NASASpaceFlight.com Forum

SpaceX Vehicles and Missions => SpaceX Super Heavy/Starship (BFR/BFS) - Earth to Deep Space => Topic started by: Chris Bergin on 03/07/2014 04:57 pm

Title: SpaceX advances drive for Mars rocket via Raptor power
Post by: Chris Bergin on 03/07/2014 04:57 pm
This article is by our very own Alejandro G. Belluscio (Baldusi). Superb debut article for the site, using the info from SpaceX Co-Founder and Vice President of Propulsion Development Tom Mueller with a fascinating engine history piece.

https://www.nasaspaceflight.com/2014/03/spacex-advances-drive-mars-rocket-raptor-power/

---


(EDIT: If you're reading this article in 2016, hi - now we have flying cars and robot dogs! Great! But Raptor has also evolved into this: https://www.nasaspaceflight.com/2016/10/its-propulsion-evolution-raptor-engine/ - anyway, back to 2014, and the lack of flying cars....)

---

This is the first article based on comments made by Mr. Mueller at an event last month, which was attended by one of our L2 members (by chance!) We've been working the information provided at that meeting in L2 - leading to a huge thread of high level evaluations into the engine and notional Mars rocket family, including a lot of renderings, and more to come.

L2 Members, start here - as this OP serves as a sub menu to key items:
http://forum.nasaspaceflight.com/index.php?topic=34145.0

NOTE: The graphics are notional, cropped from the great work by Dmitry Vorontsov in L2. SpaceX have not - to our knowledge - rendered graphics of the Mars Rockets/MCT, which is still *very* early in the planning process. We're being rocket fans and playing with the info Mr. Mueller noted. That will also foster a second article on the rocket/MCT at a later date.
Title: Re: SpaceX advances drive for Mars rocket via Raptor power
Post by: Lars_J on 03/07/2014 05:07 pm
A great article!

So just to be clear - "Full flow" = "staged combustion", as the article implies? Or is there something more to it?
Title: Re: SpaceX advances drive for Mars rocket via Raptor power
Post by: SpaceXFanMan on 03/07/2014 05:13 pm
That wasn't just a cool read, it was an education! Thanks Alejandro! :)
Title: Re: SpaceX advances drive for Mars rocket via Raptor power
Post by: butters on 03/07/2014 05:16 pm
A great article!

So just to be clear - "Full flow" = "staged combustion", as the article implies? Or is there something more to it?

Full-flow staged combustion (FFSC) means that all of the propellant flows through the preburners and turbines before entering the main combustion chamber. There is a fuel-rich preburner for the fuel turbopump and an oxidizer-rich preburner for the oxidizer turbopump. All propellants enter the main combustion chamber as gases (hence the "gas-gas" terminology).

The main advantages of FFSC over gas-liquid SC are that turbine inlet temperatures can be lower (because mass flow rate is higher) and/or chamber pressures can be higher. The design can be tuned to favor either low temps or high pressures. It appears that SpaceX is favoring low temps (i.e. reusability without exotic materials) for Raptor rather than shooting for a very high chamber pressure.
Title: Re: SpaceX advances drive for Mars rocket via Raptor power
Post by: rklaehn on 03/07/2014 05:16 pm
A great article!

So just to be clear - "Full flow" = "staged combustion", as the article implies? Or is there something more to it?

If I understood it correctly, full flow is using staged combustion on both the fuel and the oxidizer size. So
- you take a small fraction of the fuel and burn it with all the oxidizer to drive one turbine
- and you also take a small fraction of the oxidizer and burn it with the all the fuel to drive another turbine

The end result is that every drop of propellant goes through a turbine, hence "full flow". Another implication is that all propellants are gaseous once they enter the main combustion chamber, hence "gas/gas".
Title: Re: SpaceX advances drive for Mars rocket via Raptor power
Post by: baldusi on 03/07/2014 05:18 pm
Thanks Chris for giving me the opportunity to write on your site. You've been a wonderful editor and brought the best parts. BTW, those graphics are awesome. I can't believe I was part of this  :P
Title: Re: SpaceX advances drive for Mars rocket via Raptor power
Post by: Lars_J on 03/07/2014 05:18 pm
Thanks, butters & rklaehn, that helps!
Title: Re: SpaceX advances drive for Mars rocket via Raptor power
Post by: Mark Max Q on 03/07/2014 05:24 pm
Alejandro, that is what Chris would say is "meaty" work. Had no idea about the history, so interesting. LOVE that image of Korolev and Glushko....a picture that says a 1000 words.

Exciting times!
Title: Re: SpaceX advances drive for Mars rocket via Raptor power
Post by: Elmar Moelzer on 03/07/2014 05:32 pm
Great article Alejandro!
Title: Re: SpaceX advances drive for Mars rocket via Raptor power
Post by: DavidH on 03/07/2014 05:37 pm
That wasn't just a cool read, it was an education! Thanks Alejandro! :)

Wow. Quite an education. Thanks. Love L2 for being able to watch this happen!


Are the legs scaled to the same ratio as the F9? The appear to barely be able to reach the ground from their mount points, much less be a stable base.
Title: Re: SpaceX advances drive for Mars rocket via Raptor power
Post by: parham55 on 03/07/2014 05:47 pm
Great work baldusi!
Title: Re: SpaceX advances drive for Mars rocket via Raptor power
Post by: Jamziz on 03/07/2014 06:07 pm
Fantastic article, excellent job.

I'll be holding my breath, waiting for news from the Raptor's R&D test program.
Title: Re: SpaceX advances drive for Mars rocket via Raptor power
Post by: Joffan on 03/07/2014 06:27 pm
Nice work Alejo.

I got a little confused when you were telling us about the concepts presented in 2010, because I'm a skim-reader, so I forgot the context by the time you were talking about how troublesome liquid hydrogen is. :-)

The historical context of full-flow engines was fascinating.
Title: Re: SpaceX advances drive for Mars rocket via Raptor power
Post by: Lobo on 03/07/2014 06:30 pm
Very awesome article!
Title: Re: SpaceX advances drive for Mars rocket via Raptor power
Post by: baldusi on 03/07/2014 06:31 pm
Alejandro, that is what Chris would say is "meaty" work. Had no idea about the history, so interesting. LOVE that image of Korolev and Glushko....a picture that says a 1000 words.
Pictures are all Chris. And as editor he changed some parts for clarity, fact-checked content and left some extra part for a possible future article. He's an Editor (with capital E) and this site excellent record is all thanks to him. So while my name is up there, I see this more as a collaboration. He's humble and traditionally the editor don't always gets all the attribution they deserve.
Btw, some of the best read on the Korolev-Glushko break up can be read in Cherkov's "Rocket and the People vol 4". It's free from NASA's EBook section. The best public information on the RD-270 is on lrpe.de, but it's in Russian. Google Translate does a good consistent job, once you understand what it mistranslates, you can rely on that mistranslation  :P

Are the legs scaled to the same ratio as the F9? The appear to barely be able to reach the ground from their mount points, much less be a stable base.
Please understand that this is a notional drawing. But its done by an actual rocket designer. Until the full image is released, we can only follow this discussion on L2. But it does makes some sense.
You can do some back of the envelope numbers, though. The RD-191 nozzle is 1.5m wide, and supplies 1.9MN. So a 4.5MN should be something around 2.3m~2.5m nozzle diameter. The rest is left as an exercise to the reader  ;)

`
Nice work Alejo.

I got a little confused when you were telling us about the concepts presented in 2010, because I'm a skim-reader, so I forgot the context by the time you were talking about how troublesome liquid hydrogen is. :-)

The historical context of full-flow engines was fascinating.
Thanks! It's very difficult to make an article that flows, and gives information. But I think that this site is characterized exactly because articles add historical data to put each event into context. While doing research on engine cycles, I found that the full flow cycle is almost always seen as an academic concept, too expensive and risky to put into actual use. I wanted to transmit the boldness of SpaceX's move to develop such an engine. So I felt I needed to both talk about the (public) evolution of the Raptor project, at least as I live it, and of the engine cycle.
I tried to put all into a more general history of gas generator/preburner engines. But it got too big an, eventually boring. It simply didn't worked. That's why you need an Editor. In the end I'm very happy with how it turned out.
Title: Re: SpaceX advances drive for Mars rocket via Raptor power
Post by: Prober on 03/07/2014 06:37 pm
Great work baldusi!

I 2nd that ;)
Title: Re: SpaceX advances drive for Mars rocket via Raptor power
Post by: BrightLight on 03/07/2014 06:39 pm
wow
gret article - SpaceX rises one more step - just super.
Title: Re: SpaceX advances drive for Mars rocket via Raptor power
Post by: punder on 03/07/2014 06:44 pm
Yes okay, that was very tease-worthy.   ;D

I have Chertok's volumes on Kindle, so I will tackle them now.  I did read Asif Siddiqi's books--they are really good.

Thanks for an excellent article.

p.s. I am wearing my SpaceX McGregor t-shirt today.   8)
Title: Re: SpaceX advances drive for Mars rocket via Raptor power
Post by: brihath on 03/07/2014 07:04 pm
Baldusi and Chris-

Excellent article, both from a history perspective and distilling Spacex's focus on evolutionary innovation, reliability and reusability.  I am looking forward very much to your report on the Raptor's first test run.  Mr. Musk's team continues to amaze me with what they have accomplished as a privately owned company.

Thanks again for a great article!
Title: Re: SpaceX advances drive for Mars rocket via Raptor power
Post by: TomH on 03/07/2014 07:08 pm
To quote my favorite Vulcan (one eyebrow rises) Fascinating.

Question: If SpaceX builds a this or any HLV, will NASA then be legally required to give up SLS and begin purchasing from SpaceX? Would it depend upon how far along they are with SLS? I could see certain senators wanting to protect SLS. With SpaceX costs being lower and the HLV all made in US, I could also see a lot of pressure to dump SLS. I wonder how many within NASA would want to preserve their HLV and how many would want to drop it in favor of the lower cost LV to enable payload/mission funding. Say SLS has flown 4 times and now needs RS-25e and possibly advanced boosters as well at the same time the new SpaceX HLV comes on line, SLS needs to move to a new block, yet its proponents are citing its performance record as evidence it should continue in a new block rather than being replaced by SX-HLV.

How do you see any or all of these scenarios playing out?
Title: Re: SpaceX advances drive for Mars rocket via Raptor power
Post by: R7 on 03/07/2014 07:25 pm
Great work baldusi!
I 2nd that ;)

I 3rd.

Other sites: copypaste yet another site and publish
NSF: indepth volunteer group work resulting breaking news combined with encyclopedic information bomb.
Title: Re: SpaceX advances drive for Mars rocket via Raptor power
Post by: mrmandias on 03/07/2014 07:35 pm
Very, very good article.
Title: Re: SpaceX advances drive for Mars rocket via Raptor power
Post by: Lee Jay on 03/07/2014 07:43 pm
Great article!  And I agree - very "meaty".
Title: Re: SpaceX advances drive for Mars rocket via Raptor power
Post by: CJ on 03/07/2014 07:55 pm
An absolutely superb article!

That the super-heavy lifter would certainly have a lot of commercial applications if its launch cost per pound is low. Launching a large number of satellites per launch would be just one. 

Title: Re: SpaceX advances drive for Mars rocket via Raptor power
Post by: HarryM on 03/07/2014 07:59 pm
Very good and interesting article!
Title: Re: SpaceX advances drive for Mars rocket via Raptor power
Post by: RocketmanUS on 03/07/2014 08:00 pm
Quote from article "MCT project, which he later revealed to be an acronym for Mars Colonial Transport. This system"

The key word is system. This opens up more possibilities. We maybe looking at in space fueling in LEO and Mars orbit.

Sound like BFR to take crew up to LEO and tankers to LEO. With a transhab going between LEO and Mars orbit. On Mars have reusable SSTO vehicles crew and tankers. This would seem to support flexible and long term for a two world system and beyond.

If SpaceX goes with a 27 engine tri-core they would have to launch from a remote island. I think they will just go with a two stage reusable HLV with similar configurations like Sat-INT-20/21.

To quote my favorite Vulcan (one eyebrow rises) Fascinating.

Question: If SpaceX builds a this or any HLV, will NASA then be legally required to give up SLS and begin purchasing from SpaceX? Would it depend upon how far along they are with SLS? I could see certain senators wanting to protect SLS. With SpaceX costs being lower and the HLV all made in US, I could also see a lot of pressure to dump SLS. I wonder how many within NASA would want to preserve their HLV and how many would want to drop it in favor of the lower cost LV to enable payload/mission funding. Say SLS has flown 4 times and now needs RS-25e and possibly advanced boosters as well at the same time the new SpaceX HLV comes on line, SLS needs to move to a new block, yet its proponents are citing its performance record as evidence it should continue in a new block rather than being replaced by SX-HLV.

How do you see any or all of these scenarios playing out?
Lets first get the Raptor on the test stand. ( I would prefer to roll the dice with SpaceX and NASA move onto in space hardware ).

An absolutely superb article!

That the super-heavy lifter would certainly have a lot of commercial applications if its launch cost per pound is low. Launching a large number of satellites per launch would be just one. 


Five plus payloads of F9 in one launch on BFR to LEO. Payloads then could use SEP to higher orbits.
Title: Re: SpaceX advances drive for Mars rocket via Raptor power
Post by: MATTBLAK on 03/07/2014 08:10 pm
Thanks Chris for giving me the opportunity to write on your site. You've been a wonderful editor and brought the best parts. BTW, those graphics are awesome. I can't believe I was part of this  :P

It was an excellent article and I hope, an historic one.
Title: Re: SpaceX advances drive for Mars rocket via Raptor power
Post by: john smith 19 on 03/07/2014 08:19 pm
Question: If SpaceX builds a this or any HLV, will NASA then be legally required to give up SLS and begin purchasing from SpaceX?
I think in theory NASA has a legal responsibility to use commercial LV's if they meet it's requirements (see Robotbeats sig)

But of course that leaves a lot of wiggle room for wheather a commercial LV "meets" their needs.

Just because it might meet all of NASA's needs does not necessarily mean it would meet the Legislatures needs.  :(  :(

The other issue is schedule.  Right now SLS is due for 1st flight in (IIRC) 2018. Spacex's offering is (presumably) much further out.  :( :(
Title: Re: SpaceX advances drive for Mars rocket via Raptor power
Post by: darkenfast on 03/07/2014 08:20 pm
THIS is why I tell people to come to NASASpaceFlight.com if they want real writing on space flight developments that isn't written by clueless journalists for clueless readers. Good job!
Title: Re: SpaceX advances drive for Mars rocket via Raptor power
Post by: dlapine on 03/07/2014 08:34 pm
Excellent article. I now have a basic understanding of what FFSC is for a rocket engine, and why it might be useful. Keep up the good work.

Is this the engine the SpaceX guys are testing at Stennis? Well, testing the components anyways...
Title: Re: SpaceX advances drive for Mars rocket via Raptor power
Post by: arachnitect on 03/07/2014 08:42 pm
Has anybody run the numbers on a rocket using 1 of these as a first stage engine?
Title: Re: SpaceX advances drive for Mars rocket via Raptor power
Post by: Rocket Science on 03/07/2014 08:42 pm
Exciting news and a masterpiece, bravo baldusi! :)
Title: Re: SpaceX advances drive for Mars rocket via Raptor power
Post by: DJPledger on 03/07/2014 08:58 pm
Excellent article. I now have a basic understanding of what FFSC is for a rocket engine, and why it might be useful. Keep up the good work.

Is this the engine the SpaceX guys are testing at Stennis? Well, testing the components anyways...
Yes they will be testing components of Raptor at Stennis. Don't know yet where the full Raptor will be tested.
Title: Re: SpaceX advances drive for Mars rocket via Raptor power
Post by: R7 on 03/07/2014 09:54 pm
Has anybody run the numbers on a rocket using 1 of these as a first stage engine?

What would be the point of such vehicle? Inferior to F9 and almost certainly expendable.
Title: Re: SpaceX advances drive for Mars rocket via Raptor power
Post by: Coastal Ron on 03/07/2014 10:10 pm

Question: If SpaceX builds a this or any HLV, will NASA then be legally required to give up SLS and begin purchasing from SpaceX? Would it depend upon how far along they are with SLS?

No, for a number of reasons.

From a contracts standpoint the contracts have already been awarded, and there was no provision for re-competing the original need in case alternatives showed up later.

From a political standpoint, in my opinion, the SLS was only conceived to stop layoffs from the cancellation of the Constellation program, and not to address a known amount of approved or funded HLV-sized payloads that needed to be moved to space.  No need to debate this point, I'm just pointing out that this would be yet another reason why even if SpaceX had an HLV sitting on the pad ready to launch today, Senator Shelby would not vote to end the SLS.

The only thing that will stop the SLS at this point is the realization that there is no need for an HLV, regardless who owns it.

So why is SpaceX building their own?  For their own needs, and not anyone else's.  Certainly not to compete against the SLS.
Title: Re: SpaceX advances drive for Mars rocket via Raptor power
Post by: Roy_H on 03/07/2014 10:34 pm

Question: If SpaceX builds a this or any HLV, will NASA then be legally required to give up SLS and begin purchasing from SpaceX? Would it depend upon how far along they are with SLS?

No, for a number of reasons.

From a contracts standpoint the contracts have already been awarded, and there was no provision for re-competing the original need in case alternatives showed up later.

From a political standpoint, in my opinion, the SLS was only conceived to stop layoffs from the cancellation of the Constellation program, and not to address a known amount of approved or funded HLV-sized payloads that needed to be moved to space.  No need to debate this point, I'm just pointing out that this would be yet another reason why even if SpaceX had an HLV sitting on the pad ready to launch today, Senator Shelby would not vote to end the SLS.

The only thing that will stop the SLS at this point is the realization that there is no need for an HLV, regardless who owns it.

