I'm pretty sure SpaceX put ULA out of business (To some degree)

[Nibb31]

7 hours ago, Kartoffelkuchen said:

SpaceX puts ULA under pressure, surely. Their launch costs are below ULA's, and ULA just leaned back, watching SpaceX, but they did nothing to be able to really compete with SX nowadays. That's their problem now. If reusability concept would work out, ULA will have major problems, if not, they'll have trouble too. So yeah

Actually, it's quite likely that they have made their own trade studies and decided that it didn't make sense, for them, in the their market, to invest a lot of money in a technique that hasn't been proven. Maybe they have determined that it is unlikely that reusability will actually lower their costs (because their organisation is different from SpaceX's), and maybe they have determined that lowering costs doesn't necessarily increase their revenue and that the investiment isn't worth it.

Edited December 28, 2015 by Nibb31

[magnemoe]

3 hours ago, Bill Phil said:

*clears throat

Rockets are NOT easy to reuse. If they didn't break after every use, sure. If Turbopumps weren't spinning at double digit thousand RPMs, the temps weren't at thousands of K, and the pressure wasn't enormous, it might be doable.

And reusing a stage brings along even more of an infrastructure, which has startup and overhead costs. You will have to inspect every centimeter vigorously. You will have to refurb the engines, refurb the stage, and re certify it. Even more TLC will be needed. You won't be able to land, refuel, and go. Rockets aren't cars.

Rocket engines are reused as in they are tested on full trust before use. With static testing you can easy find main time before failure. 
Yes an real flight adds more stresses but not significantly more. 
However if rockets are not designed to be reused you will not design them for an long life and the only reason to do so is that the extra life adds safety margins. 
If an turbo pump is only designed to last 10 minutes its far more likely to fail after 5 minutes and before seperation than one who is designed to last 10 hours. 

No rockets are not cars more relevant to compare them with high performance warplanes. Supersonic, high g forces and lots of stress on engines and airframe. 

[Bill Phil]

1 hour ago, magnemoe said:

Rocket engines are reused as in they are tested on full trust before use. With static testing you can easy find main time before failure. 
Yes an real flight adds more stresses but not significantly more. 
However if rockets are not designed to be reused you will not design them for an long life and the only reason to do so is that the extra life adds safety margins. 
If an turbo pump is only designed to last 10 minutes its far more likely to fail after 5 minutes and before seperation than one who is designed to last 10 hours. 

No rockets are not cars more relevant to compare them with high performance warplanes. Supersonic, high g forces and lots of stress on engines and airframe. 

Individual engines aren't test fired before use, and if they are they're heavily refurbished afterwards. To the point that they're pretty much new engines. And if you want to continue with that point, then please provide a source.

The designs are test fired. But the engines used usually aren't flight certified. They're testing the pumps and other mechanics as well as the geometry, but it would need to be modified to fit into a rocket. But sometimes they do test production engines. But that's mostly for design improvements and looking for failures on occasion, like in batch production.

Those turbopumps have small margins, mostly measured in minutes.

Even high performance warplanes aren't suffering through the rigors of a rocket engine environment.

[J.Random]

Has SpaceX hired any ex-DoD/USAF procurement officers yet? No? Well then, there's no threat to ULA.

[Rakaydos]

Let's assume that, after every flight, the engine is rotated.

It spends 9 flights doing launch burns, 3 of which it also does boostback and breaking burns, and 1 doing a landing burn. Then on the 10th flight the engine is fitted with a vacuum bell and moved to the upper stage, which isnt recovered.

Throw on a factory test launchburn, boostback burn and landing burn. That's only 17 firing cycles before the engine is disposed of ANYWAY. Throw on test firings before EVERY flight, and you still arnt reaching the 40 burn design limit of the Merlin.

The lifespan of the turbopumps simply isnt an issue for the merlin.

Edited December 28, 2015 by Rakaydos

[sojourner]

The Merlin engine has been designed for re-use and has been put through many test cycles for reliability at McGregor. One of the main criteria of the design was reuse with minimal maintenance.  With all of the testing they've done on it, it's probably the smallest variable in unknown cost/maintenance items on the entire stage.  The real variables have been the parts they couldn't test repeatedly through flight like conditions. Like the tankage, landing gear and plumbing. Now that they have recovered a stage they'll get their first look at what worked and what didn't.

