Author Topic: Raptor Upper Stage consolidated thread  (Read 123936 times)

Offline envy887

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Re: Raptor Upper Stage consolidated thread
« Reply #300 on: 06/27/2017 05:47 pm »
What does a Raptor upper stage that operates like the current Merlin upper stage enable?

It could be flight testing Raptor, maybe, but like Jim says that's not really useful.

Or it could be upper stage reuse, similar to this: http://selenianboondocks.com/2008/12/falcon-ix-upper-stage-recovery-kremlinology/

But is there a pressing need for upper stage reuse? At this point the only reason for it would be enabling cheaper deployment of the constellation. GTO launches do require the extra performance, but probably are not frequent enough to justify the investment of themselves.

But a small incremental payload like constellation sats are amenable to perfecting this style reuse with the current upper stage. Even if it takes 2x as many launches as a fully reuseable Raptor system, the development costs are much smaller.

A BFS-style upper stage appears to be SpaceX's chosen direction for the future, so they will minimize development expenses that don't go in that direction.

So perhaps the question should be, how much more is a reuseable Raptor stage worth, compared to a reuseable Merlin stage?

Offline woods170

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Re: Raptor Upper Stage consolidated thread
« Reply #301 on: 06/27/2017 08:09 pm »
Here is what it all boils down to.

Why?

There has yet to be a good or marginal reason for Spacex to make a RUS for FH.  Nobody has on this forum has yet to come forth with a reason.

FH hasn't flown.  FH has yet to book a payload that needs its whole capability.  So why would they be looking at improvements.

LC-39A is going to be busy with Dragon 2 (cargo and crew), DOD vertical integrated payloads, NASA payloads, FH missions, etc.  So when and how is Spacex going to add a new upper stage that uses a new TEL and still service the existing upper stage.
Your line of reasoning is flawed Jim.

Why is there a Falcon Heavy? There was no need for it given that the heavy payloads could/can be lofted by Delta IV Heavy.

Yet, Falcon Heavy exists.

FH is made by SpaceX. It is to create money to SpaceX, DIVH cannot do that.
The money making machine for SpaceX is Falcon 9, not Falcon Heavy. Haven't you noticed how empty the manifest for FH is and how full it is for F9?
Falcon Heavy serves only a very limited market. A substantial part of that market will be NSS launches. And frankly, USAF and NRO couldn't care less if FH flies or not. They already have Delta IV Heavy. Having a second heavy lifter at their disposal is merely a "nice to have". You don't believe me? Then explain why USAF never pushed LockMart for Atlas V Heavy. I'll tell you why USAF never did. Because redundancy in heavy lift for NSS is not needed. And that brings us back to my original point. From a standpoint of heavy lifters Falcon Heavy isn't needed. That was the point I was trying to make to Jim: There is no apparent logical reason for FH to exist. Yet SpaceX built it anyway. Which is a clear indicator that SpaceX decision making is not always logical. Something that Jim IMO fails to see.

Why is SpaceX reusing rockets? There was no need for it given that the world did just fine for the past 5+ decades launching on expendable rockets only.

Yet, reusable Falcon exists.
SpaceX is reusing rockets because it makes launches cheaper.
Yeah, that's the SpaceX reason. However, none of the other launch providers ever found it necessary to make their launches cheaper. You wanna know why? Because prior to SpaceX their was no disruptive force acting on the market. The parties in need of launch services gladly paid for the higher priced launches. They had no choice for lack of a disruptive force. And was the point I was making to Jim: Logically speaking there was no reason for reusable launch vehicles. The launch market did not require it. Yet SpaceX went for reusability anyway. So, another fine example of SpaceX making a seemingly illogical decision without a clear why.

Why is SpaceX working on recovering the fairings? There is no need for it given that they are able of meeting their launch schedule even without reusing the fairing.

Yet, fairing recovering is being worked on and tested in practice.