So why is SpaceX building their own?  For their own needs, and not anyone else's.  Certainly not to compete against the SLS.

And one other point: Boeing/LM/ULA are "commercial" providers. Just because they get all their funding from NASA to build the SLS does not mean they are a government owned department. Does NASA do 100% of the design and they just build the parts to NASA's specs? If so then maybe you can claim NASA is the builder and not ULA.
Title: Re: SpaceX advances drive for Mars rocket via Raptor power
Post by: Coastal Ron on 03/07/2014 10:48 pm

Question: If SpaceX builds a this or any HLV, will NASA then be legally required to give up SLS and begin purchasing from SpaceX? Would it depend upon how far along they are with SLS?

No, for a number of reasons.

From a contracts standpoint the contracts have already been awarded, and there was no provision for re-competing the original need in case alternatives showed up later.

From a political standpoint, in my opinion, the SLS was only conceived to stop layoffs from the cancellation of the Constellation program, and not to address a known amount of approved or funded HLV-sized payloads that needed to be moved to space.  No need to debate this point, I'm just pointing out that this would be yet another reason why even if SpaceX had an HLV sitting on the pad ready to launch today, Senator Shelby would not vote to end the SLS.

The only thing that will stop the SLS at this point is the realization that there is no need for an HLV, regardless who owns it.

So why is SpaceX building their own?  For their own needs, and not anyone else's.  Certainly not to compete against the SLS.

And one other point: Boeing/LM/ULA are "commercial" providers. Just because they get all their funding from NASA to build the SLS does not mean they are a government owned department. Does NASA do 100% of the design and they just build the parts to NASA's specs? If so then maybe you can claim NASA is the builder and not ULA.

NASA is contracting to have a rocket built for them, they are not buying launch services.

So from that standpoint Boeing is just a contractor.  ULA has nothing to do with the SLS program, and if anything is a competitor for future NASA payload launches.
Title: Re: SpaceX advances drive for Mars rocket via Raptor power
Post by: Chris Bergin on 03/07/2014 10:50 pm
Let's stay focused on this engine, which is what the article is about.
Title: Re: SpaceX advances drive for Mars rocket via Raptor power
Post by: arachnitect on 03/08/2014 12:04 am
Has anybody run the numbers on a rocket using 1 of these as a first stage engine?

What would be the point of such vehicle? Inferior to F9 and almost certainly expendable.

What's the point of the 9 engined beast they say it is for?

I'm trying to figure out if this thing fits anywhere else.
Title: Re: SpaceX advances drive for Mars rocket via Raptor power
Post by: aero on 03/08/2014 12:16 am
Has anybody run the numbers on a rocket using 1 of these as a first stage engine?

What would be the point of such vehicle? Inferior to F9 and almost certainly expendable.

What's the point of the 9 engined beast they say it is for?

I'm trying to figure out if this thing fits anywhere else.

Well, the one Raptor rocket, 1 Mlb, cf the Falcon 9 at 1.5 Mlb, is not much but the 3, 5 and 7 Raptor rockets start to become respectable. I think many would like the 5 Raptor rocket. At 5 Mlb thrust it is closing in on the FH. In fact, with the superior Isp and a single Raptor on the US, it might surpass the FH. I don't feel like calculating it now, someone else can.

Edit:  Just looking at the SpaceX web pages , F 9 and FH, tells me that I should be careful about mixing vac thrust with sea level thrust.

The Raptor's 1 Mlbf thrust is where, sea level or vac? The numbers above assume it is vaccum thrust of the first stage Raptor engine.
Title: Re: SpaceX advances drive for Mars rocket via Raptor power
Post by: baldusi on 03/08/2014 12:52 am
It's vacuum 1Mlbf. So it should be more like an RD-180 at SL. The propellant would be only 78% of what they currently get since it's less dense. So 20% lighter, slightly worse T/W, but 41s/52s of isp advantage. Main issue would be upper stage. Gas generator kerolox isn't that good for high energy performance. My wild guess, close performance but reusability is highly complicated and ground ops would need RP-1 and CH4.
I simply don't see it.
Title: Re: SpaceX advances drive for Mars rocket via Raptor power
Post by: clongton on 03/08/2014 02:02 am
Awesome article Alejandro. Superb work.
Title: Re: SpaceX advances drive for Mars rocket via Raptor power
Post by: Coastal Ron on 03/08/2014 02:23 am
Has anybody run the numbers on a rocket using 1 of these as a first stage engine?

What would be the point of such vehicle? Inferior to F9 and almost certainly expendable.

What's the point of the 9 engined beast they say it is for?

I'm trying to figure out if this thing fits anywhere else.

Per the article:

"Known as the Raptor, nine of these immensely powerful engines – one or three cores – will be utilized to send SpaceX’s Super Heavy Lift Launch Vehicle (SHLV) uphill on missions to Mars.

Keep in mind though that Musk is building this for his own set of requirements.  What that will be, and who will be paying for the complete launcher and it's payloads are unknown at this point.  But Musk recently stated that for what he thinks needs to happen, there was a need for a resuable heavy lift system, hence the need for engines that can be used many times.

As to the comment from R7, I think they meant that a single Raptor engine would not be able to throttle down enough to be reusable in a one-engine-per-core configuration.
Title: Re: SpaceX advances drive for Mars rocket via Raptor power
Post by: Elmar Moelzer on 03/08/2014 02:38 am
Question: If SpaceX builds a this or any HLV, will NASA then be legally required to give up SLS and begin purchasing from SpaceX?
I think in theory NASA has a legal responsibility to use commercial LV's if they meet it's requirements (see Robotbeats sig)

But of course that leaves a lot of wiggle room for wheather a commercial LV "meets" their needs.

Just because it might meet all of NASA's needs does not necessarily mean it would meet the Legislatures needs.  :(  :(

The other issue is schedule.  Right now SLS is due for 1st flight in (IIRC) 2018. Spacex's offering is (presumably) much further out.  :( :(
From what I understand, the first version of the SLS wont have the full capability anyway and subsequent versions might use different components.
Title: Re: SpaceX advances drive for Mars rocket via Raptor power
Post by: vt_hokie on 03/08/2014 03:50 am
I can't wait to see how big the Alpha Centauri rocket ends up being!
Title: Re: SpaceX advances drive for Mars rocket via Raptor power
Post by: Damon Hill on 03/08/2014 04:13 am
I can't wait to see how big the Alpha Centauri rocket ends up being!

Check out some of the Nova-class concepts of the 60s, with SpaceX's components.

Fascinating and informative article.
Title: Re: SpaceX advances drive for Mars rocket via Raptor power
Post by: sdsds on 03/08/2014 04:22 am
Has anybody run the numbers on a rocket using 1 of these as a first stage engine?

I think the more interesting question is what a 3 engine first stage could provide. More than F9 and less than FH?

Per the article:
"Known as the Raptor, nine of these immensely powerful engines – one or three cores – will be utilized to send SpaceX’s Super Heavy Lift Launch Vehicle (SHLV) uphill on missions to Mars.
Title: Re: SpaceX advances drive for Mars rocket via Raptor power
Post by: Zed_Noir on 03/08/2014 05:07 am
Has anybody run the numbers on a rocket using 1 of these as a first stage engine?

What would be the point of such vehicle? Inferior to F9 and almost certainly expendable.

What's the point of the 9 engined beast they say it is for?

I'm trying to figure out if this thing fits anywhere else.

I posted previously that you could swapped 2 Raptors for 9 Merlins in a LV with stock F9 tankage to test out the Raptors real quick for a limited number of flights. Would not be reusable or efficient. The point is the  hacked together LV will have the Raptor engine flying the soonest at minimal development cost.

Or you can use the F9 tooling to make properly proportion tankage for an expandable dual engine core LV with Raptors near the end of their life cycle. Which in theory will also be the possibility of a tri-core heavy version with cross-feeding with 6 Raptors.

Title: Re: SpaceX advances drive for Mars rocket via Raptor power
Post by: TomH on 03/08/2014 05:24 am
We know they want to lease VAB space and Pad 39A, but a tri-core of 10m per core is too big for the doors, and the cost of building their own new assembly facilities for something that big would be immense. So unless I'm missing something, I just don't see how anyone is going to pull off a tri-core that's 30m wide. Obviously for reusability, the octagon + center engine configuration works well for RTLS.

I believe just under 7m per core is about the largest you could fit for a tri core through the VAB doors, so it would seem that they are thinking either 3 x 7m cores or a 10-13m single core. Can you say NOVA?
Title: Re: SpaceX advances drive for Mars rocket via Raptor power
Post by: Zed_Noir on 03/08/2014 05:42 am
We know they want to lease VAB space and Pad 39A, but a tri-core of 10m per core is too big for the doors, and the cost of building their own new assembly facilities for something that big would be immense. So unless I'm missing something, I just don't see how anyone is going to pull off a tri-core that's 30m wide. Obviously for reusability, the octagon + center engine configuration works well for RTLS.

I believe just under 7m per core is about the largest you could fit for a tri core through the VAB doors, so it would seem that they are thinking either 3 x 7m cores or a 10-13m single core. Can you say NOVA?

IIRC SpaceX is only interested in the 39A pad. Guess SpaceX will throw up their own HIF near the pad. After all the only currently envisaged payload is the MCT which make the whole LV stack really lightweight..

Title: Re: SpaceX advances drive for Mars rocket via Raptor power
Post by: TrevorMonty on 03/08/2014 08:22 am
Great article.

Being following this on L2 nice to see it released to the public.

I was originally of option of a 50t-70t reusable LV to replace both FH and F9 but have come around to bigger better concept. Currently there is no market for 50t-70t LV so why target that market, it is to small for going to Mars.
If they are going to create a new engine and LV they may as well go for broke and make 100t plus single core. The LV in reuseable form may even get launch prices down to <$500kg eg $25M for 50t+.

Title: Re: SpaceX advances drive for Mars rocket via Raptor power
Post by: DJPledger on 03/08/2014 08:35 am
As far as we know SpaceX are not planning a Raptor powered LV with less than 9 Raptors on the 1st stage. They have settled on 9 engine 1st stage designs for 1st stage RTLS and engine out capability. Single and 3 engined 1st stages won't have engine out capability and RTLS would be extremely difficult. Engine out capability and RTLS are both extremely important for SpaceX.

There is no point in discussing single, 3, and 5 Raptor 1st stages as there is virtually no chance that SpaceX will develop them. Raptor has been sized for 9 engine cores for SpaceX's Mars ambitions.
Title: Re: SpaceX advances drive for Mars rocket via Raptor power
Post by: woods170 on 03/08/2014 08:58 am
Are the legs scaled to the same ratio as the F9? The appear to barely be able to reach the ground from their mount points, much less be a stable base.

The images of the engine section and legs are notional. Do not read "the thruth" in them. They are just there to help people visualize what is being told in the article. Nothing more, nothing less.
Title: Re: SpaceX advances drive for Mars rocket via Raptor power
Post by: R7 on 03/08/2014 09:17 am
What's the point of the 9 engined beast they say it is for?

I'm trying to figure out if this thing fits anywhere else.

That's the five-hundred-thousand-dollars question. The economics of BFR/MCT seem a bit of taboo.

Other usages ... comsats grow a lot larger? RD-180 substitute  ;D ?
Title: Re: SpaceX advances drive for Mars rocket via Raptor power
Post by: baldusi on 03/08/2014 11:43 am
I believe that making a reusable SHLV like the 9 Raptor core they plan would be risky. As such they'll have to copy as much as they can from the F9R experience. Whatever works and they understand they should keep.
From what I see SpaceX has shown good technology risk management. If they are aiming to the most advanced engine ever, and an unproven propellant, they'll surely try to constrain the risk in other systems.
Title: Re: SpaceX advances drive for Mars rocket via Raptor power
Post by: R7 on 03/08/2014 11:44 am
We know they want to lease VAB space and Pad 39A, but a tri-core of 10m per core is too big for the doors, and the cost of building their own new assembly facilities for something that big would be immense. So unless I'm missing something, I just don't see how anyone is going to pull off a tri-core that's 30m wide.

Move the rocket through the door sideways? Does LUT have to be transported with it, leave it at the pad?
Title: Re: SpaceX advances drive for Mars rocket via Raptor power
Post by: guckyfan on 03/08/2014 12:05 pm
We know they want to lease VAB space

Do you have a source for that?

Title: Re: SpaceX advances drive for Mars rocket via Raptor power
Post by: CuddlyRocket on 03/08/2014 12:12 pm
What's the point of the 9 engined beast they say [the Raptor] is for?

A single-core with nine Raptors is probably cheaper to build than an FH with its three cores and 27 Merlins and have greater performance with easier RTLS. Thus the FH can probably be replaced when this comes into service - but lessons will have been learned in the meantime!
Title: Re: SpaceX advances drive for Mars rocket via Raptor power
Post by: Avron on 03/08/2014 01:05 pm
We know they want to lease VAB space

Do you have a source for that?



That should be interesting, do we know they want to assemble vertically  or just use it for core storage?
Title: Re: SpaceX advances drive for Mars rocket via Raptor power
Post by: Avron on 03/08/2014 01:08 pm
What's the point of the 9 engined beast they say [the Raptor] is for?

A single-core with nine Raptors is probably cheaper to build than an FH with its three cores and 27 Merlins and have greater performance with easier RTLS. Thus the FH can probably be replaced when this comes into service - but lessons will have been learned in the meantime!

What I don't get is why just three cores, look at  Buran booster concept , why not a central core and 4 attached cores?
Title: Re: SpaceX advances drive for Mars rocket via Raptor power
Post by: dante2308 on 03/08/2014 02:59 pm
What's the point of the 9 engined beast they say [the Raptor] is for?

A single-core with nine Raptors is probably cheaper to build than an FH with its three cores and 27 Merlins and have greater performance with easier RTLS. Thus the FH can probably be replaced when this comes into service - but lessons will have been learned in the meantime!

What I don't get is why just three cores, look at  Buran booster concept , why not a central core and 4 attached cores?

I have to wonder if this was a joke. Not because it's a bad question, but because 3 cores already exceeds 350mT to orbit. Speculating, it would seem that they are trying to duplicate the F9/FH and use the lessons learned.
Title: Re: SpaceX advances drive for Mars rocket via Raptor power
Post by: Avron on 03/08/2014 03:14 pm
What's the point of the 9 engined beast they say [the Raptor] is for?

A single-core with nine Raptors is probably cheaper to build than an FH with its three cores and 27 Merlins and have greater performance with easier RTLS. Thus the FH can probably be replaced when this comes into service - but lessons will have been learned in the meantime!

What I don't get is why just three cores, look at  Buran booster concept , why not a central core and 4 attached cores?

I have to wonder if this was a joke. Not because it's a bad question, but because 3 cores already exceeds 350mT to orbit. Speculating, it would seem that they are trying to duplicate the F9/FH and use the lessons learned.

Who says that all the cores need to be 10M, since we are Speculating.
Title: Re: SpaceX advances drive for Mars rocket via Raptor power
Post by: manboy on 03/08/2014 03:23 pm
We know they want to lease VAB space
Last I heard was that SpaceX was planing on building their own hanger outside of the 39A gates.
Title: Re: SpaceX advances drive for Mars rocket via Raptor power
Post by: PeanutGallery on 03/08/2014 03:28 pm
The main advantage of using the same core in a three core design is leveraging the core design for a system of launchers. Using a basic core allows a scalable system by bundling cores. This also supports efficiencies in production by focusing on a singular unit rather than producing many variations.  This is assuming the images that we've seen are what will be built. It's a very strong way of moving forward in the first stages of creating a reusable system, but at the cost of some efficiency.

One inefficiency could be redundancies in the structure. However an additive design has a great deal of flexibility in sizing the booster for the job and having a backup in case of an engine loss during launch. This seems to be the approach in the Falcon family of launchers. However, I have to wonder at what point production or performance issues will force their hand to decide to make a dedicated Raptor powered BFR designed with a more efficient structure.
Title: Re: SpaceX advances drive for Mars rocket via Raptor power
Post by: Llian Rhydderch on 03/08/2014 03:33 pm
What's the point of the 9 engined beast they say [the Raptor] is for?

A single-core with nine Raptors is probably cheaper to build than an FH with its three cores and 27 Merlins and have greater performance with easier RTLS. Thus the FH can probably be replaced when this comes into service - but lessons will have been learned in the meantime!

What I don't get is why just three cores, look at  Buran booster concept , why not a central core and 4 attached cores?

I have to wonder if this was a joke. Not because it's a bad question, but because 3 cores already exceeds 350mT to orbit. Speculating, it would seem that they are trying to duplicate the F9/FH and use the lessons learned.

Who says that all the cores need to be 10M, since we are Speculating.

Well, that was what the article by Alejandro said yesterday:  10 metre core.

Now, Alejandro and Chris and the L2 member at the Mueller meeting in February might be wrong, or SpaceX could always do something else, but there is now a very good reason to just assume that the BFR for MCT (or maybe that's called MCT, unclear) will have a 10m core.

And others on the thread have pointed out the SpaceX desire for low cost tends to drive standardization across as many product offerings as possible, which I think is quite reasonable.

I say, until we have other information, it's a 10 metre core.
Title: Re: SpaceX advances drive for Mars rocket via Raptor power
Post by: PeanutGallery on 03/08/2014 03:33 pm
Perhaps part of Avrons' question was at what point does a side-by-side architecture as used in a three core concept become problematic in operations?
Title: Re: SpaceX advances drive for Mars rocket via Raptor power
Post by: manboy on 03/08/2014 03:35 pm
What's the point of the 9 engined beast they say [the Raptor] is for?

A single-core with nine Raptors is probably cheaper to build than an FH with its three cores and 27 Merlins and have greater performance with easier RTLS. Thus the FH can probably be replaced when this comes into service - but lessons will have been learned in the meantime!