[Lukaszenko]

I know rocket engines operate in quite extreme environments, but, are they really more extreme than, say, jet engine components? Specifically, the turbine blades?

Those are often cited as about as extreme of an environment to operate in that exists. And, jet engines are considered EXTREMELY reliable. 

[PB666]

20 hours ago, Stone Blue said:

You're more than likely right, but I think it depends on a lot of economic factors... If ULA can replace everything except the engine, cheaper than what it costs SpaceX to recover & refurb a full 1st stage, AND have a lower turn-around time, ULA may be able to compete or beat...
I doubt it, tho, and I think you are correct, SpaceX's full-on recover & refurb will end up being cheaper, but I just wanted to point out there are other factors and ways to make things cheaper too...

The assumption here is that it is a zero sum game, their might be sufficient increase in business for both. The other thing is niche markets, even if one company perfects efficiency in one rocket size, another company can optimize in larger or smaller rockets.

[Nibb31]

All liquid engines are test fired at least once before launch. Solid motors aren't (obviously).

However, most engines are designed to be disposable. They have a very high performance, but are not designed for servicing (meaning that some parts aren't accessible without taking apart the whole thing) and they are designed for a total lifetime of less than 30 mins.

Airliner turbofans, on the other hand, are designed with servicing and long duration in mind. The result is that they are actually much more expensive than rocket engines. Access for maintenance actually adds cost.

Rocket engines are a bit like Formula 1 engines: very high performance, but only designed to last one race. After the race, the engine is scrapped.

[Rune]

18 hours ago, fredinno said:

The number of players increasing from the dissolution of ULA is impossible- Delta II is no longer produced, and Delta IV is impossible to run economically.

Nothing is stopping Boeing from building a Delta V on their own, if ULA implodes and Lockheed somehow grabs control of the Atlas V. Might even call it Vulcan, or work the other way around. Not talking abut tomorrow, obviously, but give it ten years, and who knows.

8 hours ago, Bill Phil said:

*clears throat

Rockets are NOT easy to reuse. If they didn't break after every use, sure. If Turbopumps weren't spinning at double digit thousand RPMs, the temps weren't at thousands of K, and the pressure wasn't enormous, it might be doable.

And reusing a stage brings along even more of an infrastructure, which has startup and overhead costs. You will have to inspect every centimeter vigorously. You will have to refurb the engines, refurb the stage, and re certify it. Even more TLC will be needed. You won't be able to land, refuel, and go. Rockets aren't cars.

Jet engines do come close (the hotter you can run the turbine, the more efficient the engine, and the higher RPM, the more TWR), and their lifetimes are measured in thousands of hours. It's not much of a stretch to posit that you can engineer a rocket engine to survive hundreds of hours of operation. It would have to be a decision on the early design steps... short of like the Merlin case.

3 hours ago, Bill Phil said:

Individual engines aren't test fired before use, and if they are they're heavily refurbished afterwards. To the point that they're pretty much new engines. And if you want to continue with that point, then please provide a source.

The designs are test fired. But the engines used usually aren't flight certified. They're testing the pumps and other mechanics as well as the geometry, but it would need to be modified to fit into a rocket. But sometimes they do test production engines. But that's mostly for design improvements and looking for failures on occasion, like in batch production.

Those turbopumps have small margins, mostly measured in minutes.

Even high performance warplanes aren't suffering through the rigors of a rocket engine environment.

SpaceX's are. At least twice before each flight, once for a full mission duration burn individually, and then another one on the pad. IIRC, there might be one more in there after integration into the first stage? I think at least it used to...

It's funny that the closer SpaceX gets to the goal ("full and rapid" reusability, or in other words, cost-saving), the louder both parties (pro and con) get on their respective positions (it'll work/it won't). You'd think the question would have become clearer, wouldn't it?

 

Rune. I would certainly give them higher odds than last year.

Edited December 28, 2015 by Rune

[Nibb31]

I've always said that there are very little technological barriers to reusability. I'm pretty confident that they will do it one day. The problems are economical. The same is true for pretty much all of our long term spaceflight goals. When there's a will, there's a way. The technical problems can be fixed, the hard part is justifying those solutions economically and politically.

[Rune]

1 minute ago, Nibb31 said:

I've always said that there are very little technological barriers to reusability. I'm pretty confident that they will do it one day. The problems are economical. The same is true for pretty much all of our long term spaceflight goals. When there's a will, there's a way. The technical problems can be fixed, the hard part is justifying those solutions economically and politically.

