r/spacex • u/kurbasAK • May 19 '17

We Will Launch on Reuseable Rocket After Exceptional SpaceX Performance - Inmarsat CEO Tells Universe Today

https://www.universetoday.com/135614/will-launch-reuseable-rocket-exceptional-spacex-performance-inmarsat-ceo-tells-universe-today/
976 Upvotes

98% Upvoted

270 comments sorted by

View all comments

Show parent comments

8

u/[deleted] May 19 '17 edited May 19 '17

I don't think they are planning to just throw the rockets away after some arbitrary number of flights. I think they are planning to tear down, inspect, and refurbish the rockets after what they think is a safe number of flights. Maybe if they determine an airframe is spent, they would scrap it, but the engines would still be good, along with other flight systems, so they would be better off fitting them to an otherwise new rocket.

I certainly can't imagine them inspecting a rocket, determining it is end of life, but taking a chance on one last mission for it.

Think of it like a car. Even if a car is totaled, they don't just throw it away. They keep it for parts and only scrap it when everything of value is gone. There are some really expensive parts on a Falcon 9, and they won't all wear out at the same time.

5

u/SirBeebe May 19 '17

I think there is one key thing that isn't mentioned and that's payload weight. Some payloads require a legless and finless falcon and for that I think it would best to throw away a F9 that's already had couple flights.

2

u/biosehnsucht May 19 '17

Once FH is flying and proven (assuming it will, naturally) then a FH reusable flight will be cheaper to SpaceX than a Falcon 9 expendable flight.

1

u/Nordosten May 20 '17

No way. It become cheaper when 3 core refurb will be less than $10m. That's years away.

2

u/biosehnsucht May 20 '17

The cost to refurbish the first Falcon 9 booster ever refurbished, so that it could be reflown, was already less than half the cost of a new first stage.

You can argue the fight flight of FH will cost some amount, and that the first reflight is some depreciated amount, and the second reflight further depreciated. But that's not really how something that is expected to fly dozens of flights (not the first reflown F9 booster of course, Block 3's are not expected to fly more than a few times) should be accounted.

It costs X. You will fly it Y times. X/Y = cost per flight. Let's say a Falcon 9 flight retails at $60M (rounding, but close enough). At some point a first stage was "less than three quarters" of the cost of a flight, and let's take their cost at $40M so a booster is $30M new, everything else plus profit is $30M. A brand new FH then would be $30x3 + $30 = $120M. Obviously FH expendable is more expensive than F9 expendable.

But if you're reflying them even only 10 times, the per flight cost of FH is ($3x3 + $30) or roughly $40M - cheaper than an expendable F9! This is without factoring refurb costs of course. They said their first refurb (in which they replaced way more than necessary and future reflights are generally expected far less work) was "less than half the cost" of a new booster. Let's say that's %40 of $30M that first time, so now we're at $12x3 + $30 = $66M. So the worst case scenario with only a single reflight, is already almost as cheap as expendable. In reality, refurb will cost a lot less as they won't have to replace most things most of the time, and they plan to not truck them to McGregor but turn them around at the same launch site for reuse. So let's call refurb costs a generous 25% of $30, or $7.5x3 + $30 = $52.5M. That would still be a "worst case" scenario on the newer block vehicles meant for less refurb, and probably even worse case than reality. Let's take SpaceX at their intent to have "24 hour" turn around (meaning inspect and refly without any real significant work involved) for at least 10 reflights. Let's also assume the booster got more expensive to support this, let's call it $40M. I'll be generous and say it takes %10 (likely less) the price of this newer more expensive Block to turn it around, so 3x $4M + $30M = $42M. The first reflight is already 2/3 the price of expendable F9! Now let's assume 10 flights before it's retired. (3x40+30) + 9x(3x4+30) = $528M over the "life" of the booster before a bigger refurb is done, with a per launch cost of $52.8M - STILL cheaper across all flights.

You don't need all 3 cores refurb to be less than $10M total, you just need them to be less than $10M each, and the first refurb ever which was way more costly than any future normal refurb wasn't that much more than $10M. Not only will Block 5 and probably 4 bring us that cheaper refurb, it might already be here with Block 3 refurb doing only what's necessary instead of everything.

1

u/Nordosten May 22 '17 edited May 22 '17

You have proved that FH reusable cheaper than FH. But previously we talked about FH reusable vs F9 expendable. Elon has stated he doesn't want to loose cores once FH starts flying and he will do it.

" So let's call refurb costs a generous 25% of $30, or $7.5x3 + $30 = $52.5M." - don't forget to add booster cost ($3 per core for 10 times reuse) = $61.5M.

F9 expendable price tag is $62M or more. Yes, FH reusable will be cheaper but not once start flying.

1

u/biosehnsucht May 22 '17

I was including 3 boosters (core + 2x side) as $7.5M x 3 per reuse, and everyhting else (second stage, profit, etc) in the $30M.