Henry:
See below:
Sent from my iPhone
On Apr 2, 2014, at 21:30, Henry Vanderbilt <hvanderbilt@xxxxxxxxxxxxxx> wrote:
On 4/2/2014 12:53 PM, Bill Claybaugh wrote:
Please.
Landing the first stage downrange uses 15% of the payload; flying it
back up range cost 30% of payload. Even if refurbishing and relaunch
were free, propulsive fly back will take four launches just to cost
the same as expending. Since they are not free, it is more likely to
take something between 12-24 launches for this system to cost exactly
the same as the expendable version.
Bill - The premises behind your math here are not clear to me. Could you
elaborate a bit?
Take a simple case where reuse "costs" 50% of payload. Then, if refurbishment
cost is zero and relaunch costs exactly as much as the expendable version, it takes twice
as many launches of the reusable version to make the cost of the reusable equal to the
cost of the expendable version.
Still ignoring refurbishment, if we want the reusable version to price at half
the price of the expendable version, it follows that it must fly (have an
economic lifetime of) four times (uses).
If we want it to get to 1/10th the price of the expendable version (say, $250
per pound) the we need 20 flights.
Now if refurbishment costs are very low--and Falcon 9 is in some ways a highly
operable vehicle--we might need another 10%; say 22 flights per vehicle.
But if refurbishment is costly (say 50%), then we could be looking at 40
flights to meet that price goal.
If you redo this for a rocket back first stage, you find that only near zero
refurbishment can get you $1000 per pound at the five-six mission lifetime that
the hardware might tolerate. If refurbishment is more costly (as a percentage
of the cost of a new stage) the economic lifetime for just breaking even with
the expendable quickly runs up to a dozen flights or more. Then add the risk
that the hardware is not going to tolerate even five uses.
Finally, it is unlikely that the two kinds of stages have the same launch
costs; the greater complexity of the reusable stages must impose some
additional launch processing costs. Add another 5% for that effect?
This also means that production rates will drop and so those cost
will go up.
Leaving aside refurbishment/reuse costs, the cost multiplier for lower
first-stage production rates would have to equal the number of stage uses
before reuse failed to reduce cost per launch. IE, if they fly each stage
twice, as long as each new stage costs less than double at the reduced
production rate, they're still ahead. Three flights, each stage only has to
cost less than triple at reduced production, and so on.
The issue here is that unless labor and plant are cut, overhead costs go up;
this effects the entire production line, reusable and expendable. There is
also a reliability effect, btw.
Yes, refurbishment/reuse costs can't be ignored. But lower stage production
rates really doesn't look like a show-stopper.
And then there's the customers who want to know why they should fly
on a used rocket....
I believe I've seen Elon address this somewhere - the gist was, he understands
NASA will probably insist on new stages; other customers will likely be more
flexible. The implication is discounts for used stages. I'd expect that the
first few flights on used F9R's will go for major discounts. Presumably once
the actual degree of reliability loss involved is demonstrated, the discount
would be adjusted appropriately.
Understood; the question is where the lower cost that allows the discounted
pricing is coming from: the implied refurbishment cost is near zero unless
these originally-designed-to-be-expendable stages can somehow tolerate a dozen
or so flyback missions.
Bill
$100 per pound is not achievable with this system.
I do tend to agree. I'd be quite surprised if F9 stages turn out to be
reliably reusable without major rework more than a handful of times. Even so,
if CSTS wasn't totally wrong about market elasticity, I see a reasonable chance
SpaceX can bring their F9 per-lb costs down into the high-to-mid three figures.
Which I would expect will then be revolutionary enough, as that demonstrated
growing market makes new investment in further cost reductions sensible rather
than visionary.
Henry
Bill
Sent from my iPhone
On Apr 2, 2014, at 10:49, marsbeyond@xxxxxxxxx wrote:
Kieth,
When is Skylon supposed to fly? In less than two years, SpaceX will
be using propulsive recovery to re-use the first stage, second
stage, and capsule, and their cost to LEO will drop to $100 a
pound!
Sent from my iPhone
On Apr 2, 2014, at 9:27 AM, Keith Henson <hkeithhenson@xxxxxxxxx>
wrote:
http://theenergycollective.com/keith-henson/362181/dollar-gallon-gasoline
$350 million committed so far to the Skylon engines.
Keith