Fairing recovery has nothing to do with launch schedule. It's all about cost.
It is not all about cost. It is about being able to increase the launch cadence. Elon himself pointed out in 2015 that fairing production is labor intensive and takes a lot of time. So much time in fact that fairing production becomes a limiting factor once the launch tempo increases beyond a certain limit. That was, and according to my sources, still is the main driver behind fairing recovery. The improved cost aspect is merely a nice side-effect.

Why is there a SpaceX? There was no need for it given that there were enough launch service providers to cater for the worlds launch needs.

Yet, SpaceX exists.


All of the previous launch providers were too expensive. There was need for cheaper rockets.
Then why is it that prior to Elon having a space-themed brainwave nobody ever bothered to succesfully market a cheaper rocket?
The answer is that there was no need for cheaper rockets. Despite the other launch service providers supposedly being "too expensive" their launch manifests were pretty full. What you don't understand is that launch service providers are interested in reliability first, and cost second. That's why one of the most expensive launch service providers -Arianespace - was capable of catching a full half of the commercial launch market: they were (and still are btw.) the worlds most reliable launch services provider.

And in case you had forgotten: SpaceX was already working on improved Falcon 9, aka v1.1, when Falcon 9 v1.0 had yet to fly. Much like SpaceX was already working on an improved launcher (aka Falcon 5) while Falcon 1 had yet to fly.

Actually no. They were working on different version of F9 than the v1.1. THis version was to have "merlin 1c+" engines and have much less capacity than v1.1 has. They canned it when they jumped to much more powerful merlin 1d instead.
Incorrect. That particular upgrade of Falcon 9 v1.0 was exactly what Falcon 9 v1.1 also is: a more powerfull version of the basic rocket.

The more your repeat your mantra of "Why?", "What's the reason?" the more you confirm the fact that your really don't "get" SpaceX.
That company is not run by logical reasoning alone. It is run by passion as well. And the latter makes for seemingly irrational or illogical decision making.

Wrong. All the engineering decisions are done by numbers and logic, not passion.
You confuse engineering decisions for business decisions. The decisions to develop a reusable launcher is a business decision, not an engineering decision. Same for the decision to do fairing recovery or develop FH.
Those business decisions come from both logical reasoning and passion for doing thing differently (like going to Mars without waiting another 4 decades for NASA to do so).
Make no mistake. SpaceX engineering is among the best there is. And engineering decisions are indeed based on logic. But the business decisions come long before those and are very much a passion-thing, courtesy of Elon's personality.

The passion is only about getting to Mars.
Disagree. SpaceX has passion for many more things than "just" Mars.

It's YOU who do not understand spaceX, and it's YOU whose logic is flawed.
I don't think Jim needs you to defend his argument. He is perfectly capable of doing so himself.


Edit: removed the snark, per Lar's suggestion.
« Last Edit: 06/27/2017 08:17 pm by woods170 »

Offline Lar

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Re: Raptor Upper Stage consolidated thread
« Reply #302 on: 06/27/2017 08:13 pm »
Let's keep the snark to a reasonable level. This topic has passionate participants on both sides. Passion is fine but be excellent to each other. Not quoting any one post because I saw a lot of it.
"I think it would be great to be born on Earth and to die on Mars. Just hopefully not at the point of impact." -Elon Musk
"We're a little bit like the dog who caught the bus" - Musk after CRS-8 S1 successfully landed on ASDS OCISLY

Offline RotoSequence

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Re: Raptor Upper Stage consolidated thread
« Reply #303 on: 06/27/2017 08:17 pm »
It's entirely wrong to construe the Falcon Heavy as an illogical choice. The Falcon 9's performance has increased far above and beyond the original baseline specification that existed when Falcon Heavy was conceived to meet the heavy lift requirements of satellites on SpaceX's launch manifest. SpaceX Marginalized the Falcon Heavy by making Falcon 9 good enough for most of the Falcon Heavy's original manifest.