What I don't get is why just three cores, look at  Buran booster concept , why not a central core and 4 attached cores?
Probably for the same reasons that Falcon Heavy only uses three cores.
Title: Re: SpaceX advances drive for Mars rocket via Raptor power
Post by: cro-magnon gramps on 03/08/2014 03:37 pm
What's the point of the 9 engined beast they say [the Raptor] is for?

A single-core with nine Raptors is probably cheaper to build than an FH with its three cores and 27 Merlins and have greater performance with easier RTLS. Thus the FH can probably be replaced when this comes into service - but lessons will have been learned in the meantime!

What I don't get is why just three cores, look at  Buran booster concept , why not a central core and 4 attached cores?

I have to wonder if this was a joke. Not because it's a bad question, but because 3 cores already exceeds 350mT to orbit. Speculating, it would seem that they are trying to duplicate the F9/FH and use the lessons learned.

Who says that all the cores need to be 10M, since we are Speculating.


ok, brainstorming here, so don't shoot the messenger... ;D all this is pipe dreaming... one of you rocket guys would have to vet the figures...
 
1 - 10m core - 9 Raptor Engines
6 - F9 3.7m cores - 3 each Raptor Engines, with a central Merlin 1D
total diameter is about 18m

plan would be, to ignite all Raptors on launch, burn out 3 F9s in the first 90-150 seconds and the other three at 180-240 seconds...
  boost back is initiated when the Raptors are switched off, and the M1D ignites to return to LS,

the central core continues on it's normal way

Still have 27 Raptor Engines, but the simplicity is, that 1) it fits the VAB Doors, and 2) experience with the F9 is retained, 3) there is maximized re-usability of the F9 cores 4) the Launch Pad might not need as extensive a series of upgrades...

Not saying it is likely... Range would have a heart attack with 6 cores coming back within an half hour ;-) but there is an elegance to the idea... and as someone on here has said, a friend of theirs says that we would think them insane, if we knew what they were working on... ;)
Title: Re: SpaceX advances drive for Mars rocket via Raptor power
Post by: DanielW on 03/08/2014 03:49 pm
ok, brainstorming here, so don't shoot the messenger... ;D all this is pipe dreaming... one of you rocket guys would have to vet the figures...
 
1 - 10m core - 9 Raptor Engines
6 - F9 3.7m cores - 3 each Raptor Engines, with a central Merlin 1D
total diameter is about 18m

plan would be, to ignite all Raptors on launch, burn out 3 F9s in the first 90-150 seconds and the other three at 180-240 seconds...
  boost back is initiated when the Raptors are switched off, and the M1D ignites to return to LS,

the central core continues on it's normal way

Still have 27 Raptor Engines, but the simplicity is, that 1) it fits the VAB Doors, and 2) experience with the F9 is retained, 3) there is maximized re-usability of the F9 cores 4) the Launch Pad might not need as extensive a series of upgrades...

Not saying it is likely... Range would have a heart attack with 6 cores coming back within an half hour ;-) but there is an elegance to the idea... and as someone on here has said, a friend of theirs says that we would think them insane, if we knew what they were working on... ;)

The M-1D RP1 vs Raptor Methane would nip this in the bud.
Title: Re: SpaceX advances drive for Mars rocket via Raptor power
Post by: R7 on 03/08/2014 03:53 pm
1 - 10m core - 9 Raptor Engines
6 - F9 3.7m cores - 3 each Raptor Engines, with a central Merlin 1D
total diameter is about 18m

You are missing a lot of propellant compared to full tricore setup. Cross-section of six F9 cores is only ~0.8 of the central core. Or are they more than twice the length?  ;)
Title: Re: SpaceX advances drive for Mars rocket via Raptor power
Post by: cro-magnon gramps on 03/08/2014 03:58 pm
1 - 10m core - 9 Raptor Engines
6 - F9 3.7m cores - 3 each Raptor Engines, with a central Merlin 1D
total diameter is about 18m

You are missing a lot of propellant compared to full tricore setup. Cross-section of six F9 cores is only ~0.8 of the central core. Or are they more than twice the length?  ;)

that's why I need you rocket guys, your my brain-trust :D it was just an idea that sprang to mind when thinking about Avron's suggestion, over morning coffee... reality bites as bad as Karma  :o
Title: Re: SpaceX advances drive for Mars rocket via Raptor power
Post by: DanielW on 03/08/2014 04:17 pm
1 - 10m core - 9 Raptor Engines
6 - F9 3.7m cores - 3 each Raptor Engines, with a central Merlin 1D
total diameter is about 18m

You are missing a lot of propellant compared to full tricore setup. Cross-section of six F9 cores is only ~0.8 of the central core. Or are they more than twice the length?  ;)

And just think of the money and weight you save on the amount of paint required for larger cores! One of the few times the square/cube rule favors bigger structures.

Question: Barlow's formula would indicate to me that mass fraction does not improve with scaling. But that is a pretty naive model of a rocket tank. Are there considerations that improve mass fraction for larger rockets? I know aerodynamics are "better."
Title: Re: SpaceX advances drive for Mars rocket via Raptor power
Post by: deltaV on 03/08/2014 04:35 pm
Question: Barlow's formula would indicate to me that mass fraction does not improve with scaling. But that is a pretty naive model of a rocket tank. Are there considerations that improve mass fraction for larger rockets? I know aerodynamics are "better."

The Dynetics F1-based SLS booster concept paper on L2 (http://forum.nasaspaceflight.com/index.php?topic=30147.0) includes a chart of PMF vs. stage size on page 3. That chart shows that larger stages tend to have better mass fractions. I do not know why this correlation exists.
Title: Re: SpaceX advances drive for Mars rocket via Raptor power
Post by: Damon Hill on 03/08/2014 05:32 pm
What's the point of the 9 engined beast they say [the Raptor] is for?

A single-core with nine Raptors is probably cheaper to build than an FH with its three cores and 27 Merlins and have greater performance with easier RTLS. Thus the FH can probably be replaced when this comes into service - but lessons will have been learned in the meantime!

What I don't get is why just three cores, look at  Buran booster concept , why not a central core and 4 attached cores?


Energia, Buran's launch vehicle, was really two different rockets with two different engines; uneconomical from the start.  (The SU should have gone with clustered Zenits and developed the reusable Zarya, a super-Soyuz).   Falcon 9H's design is one rocket, one engine.  Significantly scaling up from there with more boosters gets into the core's size limitation: not large enough for some payloads, excess complexity.  It's probably doable, but the economics seem to dictate a break point to a new core and new engine.
Title: Re: SpaceX advances drive for Mars rocket via Raptor power
Post by: notsorandom on 03/08/2014 06:00 pm
Question: Barlow's formula would indicate to me that mass fraction does not improve with scaling. But that is a pretty naive model of a rocket tank. Are there considerations that improve mass fraction for larger rockets? I know aerodynamics are "better."

The Dynetics F1-based SLS booster concept paper on L2 (http://forum.nasaspaceflight.com/index.php?topic=30147.0) includes a chart of PMF vs. stage size on page 3. That chart shows that larger stages tend to have better mass fractions. I do not know why this correlation exists.
The ratio of volume to surface area plays a major part in that.
Title: Re: SpaceX advances drive for Mars rocket via Raptor power
Post by: DanielW on 03/08/2014 06:17 pm
Question: Barlow's formula would indicate to me that mass fraction does not improve with scaling. But that is a pretty naive model of a rocket tank. Are there considerations that improve mass fraction for larger rockets? I know aerodynamics are "better."

The Dynetics F1-based SLS booster concept paper on L2 (http://forum.nasaspaceflight.com/index.php?topic=30147.0) includes a chart of PMF vs. stage size on page 3. That chart shows that larger stages tend to have better mass fractions. I do not know why this correlation exists.

Oh man, once again I need L2 access. One of these days.
Title: Re: SpaceX advances drive for Mars rocket via Raptor power
Post by: DanielW on 03/08/2014 06:21 pm
Question: Barlow's formula would indicate to me that mass fraction does not improve with scaling. But that is a pretty naive model of a rocket tank. Are there considerations that improve mass fraction for larger rockets? I know aerodynamics are "better."

The Dynetics F1-based SLS booster concept paper on L2 (http://forum.nasaspaceflight.com/index.php?topic=30147.0) includes a chart of PMF vs. stage size on page 3. That chart shows that larger stages tend to have better mass fractions. I do not know why this correlation exists.
The ratio of volume to surface area plays a major part in that.

You would think so, but as the radius of curvature increases so does the required wall thickness for a given tank pressure. http://en.wikipedia.org/wiki/Barlow%27s_formula It is exactly proportional so the weight savings have to come from more subtle considerations. Perhaps the skin thickness being more a consideration of vertical loading or clever isogrid machining.
Title: Re: SpaceX advances drive for Mars rocket via Raptor power
Post by: cambrianera on 03/08/2014 06:28 pm
Question: Barlow's formula would indicate to me that mass fraction does not improve with scaling. But that is a pretty naive model of a rocket tank. Are there considerations that improve mass fraction for larger rockets? I know aerodynamics are "better."

The Dynetics F1-based SLS booster concept paper on L2 (http://forum.nasaspaceflight.com/index.php?topic=30147.0) includes a chart of PMF vs. stage size on page 3. That chart shows that larger stages tend to have better mass fractions. I do not know why this correlation exists.
The ratio of volume to surface area plays a major part in that.
Barlow's formula says that thickness of your tank increase linearly with D.
Therefore propellant mass increases with D cubed and tank mass increases with D cubed, hence fixed mass fraction.
But while DanielW's observation is theoretically true, the "big is better" effect derives mainly from a "minimum gauge" effect also in tank construction.
Title: Re: SpaceX advances drive for Mars rocket via Raptor power
Post by: aero on 03/08/2014 07:36 pm
Question: Barlow's formula would indicate to me that mass fraction does not improve with scaling. But that is a pretty naive model of a rocket tank. Are there considerations that improve mass fraction for larger rockets? I know aerodynamics are "better."

The Dynetics F1-based SLS booster concept paper on L2 (http://forum.nasaspaceflight.com/index.php?topic=30147.0) includes a chart of PMF vs. stage size on page 3. That chart shows that larger stages tend to have better mass fractions. I do not know why this correlation exists.
The ratio of volume to surface area plays a major part in that.
Barlow's formula says that thickness of your tank increase linearly with D.
Therefore propellant mass increases with D cubed and tank mass increases with D cubed, hence fixed mass fraction.
But while DanielW's observation is theoretically true, the "big is better" effect derives mainly from a "minimum gauge" effect also in tank construction.

I'll pitch in my 2 cents worth.

Volume of a cylinder  goes as height * D^2, and cylinder mass goes as D^2 * thickness. Since thickness is proportional to D, mass is proportional to D^3, agreed. And height  for volume of a minimum mass cylinder is 2 *D, so volume is also proportional to D^3, as stated above.

We have V is proportional to D^3 = 2*D^3, and mass is proportional to D^3 = Constant * D^3 Someone must have an idea of what that Constant equals, so we get Volume/Mass = 2/Constant. The value of the constant changes when different gauge sheets are uses and when different materials are used. The "2" never changes.  ;D




Title: Re: SpaceX advances drive for Mars rocket via Raptor power
Post by: TomH on 03/08/2014 08:12 pm
We know they want to lease VAB space and Pad 39A, but a tri-core of 10m per core is too big for the doors, and the cost of building their own new assembly facilities for something that big would be immense. So unless I'm missing something, I just don't see how anyone is going to pull off a tri-core that's 30m wide.

Move the rocket through the door sideways? Does LUT have to be transported with it, leave it at the pad?

My understanding was that SLS could not do this due to orientation of ML, flame trenches, etc. If SpaceX were to completely redo all those elements for their UHLV, then that could be a possibility.
Title: Re: SpaceX advances drive for Mars rocket via Raptor power
Post by: dante2308 on 03/08/2014 08:26 pm
Needing new infrastructure is a given for a rocket that size. Building a large hanger isn't even on the same order as the factory in terms of cost. The fact that SpaceX is building their own launch site for use in two years would suggest that rebuilding everything, including a VAB would not be prohibitively expensive.
Title: Re: SpaceX advances drive for Mars rocket via Raptor power
Post by: TomH on 03/08/2014 08:30 pm
We know they want to lease VAB space

Do you have a source for that?

I do not. I have gone back to re-read and find mention only of the pad in Chris' articles. My bad.

Last I heard was that SpaceX was planing on building their own hanger outside of the 39A gates.

IIRC SpaceX is only interested in the 39A pad. Guess SpaceX will throw up their own HIF near the pad. After all the only currently envisaged payload is the MCT which make the whole LV stack really lightweight..

Thanks for the correction guys.
Title: Re: SpaceX advances drive for Mars rocket via Raptor power
Post by: go4mars on 03/08/2014 08:43 pm
Added (from Wikipedia) a flock of raptors for scale.  Velociraptors that is.    ;)


This might be the most interesting article I've read on this site.  And that's saying a LOT!
Superb!

Well done to all involved!
Title: Re: SpaceX advances drive for Mars rocket via Raptor power
Post by: R7 on 03/08/2014 08:59 pm
Wiki pressure vessel page (http://en.wikipedia.org/wiki/Pressure_vessel) has info on the mass calcs.

r radius, P internal pressure, t wall thickness, S wall stress, L pipe length, ρ material density. M mass

t = P·r/S      // thickness from Barlow using D = 2·r
M = 2·π·r·L·P·r·ρ/S   // pipe circumference times length (wall area) times wall thickness times density
M = 2·P·π·r2·L·ρ/S   // shuffling and combining
M = 2·P·V·ρ/S      // substitute V = π·r2·L

There's size discussion in gigantism thread (http://forum.nasaspaceflight.com/index.php?topic=32409.0), also good one before that but escapes the mind where it was. Buckling issues emerge when things go really big, IIRC non-pressurized structures like interstages, PLFs start to suffer relative mass increase. Taller fluid columns yield higher dynamics heads. Go really big and you may need to vertically taper wall thickness.

Added (from Wikipedia) a flock of raptors for scale.  Velociraptors that is.    ;)

Oh no, the rise of jurassic unit system...
Title: Re: SpaceX advances drive for Mars rocket via Raptor power
Post by: Elmar Moelzer on 03/08/2014 10:44 pm
Do we know anything (or do we have an educated guess) how throttle able the Raptor engine will be compared to the Merlin 1D?
Title: Re: SpaceX advances drive for Mars rocket via Raptor power
Post by: Llian Rhydderch on 03/08/2014 11:13 pm
Do we know anything (or do we have an educated guess) how throttle able the Raptor engine will be compared to the Merlin 1D?

1) I don't believe the publicly-viewable press has captured and published anything about this.
2) We can infer from the development of the SpaceX reusable technology (https://en.wikipedia.org/wiki/SpaceX_reusable_launch_system_development_program) generally that SpaceX both cares about, and needs, some level of throttle-ability on the rocket engine in order to make it reusable.  Therefore, my take is Probability>0.999 that Raptor is designed to be throttleable.
3) SpaceX is letting very little of the detail of this engine development program out to the public.  So my guess is that we will have to get used to just occasional new (juicy) details coming out in slow dribs and drabs for some years yet.  (Just like we have for the past five years since Raptor was first spoken of in public.)
4) It could be the case that the L2 folks have some more speculation about this; so maybe we'll hear something on engine throttle characteristics from one of them. 

Good question.
Title: Re: SpaceX advances drive for Mars rocket via Raptor power
Post by: llanitedave on 03/09/2014 02:16 am
Considering what was said above about the broad tradeoffs possible between chamber pressure and turbine temperature in this particular design, it would seem that throttleability would be a relatively easy development.
Title: Re: SpaceX advances drive for Mars rocket via Raptor power
Post by: Eer on 03/09/2014 10:09 am
FYI - the article link has been "slashdotted" on slashdot.com.  I'd be interested in knowing any traffic impact that drives.  external link:  http://science-beta.slashdot.org/story/14/03/09/0133210/spacex-wants-to-go-to-mars-and-has-a-plan-to-get-there
Title: Re: SpaceX advances drive for Mars rocket via Raptor power
Post by: baldusi on 03/09/2014 03:01 pm
FYI - the article link has been "slashdotted" on slashdot.com.  I'd be interested in knowing any traffic impact that drives.  external link:  http://science-beta.slashdot.org/story/14/03/09/0133210/spacex-wants-to-go-to-mars-and-has-a-plan-to-get-there
First time I've ever been slashdotted. I did get news there. But never my own.  ;D
Title: Re: SpaceX advances drive for Mars rocket via Raptor power
Post by: clongton on 03/09/2014 03:44 pm
4) It could be the case that the L2 folks have some more speculation about this; so maybe we'll hear something on engine throttle characteristics from one of them.

Not likely. Join L2 :)
Title: Re: SpaceX advances drive for Mars rocket via Raptor power
Post by: Joel on 03/09/2014 05:33 pm
Wow! Great article! Very inspiring!
Title: Re: SpaceX advances drive for Mars rocket via Raptor power
Post by: Prober on 03/09/2014 05:40 pm
FYI - the article link has been "slashdotted" on slashdot.com.  I'd be interested in knowing any traffic impact that drives.  external link:  http://science-beta.slashdot.org/story/14/03/09/0133210/spacex-wants-to-go-to-mars-and-has-a-plan-to-get-there
First time I've ever been slashdotted. I did get news there. But never my own.  ;D

Scary  :-X
Title: Re: SpaceX advances drive for Mars rocket via Raptor power
Post by: arachnitect on 03/09/2014 05:56 pm
As far as we know SpaceX are not planning a Raptor powered LV with less than 9 Raptors on the 1st stage. They have settled on 9 engine 1st stage designs for 1st stage RTLS and engine out capability. Single and 3 engined 1st stages won't have engine out capability and RTLS would be extremely difficult. Engine out capability and RTLS are both extremely important for SpaceX.

