Author Topic: Reusability effect on costs  (Read 131145 times)

Offline macpacheco

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Re: Reusability effect on costs
« Reply #20 on: 05/27/2016 05:55 AM »
Lets not forget that part of Falcon 9 reliability is due to extensive over design for reuse.
A while back there was talk that Musk's demand that a Merlin engine needed margins for dozens of flights added at least an year (I don't recall if it held the first Falcon version or the v1.0 series).
Most of that has been invested and is a sunk cost.
I don't see SpaceX going back and removing margins to reduce manufacturing costs.

But the benefit that Falcon 9 had a single launch failure that was not a design problem, but rather a QA failure caused by a bad outsourced part attests that there's a LOT of implicit advantages to the SpaceX design concept, regardless of reuse (a big implicit benefit IMO).

Then we're left with added costs to recover birds:
1 - Maintaining ASDS + entourage (tug/support ship/personnel) and the ground LZ
2 - ground transportation cost from port to hangar / LZ to hangar
3 - costs to re qualify the first few recovered boosters until they're confident they nailed the process, consumables (reapplying SPAM, re painting)
4 - Future design changes to improve landing odds and improve the conditions of toasty re-entries like JCSAT booster.

Bottom line is SpaceX is already incurring most of those costs without any payback yet, and Musk seems OK with that.
There are way too many variables to allow us to estimate the costs (with useful accuracy) moving forward.
I think it would be fair to make the Tesla -> SpaceX analogy that:
Falcon 1 was a prototype
Falcon 9 first gen was like the Tesla Roadster
Falcon 9 v1.1 and full thrust was like the Tesla Model S
but the end game are the Methalox rockets which are still in the drawing board, and pursuing reuse right now is providing ultra valuable data to enable the next generation rockets to be fully reusable from the get go. Those are like the Model 3 (high volume car).

The engineer in me only cares that SpaceX doesn't go bankrupt until they deliver fully MetaLox rockets. Cost details matter very little until then. The extra ISP afforded by MetaLox allows SpaceX to do stuff that's just impossible today, like standard boostback / gentler re-entry burns (if those are actually needed).
« Last Edit: 05/27/2016 05:58 AM by macpacheco »
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Offline Ludus

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Re: Reusability effect on costs
« Reply #21 on: 05/28/2016 03:50 AM »
If you assume reuse is completely successful as planned, the marginal cost of a launch would drop immediately and dramatically. Doing a launch with a reused core that's already been written off would cost a small fraction of using a new core. The difference between the reuse marginal cost and the reuse price would still have to contribute as much to the rest of SpaceX balance sheet as a new core launch. Otherwise they're losing money. That still allows space for both significant price cuts and bigger profits.

The big issue is how quickly can SpaceX repurpose it's complex, expensive capacity to build rockets (fixed cost) to take advance of the reuse. This is happening at a point that SpaceX has a big backlog in it's manifest and is just starting to ramp up production of cores. If they can earn as much or more per launch as they would have using a new core, they can work their way through the manifest faster while offering cuts in their already market leading prices (and capturing more business) while still covering fixed costs. They have to build proportionately more second stages in a period where an increasing number of launches are core reuse. They have to adjust the ramp up of their booster core production to match the reuse rate increase.

Because marginal internal costs for reused core launches would be MUCH lower, SpaceX could afford an increasing number of launches for internal purposes like the Internet Constellation or Red Dragons.

Offline Nibb31

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Re: Reusability effect on costs
« Reply #22 on: 05/28/2016 07:08 AM »
If you assume reuse is completely successful as planned, the marginal cost of a launch would drop immediately and dramatically. Doing a launch with a reused core that's already been written off would cost a small fraction of using a new core. The difference between the reuse marginal cost and the reuse price would still have to contribute as much to the rest of SpaceX balance sheet as a new core launch. Otherwise they're losing money.

The first stage hardware is only a small part of the cost of the launch service. There are many complex operations involved in launching a rocket: the logistics, the infrastructure, payload integration, stacking, fueling, mission control, pre-launch and post-launch operations, as well as all the administrative overhead and the R&D. The biggest center of cost is the payroll for all the people who do all that work, and none of that is affected by core reuse.

Nobody seriously expects SpaceX to save more that 20% in costs through reusing the 1st stage.

Quote
That still allows space for both significant price cuts and bigger profits.

