Quote from: Rocket Surgeon on 04/28/2015 06:55 am The question this is used to ask is whether or not the Vulcan should boost back or use the modular recovery and the conclusion is that the Vulcan should use modular recovery as it pays back quicker, .... problem is in reality, the Falcon 9 is already a very different beast. Unless they have a much more in depth analysis than this spreadsheet (I sure hope they do) then the mistake is comparing apples-to-apples, we really have apples-to-oranges.Agreed, I get the feeling that this is more of a justification as why ULA have gone this route with reusability - and for the Vulcan, it is the best route to take, than any evidence comparing economics tit-for-tat with F9 directly. Heck, since nobody has access to all the numbers at work, it's going to take a good few years of both LVs working side by side for us to gain a comprehensive understanding of how the two LV's reusability methods pan out dime for dime. Prolepsis isn't all that reliable yet.
The question this is used to ask is whether or not the Vulcan should boost back or use the modular recovery and the conclusion is that the Vulcan should use modular recovery as it pays back quicker, .... problem is in reality, the Falcon 9 is already a very different beast. Unless they have a much more in depth analysis than this spreadsheet (I sure hope they do) then the mistake is comparing apples-to-apples, we really have apples-to-oranges.
The reality is without a different engine than either of the two choices ULA currently has, or adding an additional engine just for boost back, you simply can't do boost back with Vulcan anyway. Too much thrust. So even if you could make the numbers work, it wouldn't apply anyway. With the choices they have, separating the engine module is the only option they have for reuse.
Quote from: The Amazing Catstronaut on 04/28/2015 08:33 amQuote from: Rocket Surgeon on 04/28/2015 06:55 am The question this is used to ask is whether or not the Vulcan should boost back or use the modular recovery and the conclusion is that the Vulcan should use modular recovery as it pays back quicker, .... problem is in reality, the Falcon 9 is already a very different beast. Unless they have a much more in depth analysis than this spreadsheet (I sure hope they do) then the mistake is comparing apples-to-apples, we really have apples-to-oranges.Agreed, I get the feeling that this is more of a justification as why ULA have gone this route with reusability - and for the Vulcan, it is the best route to take, than any evidence comparing economics tit-for-tat with F9 directly. Heck, since nobody has access to all the numbers at work, it's going to take a good few years of both LVs working side by side for us to gain a comprehensive understanding of how the two LV's reusability methods pan out dime for dime. Prolepsis isn't all that reliable yet.The reality is without a different engine than either of the two choices ULA currently has, or adding an additional engine just for boost back, you simply can't do boost back with Vulcan anyway. Too much thrust. So even if you could make the numbers work, it wouldn't apply anyway. With the choices they have, separating the engine module is the only option they have for reuse.
Ah, but the issue there is what do you use for the Vulcan number?
Quote from: Rocket Surgeon on 04/28/2015 06:55 amAh, but the issue there is what do you use for the Vulcan number?I asked Dr.Sowers and he said the cost ratio between upper/lower stage on Vulcan will be similar to Atlas. We know that it is roughly 40/60 for Atlas. So use 0.6 for first stage cost, and 0.65 for recovery factor, and you get a k value of 0.6*0.65 (0.39). I did my analysis a few posts upthread, but the conclusion was that boostback wins if >6 launches.
Quote from: Rocket Surgeon on 04/28/2015 06:55 am The question this is used to ask is whether or not the Vulcan should boost back or use the modular recovery and the conclusion is that the Vulcan should use modular recovery as it pays back quicker, .... problem is in reality, the Falcon 9 is already a very different beast. Unless they have a much more in depth analysis than this spreadsheet (I sure hope they do) then the mistake is comparing apples-to-apples, we really have apples-to-oranges.Agreed, I get the feeling that this is more of a justification as why ULA have gone this route with reusability - and for the Vulcan, it is the best route to take, than any evidence comparing economics tit-for-tat with F9 directly. Heck, since nobody has access to all the numbers at work, it's going to take a good few years of both LVs working side by side for us to gain a comprehensive understanding of how the two LV's reusability methods pan out dime for dime.