There is no point in discussing single, 3, and 5 Raptor 1st stages as there is virtually no chance that SpaceX will develop them. Raptor has been sized for 9 engine cores for SpaceX's Mars ambitions.

There's virtually no chance they're going to build a reusable Saturn V either.

They have many more pressing needs they could be working on. Why this? Why did it become an 800klb engine? The more modest applications of this engine are interesting.
Title: Re: SpaceX advances drive for Mars rocket via Raptor power
Post by: STS Tony on 03/09/2014 11:20 pm
Great article Alejandro!

 So I assume those who said there's no need for HLVs are back on side? ;)
Title: Re: SpaceX advances drive for Mars rocket via Raptor power
Post by: llanitedave on 03/09/2014 11:23 pm
As far as we know SpaceX are not planning a Raptor powered LV with less than 9 Raptors on the 1st stage. They have settled on 9 engine 1st stage designs for 1st stage RTLS and engine out capability. Single and 3 engined 1st stages won't have engine out capability and RTLS would be extremely difficult. Engine out capability and RTLS are both extremely important for SpaceX.

There is no point in discussing single, 3, and 5 Raptor 1st stages as there is virtually no chance that SpaceX will develop them. Raptor has been sized for 9 engine cores for SpaceX's Mars ambitions.

There's virtually no chance they're going to build a reusable Saturn V either.

They have many more pressing needs they could be working on. Why this? Why did it become an 800klb engine? The more modest applications of this engine are interesting.

A mini-raptor of comparable thrust to the Merlin would seem like a useful replacement for the second stage Merlin Vac.  It might address some of the second stage performance issues.  It would be a useful development exercise in preparation for the large raptor as well.

But I doubt that they'll change their plans on my account...
Title: Re: SpaceX advances drive for Mars rocket via Raptor power
Post by: baldusi on 03/10/2014 12:29 am
Great article Alejandro!

 So I assume those who said there's no need for HLVs are back on side? ;)
Thanks Tony! Your opinion means a lot to me.
Personally, I'm on the "mission defines the hardware" side. I completely understand the SLS situation, btw. One interesting thing about Elon is that he made the ultimate mission pretty clear. And nothing is set in stone until the MCT is defined, which won't br until they learn their lessons from F9R and FHR. And they probably are learning a bit with their Red Dragon studies.
That sort of practical approach is the one I like.
On the otherhand, I might be one of the few that think that the asteroid capture mission is genius. They want to demonstrate big SEP, robotic capture of asteroid (think asteroid shielding 101), SLS/Orion in deep space, working on zero-g with an actual asteroid and validating BEO ECLSS without the risk. For the price, it's simply genius. Regrettably, NASA seems to be failing at explaining the reasoning, otherwise known as "inspiring".
The other thing that I like about SpaceX's approach is that they are workin on the critical path first: propulsion. If that part of SLI hadn't been cancelled, things would have been much easier for EELV, COTS, crew and HLV. If I had to criticize Exploration, wjich is ridiculous being the mere amateur that I am, is that they seem to do mega programs that take a decade to finish and then use 100% of available resources for 30 years. I'd rather use 90% for 40  years and use 10% for slowly developing the next one. And thus, allow for a smoother transition. But that's just me, the conservative.
Title: Re: SpaceX advances drive for Mars rocket via Raptor power
Post by: beancounter on 03/10/2014 12:49 am
As far as we know SpaceX are not planning a Raptor powered LV with less than 9 Raptors on the 1st stage. They have settled on 9 engine 1st stage designs for 1st stage RTLS and engine out capability. Single and 3 engined 1st stages won't have engine out capability and RTLS would be extremely difficult. Engine out capability and RTLS are both extremely important for SpaceX.

There is no point in discussing single, 3, and 5 Raptor 1st stages as there is virtually no chance that SpaceX will develop them. Raptor has been sized for 9 engine cores for SpaceX's Mars ambitions.

There's virtually no chance they're going to build a reusable Saturn V either.

They have many more pressing needs they could be working on. Why this? Why did it become an 800klb engine? The more modest applications of this engine are interesting.

You're missing the point.  What is SpaceX and Elon's mission?  It's to make mankind interplantary and as a first step, get Elon to Mars. 
Both Raptor and reusable architecture is apparently essential to this mission according to the words of Elon.
Engines and vehicles will be sized accordingly along with cost.
So it's not about their current markets or payloads. 
Title: Re: SpaceX advances drive for Mars rocket via Raptor power
Post by: john smith 19 on 03/10/2014 08:04 am
If I understood it correctly, full flow is using staged combustion on both the fuel and the oxidizer size. So
- you take a small fraction of the fuel and burn it with all the oxidizer to drive one turbine
- and you also take a small fraction of the oxidizer and burn it with the all the fuel to drive another turbine

The end result is that every drop of propellant goes through a turbine, hence "full flow". Another implication is that all propellants are gaseous once they enter the main combustion chamber, hence "gas/gas".
True.

It's other big advantage (that Aerojet have been touting for decades) is that the seals between the preburners and the fluids they pump no longer have to be Critcality 1 must-not-ever-happen failures.

In contrast the system on the SSME meant the inter-propellant seal on the LOX turbopump was a maintenance nightmare. The under performance of the seal technology (later corrected but never implemented) was part of the reason each engine needed an additional 370lb GHe purge tank, as the purge gas rate was 3x it's designed level.

One thing to note about Spacex is they really don't like to maintain separate configurations of anything.

My instinct is that once Raptor proves out they will switch all engines to LNG, giving a performance boost to the F9, F9R.

F9 v 1.2? Probably a topic for another thread.
Title: Re: SpaceX advances drive for Mars rocket via Raptor power
Post by: Oli on 03/10/2014 10:46 am
My instinct is that once Raptor proves out they will switch all engines to LNG, giving a performance boost to the F9, F9R.

F9 v 1.2? Probably a topic for another thread.

Yeah I think people focus too much on MCT and other fantansies.

Raptor how it is envisaged would be a good first stage engine for F9/F9H and also for a SLS booster for example.

It's other big advantage (that Aerojet have been touting for decades) is that the seals between the preburners and the fluids they pump no longer have to be Critcality 1 must-not-ever-happen failures.

Now everyone is emphasizing the advantages of full flow because SpaceX has chosen it, but its still the most difficult cycle. Funny how fast people deviate from the "keep it simple, stupid" mantra once SpaceX does.
 
Title: Re: SpaceX advances drive for Mars rocket via Raptor power
Post by: IRobot on 03/10/2014 10:54 am
Now everyone is emphasizing the advantages of full flow because SpaceX has chosen it, but its still the most difficult cycle. Funny how fast people deviate from the "keep it simple, stupid" mantra once SpaceX does.
Difficult to develop, maybe simple to operate. So it may end up being a KISS approach.
Title: Re: SpaceX advances drive for Mars rocket via Raptor power
Post by: docmordrid on 03/10/2014 11:39 am
In the NSF article it states one of NASA'S IPD goals was an engine good for 200 missions, which fits squarely into SpaceX's stated reusability plans. Sounds like exactly the kind of choice they'd be expected to make.
Title: Re: SpaceX advances drive for Mars rocket via Raptor power
Post by: Proponent on 03/10/2014 12:25 pm
Question: Barlow's formula would indicate to me that mass fraction does not improve with scaling. But that is a pretty naive model of a rocket tank. Are there considerations that improve mass fraction for larger rockets? I know aerodynamics are "better."

The Dynetics F1-based SLS booster concept paper on L2 (http://forum.nasaspaceflight.com/index.php?topic=30147.0 (http://forum.nasaspaceflight.com/index.php?topic=30147.0)) includes a chart of PMF vs. stage size on page 3. That chart shows that larger stages tend to have better mass fractions. I do not know why this correlation exists.

There is also the attached paper by John Whitehead about mass ratios.  It's focused on SSTO, but it analyses some classic rocket stages and shows how weight breaks down by different components.  It's not just about the tankage....
Title: Re: SpaceX advances drive for Mars rocket via Raptor power
Post by: Oli on 03/10/2014 01:17 pm
Now everyone is emphasizing the advantages of full flow because SpaceX has chosen it, but its still the most difficult cycle. Funny how fast people deviate from the "keep it simple, stupid" mantra once SpaceX does.
Difficult to develop, maybe simple to operate. So it may end up being a KISS approach.

The only obvious advantage I see is that the seal on the oxidizer side is not that critical (or on the fuel side if the pre-burner is oxygen rich), otherwise it looks more complex and more expensive. Anyway, not an engine expert.
Title: Re: SpaceX advances drive for Mars rocket via Raptor power
Post by: IRobot on 03/10/2014 01:35 pm
Now everyone is emphasizing the advantages of full flow because SpaceX has chosen it, but its still the most difficult cycle. Funny how fast people deviate from the "keep it simple, stupid" mantra once SpaceX does.
Difficult to develop, maybe simple to operate. So it may end up being a KISS approach.

The only obvious advantage I see is that the seal on the oxidizer side is not that critical (or on the fuel side if the pre-burner is oxygen rich), otherwise it looks more complex and more expensive. Anyway, not an engine expert.
It extends engine life, increases isp, lower pressure in the pumping system...
Title: Re: SpaceX advances drive for Mars rocket via Raptor power
Post by: JBF on 03/10/2014 01:52 pm
My instinct is that once Raptor proves out they will switch all engines to LNG, giving a performance boost to the F9, F9R.
F9 v 1.2? Probably a topic for another thread.

I disagree, looking at how big the initial raptor engine is, they would loose the engine out capability.  They would have to develop a smaller version and so far there is no indication they are working on that.
Title: Re: SpaceX advances drive for Mars rocket via Raptor power
Post by: muomega0 on 03/10/2014 01:56 pm
Quote
However, the most interesting engine shown was the Raptor engine.

In a complete break with the company’s tradition, it introduced both a new propellant and a new engine cycle.

The Raptor engine, as presented, was planned as a staged combustion, liquid hydrogen and oxygen engine with a vacuum thrust of 150klbf (667kN) and 470s of isp – designated to power the upper stage of the super heavy rockets.

LOX/LH2 Raptor...should turn a few heads.

Out of the gravity well, ISP rules, so a LH2 version is not surprising at all.  Expensive LH2 transfer stage engines can cost way more than methane and still minimize costs deep space because of the relative mass fraction of LH2 vs methane--GTO, perhaps not.

Extra product line and complexity? -  Aerojet has many lines.  LH2 Centaur has over 150 deep space missions over the decades (http://forum.nasaspaceflight.com/index.php?topic=33862.msg1151128#msg1151128)

RL-10:  LH2/LOX  5.5 or 5.85:1  Thrust (vac.)    110 kN (25,000 lbf)
Isp (vac.) 450 to 465.5 seconds (4.413 to 4.565 km/s)  Burn time  700 seconds Dry weight 277 kg (611 lb)

In the gas n go architecture, SpaceX can actually deliver and then transfer payload with several blends of fuel.  Perhaps they want to meet the (actual) needs of many customers, not just a few and fit into An Exploration Roadmap that is launch vehicle independent-NASA's new charter. (http://forum.nasaspaceflight.com/index.php?topic=34115.msg1169086#msg1169086)
Title: Re: SpaceX advances drive for Mars rocket via Raptor power
Post by: Elmar Moelzer on 03/10/2014 02:02 pm
Quote
However, the most interesting engine shown was the Raptor engine.

In a complete break with the company’s tradition, it introduced both a new propellant and a new engine cycle.

The Raptor engine, as presented, was planned as a staged combustion, liquid hydrogen and oxygen engine with a vacuum thrust of 150klbf (667kN) and 470s of isp – designated to power the upper stage of the super heavy rockets.

LOX/LH2 Raptor...should turn a few heads.

Out of the gravity well, ISP rules, so a LH2 version is not surprising at all.  Expensive LH2 transfer stage engines can cost way more than methane and still minimize costs deep space because of the relative mass fraction of LH2 vs methane--GTO, perhaps not.

Extra product line and complexity? -  Aerojet has many lines.  LH2 Centaur has over 150 deep space missions over the decades (http://forum.nasaspaceflight.com/index.php?topic=33862.msg1151128#msg1151128)

RL-10:  LH2/LOX  5.5 or 5.85:1  Thrust (vac.)    110 kN (25,000 lbf)
Isp (vac.) 450 to 465.5 seconds (4.413 to 4.565 km/s)  Burn time  700 seconds Dry weight 277 kg (611 lb)

In the gas n go architecture, SpaceX can actually deliver and then transfer payload with several blends of fuel.  Perhaps they want to meet the (actual) needs of many customers, not just a few and fit into An Exploration Roadmap that is launch vehicle independent-NASA's new charter. (http://forum.nasaspaceflight.com/index.php?topic=34115.msg1169086#msg1169086)
Unless I misunderstood something, the LH2 version of the Raptor engine has been abandoned in favor of the methane version.
Title: Re: SpaceX advances drive for Mars rocket via Raptor power
Post by: JBF on 03/10/2014 02:03 pm
Quote
However, the most interesting engine shown was the Raptor engine.

In a complete break with the company’s tradition, it introduced both a new propellant and a new engine cycle.

The Raptor engine, as presented, was planned as a staged combustion, liquid hydrogen and oxygen engine with a vacuum thrust of 150klbf (667kN) and 470s of isp – designated to power the upper stage of the super heavy rockets.

LOX/LH2 Raptor...should turn a few heads.

Out of the gravity well, ISP rules, so a LH2 version is not surprising at all.  Expensive LH2 transfer stage engines can cost way more than methane and still minimize costs deep space because of the relative mass fraction of LH2 vs methane--GTO, perhaps not.

Extra product line and complexity? -  Aerojet has many lines.  LH2 Centaur has over 150 deep space missions over the decades (http://forum.nasaspaceflight.com/index.php?topic=33862.msg1151128#msg1151128)

RL-10:  LH2/LOX  5.5 or 5.85:1  Thrust (vac.)    110 kN (25,000 lbf)
Isp (vac.) 450 to 465.5 seconds (4.413 to 4.565 km/s)  Burn time  700 seconds Dry weight 277 kg (611 lb)

In the gas n go architecture, SpaceX can actually deliver and then transfer payload with several blends of fuel.  Perhaps they want to meet the (actual) needs of many customers, not just a few and fit into An Exploration Roadmap that is launch vehicle independent-NASA's new charter. (http://forum.nasaspaceflight.com/index.php?topic=34115.msg1169086#msg1169086)

Where is that quote from?  I have a hard time believing they will go to LH2 due to the increased costs associated with using it.
Title: Re: SpaceX advances drive for Mars rocket via Raptor power
Post by: muomega0 on 03/10/2014 02:16 pm
Quote from: NSF-AlejandroG.Belluscio(Baldusi)
However, the most interesting engine shown was the Raptor engine.

In a complete break with the company’s tradition, it introduced both a new propellant and a new engine cycle.

The Raptor engine, as presented, was planned as a staged combustion, liquid hydrogen and oxygen engine with a vacuum thrust of 150klbf (667kN) and 470s of isp – designated to power the upper stage of the super heavy rockets.

LOX/LH2 Raptor...should turn a few heads.

Out of the gravity well, ISP rules, so a LH2 version is not surprising at all.  Expensive LH2 transfer stage engines can cost way more than methane and still minimize costs deep space because of the relative mass fraction of LH2 vs methane--GTO, perhaps not.

Extra product line and complexity? -  Aerojet has many lines.  LH2 Centaur has over 150 deep space missions over the decades (http://forum.nasaspaceflight.com/index.php?topic=33862.msg1151128#msg1151128)

RL-10:  LH2/LOX  5.5 or 5.85:1  Thrust (vac.)    110 kN (25,000 lbf)
Isp (vac.) 450 to 465.5 seconds (4.413 to 4.565 km/s)  Burn time  700 seconds Dry weight 277 kg (611 lb)

In the gas n go architecture, SpaceX can actually deliver and then transfer payload with several blends of fuel.  Perhaps they want to meet the (actual) needs of many customers, not just a few and fit into An Exploration Roadmap that is launch vehicle independent-NASA's new charter. (http://forum.nasaspaceflight.com/index.php?topic=34115.msg1169086#msg1169086)

Where is that quote from?  I have a hard time believing they will go to LH2 due to the increased costs associated with using it.

I just read the first post of this thread and read the article by Alejandro G. Belluscio "SpaceX advances drive for Mars rocket via Raptor power",    March 7, 2014  From the article, L2 viewers knew of this earlier.

This article is by our very own Alejandro G. Belluscio (Baldusi). Superb debut article for the site, using the info from SpaceX Co-Founder and Vice President of Propulsion Development Tom Mueller with a fascinating engine history piece.

http://www.nasaspaceflight.com/2014/03/spacex-advances-drive-mars-rocket-raptor-power/

This is the first article based on comments made by Mr. Mueller at an event last month, which was attended by one of our L2 members (by chance!) We've been working the information provided at that meeting in L2 - leading to a huge thread of high level evaluations into the engine and notional Mars rocket family, including a lot of renderings, and more to come.

L2 Members, start here - as this OP serves as a sub menu to key items:
http://forum.nasaspaceflight.com/index.php?topic=34145.0

NOTE: The graphics are notional, cropped from the great work by Dmitry Vorontsov in L2. SpaceX have not - to our knowledge - rendered graphics of the Mars Rockets/MCT, which is still *very* early in the planning process. We're being rocket fans and playing with the info Mr. Mueller noted. That will also foster a second article on the rocket/MCT at a later date.
Title: Re: SpaceX advances drive for Mars rocket via Raptor power
Post by: MikeAtkinson on 03/10/2014 02:20 pm

http://www.nasaspaceflight.com/2014/03/spacex-advances-drive-mars-rocket-raptor-power/

"However, information on the Raptor was updated on February 19, when VP of Propulsion Development Tom Mueller – speaking at the “Exploring the Next Frontier: The Commercialization of Space is Lifting Off” event in Santa Barbara, California - revealed the Raptor had mutated to a 1Mlbf (4,500kN) gas-gas (full flow) liquid methane and oxygen engine, with an isp of 321s at sea level 363s at vacuum."

my bold, Seems pretty clear to me!
Title: Re: SpaceX advances drive for Mars rocket via Raptor power
Post by: Oli on 03/10/2014 02:36 pm
Now everyone is emphasizing the advantages of full flow because SpaceX has chosen it, but its still the most difficult cycle. Funny how fast people deviate from the "keep it simple, stupid" mantra once SpaceX does.
Difficult to develop, maybe simple to operate. So it may end up being a KISS approach.