It's one or the other really. SpaceX is already the cheapest shop in town with a growing backlog. They have nothing to gain by cutting prices.

In fact, if they want their Mars plans to come into fruition, they are going to need deeper pockets, because nobody else is going to pay for them. So their best option would be not to cut prices and to use any cost savings to pay for Musk's expensive hobby.

I suspect that whether the core is reused or not will be transparent to the user, just like you don't get the flight history of a Boeing 737 when you book a flight as a passenger. I don't see them handing out discounts for pre-flown boosters. After all, customers don't buy rockets, they buy a launch service.

SpaceX will likely be offering a service to put a given payload into a given orbit for a given price, which would be calculated based on the total dV cost. Planning the trajectory, operating the launch, recovery, maintenance, fleet management, etc... is their job and those internal costs will be spread over the number of launches that they expect to get out of the hardware, just like any other transportation service.
« Last Edit: 05/28/2016 07:24 AM by Nibb31 »

Offline guckyfan

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Re: Reusability effect on costs
« Reply #23 on: 05/28/2016 09:12 AM »
Nobody seriously expects SpaceX to save more that 20% in costs through reusing the 1st stage.

Except SpaceX perhaps. They are talking about launch prices in the 40 million $ range which would be over 30% price cut and we can safely assume their profit in $, not in % will remain at least the same per launch, or else they would cut less.

Offline Nibb31

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Re: Reusability effect on costs
« Reply #24 on: 05/28/2016 09:37 AM »
Nobody seriously expects SpaceX to save more that 20% in costs through reusing the 1st stage.

Except SpaceX perhaps. They are talking about launch prices in the 40 million $ range which would be over 30% price cut and we can safely assume their profit in $, not in % will remain at least the same per launch, or else they would cut less.

Which assumes that a Falcon 9 first stage alone costs over $20 million to make and that the rest of the rocket hardware, infrastructure costs, R&D, personnel, logistics, operations, account for less than 60% of the total cost.

I find that cost structure hard to believe.

Experience show that you've got to take a lot of the optimistic PR that comes out of SpaceX and Musk's twitter account with a pinch of salt.

Offline Ikarie XB-1

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Re: Reusability effect on costs
« Reply #25 on: 05/28/2016 10:35 AM »
Elon reasons from first principles and some of his statements are also reduced to first principles. Obviously, even if S1 was rendered free as in beer, cost of launch wouldn't drop even to one half, let alone by an order of magnitude. It's just that w/o stage reuse, there's not even a path towards substantially lowering costs. I find it hard to believe that building S1s in California and then qualifying them in Texas is that cheap - even with vertical integration and in startup mode. Returned cores should soon enough require limited checkup/refurb in known spots before being flight ready.

I believe the notional 30% price reduction fully preserves (if not increases) SpaceX's margins in $ terms. That implies through reuse their internal costs drop by at least $19m, which means S1 must cost somewhat more than that to amortise initial mfg costs. A good indication of internal S1 costs from factory to pad. R&D costs are largely independent on whether you build new cores or reuse existing ones - in either case they had to be designed first.

Also interesting that they're spending effort to reuse the relatively cheap fairings. Could be either a good exercise or those couple of million $ make up a significant enough portion of internal costs of launch - in post S1 reuse scenario.

Also Jurvetson's 'financial porn' comments could be understood as a fact that SpaceX would be doing fine with reasonable margins flying expendable as they are, but once reuse enters the picture, their margins in % terms will give Apple a blush...
« Last Edit: 05/28/2016 10:46 AM by Ikarie XB-1 »

Online AncientU

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Re: Reusability effect on costs
« Reply #26 on: 05/28/2016 12:29 PM »
If you assume reuse is completely successful as planned, the marginal cost of a launch would drop immediately and dramatically. Doing a launch with a reused core that's already been written off would cost a small fraction of using a new core. The difference between the reuse marginal cost and the reuse price would still have to contribute as much to the rest of SpaceX balance sheet as a new core launch. Otherwise they're losing money.

The first stage hardware is only a small part of the cost of the launch service. There are many complex operations involved in launching a rocket: the logistics, the infrastructure, payload integration, stacking, fueling, mission control, pre-launch and post-launch operations, as well as all the administrative overhead and the R&D. The biggest center of cost is the payroll for all the people who do all that work, and none of that is affected by core reuse.