Offline Chris Bergin

Re: Raptor Upper Stage consolidated thread
« Reply #304 on: 06/27/2017 08:21 pm »
There's people in Syria saying "I know we think we have it bad, but I've just read the "Raptor Upper Stage consolidated thread" on NSF and I'm praying for the folk posting on there". ;)

Keep. It. Civil.

Oh, Lar already beat me. Well, perhaps the thread needs double-teaming.
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Offline abaddon

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Re: Raptor Upper Stage consolidated thread
« Reply #305 on: 06/27/2017 10:16 pm »
The money making machine for SpaceX is Falcon 9, not Falcon Heavy. Haven't you noticed how empty the manifest for FH is and how full it is for F9?
Falcon Heavy serves only a very limited market.
Well... maybe, maybe not.

FH is late.  FH has lost payloads (two?) because of that, and also has not signed payloads (unknown) because of that.  F9 has several launches (three+?) that are expendable that would be candidates for FH if it were available.  At least one of those was signed as an FH payload.

6+ metric ton satellites are not that uncommon.  Chances are SpaceX will be able to win a larger share of that market with FH operational, eating into Proton and Ariane 5 market - as long as FH proves to be successful.

Even with Block 5 upgrades, it seems unlikely a regular F9 will be able to launch these birds and recover the first stage.  So I think FH could have a bigger role to play moving forward than you are thinking here.

Offline docmordrid

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Re: Raptor Upper Stage consolidated thread
« Reply #306 on: 06/27/2017 11:36 pm »
The USAF is planning on DIVH going away by 2023 and choosing a replacement, and only Falcon Heavy, New Glenn, and maybe Vulcan ACES look to be in the hunt.

Add a backup launcher and the notion that the USAF has no interest in FH seems quite unlikely.

http://spacenews.com/delta-4-replacement-ready-by-2023-top-general-says/

Quote
Delta 4 replacement ready by 2023, top general says

Testifying before the House Armed Services Committee’s strategic forces subcommittee, Raymond said that the Air Force expects to have uninterrupted access to heavy launch for national security missions.

Several companies have heavy-lift vehicles in development, including SpaceX’s Falcon Heavy and Blue Origin’s New Glenn, that could replace the Delta 4 Heavy built by United Launch Alliance.

The Air Force has purchased launches on seven more Delta 4 Heavy rockets, Raymond said, though one launch will be a NASA mission. The final launch is scheduled for 2023.
>
« Last Edit: 06/27/2017 11:44 pm by docmordrid »
DM

Offline Space Ghost 1962

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Re: Raptor Upper Stage consolidated thread
« Reply #307 on: 06/27/2017 11:40 pm »
One of the best posts this year.
Here is what it all boils down to.

Why?

There has yet to be a good or marginal reason for Spacex to make a RUS for FH.  Nobody has on this forum has yet to come forth with a reason.

FH hasn't flown.  FH has yet to book a payload that needs its whole capability.  So why would they be looking at improvements.

LC-39A is going to be busy with Dragon 2 (cargo and crew), DOD vertical integrated payloads, NASA payloads, FH missions, etc.  So when and how is Spacex going to add a new upper stage that uses a new TEL and still service the existing upper stage.
Your line of reasoning is flawed Jim.

Why is there a Falcon Heavy? There was no need for it given that the heavy payloads could/can be lofted by Delta IV Heavy.

Yet, Falcon Heavy exists.

FH is made by SpaceX. It is to create money to SpaceX, DIVH cannot do that.
The money making machine for SpaceX is Falcon 9, not Falcon Heavy. Haven't you noticed how empty the manifest for FH is and how full it is for F9?
Cannot get why this is so hard for many here to grasp. F9 is "bread and butter". It is an excellent design for exactly what it's supposed to do.

But it is not Atlas-V. Nor any of the other vehicles. IMHO, Musk is pivoting the entire launch service provider business around F9. And "they" collectively ... don't like it. Too bad.