"We can lick gravity, but sometimes the paperwork is overwhelming", right? Well, good thing the world economy keeps on growing then. Let's hope space expenditure as a percentage at least stays the same!

 

Rune. Because at a certain flight rate, reusability has to pay off.

[fredinno]

24 minutes ago, Rune said:

"We can lick gravity, but sometimes the paperwork is overwhelming", right? Well, good thing the world economy keeps on growing then. Let's hope space expenditure as a percentage at least stays the same!

 

Rune. Because at a certain flight rate, reusability has to pay off.

Unfortunately, we generally don't have that flight rate- unless we consolidate all world launches into 2 or 3 RLVs.

 

1 hour ago, Rune said:

Nothing is stopping Boeing from building a Delta V on their own, if ULA implodes and Lockheed somehow grabs control of the Atlas V. Might even call it Vulcan, or work the other way around. Not talking abut tomorrow, obviously, but give it ten years, and who knows.

Jet engines do come close (the hotter you can run the turbine, the more efficient the engine, and the higher RPM, the more TWR), and their lifetimes are measured in thousands of hours. It's not much of a stretch to posit that you can engineer a rocket engine to survive hundreds of hours of operation. It would have to be a decision on the early design steps... short of like the Merlin case.

SpaceX's are. At least twice before each flight, once for a full mission duration burn individually, and then another one on the pad. IIRC, there might be one more in there after integration into the first stage? I think at least it used to...

It's funny that the closer SpaceX gets to the goal ("full and rapid" reusability, or in other words, cost-saving), the louder both parties (pro and con) get on their respective positions (it'll work/it won't). You'd think the question would have become clearer, wouldn't it?

 

Rune. I would certainly give them higher odds than last year.

Yes, because Boeing is almost certainly going to enter a crowded US LV market- what with Antares- Orbital ATK, Falcon 9- SpaceX, and possibly BO-OLV - Blue Origin soon, not to mention Vulcan -LockMart, good luck to them.

[KSK]

5 hours ago, Bill Phil said:

Individual engines aren't test fired before use, and if they are they're heavily refurbished afterwards. To the point that they're pretty much new engines. And if you want to continue with that point, then please provide a source.

The designs are test fired. But the engines used usually aren't flight certified. They're testing the pumps and other mechanics as well as the geometry, but it would need to be modified to fit into a rocket. But sometimes they do test production engines. But that's mostly for design improvements and looking for failures on occasion, like in batch production.

Those turbopumps have small margins, mostly measured in minutes.

Even high performance warplanes aren't suffering through the rigors of a rocket engine environment.

Here you go. Straight from the SpaceX website. Tested individually after manufacture, test-firing of all nine engines together, then tested again before launch. No mention of refurbishing - understandably so, since refurbishing the engines after a test-fire pretty much negates the point of the test.

[Steel]

2 hours ago, Nibb31 said:

Rocket engines are a bit like Formula 1 engines: very high performance, but only designed to last one race. After the race, the engine is scrapped.

*OFF TOPIC*

Interesting analogy, these days formula 1 engines have to last 4 races or so as they have a limited number per season

[Bill Phil]

48 minutes ago, KSK said:

Here you go. Straight from the SpaceX website. Tested individually after manufacture, test-firing of all nine engines together, then tested again before launch. No mention of refurbishing - understandably so, since refurbishing the engines after a test-fire pretty much negates the point of the test.

Absence of evidence is not evidence of absence. It could be refurbished afterwards.

It is possible to have engines that can fire multiple times. It's not impossible, the J-2 did it in the 60s. But getting it to burn for a test and then burn for flight isn't resusing an engine. It's part of its firing cycle, which means it was intended. Reusing an engine takes place after a complete firing cycle. Usually, at least. Getting that firing cycle to encompass multiple flights is the key.

1 hour ago, Nibb31 said:

I've always said that there are very little technological barriers to reusability. I'm pretty confident that they will do it one day. The problems are economical. The same is true for pretty much all of our long term spaceflight goals. When there's a will, there's a way. The technical problems can be fixed, the hard part is justifying those solutions economically and politically.

You're correct. It can, or at least will be, done. Although it might take a while, since there's s few engineering problems in the way.