Nobody seriously expects SpaceX to save more that 20% in costs through reusing the 1st stage.

Quote
That still allows space for both significant price cuts and bigger profits.

It's one or the other really. SpaceX is already the cheapest shop in town with a growing backlog. They have nothing to gain by cutting prices.

In fact, if they want their Mars plans to come into fruition, they are going to need deeper pockets, because nobody else is going to pay for them. So their best option would be not to cut prices and to use any cost savings to pay for Musk's expensive hobby.

<snip>

Taking the three bolded statements in order:
1) The $19M reduction advertised by GS indicates that first stage cost minus retrieval/refurbishment equals that figure.  Assuming rework costs are $3-5M, the first stage hardware costs are $22-24M -- let's use $24M (40% or so of the launch price).  The first stage is quoted at 75% of the F9 hardware costs.  Entire F9 would then cost $32M.  This leaves $30M-ish for all other operations plus profit.
2) Gwynne Shotwell does, and she's not nobody.
3) In someone else's world, the best option would be to not cut prices, but this is Elon Musk's world.  He has declared that cutting the cost to orbit is why SpaceX was founded. He could already be charging significantly more per launch and be competitive -- but the fact that he is not doing that is an important data point informing against your 'best option.' 

By the way, his expensive hobby happens to be NASA's stated goal for the last few decades.  And I think they will finally have an affordable ride to reach that goal.
« Last Edit: 05/28/2016 12:54 PM by AncientU »
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Offline AC in NC

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Re: Reusability effect on costs
« Reply #27 on: 05/28/2016 08:00 PM »
The first stage hardware is only a small part of the cost of the launch service. There are many complex operations involved in launching a rocket: the logistics, the infrastructure, payload integration, stacking, fueling, mission control, pre-launch and post-launch operations, as well as all the administrative overhead and the R&D. The biggest center of cost is the payroll for all the people who do all that work, and none of that is affected by core reuse.

Nobody seriously expects SpaceX to save more that 20% in costs through reusing the 1st stage.

This is a good point but I suggest there's a flaw with the conclusion you are trying to draw.

1) As is expressed above, the cost of hardware is not a small part.  If it were the case for reuse would be greatly reduced.  Hardware is a significant cost.

2) True there are many other costs however absent the extreme hypothetical that SpaceX contracts for everything launch related on a mission by mission basis, most of those costs are fixed.  The question is what are the marginal costs associated with a launch and how much can those marginal costs be driven down.

3) The fixed costs would be amortized across the yearly launches and from an accounting perspective you would be able to calculate profit for each launch.

4) So I think the proper articulation of the benchmark against which to compare hardware costs would be variable costs per launch.  Fuel, Refurb, Replacement Parts, delta Processing and Handling, range related costs, rentals, contract labor, allocation of additional labor required by increase launch cadence,.

5) Elon stated 100x reduction.  While I don't read that statement too literally, I do think it suggests that a very large reduction is possible.  Let me suggest it would be something on the order of Elon being able to purchase a launch pre-SpaceX or from SpaceX for market price vs. the marginal cost to SpaceX to let Elon give away a launch for free.
 


« Last Edit: 05/28/2016 08:58 PM by AC in NC »

Online AncientU

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Re: Reusability effect on costs
« Reply #28 on: 05/28/2016 09:47 PM »
Once first stage reuse with minimal refurbishment becomes standard practice, two major reductions are still possible -- build reusable second stage/fairing and increase launch rate/efficiency.  The latter has been discussed at length with 1-2 hour roll-out to launch, automated roll-out, no static fire in future, etc.  Doubling the launch rate with same ground ops crew halves the per launch cost.  The former is postponed except for fairing recovery... but it will resurface again (maybe in 1-2 years).  Fairing recovery seems incongruous until you realize that cost, though small, is seen as significant down the road... not a good sign for those who believe that there is little cost reduction possible from this point forward.