The only obvious advantage I see is that the seal on the oxidizer side is not that critical (or on the fuel side if the pre-burner is oxygen rich), otherwise it looks more complex and more expensive. Anyway, not an engine expert.
It extends engine life, increases isp, lower pressure in the pumping system...

And you need an additional preburner/turbine running on oxygen-rich gas. How does that affect reusability? On the positive side you avoid the aforementioned sealing issues. In the document below there is a comparison of the 2 cycles for a hydrolox engine with the same specs (thrust, CC pressure, ISP):

http://elib.dlr.de/78208/1/Prop2012-2.pdf

While the conclusion says the full-flow cycle appears to be more promising for the future due to operational issues, I wish people here would not always make it look like it was such an obvious choice.

Title: Re: SpaceX advances drive for Mars rocket via Raptor power
Post by: muomega0 on 03/10/2014 02:37 pm

http://www.nasaspaceflight.com/2014/03/spacex-advances-drive-mars-rocket-raptor-power/

"However, information on the Raptor was updated on February 19, when VP of Propulsion Development Tom Mueller – speaking at the “Exploring the Next Frontier: The Commercialization of Space is Lifting Off” event in Santa Barbara, California - revealed the Raptor had mutated to a 1Mlbf (4,500kN) gas-gas (full flow) liquid methane and oxygen engine, with an isp of 321s at sea level 363s at vacuum."

my bold, Seems pretty clear to me!
The result is contrary to intuition and many other studies, but should have read further..oops :P
 
Clearly the mT/year is reduced dramatically for this approach to be more cost effective, the ever changing goal posts.  Thanks for the clarification.
Title: Re: SpaceX advances drive for Mars rocket via Raptor power
Post by: Valcan on 03/10/2014 02:55 pm
Really as the article states there are multiple reasons for the shift. Part of it is the ability to produce Methane on Mars. Another is the cost/benefits of hydrogen vs methane

Methane is a much more robust design less ware over all.
Title: Re: SpaceX advances drive for Mars rocket via Raptor power
Post by: baldusi on 03/10/2014 03:28 pm
Quote
However, the most interesting engine shown was the Raptor engine.

In a complete break with the company’s tradition, it introduced both a new propellant and a new engine cycle.

The Raptor engine, as presented, was planned as a staged combustion, liquid hydrogen and oxygen engine with a vacuum thrust of 150klbf (667kN) and 470s of isp – designated to power the upper stage of the super heavy rockets.

LOX/LH2 Raptor...should turn a few heads.

Out of the gravity well, ISP rules, so a LH2 version is not surprising at all.  Expensive LH2 transfer stage engines can cost way more than methane and still minimize costs deep space because of the relative mass fraction of LH2 vs methane--GTO, perhaps not.

Extra product line and complexity? -  Aerojet has many lines.  LH2 Centaur has over 150 deep space missions over the decades (http://forum.nasaspaceflight.com/index.php?topic=33862.msg1151128#msg1151128)

RL-10:  LH2/LOX  5.5 or 5.85:1  Thrust (vac.) 110 kN (25,000 lbf)
Isp (vac.) 450 to 465.5 seconds (4.413 to 4.565 km/s)  Burn time  700 seconds Dry weight 277 kg (611 lb)

In the gas n go architecture, SpaceX can actually deliver and then transfer payload with several blends of fuel.  Perhaps they want to meet the (actual) needs of many customers, not just a few and fit into An Exploration Roadmap that is launch vehicle independent-NASA's new charter. (http://forum.nasaspaceflight.com/index.php?topic=34115.msg1169086#msg1169086)
Please continue reading the article. The H2/LOX version of Raptor was presented by Muller in 2010 and Elon called it a "bunch of brainstorming ideas". If you continue reading you'll see what public info there is to how the Raptor project went mutating from H2/LOX FRSC upper stage engine to a CH4/LOX FFSC first stage engine.
Title: Re: SpaceX advances drive for Mars rocket via Raptor power
Post by: baldusi on 03/10/2014 03:37 pm
Now everyone is emphasizing the advantages of full flow because SpaceX has chosen it, but its still the most difficult cycle. Funny how fast people deviate from the "keep it simple, stupid" mantra once SpaceX does.
Difficult to develop, maybe simple to operate. So it may end up being a KISS approach.

The only obvious advantage I see is that the seal on the oxidizer side is not that critical (or on the fuel side if the pre-burner is oxygen rich), otherwise it looks more complex and more expensive. Anyway, not an engine expert.
It extends engine life, increases isp, lower pressure in the pumping system...

And you need an additional preburner/turbine running on oxygen-rich gas. How does that affect reusability? On the positive side you avoid the aforementioned sealing issues. In the document below there is a comparison of the 2 cycles for a hydrolox engine with the same specs (thrust, CC pressure, ISP):

http://elib.dlr.de/78208/1/Prop2012-2.pdf

While the conclusion says the full-flow cycle appears to be more promising for the future due to operational issues, I wish people would not always make it look like it was such an obvious choice.
Well, one issue with full flow is that you can tune for reusability or performance. Which is what the Russians seem to have done with the fuel rich staged combustion RD-0162. It's run at 15MPa, which is one of the lowest MCC pressure I've heard for SC. But it's supposed to las 25 firings and can do 133%.
My RPA calculations on the Raptor was 20.5MPa of MCC and 45 expansion ratio o  the nozzle. I didn't run the numbers, but I guess the OR preburner is run unde 700K. And the TP outlet pressure should be under 50MPa. I'm guessing, of course. But that is a much more benign environment than an RD-171M, and that is rated for 10 uses.
Title: Re: SpaceX advances drive for Mars rocket via Raptor power
Post by: Oli on 03/10/2014 03:53 pm
Now everyone is emphasizing the advantages of full flow because SpaceX has chosen it, but its still the most difficult cycle. Funny how fast people deviate from the "keep it simple, stupid" mantra once SpaceX does.
Difficult to develop, maybe simple to operate. So it may end up being a KISS approach.

The only obvious advantage I see is that the seal on the oxidizer side is not that critical (or on the fuel side if the pre-burner is oxygen rich), otherwise it looks more complex and more expensive. Anyway, not an engine expert.
It extends engine life, increases isp, lower pressure in the pumping system...

And you need an additional preburner/turbine running on oxygen-rich gas. How does that affect reusability? On the positive side you avoid the aforementioned sealing issues. In the document below there is a comparison of the 2 cycles for a hydrolox engine with the same specs (thrust, CC pressure, ISP):

http://elib.dlr.de/78208/1/Prop2012-2.pdf

While the conclusion says the full-flow cycle appears to be more promising for the future due to operational issues, I wish people would not always make it look like it was such an obvious choice.
Well, one issue with full flow is that you can tune for reusability or performance. Which is what the Russians seem to have done with the fuel rich staged combustion RD-0162. It's run at 15MPa, which is one of the lowest MCC pressure I've heard for SC. But it's supposed to las 25 firings and can do 133%.
My RPA calculations on the Raptor was 20.5MPa of MCC and 45 expansion ratio o  the nozzle. I didn't run the numbers, but I guess the OR preburner is run unde 700K. And the TP outlet pressure should be under 50MPa. I'm guessing, of course. But that is a much more benign environment than an RD-171M, and that is rated for 10 uses.

It seems though that at least for lower CC pressures the additional turbine power you get with full flow (which you can use to tune for reusability) isn't that big.

In any case, I came across this post about the RD-0162:

http://forum.nasaspaceflight.com/index.php?topic=26995.msg819880#msg819880

If the translation of the Russian article by krytek is accurate, it says

" - Fuel rich staged combustion increases reliability several times while being much cheaper than comparable oxidizer rich engines."

Of all people, shouldn't the Russians know what they talk about in that respect?

Title: Re: SpaceX advances drive for Mars rocket via Raptor power
Post by: guckyfan on 03/10/2014 04:14 pm
This engine will run fuel rich. Only the preburner of the LOX pump will be oxygen rich. That preburner may be a part that can be swapped frequently and easily. Not too hard or expensive if the engine is designed that way.

Title: Re: SpaceX advances drive for Mars rocket via Raptor power
Post by: Lobo on 03/10/2014 04:25 pm
My instinct is that once Raptor proves out they will switch all engines to LNG, giving a performance boost to the F9, F9R.
F9 v 1.2? Probably a topic for another thread.

I disagree, looking at how big the initial raptor engine is, they would loose the engine out capability.  They would have to develop a smaller version and so far there is no indication they are working on that.

How would they land the booster stage with just one single engine on it?  They'd need a throttle range of down to probably less than 10% in order to approximate a single M1D at it's 70% throttle point. 

Not to mention Raptor is WAY too big to replace M1D-Vac on the upper stage.

As JBF said, if F9 is ever switched to a methalox engine it might be in conjunction with the need for MCT to have a lower power "thruster" engine to land on Mars with, as the 1Mlbf Raptor could be much to powerful to land.  Good to take off again, but not to land, wher eMCT will be almost empty, and in 1/3 Mars gravity. 
So perhaps there could be a smaller version of Raptor developed that would be desiegned to work in a cluster on F9, and as a landing thruster for MCT.

Title: Re: SpaceX advances drive for Mars rocket via Raptor power
Post by: Lobo on 03/10/2014 04:33 pm
In the NSF article it states one of NASA'S IPD goals was an engine good for 200 missions, which fits squarely into SpaceX's stated reusability plans. Sounds like exactly the kind of choice they'd be expected to make.

Hmmm...sonds like this would have made for a good SSME, in a different history...

Title: Re: SpaceX advances drive for Mars rocket via Raptor power
Post by: Oli on 03/10/2014 04:38 pm
This engine will run fuel rich. Only the preburner of the LOX pump will be oxygen rich. That preburner may be a part that can be swapped frequently and easily. Not too hard or expensive if the engine is designed that way.

I don't know what you mean, "half" of the engine will run oxygen-rich, from preburner to injection into the CC.
Title: Re: SpaceX advances drive for Mars rocket via Raptor power
Post by: Lobo on 03/10/2014 04:40 pm
We know they want to lease VAB space and Pad 39A, but a tri-core of 10m per core is too big for the doors, and the cost of building their own new assembly facilities for something that big would be immense. So unless I'm missing something, I just don't see how anyone is going to pull off a tri-core that's 30m wide.

Move the rocket through the door sideways? Does LUT have to be transported with it, leave it at the pad?

My understanding was that SLS could not do this due to orientation of ML, flame trenches, etc. If SpaceX were to completely redo all those elements for their UHLV, then that could be a possibility.

They couldn't using the VAB.

Possibly they could put it at a 90 deg angle to the flame trench if they stack at the pad, but it's still over 2X as much thrust as the pad can handle.

There will have to a be a new, purpose built pad somewhere for the tri-core.  39A and 39B just weren't built for something like that.  There could be a "39C" buit there just to the Northwest of 39B.  kind of where the original 39C was supposed to go, but south of highway 402.  Maybe horizontal integration and putting up vertical on the pad.
There's areas in South Texas that might have potential too.  Inland from the coast a bit.
Title: Re: SpaceX advances drive for Mars rocket via Raptor power
Post by: JBF on 03/10/2014 04:43 pm
Once they get to full 1st and 2nd stage reusability a coast launch site becomes less necessary.
Title: Re: SpaceX advances drive for Mars rocket via Raptor power
Post by: Lobo on 03/10/2014 04:48 pm
Do we know anything (or do we have an educated guess) how throttle able the Raptor engine will be compared to the Merlin 1D?

1) I don't believe the publicly-viewable press has captured and published anything about this.
2) We can infer from the development of the SpaceX reusable technology (https://en.wikipedia.org/wiki/SpaceX_reusable_launch_system_development_program) generally that SpaceX both cares about, and needs, some level of throttle-ability on the rocket engine in order to make it reusable.  Therefore, my take is Probability>0.999 that Raptor is designed to be throttleable.
3) SpaceX is letting very little of the detail of this engine development program out to the public.  So my guess is that we will have to get used to just occasional new (juicy) details coming out in slow dribs and drabs for some years yet.  (Just like we have for the past five years since Raptor was first spoken of in public.)
4) It could be the case that the L2 folks have some more speculation about this; so maybe we'll hear something on engine throttle characteristics from one of them. 

Good question.

RD-180 is supposed to be able to throttle down to 30%, so I would assume Raptor could do at least that too, perhaps more.  A driver will be if SpaceX wants MCT to land on Mars using Raptor.  It will need a very deep throttle for that. 
Raptors is a 450mt-f engine.  Even if MCT is a whopping 100mt (1/3 of what a tri-core heavy should at least be able to throw into LEO) when landing almost dry, given Mars gravity is about 1/3 of Earth, that's the equivalent of 33mt of mass.  So it would need 7% throttle to hover on Mars.
That might be difficult, but necessary unless they have smaller landing thrusters.
If they do have smaller landing thrusters, then Raptor probably would be ok with a throttle range like the RD-180.
Title: Re: SpaceX advances drive for Mars rocket via Raptor power
Post by: starsilk on 03/10/2014 04:56 pm
We know they want to lease VAB space and Pad 39A, but a tri-core of 10m per core is too big for the doors, and the cost of building their own new assembly facilities for something that big would be immense. So unless I'm missing something, I just don't see how anyone is going to pull off a tri-core that's 30m wide.

Move the rocket through the door sideways? Does LUT have to be transported with it, leave it at the pad?

My understanding was that SLS could not do this due to orientation of ML, flame trenches, etc. If SpaceX were to completely redo all those elements for their UHLV, then that could be a possibility.

They couldn't using the VAB.

Possibly they could put it at a 90 deg angle to the flame trench if they stack at the pad, but it's still over 2X as much thrust as the pad can handle.

There will have to a be a new, purpose built pad somewhere for the tri-core.  39A and 39B just weren't built for something like that.  There could be a "39C" buit there just to the Northwest of 39B.  kind of where the original 39C was supposed to go, but south of highway 402.  Maybe horizontal integration and putting up vertical on the pad.
There's areas in South Texas that might have potential too.  Inland from the coast a bit.

they could launch with some or all of the engines throttled down. would cut into the mass to orbit, but might be worth it to stay within 39A's capabilities...
Title: Re: SpaceX advances drive for Mars rocket via Raptor power
Post by: guckyfan on 03/10/2014 05:55 pm
This engine will run fuel rich. Only the preburner of the LOX pump will be oxygen rich. That preburner may be a part that can be swapped frequently and easily. Not too hard or expensive if the engine is designed that way.

I don't know what you mean, "half" of the engine will run oxygen-rich, from preburner to injection into the CC.

The vast majority of the total energy released is in the combustion chamber. That runs fuel rich. The oxygen pump turbine runs oxygen rich. But with all of the oxygen running through it the temperature will be quite moderate, not like an oxygen rich engine combustion chamber.
Title: Re: SpaceX advances drive for Mars rocket via Raptor power
Post by: Oli on 03/10/2014 06:47 pm
This engine will run fuel rich. Only the preburner of the LOX pump will be oxygen rich. That preburner may be a part that can be swapped frequently and easily. Not too hard or expensive if the engine is designed that way.

I don't know what you mean, "half" of the engine will run oxygen-rich, from preburner to injection into the CC.

The vast majority of the total energy released is in the combustion chamber. That runs fuel rich. The oxygen pump turbine runs oxygen rich. But with all of the oxygen running through it the temperature will be quite moderate, not like an oxygen rich engine combustion chamber.

AFAIK the mixture ratio in the combustion chamber is not related to whether the engine has oxygen-rich or fuel-rich preburners. I think the problem are the oxygen-rich corrosive gases running through the turbine, pipes, injectors.

The RD-0162, and the Volga engine that preceded it, are, to my knowledge, fuel-rich designs.
Title: Re: SpaceX advances drive for Mars rocket via Raptor power
Post by: baldusi on 03/10/2014 07:32 pm
All H2, CH4 and RP-1 engines are run fuel rich in the MCC. No material could tolerate stoicometric temperature. And running fuel rich improves isp significantly. The nomenclature is Fuel or Oxidizer Rich STAGED COMBUSTION. That means how do the preburner and turbine runs. Plain and simple.
The good question of Oli is if the lower temperature and pressure on the fuel rich side, makes that part easier to reuse, doesn't the increased temperature and pressure of the much more corrosive oxidizer rich side makes it worse in all?
It's a very valid discussion. But it is into uncharted territory. Regarding the manufacturer statement regarding cost and reliability of the RD-0162, I would state that they might be saying that, but Russians keep deploying RP-1 based ORSC enginrs and LV. That those are disposable might say something.
Title: Re: SpaceX advances drive for Mars rocket via Raptor power
Post by: Lobo on 03/10/2014 07:34 pm
We know they want to lease VAB space and Pad 39A, but a tri-core of 10m per core is too big for the doors, and the cost of building their own new assembly facilities for something that big would be immense. So unless I'm missing something, I just don't see how anyone is going to pull off a tri-core that's 30m wide.

Move the rocket through the door sideways? Does LUT have to be transported with it, leave it at the pad?

My understanding was that SLS could not do this due to orientation of ML, flame trenches, etc. If SpaceX were to completely redo all those elements for their UHLV, then that could be a possibility.