Marginal cost per flight of expendable vehicles is the cost of the vehicle ($100.0M+)**Marginal cost per flight of reuseable vehicles is cost of propellant ($0.200M).But vehicles cannot be reused if they are not refueled. So rather than add solids, why not top off at the ZBO depot? which would help NASA significantly reduce launch costs as well. IOW: Life Cycle Cost per Pound of Payload for Multiple Launchers, not individual launcherso Reuseability is Key to Low Cost Operationso Refuelability is Key to Reuseabilityo In-space Propellant Deliver, Storage, and Transfer Holds the Key to the Future And if you cannot economically compete for propellant launches.....
I asked Dr.Sowers and he said the cost ratio between upper/lower stage on Vulcan will be similar to Atlas. We know that it is roughly 40/60 for Atlas. So use 0.6 for first stage cost, and 0.65 for recovery factor, and you get a k value of 0.6*0.65 (0.39). I did my analysis a few posts upthread, but the conclusion was that boostback wins if >6 launches.
For example, if in the future ULA's engine price doubles, and thus becomes a far greater percentage of the recoverable cost, then in the abstract it appears to be much more attractive and beats SpaceX's boostback. See figure below where a doubling of the ULA engine price, which results in a Vulcan k of 0.56, appears to beat SpaceX boostback with a k of 0.7.Obviously that does not tell the whole story and we could play this game forever.
Actually, this thread is not specifically about Vulcan vs. Falcon, it is about Boostback vs. Engine-reuse.The claim Dr.Sowers was making is that Engine-reuse is superior to boostback on the same vehicle! we are not directly comparing SpaceX and ULA; that is a different issue and not the point of this thread. ...
Quote from: falconeer on 05/03/2015 02:15 amActually, this thread is not specifically about Vulcan vs. Falcon, it is about Boostback vs. Engine-reuse.The claim Dr.Sowers was making is that Engine-reuse is superior to boostback on the same vehicle! we are not directly comparing SpaceX and ULA; that is a different issue and not the point of this thread. ...The scenarios presented by Dr. Sowers are specifically for Vulcan engine reuse vs. Falcon first stage reuse. If Dr. Sowers presented the same for both vehicles (or only one), then yes we could make a comparison based on the same vehicle. However, that is not what was presented.
Yes, the values (k,p,etc..) were taken from Falcon and Vulcan, but I repeat: the intent is not to compare Falcon and Vulcan, only the reuse modes themselves.
Quote from: falconeer on 05/03/2015 09:37 pmYes, the values (k,p,etc..) were taken from Falcon and Vulcan, but I repeat: the intent is not to compare Falcon and Vulcan, only the reuse modes themselves.You can compare reuse modes only if costs are comparable; demonstrably they are not, nor do we have the information on which to base such a comparison. The fact that the model and scenarios as presented are not comparable except in the abstract speaks for itself.Provide comparable numbers for comparable reuse modes for F9 and Vulcan and we might have something to discuss. Until then, this is at best an academic apples-oranges comparison which tells us nothing about which is optimal.
I repeat myself for a third time: this is not a comparison of Falcon and Vulcan. It is a comparison of Vulcan engine-reuse AND Vulcan boostback reuse....Look at it this way:1) Dr.Sowers provided engine-reuse numbers for Vulcan. Those numbers are based on ULA's own estimates and are as good as they're ever going to get. All with the exception of 'k', which Dr.Sowers includes fixed costs: an error which people on this thread have attempted to correct.2) Dr.Sowers provided boostback numbers for Vulcan. Most of those numbers are based on ULA estimates for Vulcan boostback refurb costs etc. These numbers are not better/worse than the estimates for engine-reuse....
Assume ULA has four business areas of cost....
This is clearly an attempt to compare F9 boostback with Vulcan engine reuse. That is not a valid comparison using this model.
If it's not a valid comparison, then you should be able to show the results change dramatically depending on the assumptions you make for Vulcan boostback vs the Falcon boostback.