It is possible to get to $20-30M on this path in next few years.
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Online oldAtlas_Eguy

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Re: Reusability effect on costs
« Reply #29 on: 05/29/2016 01:15 AM »
When I look at the cost of F9 operations optimisticly but with a spreadsheet backing up my estimations I do not see costs (internal to SpaceX and no -profit) getting as low as $20M. My lowest number for costs (not price) [full reusability] is ~$23M with a price of ~$30M. Note this price is also a profit reduction per launch ($7M of profit vs current). But the real shocker here is that FH could have as low of a cost (not price) of $30M and a price of $40M. While that $23M for F9 could be shaved down as much as $3M (refurbishment cost 0) the FH would see a reduction of $9M making an FH cost (not price) nearly the same as an F9 per launch. Litterally just $2M different even if the manufacturing costs are amortized accross 20 launches.

On another note is that once SpaceX figures out what their costs are for reuse they could get to the "it does not matter if it is launch #1 or #20 the price is the same". In this scenario, it takes only 2 succesfull flights of a booster to break even with all costs. If the average is 20 flights except the very infrequent failure that would cause the booster to not be reused if recovered or not recovered SpaceX will not have many cases if any where they don't break even on costs for a booster. Once SpaceX is at this point then the all flights have same price and that price is the used booster price. SpaceX sacrifices $1-4M [20 down to 5 flights per booster] in profit, maybe. They could have reduced their costs for the reuse that increased their profit to equal the amortization charge for manufacturing costs.

Offline Ikarie XB-1

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Re: Reusability effect on costs
« Reply #30 on: 05/29/2016 02:50 AM »
I like how they aim to standardise on a single GTO launch/landing trajectory, regardless of payload flown. This should commoditise their operations to a degree and could lower per mission NRE costs. The same trick could probably work for S2 as well, should they ballasted payloads for nominal mass and always target the same orbital parameters. Clearly it's more valuable to customise the S2 trajectory to minimise sat's final delta-V to GTO than it is to save a bit of launch costs. Could 2~3 standard flight profiles to choose from do the trick?

Also, I imagine the number of different payload interfaces required by different sat buses is finite and not very high. Once they've been through most, isn't the initial NRE and effort amortised? From that point on, it's just the variable costs.
« Last Edit: 05/29/2016 02:53 AM by Ikarie XB-1 »

Offline Nilof

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Re: Reusability effect on costs
« Reply #31 on: 05/29/2016 05:04 AM »
I think a lot of people here are forgetting that SpaceX is vertically integrated. They do not have significant marginal costs associated with making new Falcon 9 rockets, so calculations of the internal cost of a booster are mostly meaningless unless you consider it as an alternative cost. SpaceX has mostly fixed costs due to keeping their workforce employed, and the marginal costs that they do have (such as range use) would be mostly independent of reuse.

Reuse isn't really a way to reduce costs, it is a way to increase the launch rate without increasing the size of the production line. A booster doesn't get any cheaper because you reuse it if the fixed costs and the launch rate stay constant. You need to take advantage of the new capabilities of your launcher.

Regarding the cost of the F9/FH variants, I interpret the F9 cost as the price for a new rocket, but which SpaceX is allowed to use in their development program. In other words, the cost is reduced because it helps SpaceX to introduce reuse earlier, which allows them to expand their launch rates in the future making this a direct investment in their growth from their perspective. From an investor's perspective, company growth is a form of profit, so reduced cashflow due to investments in growth are reasonable.

For FH it could be either way, but I don't expect SX to ever fly the FH without side core RTLS because of how early the boosters separate.
For a variable Isp spacecraft running at constant power and constant acceleration, the mass ratio is linear in delta-v.   Δv = ve0(MR-1). Or equivalently: Δv = vef PMF. Also, this is energy-optimal for a fixed delta-v and mass ratio.

Offline Geron

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Re: Reusability effect on costs
« Reply #32 on: 05/29/2016 07:32 AM »
What I think a lot of people are missing is that SpaceX has ambitions beyond building first stages.

I believe that when they master first stage reuse and have an armada of falcon 9 and heavy first stages, they will not leave their production lines idle. Instead they will either be building payloads in the form of satellites or dragons; or habitats; cargo; isru infrastructure; and/or methalox rocket parts.

The falcon 9 rocket line is a means to an end. When I visited SpaceX I was told that the vision is to have many many launch sites launching almost daily. They plan to get their with methalox rockets as they are easier to reuse.

Their track record for successful landings with falcon 9 is looking better every month, but coking may be an issue with multiple reuses with rp 1.