Quote
Falcon Heavy serves only a very limited market. A substantial part of that market will be NSS launches. And frankly, USAF and NRO couldn't care less if FH flies or not. They already have Delta IV Heavy. Having a second heavy lifter at their disposal is merely a "nice to have". You don't believe me? Then explain why USAF never pushed LockMart for Atlas V Heavy. I'll tell you why USAF never did. Because redundancy in heavy lift for NSS is not needed. And that brings us back to my original point. From a standpoint of heavy lifters Falcon Heavy isn't needed. That was the point I was trying to make to Jim: There is no apparent logical reason for FH to exist. Yet SpaceX built it anyway. Which is a clear indicator that SpaceX decision making is not always logical. Something that Jim IMO fails to see.
Agreed.

The biggest benefactor after SX of FH flying 3+ times successfully is likely ULA! Advancing the EOL clock on DIVH likely allows a more nimble ULA. Not because DIVH doesn't ... but because it takes to much, to do it.

FH is a useful luxury. Affordable because of F9 leverage/commonality.

But FH payloads won't be a major increment to SX annual revenue yield, nor net profit. (Not much of a burden either, so by not flying it much won't require as much overhead as other rivals.)

Quote
Why is SpaceX reusing rockets? There was no need for it given that the world did just fine for the past 5+ decades launching on expendable rockets only.

Yet, reusable Falcon exists.
SpaceX is reusing rockets because it makes launches cheaper.
Yeah, that's the SpaceX reason. However, none of the other launch providers ever found it necessary to make their launches cheaper. You wanna know why? Because prior to SpaceX their was no disruptive force acting on the market. The parties in need of launch services gladly paid for the higher priced launches. They had no choice for lack of a disruptive force. And was the point I was making to Jim: Logically speaking there was no reason for reusable launch vehicles. The launch market did not require it. Yet SpaceX went for reusability anyway. So, another fine example of SpaceX making a seemingly illogical decision without a clear why.
Well put.

Space launch has been long overdue for disruption. "They've" fought against it bitterly and are losing that battle.

So "they'll" either have to get good at competing on the edge of the wave of disruption, or fade away.

It has been mostly good our heritage. We shall build upon it, respect it, and take it to the next level as a new heritage.

Disruption means you can get access to business structural problems inside a market. In doing so, you rip it apart, make it work by means that address the structural issue, then put it back together.

To address unserved market that will not accept prior launch service provider offerings, you cannot simply address customers where price is no object. Because those simply raise the cost level when they need something, anything. This is the structural problem.

Quote
Why is SpaceX working on recovering the fairings? There is no need for it given that they are able of meeting their launch schedule even without reusing the fairing.

Yet, fairing recovering is being worked on and tested in practice.

Fairing recovery has nothing to do with launch schedule. It's all about cost.
It is not all about cost. It is about being able to increase the launch cadence. Elon himself pointed out in 2015 that fairing production is labor intensive and takes a lot of time. So much time in fact that fairing production becomes a limiting factor once the launch tempo increases beyond a certain limit. That was, and according to my sources, still is the main driver behind fairing recovery. The improved cost aspect is merely a nice side-effect.
Indeed.

Booster reuse already is speeding up manifest consumption.

Quote
Why is there a SpaceX? There was no need for it given that there were enough launch service providers to cater for the worlds launch needs.

Yet, SpaceX exists.


All of the previous launch providers were too expensive. There was need for cheaper rockets.
Then why is it that prior to Elon having a space-themed brainwave nobody ever bothered to succesfully market a cheaper rocket?
The answer is that there was no need for cheaper rockets. Despite the other launch service providers supposedly being "too expensive" their launch manifests were pretty full. What you don't understand is that launch service providers are interested in reliability first, and cost second. That's why one of the most expensive launch service providers -Arianespace - was capable of catching a full half of the commercial launch market: they were (and still are btw.) the worlds most reliable launch services provider.
Arianespace is also the leader in selling additional launch services to a cautious customer base.