[Rune]

1 hour ago, fredinno said:

Unfortunately, we generally don't have that flight rate- unless we consolidate all world launches into 2 or 3 RLVs.

Not saying no, but also not saying yes. Some launchers do have a political cloaks of invulnerability (Arianne, H-II, PSLV/GSLV, and others), but it seems like a time of major reorganization in the launch provider scene is certainly approaching. No need to fear it, if it brings about positive change. I reckon abut the same amount of money will be spent on about the same number of paychecks.

1 hour ago, fredinno said:

Yes, because Boeing is almost certainly going to enter a crowded US LV market- what with Antares- Orbital ATK, Falcon 9- SpaceX, and possibly BO-OLV - Blue Origin soon, not to mention Vulcan -LockMart, good luck to them.

Hey, they can compete with the rest, and they certainly have the muscle to do so. What makes you think Vulcan is exclusively LockMart's baby? Now, that they succeed is far from a given, of course. Maybe they will fall off the launch market. Maybe LockMart will. Perhaps ULA can even out-compete Orbital and BO. That is precisely what this thread is about, the fact that a rather drastic change on the launch provider scene may be starting to happen as a consequence of the disruption created by SpaceX accomplishments in lowering cost.

 

Rune. And you can say what you want about SpaceX, but I think calling them "disruptive" is pretty much irrefutable.

[AngelLestat]

10 hours ago, Nibb31 said:

Reusing and refurbishing the first stage might allow some cost savings compared to building a new one, but there are many more factors involved in the cost of orbital launch. The manufacturing cost of the first stage is actually only a small part of the total cost of launching a rocket, maybe only 30% (optimistically). The rest of the cost is mainly the workforce, planning, infrastructure, logistics, R&D, transport, administrative overhead, etc... And there's transport, integration, launch services, and a lot of stuff that isn't recoverable (upper stage, fairing...). 

Is not a 30% :P, but wherever...  Lets said you have a big cost in planning and all the other things you said.
If you launch rockets more often all those cost goes down because is not the same launch 1 rocket every 2 months when you are still testing all the systems, than launch 2 or 3 rockets by month when you already have a lot of experience and practice in all those procedures.
Because at the end, it all resume to a simple check of the stages, relocation, assembly, a more automated planning system, refuel the rocket, and launch.  Then you repeat the process.
Those are the things that Elon Musk and Gwynne Shotwell (between others) knows, in the same way they knew (time ago) how to improve all the process and systems to reduce the rocket launch cost to 1/3 of the current launch for that time.

 

Quote

Disposable rockets (especially the Falcon 9) are actually designed to be (relatively) cheap, partly because they are produced in numbers. Manufacturing costs diminish with volume, meaning that as launch volume increases, the unit cost of each booster decreases.If you have 50 launches per year, with a disposable model, you need to mass produce 500 Merlin engines and 50 first stages. With 100% first stage reusability, the same factory has to build only 2.5 first stages and 72.5 engines. The result is that due to lower procurement volumes and higher fixed costs, those reusable stages are going to cost a lot more than the disposable ones. Enough to seriously cut into the reduction induced by reusing the stages in the first place. Instead of saving 95% on the manufacturing cost of the first stage, for the same amount of flights, the real cost reduction might only be 50%.

They dont need to produce all the time falcon stages or parts, they have other rocket designs and future parts to manufacture, the same for other business to come. They know how to take advantage of their employees.
 

Quote

Now, from the customer's point of view, the actual launch is only a small part of the total cost of a typical project. Maybe, again, 20%. The rest is the satellite itself (the biggest part of the budget), the ground stations, the insurance, and the actual operations. This means that in the grand scheme of things, the total saving that a customer can expect when they put a satellite in service is 15% of 20%, which is only 3%. On a $200 million comsat project, that's a whopping $6 million saving on their total expenses. Again, it's a nice saving, but it's not a revolution.

We had this same discussion over and over since 2013 I think..  I already explain you with plenty of details how satellites will become cheap and demand will increase with many other applications for space, with possible strategies that elon musk may take to improve that, in fact two year after those explanations, all the constellations plans from different companies started to appear, with cheap sats using cheap manufacture techniques. Still you are unable to see the evidence that is in front of your eyes, because you keep applying a old space logic that already fail.  