Online AncientU

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Re: Reusability effect on costs
« Reply #33 on: 05/29/2016 11:46 AM »
When I look at the cost of F9 operations optimisticly but with a spreadsheet backing up my estimations I do not see costs (internal to SpaceX and no -profit) getting as low as $20M. My lowest number for costs (not price) [full reusability] is ~$23M with a price of ~$30M. Note this price is also a profit reduction per launch ($7M of profit vs current). But the real shocker here is that FH could have as low of a cost (not price) of $30M and a price of $40M. While that $23M for F9 could be shaved down as much as $3M (refurbishment cost 0) the FH would see a reduction of $9M making an FH cost (not price) nearly the same as an F9 per launch. Litterally just $2M different even if the manufacturing costs are amortized accross 20 launches.

On another note is that once SpaceX figures out what their costs are for reuse they could get to the "it does not matter if it is launch #1 or #20 the price is the same". In this scenario, it takes only 2 succesfull flights of a booster to break even with all costs. If the average is 20 flights except the very infrequent failure that would cause the booster to not be reused if recovered or not recovered SpaceX will not have many cases if any where they don't break even on costs for a booster. Once SpaceX is at this point then the all flights have same price and that price is the used booster price. SpaceX sacrifices $1-4M [20 down to 5 flights per booster] in profit, maybe. They could have reduced their costs for the reuse that increased their profit to equal the amortization charge for manufacturing costs.

Would you be willing to share your spreadsheets? (Maybe you have on another thread, so a link would be great.) Would be very interested in seeing what factor(s) you find to be holding the cost/price at this level -- I agree that this is achievable, but not a floor.  Also, is this $23M figure for RTLS or down range recovery?
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Offline dante2308

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Re: Reusability effect on costs
« Reply #34 on: 05/30/2016 12:30 AM »
I think a lot of people here are forgetting that SpaceX is vertically integrated. They do not have significant marginal costs associated with making new Falcon 9 rockets, so calculations of the internal cost of a booster are mostly meaningless unless you consider it as an alternative cost. SpaceX has mostly fixed costs due to keeping their workforce employed, and the marginal costs that they do have (such as range use) would be mostly independent of reuse.

Reuse isn't really a way to reduce costs, it is a way to increase the launch rate without increasing the size of the production line. A booster doesn't get any cheaper because you reuse it if the fixed costs and the launch rate stay constant. You need to take advantage of the new capabilities of your launcher.

Regarding the cost of the F9/FH variants, I interpret the F9 cost as the price for a new rocket, but which SpaceX is allowed to use in their development program. In other words, the cost is reduced because it helps SpaceX to introduce reuse earlier, which allows them to expand their launch rates in the future making this a direct investment in their growth from their perspective. From an investor's perspective, company growth is a form of profit, so reduced cashflow due to investments in growth are reasonable.

For FH it could be either way, but I don't expect SX to ever fly the FH without side core RTLS because of how early the boosters separate.

I think this overstates a few things including how vertically integrated they are.

1) Employment is not a fixed cost. People can be laid off or hired as needed. In SpaceX's case, they will likely be re-tasked where possible to other funded ventures such as CC or satellites with no real bearing on the cost per rocket.

2) As long as SpaceX is reusing only the first stage, they will need to produce fresh second stages for every launch.

3) They do in fact have suppliers, material costs, and transportation costs.

Offline dante2308

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Re: Reusability effect on costs
« Reply #35 on: 05/30/2016 12:35 AM »
I don't know how much it has been stated, but the real issue I'm seeing is with second stage reuse being tied to Mars transportation. I'm not quite understanding the business case for reusing an interplanetary stage that makes 4 trips per decade (assuming Mars launch windows) unless it also doubles as a well-used transportation system to Earth orbit. However Elon is adamant that the Falcon line will take care of the satellite market for the foreseeable future and has indicated that the second state reuse plans aren't compatible with the Falcon rocket architecture.

I attached a porkchop plot showing the delta-v space for Mars as the sum of hyperbolic excess velocities. Sorry, I didn't spend any time making it pretty. The point the plot makes is simply that the Mars windows are not really voluntary.
« Last Edit: 05/30/2016 12:50 AM by dante2308 »

Offline AC in NC

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Re: Reusability effect on costs
« Reply #36 on: 05/30/2016 12:39 AM »
I think this overstates a few things including how vertically integrated they are.

1) Employment is not a fixed cost. People can be laid off or hired as needed. In SpaceX's case, they will likely be re-tasked where possible to other funded ventures such as CC or satellites with no real bearing on the cost per rocket.