This is the "top of the pyramid" of launch service sales. The most valuable component.

But also the slowest growth rate. The only ones slower are institutional/NSS. Which also have "special needs".

The high growth rate is at the bottom of the pyramid. The business has yet to really reach the level to access it.

And until now, no one has attempting to reach for it. It has been considered "foolish" to do so. Why risk so much for such a difficult opportunity.

Thank you woods170 for saying what needed to be said.

Offline RoboGoofers

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Re: Raptor Upper Stage consolidated thread
« Reply #308 on: 06/28/2017 01:25 am »
...

Neither you nor woods170 mentioned a raptor upper stage in your long posts.

Offline Space Ghost 1962

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Re: Raptor Upper Stage consolidated thread
« Reply #309 on: 06/28/2017 01:49 am »
...

Neither you nor woods170 mentioned a raptor upper stage in your long posts.

Sometimes you have to correct a mis-impression, of the kind Jim (and a few others) brought in.

Otherwise one does not get the point.

I'd stopped posting about Raptor til it became better understood of the difference in strategy, operations, business intent, and the function of disruption. (Most of the money made in the past two decades has been due to disruption, that's why its so important.)

Some don't get what's going on. Largely because ... they don't want to.

How can you get inside the head of Musk unless you at least accept some of his perspective. Especially when its on the cusp, like here with the "on again, off again" Falcon + Raptor.

I disagree about testing a RVac stage:
 1. They don't have a vaccuum test stand.
 2. One for RVac would be enormously expensive, more than a F9R launch.
 3. What would you test? In flight chill down, pressurization, ignition, throttle up, shutdown, coast, re-ignition, and burn to depletion.
 4. Benefit would be a competitive to ACES stage
 5. Alongside recovery of a F9US, might turn a limited concept into a 100% reusable vehicle in 1-2 years.
 6. Which might make cost recovery of the LV 3x more aggressive

Musk would not do it for immediate revenue or cost recovery. He'd do it to disrupt with a vehicle that could do what others could not. As before.

Such would be more effective than FH, because we already have a DIVH. "Good enough".

We don't have an ACES class reusable US.

What might the effect look like - alongside a consistent cadence of F9, an occasional experimental RUS launch. (I'll explain in another post later.) So like the march for booster reuse we watched, a similar for RUS.

Won't bring in much revenue. Will up the competitive ante. Perhaps the springboard for more C3 and Raptor adventures.

Please continue to push back as you did.

Offline BobHk

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Re: Raptor Upper Stage consolidated thread
« Reply #310 on: 06/28/2017 03:41 am »
"Despite describing the Block 5 as the final version of the Falcon 9, Shotwell hinted at the possibility of a future version of the rocket that could use the Raptor engines designed for transportation to Mars. Shotwell said Raptor, a liquid methane and oxygen engine for SpaceX’s interplanetary spaceship, has undergone “many dozens of tests” and is progressing well.

“The original idea for those engines were to serve as a propulsion system for the big Mars system, but we are looking at the utility of it on the Falcon program,” she said."

Yeah.  Can we be released from this single thread now that the Raptor on F9 is no longer speculative?

FROM HERE:  http://spacenews.com/spacexs-final-falcon-9-design-coming-this-year-two-falcon-heavy-launches-next-year/

« Last Edit: 06/28/2017 03:44 am by BobHk »

Offline rakaydos

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Re: Raptor Upper Stage consolidated thread
« Reply #311 on: 06/28/2017 04:36 am »
"Despite describing the Block 5 as the final version of the Falcon 9, Shotwell hinted at the possibility of a future version of the rocket that could use the Raptor engines designed for transportation to Mars. Shotwell said Raptor, a liquid methane and oxygen engine for SpaceX’s interplanetary spaceship, has undergone “many dozens of tests” and is progressing well.

“The original idea for those engines were to serve as a propulsion system for the big Mars system, but we are looking at the utility of it on the Falcon program,” she said."