 

10 hours ago, Bill Phil said:

And reusing a stage brings along even more of an infrastructure, which has startup and overhead costs. You will have to inspect every centimeter vigorously. You will have to refurb the engines, refurb the stage, and re certify it. Even more TLC will be needed. You won't be able to land, refuel, and go. Rockets aren't cars.

Why you would do that?   Why try to fix something that is not broken..  In fact, there is more chances to broke something in that "vigorously inspection" than without it.

 

6 hours ago, Nibb31 said:

Actually, it's quite likely that they have made their own trade studies and decided that it didn't make sense, for them, in the their market, to invest a lot of money in a technique that hasn't been proven. Maybe they have determined that it is unlikely that reusability will actually lower their costs (because their organisation is different from SpaceX's), and maybe they have determined that lowering costs doesn't necessarily increase their revenue and that the investiment isn't worth it.

There are a lot of maybe there.   Or maybe... they don't have a clue how they do that, in the same way they didn't have a clue how spacex cut the prices more than half without reusability. 

So their solutions was come out with a very weird helicopter stunt method to recover the engine, which in fact it needs an extra joint and stage that adds complexity.  mmm.. I am still trying to figure out this strategy that it is already 7 years delay vs the competence.

maybe.. is just another silly excuse to keep receiving money from the government.

 

5 hours ago, Bill Phil said:

Individual engines aren't test fired before use, and if they are they're heavily refurbished afterwards. To the point that they're pretty much new engines. And if you want to continue with that point, then please provide a source.

Ok do the same (show the source) where it said that spacex merlin needs heavily refurbished after the static fire test. 

 

[Rakaydos]

2 hours ago, fredinno said:

Unfortunately, we generally don't have that flight rate- unless we consolidate all world launches into 2 or 3 RLVs.

.

National Security launches will always be their own thing, but if one company can both underbid the competition for commercial launches via a lean corporate structure, and keep up with demand via reusability, then I believe water will flow down hill. Even if it's a glacier.

And really, Falcon 9 and Falcon Heavy are, for manufacturing purposes, the same RLV. Tha gives SpaceX a broad base of capability while specializing the manufacturing end.

Edited December 29, 2015 by Rakaydos

[KSK]

9 hours ago, Bill Phil said:

Absence of evidence is not evidence of absence. It could be refurbished afterwards.

It is possible to have engines that can fire multiple times. It's not impossible, the J-2 did it in the 60s. But getting it to burn for a test and then burn for flight isn't resusing an engine. It's part of its firing cycle, which means it was intended. Reusing an engine takes place after a complete firing cycle. Usually, at least. Getting that firing cycle to encompass multiple flights is the key.

You're correct. It can, or at least will be, done. Although it might take a while, since there's s few engineering problems in the way.

 I have no idea (and I suspect SpaceX doesn't yet have much idea) how much post-flight refurbishment their engines will need. But your original comment:

"Individual engines aren't test fired before use, and if they are they're heavily refurbished afterwards. To the point that they're pretty much new engines. And if you want to continue with that point, then please provide a source.

The designs are test fired. But the engines used usually aren't flight certified. They're testing the pumps and other mechanics as well as the geometry, but it would need to be modified to fit into a rocket. But sometimes they do test production engines. But that's mostly for design improvements and looking for failures on occasion, like in batch production."

That is flat-out wrong and yes I did provide a source.

[Bill Phil]

21 minutes ago, KSK said:

 I have no idea (and I suspect SpaceX doesn't yet have much idea) how much post-flight refurbishment their engines will need. But your original comment:

"Individual engines aren't test fired before use, and if they are they're heavily refurbished afterwards. To the point that they're pretty much new engines. And if you want to continue with that point, then please provide a source.

The designs are test fired. But the engines used usually aren't flight certified. They're testing the pumps and other mechanics as well as the geometry, but it would need to be modified to fit into a rocket. But sometimes they do test production engines. But that's mostly for design improvements and looking for failures on occasion, like in batch production."

That is flat-out wrong and yes I did provide a source.

I think you missed the point. Most engines aren't test fired individually before a launch. That adds to the requirements of each individual engine. But test firing is different. It isn't necessarily the same as other testing types.

That source doesn't specify if it's test fired. It says they do a bunch of quality tests and other tests. It never quite specified.