2) As long as SpaceX is reusing only the first stage, they will need to produce fresh second stages for every launch.

3) They do in fact have suppliers, material costs, and transportation costs.

These points are true but the point remains that the variable costs of an additional launch are the comparison point for  reuse savings calculations.

1)  If the are reusing more and the cannot layoff (I don't think they do the between launches) or need to hire due to increased cadence, that is a variable cost in the short term.

2)  2nd Stages are a variable cost until they get to reuse.

3)  Suppliers, material, and transportation are only variable to the extent they are variable.  If they have to rent Range Resources that's variable.  If they need more SPAM, that's variable.  If they don't integrate transportation, that's variable except for gas and maintenance.
« Last Edit: 05/30/2016 12:41 AM by AC in NC »

Offline dante2308

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Re: Reusability effect on costs
« Reply #37 on: 05/30/2016 12:47 AM »
I think this overstates a few things including how vertically integrated they are.

1) Employment is not a fixed cost. People can be laid off or hired as needed. In SpaceX's case, they will likely be re-tasked where possible to other funded ventures such as CC or satellites with no real bearing on the cost per rocket.

2) As long as SpaceX is reusing only the first stage, they will need to produce fresh second stages for every launch.

3) They do in fact have suppliers, material costs, and transportation costs.

These points are true but the point remains that the variable costs of an additional launch are the comparison point for  reuse savings calculations.

1)  If the are reusing more and the cannot layoff (I don't think they do the between launches) or need to hire due to increased cadence, that is a variable cost in the short term.

2)  2nd Stages are a variable cost until they get to reuse.

3)  Suppliers, material, and transportation are only variable to the extent they are variable.  If they have to rent Range Resources that's variable.  If they need more SPAM, that's variable.  If they don't integrate transportation, that's variable except for gas and maintenance.

Everything you're saying is true. I think that SpaceX will naturally have to reorganize their entire organization to optimize around reuse eventually anyway and I think that means that they will try to eliminate fixed costs where they have the luxury to even if they lose some of their vertical integration. That should be on the table at least.
« Last Edit: 05/30/2016 12:50 AM by dante2308 »

Offline Robotbeat

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Re: Reusability effect on costs
« Reply #38 on: 05/30/2016 01:24 AM »
I don't know how much it has been stated, but the real issue I'm seeing is with second stage reuse being tied to Mars transportation. I'm not quite understanding the business case for reusing an interplanetary stage that makes 4 trips per decade (assuming Mars launch windows) unless it also doubles as a well-used transportation system to Earth orbit. However Elon is adamant that the Falcon line will take care of the satellite market for the foreseeable future and has indicated that the second state reuse plans aren't compatible with the Falcon rocket architecture.

I attached a porkchop plot showing the delta-v space for Mars as the sum of hyperbolic excess velocities. Sorry, I didn't spend any time making it pretty. The point the plot makes is simply that the Mars windows are not really voluntary.
Realize that the interplanetary stage will be reused multiple times per each mission cycle:
1) launch
2) refuel and fire again from Earth orbit toward Mars
3) landing on Mars
4) refuel and ascent from Mars
(possible refueling in Mars orbit, perhaps not required)
5) landing on Earth

The stage has to be intact at each stage, not shedding parts that it'll need in the rest of the mission. So you ALREADY need a reusable stage (really a spacecraft, but I'll stick with your terminology) just so the architecture works, so you might as well use it again. And getting 10-15 mission cycles out of each manufactured stage makes a non-insignificant reduction in cost! ...even if it is over 2-3 decades.

...additionally, SpaceX will require the stage to do refueler duty and cargo duty. They need the stage to be capable of a lot more than 10-15 reuses in those configurations.

And yeah, the potential cost reduction of 4-5 mission cycles per decade is still important. They need the cost as low as possible in order to achieve the sub-$500k/person ticket price, and at the full swing of 80,000 people to Mars per year, they'll need that reuse just to keep up.
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Offline envy887

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Re: Reusability effect on costs
« Reply #39 on: 05/30/2016 01:49 AM »
The reusable second stage will be shuttling enormous amounts of propellent and cargo in LEO, roughly 5000 tonnes per 100 people sent to Mars. That's not feasible with disposable upper stages.

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