They couldn't using the VAB.

Possibly they could put it at a 90 deg angle to the flame trench if they stack at the pad, but it's still over 2X as much thrust as the pad can handle.

There will have to a be a new, purpose built pad somewhere for the tri-core.  39A and 39B just weren't built for something like that.  There could be a "39C" buit there just to the Northwest of 39B.  kind of where the original 39C was supposed to go, but south of highway 402.  Maybe horizontal integration and putting up vertical on the pad.
There's areas in South Texas that might have potential too.  Inland from the coast a bit.

they could launch with some or all of the engines throttled down. would cut into the mass to orbit, but might be worth it to stay within 39A's capabilities...

Sitting on the pad, the propellant mass is by far the largest factor.  The payload mass itself is pretty nominal compared to that.  Take the payload away completely and most LV's still can only just barely get themselves off the pad.  The payloads mass becomes more of a factor later on the upper stages, but not on the pad.
So if the boosters are full, the engines will need to be at 100% at lift off.  Maybe they could do propellant offloading and launch partially fueled, and maybe then it could launch at reduced throttle.  But it'd have to be at 1/2 throttle or less for 39A to handle it.   So what would be the point?
Just stick with the single core at that point.  Maybe bump up the thrust of the Raptors some and stretch the core if needed.  Then you can probably get the same payload as a tri-core with half the fuel and thrust (but a lot more dry mass), and the pads at KSC can handle it just fine.  If needed, the VAB could handle it too, if that was ever in the mix.

I think the single core will be launching for some time before a tri-core would come into play, so they -can- continue to use KSC, and grow their business and manifest until such a time when they are ready to break ground on a new, purpose-built pad for that tri-core monster.
Title: Re: SpaceX advances drive for Mars rocket via Raptor power
Post by: john smith 19 on 03/10/2014 07:41 pm
And you need an additional preburner/turbine running on oxygen-rich gas. How does that affect reusability? On the positive side you avoid the aforementioned sealing issues. In the document below there is a comparison of the 2 cycles for a hydrolox engine with the same specs (thrust, CC pressure, ISP):
No. Historically the only US SC engine, the SSME, also had 2 preburners, one for LO2, one for LH2, both fed by fuel rich preburners.
Going with SC increases Isp. Going full flow with separate pre burners gives a safe-by-chemistry (the SSME seal between the  fuel rich preburner/LO2 turbopump was a real PITA) rather than safe-by-design/inspection/monitoring. Going LNG either grossly reduces or eliminates coking. This is important if you want low/no maintenance turnaround. 
Quote
While the conclusion says the full-flow cycle appears to be more promising for the future due to operational issues, I wish people here would not always make it look like it was such an obvious choice.
Personally I thought Spacex would have a go at the gas tapoff cycle, but I guess their research didn't really show enough data on it.  :(
Better Isp (than a GG), better T/W (no GG) but not up with the SC cycle.

Pity.
My instinct is that once Raptor proves out they will switch all engines to LNG, giving a performance boost to the F9, F9R.
F9 v 1.2? Probably a topic for another thread.

I disagree, looking at how big the initial raptor engine is, they would loose the engine out capability.  They would have to develop a smaller version and so far there is no indication they are working on that.
Note I was talking about the fuel.

I think they will be hanging on to Merlin for a while yet.  :)

I think the benefits of engine out capability have been proved and I don't think they want to give those up, and I think any future Spacex LV will retain that capability, which suggests you would need something with a minimum of 5 Raptors.

How big a Raptor engined LV will be is another question.
In the NSF article it states one of NASA'S IPD goals was an engine good for 200 missions, which fits squarely into SpaceX's stated reusability plans. Sounds like exactly the kind of choice they'd be expected to make.
Actually it was pretty much the same requirement that the SSME was designed to deliver.

Historically the big issues with turn around were the bearings but seal failure was a major worry, hence the triple layer seals and the high pressure GHe bleed on the SSME.

Moving to hydrodynamic bearings (tested but not implemented on the SSME) and seals that are 3x better than those on the SSME (AFAIK analyzed but never implimeted), as well as operating at a lower pressure than the SSME, will likely radically improve it's maintainability while raising Isp.
Title: Re: SpaceX advances drive for Mars rocket via Raptor power
Post by: Oli on 03/10/2014 08:14 pm
And you need an additional preburner/turbine running on oxygen-rich gas. How does that affect reusability? On the positive side you avoid the aforementioned sealing issues. In the document below there is a comparison of the 2 cycles for a hydrolox engine with the same specs (thrust, CC pressure, ISP):
No. Historically the only US SC engine, the SSME, also had 2 preburners, one for LO2, one for LH2, both fed by fuel rich preburners.
Going with SC increases Isp. Going full flow with separate pre burners gives a safe-by-chemistry (the SSME seal was a preburner/LO2 turbopump was a real PITA. Going LNG either grossly reduces or eliminates coking. This is important if you want low/no maintenance turnaround. 

Well, yes, in the hydrolox case you'd need an oxygen-rich preburner/turbine instead of a fuel-rich one (although some designs apparently work with one preburner). For methane, I was comparing it to the Volga design with a fuel-rich preburner and a single-shaft turbopump. In any case, you have to go oxygen-rich.

Quote from: john smith
Moving to hydrodynamic bearings (tested but not implemented on the SSME) and seals that are 3x better than those on the SSME, as well as operating at a lower pressure than the SSME, will likely radically improve it's maintainability while raising Isp.

Does that imply going full-flow?
Title: Re: SpaceX advances drive for Mars rocket via Raptor power
Post by: john smith 19 on 03/10/2014 08:33 pm
Well, yes, in the hydrolox case you'd need an oxygen-rich preburner/turbine instead of a fuel-rich one (although some designs apparently work with one preburner). For methane, I was comparing it to the Volga design with a fuel-rich preburner and a single-shaft turbopump. In any case, you have to go oxygen-rich.
You only get the safe-by-chemistry benefits with separate fuel and oxidizer pre burners.
Putting both the O and F turbo pumps on a single shaft with the LO2 close to the pre burner is possible but still leaves the leakage path LCH4 -->LO2

The trade off between design and operational simplicity is tricky. I'm guessing Spacex have by now accumulated a lot  of engine operating experience and know wheather the design simplicity is worth the (potential) failure.

Quote
Does that imply going full-flow?
No.
Title: Re: SpaceX advances drive for Mars rocket via Raptor power
Post by: Robotbeat on 03/10/2014 08:39 pm
My instinct is that once Raptor proves out they will switch all engines to LNG, giving a performance boost to the F9, F9R.

F9 v 1.2? Probably a topic for another thread.

Yeah I think people focus too much on MCT and other fantansies.

Raptor how it is envisaged would be a good first stage engine for F9/F9H and also for a SLS booster for example....
I totally disagree. SpaceX won't win a SLS booster award because support for SLS is largely based on political support from SpaceX's competitors (okay, and a lot of good people at some NASA centers believe that NASA must have their own HLV... something I disagree with).

Also, switching to methalox for the first stage wouldn't necessarily mean a performance increase unless you either widened F9's tanks (so wouldn't be road transportable) or lengthened them (already is crazy long). Kerolox has significant density advantages over methalox /especially/ if you're volume-constrained. Methalox makes more sense for the upper stage, though obviously Raptor as we understand now is far too high thrust for a Falcon 9 upper stage. So I expect Falcon 9 to stick with something like kerolox for the first stage especially. Though interesting to hear about the subcooling!

By the way, do Zenit or Soyuz do subcooling? I mean, other than the typical "it's cold in Star City." ;)
Title: Re: SpaceX advances drive for Mars rocket via Raptor power
Post by: guckyfan on 03/10/2014 08:47 pm
All H2, CH4 and RP-1 engines are run fuel rich in the MCC. No material could tolerate stoicometric temperature. And running fuel rich improves isp significantly. The nomenclature is Fuel or Oxidizer Rich STAGED COMBUSTION. That means how do the preburner and turbine runs. Plain and simple.

Learned something again, thanks.

Still, isn't it less bad with full flow and resulting lower temperatures?
Title: Re: SpaceX advances drive for Mars rocket via Raptor power
Post by: JBF on 03/10/2014 09:17 pm
Still, isn't it less bad with full flow and resulting lower temperatures?

Like all engineering it depends on what results you want. If you run it at lower temperatures you gain in reuseability but loose in ISP.
Title: Re: SpaceX advances drive for Mars rocket via Raptor power
Post by: Robotbeat on 03/10/2014 09:22 pm
Still, isn't it less bad with full flow and resulting lower temperatures?

Like all engineering it depends on what results you want. If you run it at lower temperatures you gain in reuseability but loose in ISP.
Well, sometimes running fuel rich can improve performance if your fuel has low molecular mass.
Title: Re: SpaceX advances drive for Mars rocket via Raptor power
Post by: Oli on 03/10/2014 09:33 pm
Well, yes, in the hydrolox case you'd need an oxygen-rich preburner/turbine instead of a fuel-rich one (although some designs apparently work with one preburner). For methane, I was comparing it to the Volga design with a fuel-rich preburner and a single-shaft turbopump. In any case, you have to go oxygen-rich.
You only get the safe-by-chemistry benefits with separate fuel and oxidizer pre burners.
Putting both the O and F turbo pumps on a single shaft with the LO2 close to the pre burner is possible but still leaves the leakage path LCH4 -->LO2

Sure, you need an additional preburner/turbine, that's what I meant.

My instinct is that once Raptor proves out they will switch all engines to LNG, giving a performance boost to the F9, F9R.

F9 v 1.2? Probably a topic for another thread.

Yeah I think people focus too much on MCT and other fantansies.

Raptor how it is envisaged would be a good first stage engine for F9/F9H and also for a SLS booster for example....
I totally disagree. SpaceX won't win a SLS booster award because support for SLS is largely based on political support from SpaceX's competitors (okay, and a lot of good people at some NASA centers believe that NASA must have their own HLV... something I disagree with).

Assuming SpaceX can take part in the booster competition, can politicians really influence the decision so shamelessly? I don't think so.

You may have noticed there is no business case for HLV/Mars and Musk has always been good at finding someone who pays for his endeavours. The NASA heavy lift pie is huge and Musk may try to get a piece of it.

Title: Re: SpaceX advances drive for Mars rocket via Raptor power
Post by: Lobo on 03/10/2014 09:35 pm
My instinct is that once Raptor proves out they will switch all engines to LNG, giving a performance boost to the F9, F9R.

F9 v 1.2? Probably a topic for another thread.

Yeah I think people focus too much on MCT and other fantansies.

Raptor how it is envisaged would be a good first stage engine for F9/F9H and also for a SLS booster for example....
I totally disagree. SpaceX won't win a SLS booster award because support for SLS is largely based on political support from SpaceX's competitors (okay, and a lot of good people at some NASA centers believe that NASA must have their own HLV... something I disagree with).

Also, switching to methalox for the first stage wouldn't necessarily mean a performance increase unless you either widened F9's tanks (so wouldn't be road transportable) or lengthened them (already is crazy long). Kerolox has significant density advantages over methalox /especially/ if you're volume-constrained. Methalox makes more sense for the upper stage, though obviously Raptor as we understand now is far too high thrust for a Falcon 9 upper stage. So I expect Falcon 9 to stick with something like kerolox for the first stage especially. Though interesting to hear about the subcooling!

By the way, do Zenit or Soyuz do subcooling? I mean, other than the typical "it's cold in Star City." ;)

I don't know about that.  SpaceX could complete for the Advanced Booster competition if they wanted, with Raptor.  It's efficiency would mean less propellant is required.  A 5.5m booster could be made a little taller if necessary.  Three Raptors should be powerful enough per booster.  Perhaps they'll need to be pumped up some in power.
Other than possibly using such a contract to help fund finishing up Raptor itself, such a contract probably wouldn't help much with SpaceX's other projects.  They'd need to develop a brand new booster core at 5.5m which won't help the F9/FH or FXX, but Dynetics or Aerojet will have to develop it too.  Maybe the Ares 1 US tooling at MAF could be leased by the winning contractor so they wouldn't have to develop new tooling?

The advantage SpaceX would have, is Raptor is an engine in the pipe to develop anyway.  F-1B will only be developed if Dynetics gets the contract (of course, AJR would have to build it...so that could be awkward).
If AJR gets the contract, they'll have to develop a US made version of NK-33, and then up rate it, and then make a two chamber version of it.  So they have a ways to go too, and then engine would pretty much hinge only on the SLS Advanced booster contract.  Unless ULA or OSC wants to use it for Atlas V and Antares.  OSC seems to want to get RD-180 right now though, and I've never heard of ULA wanting to use anything but the Russian made RD-180.

SpaceX could, if they wanted, offer a low ball price for SLS booster development, as they'll be bankrolling the engine development anyway.  NASA really would only need to pay for the special 5.5m core development.  Whoever gets such a contract, it'll be a very expensive and very custom supply contract.  But if there's money in it, why wouldn't SpaceX consider it?  The profits just helps fund their other projects.

However, with all of that said, SpaceX's new 10m HLV is almost certainly hoped to make things shaking politically for SLS, so offering SLS a way to save some money and perhaps help avoid the axe, could be counter productive to SpaceX.  They may figure the high price tag of an Aerjet booster, Dynetics booster, or ATK booster could help drive up the costs of SLS, putting SpaceX in a better position to offer a low cost alternative.  Help hurry the axe along, as it were.

Title: Re: SpaceX advances drive for Mars rocket via Raptor power
Post by: Lobo on 03/10/2014 09:54 pm
The NASA heavy lift pie is huge and Musk may try to get a piece of it.

Unless he's angling to get the -whole- pie rather than just a pices of it?

When will there be an advanced booster contract anyway?  Maybe the 2018-2021 time frame.?

Meanwhile, [assuming] there's a SpaceX HLV already developed and flying off of 39A during that same time frame.  It's cheaper and has as much capacity as Block 2 SLS already.  No upgrades needed.  It may become hard to justify that further investment into SLS, even from it's biggest supporters in Congress.



Title: Re: SpaceX advances drive for Mars rocket via Raptor power
Post by: Elmar Moelzer on 03/10/2014 10:10 pm
It may become hard to justify that further investment into SLS, even from it's biggest supporters in Congress.
Oh, they will just argue the usual, that you will Need the SLS in order to provide a backup for the BFR, which is after only developed by "a bunch of hobbyists".
Title: Re: SpaceX advances drive for Mars rocket via Raptor power
Post by: llanitedave on 03/10/2014 11:08 pm
Now everyone is emphasizing the advantages of full flow because SpaceX has chosen it, but its still the most difficult cycle. Funny how fast people deviate from the "keep it simple, stupid" mantra once SpaceX does.
Difficult to develop, maybe simple to operate. So it may end up being a KISS approach.

The only obvious advantage I see is that the seal on the oxidizer side is not that critical (or on the fuel side if the pre-burner is oxygen rich), otherwise it looks more complex and more expensive. Anyway, not an engine expert.
It extends engine life, increases isp, lower pressure in the pumping system...

I've only read about the advantages.  What are the difficulties, and why has it not been used to date?
Title: Re: SpaceX advances drive for Mars rocket via Raptor power
Post by: butters on 03/10/2014 11:50 pm
I don't think that SpaceX has much interest in the SLS Advanced Booster contract. Unless they get an offer they can't refuse, it would be counterproductive for SpaceX to invest in 5.5m airframe production when they have a Mars roadmap of their own which calls for 10m airframes. It would be foolish for SpaceX to hitch their destiny to SLS and NASA's HSF roadmap, and Elon Musk knows that. The ISS business is great, but they can't bet the company on whatever NASA ends up doing next.

SpaceX is going to build a BFR regardless of what NASA does, and they'll be quite pleased if NASA ends up launching their exploration missions on SpaceX rockets. If SLS continues to exist, then it will be an uncomfortable existence as every pundit's leading example of government waste. SpaceX is betting that if they deliver similar capability at significantly lower prices, they can flex their public relations muscle and undermine political support for SLS.
Title: Re: SpaceX advances drive for Mars rocket via Raptor power
Post by: sdsds on 03/11/2014 01:59 am
So in what year do people expect the first launch to orbit powered by a Raptor engine? They've been at least thinking about it since 2011....
Title: Re: SpaceX advances drive for Mars rocket via Raptor power
Post by: docmordrid on 03/11/2014 02:23 am
So in what year do people expect the first launch to orbit powered by a Raptor engine? They've been at least thinking about it since 2011....

L2 is your friend

http://forum.nasaspaceflight.com/index.php?topic=33488.msg1167982#msg1167982
Title: Re: SpaceX advances drive for Mars rocket via Raptor power
Post by: Hyperion5 on 03/11/2014 03:08 am
So in what year do people expect the first launch to orbit powered by a Raptor engine? They've been at least thinking about it since 2011....

L2 is your friend

http://forum.nasaspaceflight.com/index.php?topic=33488.msg1167982#msg1167982

Let's just say Spacex is definitely ambitious and leave it at that for our non-L2 members.  :) 

---

Btw, if Alejandro isn't reading this, someone needs to point out how many Wikipedia articles are now citing his work:

http://en.wikipedia.org/wiki/SpaceX_rocket_engine_family

http://en.wikipedia.org/wiki/Raptor_(rocket_engine)

http://en.wikipedia.org/wiki/Mars_Colonial_Transporter

http://en.wikipedia.org/wiki/Full-flow_staged_combustion#Full-flow_staged_combustion_cycle

4 citations in 4 different topics from one article!  This is what I like to call the "Wikipedia Grand Slam".  :) 
Title: Re: SpaceX advances drive for Mars rocket via Raptor power
Post by: Llian Rhydderch on 03/11/2014 03:49 am

You may have noticed there is no business case for HLV/Mars and Musk has always been good at finding someone who pays for his endeavours. The NASA heavy lift pie is huge and Musk may try to get a piece of it.