Yeah.  Can we be released from this single thread now that the Raptor on F9 is no longer speculative?

FROM HERE:  http://spacenews.com/spacexs-final-falcon-9-design-coming-this-year-two-falcon-heavy-launches-next-year/

It's just as speculative as ever. Listen to the actual interview, GS was trying to navigate around a leading question and give a noncomittal answer.

Offline hkultala

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Re: Raptor Upper Stage consolidated thread
« Reply #312 on: 06/28/2017 08:04 am »
"Despite describing the Block 5 as the final version of the Falcon 9, Shotwell hinted at the possibility of a future version of the rocket that could use the Raptor engines designed for transportation to Mars. Shotwell said Raptor, a liquid methane and oxygen engine for SpaceX’s interplanetary spaceship, has undergone “many dozens of tests” and is progressing well.

“The original idea for those engines were to serve as a propulsion system for the big Mars system, but we are looking at the utility of it on the Falcon program,” she said."

I think of of the reasons why they are changing their mind about using raptor in falcon rocket is that originally they thought they cannot land raptor-based falcon first stage because of too high minimum T/W, but now they are getting confident that they can do it, and they already proved the minimum T/W is not too high by landing the bulgariasat booster with 3 merlin 1d engines.
« Last Edit: 06/28/2017 08:04 am by hkultala »

Offline envy887

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Re: Raptor Upper Stage consolidated thread
« Reply #313 on: 06/28/2017 11:55 am »
"Despite describing the Block 5 as the final version of the Falcon 9, Shotwell hinted at the possibility of a future version of the rocket that could use the Raptor engines designed for transportation to Mars. Shotwell said Raptor, a liquid methane and oxygen engine for SpaceX’s interplanetary spaceship, has undergone “many dozens of tests” and is progressing well.

“The original idea for those engines were to serve as a propulsion system for the big Mars system, but we are looking at the utility of it on the Falcon program,” she said."

I think of of the reasons why they are changing their mind about using raptor in falcon rocket is that originally they thought they cannot land raptor-based falcon first stage because of too high minimum T/W, but now they are getting confident that they can do it, and they already proved the minimum T/W is not too high by landing the bulgariasat booster with 3 merlin 1d engines.

Or maybe they are considering a actual production run of the 1,000 kN version of Raptor which they already have, which would be a lot closer to a drop-in replacement for Merlin.

Past 3-engine landing burns have gone from 100% on three engines to 40% on just one engine, according to Musk. That's equivalent to a 13% throttle, which I doubt a 3 MN Raptor could do. 25% on a 2 MN version might be possible. But they would have to rework the octaweb for 4 bigger engines.

Online JamesH65

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Re: Raptor Upper Stage consolidated thread
« Reply #314 on: 06/28/2017 11:58 am »
"Despite describing the Block 5 as the final version of the Falcon 9, Shotwell hinted at the possibility of a future version of the rocket that could use the Raptor engines designed for transportation to Mars. Shotwell said Raptor, a liquid methane and oxygen engine for SpaceX’s interplanetary spaceship, has undergone “many dozens of tests” and is progressing well.

“The original idea for those engines were to serve as a propulsion system for the big Mars system, but we are looking at the utility of it on the Falcon program,” she said."

I think of of the reasons why they are changing their mind about using raptor in falcon rocket is that originally they thought they cannot land raptor-based falcon first stage because of too high minimum T/W, but now they are getting confident that they can do it, and they already proved the minimum T/W is not too high by landing the bulgariasat booster with 3 merlin 1d engines.

We have not had any evidence to show they are chaining their mind about a Raptor US. We have one off the cuff comment that they might take a look at it. That's all. Their investigation may be as simple as "We reckon this is a stupid idea, just go and confirm it is"

I've with Jim on this one, it just doesn't seem to have any real reason for existence. Test bed for Raptor? Nah. Not needed. Makes the stage reusable? Nah, too expensive to implement and would never make the cash back. Need for bigger payloads? Nah, not enough payloads to make it pay.