Edited December 29, 2015 by Bill Phil

[Bill Phil]

8 hours ago, AngelLestat said:

Is not a 30% :P, but wherever...  Lets said you have a big cost in planning and all the other things you said.
If you launch rockets more often all those cost goes down because is not the same launch 1 rocket every 2 months when you are still testing all the systems, than launch 2 or 3 rockets by month when you already have a lot of experience and practice in all those procedures.
Because at the end, it all resume to a simple check of the stages, relocation, assembly, a more automated planning system, refuel the rocket, and launch.  Then you repeat the process.
Those are the things that Elon Musk and Gwynne Shotwell (between others) knows, in the same way they knew (time ago) how to improve all the process and systems to reduce the rocket launch cost to 1/3 of the current launch for that time.

 

They dont need to produce all the time falcon stages or parts, they have other rocket designs and future parts to manufacture, the same for other business to come. They know how to take advantage of their employees.
 

We had this same discussion over and over since 2013 I think..  I already explain you with plenty of details how satellites will become cheap and demand will increase with many other applications for space, with possible strategies that elon musk may take to improve that, in fact two year after those explanations, all the constellations plans from different companies started to appear, with cheap sats using cheap manufacture techniques. Still you are unable to see the evidence that is in front of your eyes, because you keep applying a old space logic that already fail.  

 

Why you would do that?   Why try to fix something that is not broken..  In fact, there is more chances to broke something in that "vigorously inspection" than without it.

 

There are a lot of maybe there.   Or maybe... they don't have a clue how they do that, in the same way they didn't have a clue how spacex cut the prices more than half without reusability. 

So their solutions was come out with a very weird helicopter stunt method to recover the engine, which in fact it needs an extra joint and stage that adds complexity.  mmm.. I am still trying to figure out this strategy that it is already 7 years delay vs the competence.

maybe.. is just another silly excuse to keep receiving money from the government.

 

Ok do the same (show the source) where it said that spacex merlin needs heavily refurbished after the static fire test. 

 

Why try to fix what isn't broken? Can you prove beyond a shadow of a doubt, betting the safety of a person, on that stage? Simply put: it might be broken. Vigorous inspection means to heavily scrutinize the state of the stage.

If you want a source, you only need to look at the shuttle. Engines were heavily refurbished. Now, Merlins aren't SSMEs, so it might very well be easier. 

[KSK]

29 minutes ago, Bill Phil said:

I think you missed the point. Most engines aren't test fired individually before a launch. That adds to the requirements of each individual engine. But test firing is different. It isn't necessarily the same as other testing types.

That source doesn't specify if it's test fired. It says they do a bunch of quality tests and other tests. It never quite specified.

http://www.spacex.com/about/capabilities

Which strongly implies that each engine is test fired before use. Or, there's this prepared testimony to the committee on armed services sub-committee (where, I imagine, the penalties for lying are rather severe):

"For test operations, SpaceX's 4,000 acre Rocket Development Facility in Central Texas includes 12 test stands that support engine component testing; design, qualification and acceptance testing of Merlin engines; structural testing of the first and second stages; and fully integrated stage testing for full mission durations. The state-of-the-art facility has remote and/or automatic controls and high-speed data acquisition systems, and post test data are available for analysis upon test completion. To date, more than 4,000 Merlin engine tests including nearly 50 firings of the integrated first stagehave been conducted at the site's multiple test stands. Currently, we conduct an average of two static-fire engine tests there each day." (emphasis added)"

Earlier in the same testimony, it's stated that SpaceX are currently building four Merlin 1Ds per week, so either they're test-firing each production engine more than once, or those test-firings include Draco and SuperDraco tests. Either way, two static-fire tests per day adds up to a whole lot of pre-launch test firing.

If you're still not convinced then play by your own rules and find us a source which demonstrates that SpaceX don't test-fire their engines before launch.

 

[Nibb31]

Each engine is test fired routinely several times before it's launched. This goes for pretty much all liquid engines since the early days. Bill Phil is wrong about this. 

Edited December 29, 2015 by Nibb31

[fredinno]

8 hours ago, Bill Phil said:

Why try to fix what isn't broken? Can you prove beyond a shadow of a doubt, betting the safety of a person, on that stage? Simply put: it might be broken. Vigorous inspection means to heavily scrutinize the state of the stage.

If you want a source, you only need to look at the shuttle. Engines were heavily refurbished. Now, Merlins aren't SSMEs, so it might very well be easier. 

It may also be harder, because Merlins have to deal with coking.