You say:  "Musk has always been good at finding someone who pays for his endeavours." (emphasis mine)

That is plainly untrue!

SpaceX got only partial development funding for
  * Merlin 1C, Falcon 9 version 1.0, Dragon cargo,
and now, currently under way, the
  * Dragon Crew and launch escape system, and SuperDraco storable-propellent engine.

SpaceX developed on their own dime: 
  * Merlin 1A, Merlin 1B, Kestrel and Merlin 1D LOX/RP1 engines, as well as the Falcon 1 and Falcon 9 v1.1 launch vehicles;
they are currently self-funding the development of:
  * Falcon Heavy, all of the many reusable technologies (https://en.wikipedia.org/wiki/SpaceX_reusable_launch_system_development_program) they are developing for three launch vehicles (F9-R, FH-R, and MCT/BFR), and the Raptor LOX/CH4 engine;
and they are funding all of the preliminary design work for
  * MCT, BFR launch vehicle, etc., presumably at a somewhat detailed level as they certainly want the entire launch and spacecraft system to accomplish their interplanetary requirements with the Raptor engine as they are now beginning to commit metal parts.

I don't know where the Draco RCS thruster development fits, and I've probably left some off; but I believe these examples ought to be sufficient to make the point.  It is clear as day that Musk is not sitting around  and "always" finding someone to pay for his endeavors.

On the other hand, Musk has to date, shown good business sense in keeping the company afloat with both investment funding and retained earnings from profits.  This is just what one would expect from any private company where the primary business imperative requires that they develop technology and sell operational launch services at revenue that exceeds their long term costs in order to remain profitable without a government-backed cost-plus guaranteed safety net.
Title: Re: SpaceX advances drive for Mars rocket via Raptor power
Post by: fatjohn1408 on 03/11/2014 09:56 am
So if this thing really fits 9 engines can we assume that since the engine has 5.555 times the thrust of the Merlin, the GLOW will be about 5.555 times as high? Note that the current T/W is on the low side so perhaps a GLOW of about 2500 metric tonnes could be expected. That's pretty big, probably 100-150t to LEO
The Heavy version could easily be over 7000t with 300-450t to LEO.

Crazy.
Title: Re: SpaceX advances drive for Mars rocket via Raptor power
Post by: Dudely on 03/11/2014 02:00 pm
So if this thing really fits 9 engines can we assume that since the engine has 5.555 times the thrust of the Merlin, the GLOW will be about 5.555 times as high? Note that the current T/W is on the low side so perhaps a GLOW of about 2500 metric tonnes could be expected. That's pretty big, probably 100-150t to LEO
The Heavy version could easily be over 7000t with 300-450t to LEO.

Crazy.

There are other threads with detailed discussion on possible payloads given 9 engines @ 1glbf. The numbers you are throwing around are not far off, if I remember correctly.

It will be a very, very big rocket.
Title: Re: SpaceX advances drive for Mars rocket via Raptor power
Post by: baldusi on 03/11/2014 03:54 pm
[...]
Btw, if Alejandro isn't reading this, someone needs to point out how many Wikipedia articles are now citing his work:

http://en.wikipedia.org/wiki/SpaceX_rocket_engine_family

http://en.wikipedia.org/wiki/Raptor_(rocket_engine)

http://en.wikipedia.org/wiki/Mars_Colonial_Transporter

http://en.wikipedia.org/wiki/Full-flow_staged_combustion#Full-flow_staged_combustion_cycle

4 citations in 4 different topics from one article!  This is what I like to call the "Wikipedia Grand Slam".  :)
I've been slashdotted, I've been cited by wikipedia, Mars Society retweeted the article, and I know for a fact that even some politicians have read it. And I just wrote the draft of the article. But most of the info came from NSF, pictures and editing by Chris, it's like I'm getting more credit than its due. But I'm a happy camper nonetheless.  ;D
Title: Re: SpaceX advances drive for Mars rocket via Raptor power
Post by: john smith 19 on 03/11/2014 09:30 pm
I've only read about the advantages.  What are the difficulties, and why has it not been used to date?
Historically the big thing is the fear that metal + hot oxygen --> burning metal.
This is basically the process behind a thermic lance.  :( :(

The actual lesson (rather than the superficial one most US rocket engineers seemed to have taken away) is don't build an oxdizer rich combustion engine a) Out of Iron (because it burns)  or b) Out of Iron without elements that form strongly adherent metal oxide "scale" (EG Aluminum or Chrome).

Which is a tricky materials and design problem, although NASA tested a LOX cooled (similar issues but more cooling) 40000lb test chamber in the late 80s and Rotary Rocket around the same time.

The basic issue is the enormous inertia in the US engine design teams.  :(
Title: Re: SpaceX advances drive for Mars rocket via Raptor power
Post by: QuantumG on 03/12/2014 03:29 am
I remember back around the time of the Falcon Heavy announcement (this (http://shitelonsays.com/transcript/spacex-next-falcon-heavy-press-conference-2011-04-05)) there was a number of people who found it quite contradictory that SpaceX fans were cheering along with Elon's announcement of a heavy lift vehicle.. while simultaneously poopooing NASA's HLV options - as many of us have been doing for years.

Some of it was just cognitive dissonance, I'll grant that, but what a few of us said was this: there's a difference between affordable heavy lift like the Falcon Heavy and unaffordable Ares/SLS heavy lift. So long as there are customers other than NASA for the Falcon Heavy, you can imagine the price being low enough that NASA could actually afford to do something with it.

That said, this Mars monster rocket has no customers. It's commercially useless, just like Ares was and SLS is. The costs can't be shared. It can't be affordable. So far the only argument I've heard as to why this is more than just like the other heavy lift fantasies is that Elon's monster rocket will be reusable. Well, so what? Making something reusable doesn't immediately make it affordable. In fact, it typically costs more to make a launch vehicle reusable than it does to make it expendable. The only way to get cheap launch from a reusable launch vehicle is to fly it a lot, and for that you have to have a lot of customers.

Anyway, I think this needs to be said.
Title: Re: SpaceX advances drive for Mars rocket via Raptor power
Post by: su27k on 03/12/2014 03:45 am
Isn't it too early to consider whether a Raptor HLV would be affordable? I doubt even SpaceX knows for sure how much it would cost. But IF SpaceX can get reusability to work and IF they can then get launch price down to $7 million per F9, and finally assuming the launch price scale up linearly with rocket size, then we're looking at $70 to $100 million for a Raptor HLV launch, seems pretty affordable to me.
Title: Re: SpaceX advances drive for Mars rocket via Raptor power
Post by: QuantumG on 03/12/2014 03:55 am
Isn't it too early to consider whether a Raptor HLV would be affordable? I doubt even SpaceX knows for sure how much it would cost. But IF SpaceX can get reusability to work and IF they can then get launch price down to $7 million per F9, and finally assuming the launch price scale up linearly with rocket size, then we're looking at $70 to $100 million for a Raptor HLV launch, seems pretty affordable to me.

That's just ridiculous.

If SpaceX get Falcon 9 flights down to $7 million each it'll be because multiple customers are sharing the cost of the vehicle through reuse. There isn't multiple customers for a monster rocket.. it's debatable that there's even one.
Title: Re: SpaceX advances drive for Mars rocket via Raptor power
Post by: neilh on 03/12/2014 03:56 am
I've been trying to brainstorm some sort of way that the Super Heavy would make any sort of economic sense, and I guess it would need to involve some combination of the following:

* ridiculous margin mean that design/manufacturing choices can favor cost instead of mass-efficiency
* much lower SH-specific development costs than most expect
* much lower SH-specific fixed annual costs than most would expect
* margin would make reuse of both first and second stage easier
* reusably launch multiple satellites at a time
* maybe there's some commercial application for such a launcher that hasn't been made public yet? Maybe point-to-point travel?
Title: Re: SpaceX advances drive for Mars rocket via Raptor power
Post by: QuantumG on 03/12/2014 04:01 am
* maybe there's some commercial application for such a launcher that hasn't been made public yet? Maybe point-to-point travel?

The common invent-a-market for absurdly large rockets is space solar power.

But you're implying this a rational decision process.. it's not. Elon wants to go to Mars and he seems to think you need a really big rocket to do that, so that's what he wants to build. When he inevitably going to NASA for the funding he'll see it as just another SpaceX vs BoeLockmart fight.


Title: Re: SpaceX advances drive for Mars rocket via Raptor power
Post by: su27k on 03/12/2014 05:24 am
Isn't it too early to consider whether a Raptor HLV would be affordable? I doubt even SpaceX knows for sure how much it would cost. But IF SpaceX can get reusability to work and IF they can then get launch price down to $7 million per F9, and finally assuming the launch price scale up linearly with rocket size, then we're looking at $70 to $100 million for a Raptor HLV launch, seems pretty affordable to me.

That's just ridiculous.

If SpaceX get Falcon 9 flights down to $7 million each it'll be because multiple customers are sharing the cost of the vehicle through reuse. There isn't multiple customers for a monster rocket.. it's debatable that there's even one.

Forget about the monster rocket aspect, size doesn't matter, only price matters. If SpaceX can get Raptor9 to $70 to $100 million, there're plenty of customers. NASA and LEO tourism are obvious ones, but let's assume worst case scenario where demand doesn't go up with lower prices. Then an obvious move would be phasing out FH, this has the additional benefit of only one core to fly back and reuse instead of 3. Or they could even phase out F9 too, if nobody else is reducing the launch price. $70m to $100m is a pretty attractive price no matter how you look at it, especially considering Ariane 6's $90m goal. So you could be launching a 5 ton comsat using rocket capable of launching 14 tons to GTO, but if the price is right, who cares?
Title: Re: SpaceX advances drive for Mars rocket via Raptor power
Post by: sdsds on 03/12/2014 05:32 am
you're implying this a rational decision process.. it's not. Elon wants to go to Mars and he seems to think you need a really big rocket to do that

Elon wants to send hundreds and hundreds of people to Mars. Despite the sh*t he says, he knows that's not likely to start happening in just a couple of decades. So why is he putting any effort into this now? Maybe it's because he sees value in developing full flow staged combustion reusable methane engine technology.

Others have said he will only use Raptor in a 9 engine mega-core, because that's what preserves engine-out capability. I think that's missing the forest for the trees. A core powered by a small number of Raptor engines would have economic value, and I think we'll see that result generated by your "rational decision process" long before we see the 9 engine monster.
Title: Re: SpaceX advances drive for Mars rocket via Raptor power
Post by: Confusador on 03/12/2014 06:21 am
you're implying this a rational decision process.. it's not. Elon wants to go to Mars and he seems to think you need a really big rocket to do that

Elon wants to send hundreds and hundreds of people to Mars. Despite the sh*t he says, he knows that's not likely to start happening in just a couple of decades. So why is he putting any effort into this now? Maybe it's because he sees value in developing full flow staged combustion reusable methane engine technology.

Others have said he will only use Raptor in a 9 engine mega-core, because that's what preserves engine-out capability. I think that's missing the forest for the trees. A core powered by a small number of Raptor engines would have economic value, and I think we'll see that result generated by your "rational decision process" long before we see the 9 engine monster.

I don't think engine-out has much to do with it - I think it's reuseability.  Without reuseability this thing is dead in the water, and you'd have to be able to throttle pretty far with only 5 engines.
Title: Re: SpaceX advances drive for Mars rocket via Raptor power
Post by: woods170 on 03/12/2014 06:41 am
I remember back around the time of the Falcon Heavy announcement (this (http://shitelonsays.com/transcript/spacex-next-falcon-heavy-press-conference-2011-04-05)) there was a number of people who found it quite contradictory that SpaceX fans were cheering along with Elon's announcement of a heavy lift vehicle.. while simultaneously poopooing NASA's HLV options - as many of us have been doing for years.

Some of it was just cognitive dissonance, I'll grant that, but what a few of us said was this: there's a difference between affordable heavy lift like the Falcon Heavy and unaffordable Ares/SLS heavy lift. So long as there are customers other than NASA for the Falcon Heavy, you can imagine the price being low enough that NASA could actually afford to do something with it.

That said, this Mars monster rocket has no customers. It's commercially useless, just like Ares was and SLS is. The costs can't be shared. It can't be affordable. So far the only argument I've heard as to why this is more than just like the other heavy lift fantasies is that Elon's monster rocket will be reusable. Well, so what? Making something reusable doesn't immediately make it affordable. In fact, it typically costs more to make a launch vehicle reusable than it does to make it expendable. The only way to get cheap launch from a reusable launch vehicle is to fly it a lot, and for that you have to have a lot of customers.

Anyway, I think this needs to be said.
Your assessment is correct. If one only looks at market demand for deciding on a rocket being affordable-or-not than BFR will never be affordable.
But that's not the point. Musk wants to go to Mars and do Mars colonization. He envisions needing an MCT and BFR to be able to do Mars colonization, regardless of MCT and BFR being affordable-or-not.
Remember; most people with a clear vision of what their (personal) long-term goal should be sometimes do things that do not seem logical to most of us.
Title: Re: SpaceX advances drive for Mars rocket via Raptor power
Post by: guckyfan on 03/12/2014 06:43 am

I don't think engine-out has much to do with it - I think it's reuseability.  Without reuseability this thing is dead in the water, and you'd have to be able to throttle pretty far with only 5 engines.

I agree with the reusbility as a driver for the decision. But throttling down should be doable. Some here on the forum stated the concept lends itself well to deep throttle. I still don't think they would do it. A separate rocket line will have its associated cost. As long as there is no competition flying cost effective reusable systems and large demand justifies it they don't need a 5 Raptor launch vehicle.

I am confident they can price the 9 engine LV well below Falcon Heavy and fly it very competetive.
Title: Re: SpaceX advances drive for Mars rocket via Raptor power
Post by: beancounter on 03/12/2014 07:12 am
Isn't it too early to consider whether a Raptor HLV would be affordable? I doubt even SpaceX knows for sure how much it would cost. But IF SpaceX can get reusability to work and IF they can then get launch price down to $7 million per F9, and finally assuming the launch price scale up linearly with rocket size, then we're looking at $70 to $100 million for a Raptor HLV launch, seems pretty affordable to me.

That's just ridiculous.

If SpaceX get Falcon 9 flights down to $7 million each it'll be because multiple customers are sharing the cost of the vehicle through reuse. There isn't multiple customers for a monster rocket.. it's debatable that there's even one.

If it can get to Mars then Elon will probably use it.  I guess that would make one.  What d'ya reckon?  Would Elon count? :)
Title: Re: SpaceX advances drive for Mars rocket via Raptor power
Post by: sdsds on 03/12/2014 07:38 am
you'd have to be able to throttle pretty far

throttling down should be doable

In theory you don't have to throttle down to land. You just have to cut the engine and simultaneously reach zero acceleration, zero velocity, and zero altitude. How hard can it be? ;)
Title: Re: SpaceX advances drive for Mars rocket via Raptor power
Post by: Ben the Space Brit on 03/12/2014 09:35 am
That said, this Mars monster rocket has no customers. It's commercially useless, just like Ares was and SLS is.

Agreed and this is why I've always been completely opposed to (and largely uncomprehending of the positive reaction to) the monolithic 10m-diameter concept for MCT. Something closer to the Atlas-V Phase-2/3A would potentially be commercially viable in its single-stick form and could be used for Elon's Mars ambitions (assuming he can ever put together the funding) in a multi-core/wide-body upper stage form.
Title: Re: SpaceX advances drive for Mars rocket via Raptor power
Post by: MikeAtkinson on 03/12/2014 10:19 am
you'd have to be able to throttle pretty far

throttling down should be doable

In theory you don't have to throttle down to land. You just have to cut the engine and simultaneously reach zero acceleration, zero velocity, and zero altitude. How hard can it be? ;)

Actually just zero velocity, and zero altitude, the acceleration will be quite high.
Title: Re: SpaceX advances drive for Mars rocket via Raptor power
Post by: MP99 on 03/12/2014 10:33 am
I have a query regarding the choice of gas-gas for Raptor's engine cycle...

Merlin engines famously use pintle injectors.

Is this something that would be suitable for use in a FFSC engine? In a very large thrust chamber? I assume this choice could affect combustion efficiency. I have this mental image that gasses (which will be relatively hot, as well) might mix relatively easily - is that true?

If pintle is not suitable, I wonder if part of the work scheduled for Stennis is to investigate alternative injector arrangements?

As I understand it, pintle makes it relatively easy to throttle an engine, and everyone seems to be assuming deep throttling will be required on Raptor.

Cheers, Martin
Title: Re: SpaceX advances drive for Mars rocket via Raptor power
Post by: luinil on 03/12/2014 10:55 am
On the absence of a market for the raptor rocket, the market may be nonexistent because there are no rocket to provide that kind of market and if there was, it would be too expensive.

Now, SpaceX is doing rocket a lot cheaper than the others, I do not know what will be the price of this rocket in it expansible version, but if it is low enough, it might well create a market. (after all innovative companies creating new markets are not something new).

Musk want's to lower the cost of space access and encourage human activity in space, this rocket would be a big step in this direction.

Moreover Musk want's to create a Mars colony, but it never said that he would create the colony alone. This rocket could also be of used for the other companies/governments working on Mars.

Musk is clearly turned to a future where there is heavy human and robotic activity in space, this is necessary for the creation of the Mars colony, this rocket would have a market if there is a such activity.

Title: Re: SpaceX advances drive for Mars rocket via Raptor power
Post by: JBF on 03/12/2014 11:40 am
That said, this Mars monster rocket has no customers. It's commercially useless, just like Ares was and SLS is.

Agreed and this is why I've always been completely opposed to (and largely uncomprehending of the positive reaction to) the monolithic 10m-diameter concept for MCT. Something closer to the Atlas-V Phase-2/3A would potentially be commercially viable in its single-stick form and could be used for Elon's Mars ambitions (assuming he can ever put together the funding) in a multi-core/wide-body upper stage form.