The only thing I can think of that might make a Raptor engined stage on top of an F9 even vaguely useful would be a custom combined stage/satellite dispenser for the constellation. That might be cost effective if they are able to make it reusable.


Offline envy887

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Re: Raptor Upper Stage consolidated thread
« Reply #315 on: 06/28/2017 12:41 pm »
...
The only thing I can think of that might make a Raptor engined stage on top of an F9 even vaguely useful would be a custom combined stage/satellite dispenser for the constellation. That might be cost effective if they are able to make it reusable.

Agree with this, but it would need an integrated fairing with TPS, which starts looking an awful lot like a mini-BFS, which isn't what this thread is about.

Thread for mini-BFS type vehicles is here:
https://forum.nasaspaceflight.com/index.php?topic=43219.0

Offline spacenut

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Re: Raptor Upper Stage consolidated thread
« Reply #316 on: 06/28/2017 12:53 pm »
Since F9 is their bread and butter, and FH will not launch that much.  FH with a Raptor upper stage could become the Mars prep rocket.  They are going to have to install communication satellites in orbit around Mars and some satellites in an orbit between earth and Mars if they want continuous communication with a Martian colony.  This means also if Mars is on the other side of the sun from earth.  FH with a high ISP Raptor upper stage can deploy these satellites.  Also, a colony site that is flat for landings yet close to a large water supply will have to be found.  More drilling will need to be done on Mars to find suitable sites.

This is where a reusable Raptor upper stage comes in.  For deep space use, Mars landings, and Mars satellite deployments. 

They can develop a refuelable upper stage, and use it for Mars deployments.  All of this to test the BFS/ITS equipment. 

Offline envy887

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Re: Raptor Upper Stage consolidated thread
« Reply #317 on: 06/28/2017 01:02 pm »
Since F9 is their bread and butter, and FH will not launch that much.  FH with a Raptor upper stage could become the Mars prep rocket.  They are going to have to install communication satellites in orbit around Mars and some satellites in an orbit between earth and Mars if they want continuous communication with a Martian colony.  This means also if Mars is on the other side of the sun from earth.  FH with a high ISP Raptor upper stage can deploy these satellites.  Also, a colony site that is flat for landings yet close to a large water supply will have to be found.  More drilling will need to be done on Mars to find suitable sites.

This is where a reusable Raptor upper stage comes in.  For deep space use, Mars landings, and Mars satellite deployments. 

They can develop a refuelable upper stage, and use it for Mars deployments.  All of this to test the BFS/ITS equipment.

The current upper stage can do everything that a Raptor stage operating the same way could. Neither would be able to land on Mars.

Offline spacenut

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Re: Raptor Upper Stage consolidated thread
« Reply #318 on: 06/28/2017 01:21 pm »
If the stage is reusable, it could land on Mars if it is refueled in orbit with enough fuel to get there and land.  A reusable stage would have a deep throttling Raptor to land back on earth, so it could land on Mars.   Again, pre testing ITS equipment on a smaller scale.   

The Kerolox upper stage doesn't have the ISP for deep space work and fuel is heavier.  Raptor is going to be able to deep throttle, Merlin can't. 

Offline Ictogan

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Re: Raptor Upper Stage consolidated thread
« Reply #319 on: 06/28/2017 01:42 pm »
If the stage is reusable, it could land on Mars if it is refueled in orbit with enough fuel to get there and land.  A reusable stage would have a deep throttling Raptor to land back on earth, so it could land on Mars.   Again, pre testing ITS equipment on a smaller scale.   

The Kerolox upper stage doesn't have the ISP for deep space work and fuel is heavier.  Raptor is going to be able to deep throttle, Merlin can't.
Landing on Mars is much more complicated than landing on earth. You need much more powerful communication equipment, different guidance, very low boiloff and solar panels(or some other way of generating power or very large batteries).

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