it raises the costs of launching a Falcon, rather than lowering them.

My previous post was about upgrading the Falcon Heavy upper stage. Nothing was said about the Falcon 9.

Why would a more capable Falcon Heavy upper stage increase the cost of the price per kilogram going up?

If the stage is more expensive, of course. Do you think Raptor development and individual cost would be trivial? Or the production line (and transport) for 5.2m tanks?

To bring down costs you need a *cheaper* stage, not a higher performance one.

F9 and FH are already capable enough for all current and near future payloads. So again... why?

[Lars-J]

F9 and FH are already capable enough for all current and near future payloads. So again... why?

Not so near future. Moon, Mars, other deep space.  Even if ITS is operational, there might be payloads that don't require it. And the USAF might have ideas that are beyond DH ability.

Your 'near future' doesn't mean the same as my 'near future'.

And the less we hear about mythical super heavy USAF payloads, the better. That myth needs to die. They aren't going to spend billions on something that lacks a launcher without contracting for such a development. And they have not.

EDIT: D'oh, I misread your "not so near future". Sorry.

[Nomadd]

F9 and FH are already capable enough for all current and near future payloads. So again... why?

Not so near future. Moon, Mars, other deep space.  Even if ITS is operational, there might be payloads that don't require it. And the USAF might have ideas that are beyond DH ability.

Your 'near future' doesn't mean the same as my 'near future'.

And the less we hear about mythical super heavy USAF payloads, the better. That myth needs to die. They aren't going to spend billions on something that lacks a launcher without contracting for such a development. And they have not.

I guess you don't understand the phrase "not so near future. And there's a possibility that the Air Force did't issue a contract for intial work on a methane upper stage for the Falcon just to throw money away.

[Jim]

I guess you don't understand the phrase "not so near future. And there's a possibility that the Air Force did't issue a contract for intial work on a methane upper stage for the Falcon just to throw money away.

There is no possibility.  It was for an engine and no "upper stage" work was done.  There is no real  payload that needs it.  You would see an equivalent contract for ULA if it were real.

[envy887]

Instead of stretching the 2nd stage or introducing the Raptor Vac.

Can a new composite 2nd stage of 5.2 meter diameter with a Merlin Vac and the same length as the current stage make sense for the Falcon Heavy in the future?

No because it raises the costs of launching a Falcon, rather than lowering them.

My previous post was about upgrading the Falcon Heavy upper stage. Nothing was said about the Falcon 9.

Why would a more capable Falcon Heavy upper stage increase the cost of the price per kilogram going up?

If the stage is more expensive, of course. Do you think Raptor development and individual cost would be trivial? Or the production line (and transport) for 5.2m tanks?

To bring down costs you need a *cheaper* stage, not a higher performance one.

F9 and FH are already capable enough for all current and near future payloads. So again... why?

To be fair, he specified a kerolox stage with MVac. However, MVac is too small for a bigger stage to make much of a difference. The upper stage ends up having to fly a less efficient lofted profile.

The main advantage of a bigger US is enabling booster recovery on otherwise expendable missions, or enabling US recovery. I'm not sure there are any payloads that currently require expending the center core on FH - would have to be >15t to GTO or >10t to TLI.

[Lar]

Do we need a thread retitle? I think people are coming at this from different angles. I know we've discussed this topic over and over... the OP should go find the prior threads and modify the header... That might cut down on a bit of the frustration from some of the older hands at rehashing this again.

And everyone else should be excellent to each other. As usual.

Thank you,
that one guy who got made mod that one time

[docmordrid]

I guess you don't understand the phrase "not so near future. And there's a possibility that the Air Force did't issue a contract for intial work on a methane upper stage for the Falcon just to throw money away.

There is no possibility.  It was for an engine and no "upper stage" work was done.  There is no real  payload that needs it.  You would see an equivalent contract for ULA if it were real.

USAF apparently gave ULA money for ACES, and they subcontracted XCOR for engine development.

http://spaceref.biz/company/usaf-awards-ula-and-xcor-rocket-contract-for-upper-stage-propulsion.html

[macpacheco]

Instead of stretching the 2nd stage or introducing the Raptor Vac.

Can a new composite 2nd stage of 5.2 meter diameter with a Merlin Vac and the same length as the current stage make sense for the Falcon Heavy in the future?

No because it raises the costs of launching a Falcon, rather than lowering them.

My previous post was about upgrading the Falcon Heavy upper stage. Nothing was said about the Falcon 9.

Why would a more capable Falcon Heavy upper stage increase the cost of the price per kilogram going up?

Adding more capacity only increase costs unless that extra capability is used often.
Think about the economics of the rocket instead. Price per Kg needs to be computed over the missions the rocket is expected to actually fly.
Far more important to reduce the cost per flight instead.