The reason I disapprove of SLS is that the rocket should be designed to accomplish the mission, SLS is the opposite.  Musk has a mission and has determined that the most cost effective way to do it is go big. As the mission is driving the rocket I approve.
Title: Re: SpaceX advances drive for Mars rocket via Raptor power
Post by: rcoppola on 03/12/2014 11:57 am
* maybe there's some commercial application for such a launcher that hasn't been made public yet? Maybe point-to-point travel?

The common invent-a-market for absurdly large rockets is space solar power.

But you're implying this a rational decision process.. it's not. Elon wants to go to Mars and he seems to think you need a really big rocket to do that, so that's what he wants to build. When he inevitably going to NASA for the funding he'll see it as just another SpaceX vs BoeLockmart fight.
Pardon but what exactly about his decision making has been or can currently be deemed as irrational?
Title: Re: SpaceX advances drive for Mars rocket via Raptor power
Post by: AncientU on 03/12/2014 12:20 pm
That said, this Mars monster rocket has no customers. It's commercially useless, just like Ares was and SLS is.

Agreed and this is why I've always been completely opposed to (and largely uncomprehending of the positive reaction to) the monolithic 10m-diameter concept for MCT. Something closer to the Atlas-V Phase-2/3A would potentially be commercially viable in its single-stick form and could be used for Elon's Mars ambitions (assuming he can ever put together the funding) in a multi-core/wide-body upper stage form.
The future is difficult to comprehend...
Quote
1943    "I think there is a world market for maybe five computers.", Thomas Watson, chairman of IBM.
Quote
1977    "There is no reason anyone would want a computer in their home." Ken Olson, president, chairman and founder of Digital Equipment Corp..
Quote
1981    "640k ought to be enough for anybody.", Bill Gates
Quote
1992    "Windows NT addresses 2 Gigabytes of RAM which is more than any application will ever need". Microsoft on the development of Windows NT
http://trillian.randomstuff.org.uk/~stephen/history/timeline-QUOTES.html

My computers each have 4GB of RAM and the desktop has 2TB storage.  We are a two-person, five computer household -- not counting our iPhones, etc.

EM wants to make travel to space affordable (and go to Mars)... let us then see what happens.
Title: Re: SpaceX advances drive for Mars rocket via Raptor power
Post by: rcoppola on 03/12/2014 12:48 pm
That said, this Mars monster rocket has no customers. It's commercially useless, just like Ares was and SLS is.

Agreed and this is why I've always been completely opposed to (and largely uncomprehending of the positive reaction to) the monolithic 10m-diameter concept for MCT. Something closer to the Atlas-V Phase-2/3A would potentially be commercially viable in its single-stick form and could be used for Elon's Mars ambitions (assuming he can ever put together the funding) in a multi-core/wide-body upper stage form.
The future is difficult to comprehend...
Quote
1943    "I think there is a world market for maybe five computers.", Thomas Watson, chairman of IBM.
Quote
1977    "There is no reason anyone would want a computer in their home." Ken Olson, president, chairman and founder of Digital Equipment Corp..
Quote
1981    "640k ought to be enough for anybody.", Bill Gates
Quote
1992    "Windows NT addresses 2 Gigabytes of RAM which is more than any application will ever need". Microsoft on the development of Windows NT
http://trillian.randomstuff.org.uk/~stephen/history/timeline-QUOTES.html

My computers each have 4GB of RAM and the desktop has 2TB storage.  We are a two-person, five computer household -- not counting our iPhones, etc.

EM wants to make travel to space affordable (and go to Mars)... let us then see what happens.
I wish there was a "Double Like" button for this post. And what especially made me chuckle, is that when my MacPro arrives, it'll have 64gigs of Ram and be smaller then my Keurig coffee maker.
Title: Re: SpaceX advances drive for Mars rocket via Raptor power
Post by: RedLineTrain on 03/12/2014 12:57 pm
For sure, if Musk builds his monster rocket, it will be dreadfully expensive for any other entity to replicate.
Title: Re: SpaceX advances drive for Mars rocket via Raptor power
Post by: mikegi on 03/12/2014 01:21 pm
The future is difficult to comprehend...
Quote
1943    "I think there is a world market for maybe five computers.", Thomas Watson, chairman of IBM.
Quote
1977    "There is no reason anyone would want a computer in their home." Ken Olson, president, chairman and founder of Digital Equipment Corp..
Quote
1981    "640k ought to be enough for anybody.", Bill Gates
Quote
1992    "Windows NT addresses 2 Gigabytes of RAM which is more than any application will ever need". Microsoft on the development of Windows NT
http://trillian.randomstuff.org.uk/~stephen/history/timeline-QUOTES.html

My computers each have 4GB of RAM and the desktop has 2TB storage.  We are a two-person, five computer household -- not counting our iPhones, etc.

EM wants to make travel to space affordable (and go to Mars)... let us then see what happens.
The near future is *not* difficult to comprehend. Those computer memory quotes (if even accurate) were perfectly valid at the time and for at least 10 years into the future. I had to populate and install memory expansion boards into PCs in the 1980s to get them to 1 MB of system memory for my small company. It was *very* expensive back then. The 2 GB of RAM issue in the early 1990s is even valid today -- 99.99% of programs right now do not need 2 GB of address space. Back then, most computers had 4-8MB of system memory so having an address space several orders-of-magnitude higher was a perfectly valid limit. Two GB of system memory would have bankrupted you (and if you could have even afforded 2 GB of memory you would not have had enough SIMM slots on your motherboard).

The bottom line: proving those quotes wrong at the time would have bankrupted you. You wouldn't have any money left to actually use the souped up computer you created. Just like SLS (are there any 100+ mT payloads planned?).
Title: Re: SpaceX advances drive for Mars rocket via Raptor power
Post by: AncientU on 03/12/2014 01:26 pm
For sure, if Musk builds his monster rocket, it will be dreadfully expensive for any other entity to replicate.
Actually, it would cost less! (expensive still, of course)
If another 'entity' has baggage from years of doing business under a different model, then I agree with the 'dreadfully' part.   But if you have the cojones to go clean sheet, knowing what worked for SpaceX...
Title: Re: SpaceX advances drive for Mars rocket via Raptor power
Post by: R7 on 03/12/2014 01:40 pm
Reminiscence of IT bloopers is fun but alas, rockets are not computers. If available Newton-seconds from a unit of propellant would double every two years space colonization would be much easier  :-\
Title: Re: SpaceX advances drive for Mars rocket via Raptor power
Post by: baldusi on 03/12/2014 01:41 pm
I have a query regarding the choice of gas-gas for Raptor's engine cycle...

Merlin engines famously use pintle injectors.

Is this something that would be suitable for use in a FFSC engine? In a very large thrust chamber? I assume this choice could affect combustion efficiency. I have this mental image that gasses (which will be relatively hot, as well) might mix relatively easily - is that true?

If pintle is not suitable, I wonder if part of the work scheduled for Stennis is to investigate alternative injector arrangements?

As I understand it, pintle makes it relatively easy to throttle an engine, and everyone seems to be assuming deep throttling will be required on Raptor.

Cheers, Martin
Quite a question. There isn't much experience in gas-gas injectors. All American experience resides in AerojetRocketdyne now. But Tom Müller did work on many injector types while at TRW.
From my limited understanding, gas-gas injectors have lower pressure losses than liquid/liquid or g/l. But you need a lot more section. I estimated Raptor (using RPA 1.2 and the given isp) as a 20.5MPa MCC engine. That would mean that gas would be around 4 times less dense than liquid. But I don't know how to calculate the speed, which is the other critical parameter in mass flow. If someone could do the calculation, or at least point me to the math so I can get an estimation I would be grateful.
In general, mixing gases seems to be easier, but, as stated above, speed is a huge issue. SpaceX are the current pintle experts. And the great thing about pintle injectors is cost. Go to LRPE.DE and look at the images of injectors for RD-171/180/191 family. Those things are extremely expensive and difficult to develop. They have to point each individual injector with a certain angle to get stable combustion. But pintle injector work forming a sort of doughnut around them. Doing this with liquid is one thing. How this would behave with gas, might be completely different. The ablative Merlin 1 had to be replaced with regen exactly because that doughnut was eating the ablative material too fast. So I don't know if the lighter gas wouldn't simply impinge on the MCC walls.
If there's anything that's it's probable that there's little info and tools available, is the gas-gas injector and stability issues. Most literature on combustion is liquid or gas-liquid. Beside the RD-270 and IPD, I can only think of MHXMHX LES design, which used pressure fed gaseous oxygen and (I think) NOx. But I can't recall it. And that was for pressure stored gases. Very different T/P relationship and requirements.
I'd guess that they'll be doing a lot of experimentation on injector design and combustion stability. Go to this post (http://forum.nasaspaceflight.com/index.php?topic=32477.msg1170433#msg1170433)  and the next on the Indian SCE-200 semicryo engine. You'll see how they are experimenting with single element injectors in ablative tubes to get a hold of the injector and combustion behavior. Somehow, I believe they have already done that part at Texas. Specially since I remember reading that USAF went to their Waco test facility to learn and understand about CH4 handling.
One issue is that you can't really do cold flow tests on gas-gas injectors. With liquid-liquid, you can use high speed photography and get a good idea of the behavior. With gas-liquid, you get some. But with gas-gas, I don't think you'd get much info besides flow and pressure losses behaviors. Overall, I've guess that oxidizer-rich metallurgy and injector design are the two riskier parts of this project.
One last couple of points about pintle injectors. First, nobody has done pintle to such a thrust level engine. In fact, we're talking about 6 times the previous record holder (Merlin 1D Vac). And with a liquid-liquid design. I don't believe nobody have done gas-liquid pintle injectors, much less gas-gas. The second point is that throttlability is limited by combustion instability and the throat choke point in vacuum. But at sea level it's flow instability at the nozzle. So there's some hard limit on how much you can throttle at sea that's intimately related to expansion ratio (the less the easier) and MCC pressure (the higher the easier). If my estimation is right (45 exp. and 20.5MPa), both are high. But for a point of reference RD-180 has 25.7MPa and 36.9 exp. ratio. And can do 47%, I believe. So for Raptor to do better than that it would be quite a feat.
Title: Re: SpaceX advances drive for Mars rocket via Raptor power
Post by: clongton on 03/12/2014 01:54 pm
RD-180 is supposed to be able to throttle down to 30%, so I would assume Raptor could do at least that too, perhaps more.  A driver will be if SpaceX wants MCT to land on Mars using Raptor.  It will need a very deep throttle for that. 
Raptors is a 450mt-f engine.  Even if MCT is a whopping 100mt (1/3 of what a tri-core heavy should at least be able to throw into LEO) when landing almost dry, given Mars gravity is about 1/3 of Earth, that's the equivalent of 33mt of mass.  So it would need 7% throttle to hover on Mars.
That might be difficult, but necessary unless they have smaller landing thrusters.
If they do have smaller landing thrusters, then Raptor probably would be ok with a throttle range like the RD-180.
You’re assuming a single engine. But if the EDL vehicle uses a small cluster of engines then slow descent and hover could be achieved by shutting down some and only running the remainder, with those engines throttled down to a higher percent than the 7% you speak of. This approach would eliminate the need for a deep throttle engine. Just as a cluster magnifies the available thrust, shutting down some of the cluster magnifies the throttle capability of the cluster. –Pure speculation of course.
Title: Re: SpaceX advances drive for Mars rocket via Raptor power
Post by: cambrianera on 03/12/2014 02:03 pm

One last couple of points about pintle injectors. First, nobody has done pintle to such a thrust level engine. In fact, we're talking about 6 times the previous record holder (Merlin 1D Vac).

Are you forgetting TRW TR-106? It was 2900 kN.
And guess who designed it?
Title: Re: SpaceX advances drive for Mars rocket via Raptor power
Post by: rcoppola on 03/12/2014 02:09 pm
Reminiscence of IT bloopers is fun but alas, rockets are not computers. If available Newton-seconds from a unit of propellant would double every two years space colonization would be much easier  :-\
Understood but it's not about IT specifically.  History is littered with examples of things many said were either not-needed, impractical and/or impossible. Chose the field... atomic, telephony, architecture, aeronautics, hell, even the creator of Fed-Ex  was given a C by his professor for proposing in impractical idea.

The main point is, not to judge the validity of an idea based on either historical precedent, current assumptions or near future extrapolations. I chose to celebrate the crazy ones.
Title: Re: SpaceX advances drive for Mars rocket via Raptor power
Post by: AncientU on 03/12/2014 02:23 pm
Reminiscence of IT bloopers is fun but alas, rockets are not computers. If available Newton-seconds from a unit of propellant would double every two years space colonization would be much easier  :-\
Understood but it's not about IT specifically.  History is littered with examples of things many said were either not-needed, impractical and/or impossible. Chose the field... atomic, telephony, architecture, aeronautics, hell, even the creator of Fed-Ex  was given a C by his professor for proposing in impractical idea.

The main point is, not to judge the validity of an idea based on either historical precedent, current assumptions or near future extrapolations. I chose to celebrate the crazy ones.
what he said
...and SpaceX call themselves insane for what they are building.
(see quote below)

Edit: More correctly, people would think them insane -- maybe they don't themselves.
Title: Re: SpaceX advances drive for Mars rocket via Raptor power
Post by: R7 on 03/12/2014 02:26 pm
TRW pintle paper (http://smartdata.usbid.com/datasheets/usbid/2001/2001-q1/pintleenginepaperaiaafinal.pdf) list quite a lot of propellant combinations already tested, including FLOX/gaseous CH4 and air/coal dust. So I guess it'll work in Raptor too.
Title: Re: SpaceX advances drive for Mars rocket via Raptor power
Post by: RedLineTrain on 03/12/2014 02:45 pm
For sure, if Musk builds his monster rocket, it will be dreadfully expensive for any other entity to replicate.
Actually, it would cost less! (expensive still, of course)
If another 'entity' has baggage from years of doing business under a different model, then I agree with the 'dreadfully' part.   But if you have the cojones to go clean sheet, knowing what worked for SpaceX...

Rather, it would cost them less than what they would have spent otherwise.  But this new less costly amount, with a clean sheet design, would still be outside the means of other entities.

A F9R-equivalent based on a clean sheet design is within the means of several.
Title: Re: SpaceX advances drive for Mars rocket via Raptor power
Post by: R7 on 03/12/2014 03:08 pm
Reminiscence of IT bloopers is fun but alas, rockets are not computers. If available Newton-seconds from a unit of propellant would double every two years space colonization would be much easier  :-\
Understood but it's not about IT specifically.  History is littered with examples of things many said were either not-needed, impractical and/or impossible. Chose the field... atomic, telephony, architecture, aeronautics, hell, even the creator of Fed-Ex  was given a C by his professor for proposing in impractical idea.
Note that I didn't question practicality or possibility but the rate at which things change and how far certain things can improve. Semiconductor mfg was able to shrink line width from 10 micrometers in 1971 to 22 nanometers currently in widespread use while at the same time raising clock speeds from subMHz to several GHz. This enabled gigaflops and -bytes in everybody's pockets today. Try as I may can't imagine performance explosion of equal magnitude in chemical rocketry. I hope to be wrong and soon 3Dprinters produce Raptors like sausages.
Title: Re: SpaceX advances drive for Mars rocket via Raptor power
Post by: AncientU on 03/12/2014 03:20 pm
TRW pintle paper (http://smartdata.usbid.com/datasheets/usbid/2001/2001-q1/pintleenginepaperaiaafinal.pdf) list quite a lot of propellant combinations already tested, including FLOX/gaseous CH4 and air/coal dust. So I guess it'll work in Raptor too.
Thanks for the excellent article!!!
Note that reference #14 co-author is someone named T. Mueller.
Sounds familiar... as does the 650,000 lbf engine in the title.
Title: Re: SpaceX advances drive for Mars rocket via Raptor power
Post by: butters on 03/12/2014 03:32 pm
My imagination suggests that the applicability of pintle injectors may be affected more by the gas-gas nature of the Raptor engine rather than by its propellant combination or thrust level. Have there been any gas-gas pintles?
Title: Re: SpaceX advances drive for Mars rocket via Raptor power
Post by: R7 on 03/12/2014 03:33 pm
Sounds familiar... as does the 650,000 lbf engine in the title.

Yeah, while back when Raptor was still assumed as 650klbf engine people were discussing how this figure must be Chief Designer's carefully calculated sweet spot. Tried to offer alternate explanation (http://forum.nasaspaceflight.com/index.php?topic=26995.msg1139646#msg1139646) ;)
Title: Re: SpaceX advances drive for Mars rocket via Raptor power
Post by: aero on 03/12/2014 03:35 pm
Do we have any data giving the chamber pressure of the 4,500 kN engine? Where did I get 69 MPa from?
Title: Re: SpaceX advances drive for Mars rocket via Raptor power
Post by: llanitedave on 03/12/2014 03:38 pm
I have a query regarding the choice of gas-gas for Raptor's engine cycle...

Merlin engines famously use pintle injectors.

Is this something that would be suitable for use in a FFSC engine? In a very large thrust chamber? I assume this choice could affect combustion efficiency. I have this mental image that gasses (which will be relatively hot, as well) might mix relatively easily - is that true?

If pintle is not suitable, I wonder if part of the work scheduled for Stennis is to investigate alternative injector arrangements?

As I understand it, pintle makes it relatively easy to throttle an engine, and everyone seems to be assuming deep throttling will be required on Raptor.

Cheers, Martin

I was getting ready to ask a very similar question -- thanks!
Title: Re: SpaceX advances drive for Mars rocket via Raptor power
Post by: AncientU on 03/12/2014 03:41 pm
Sounds familiar... as does the 650,000 lbf engine in the title.

Yeah, while back when Raptor was still assumed as 650klbf engine people were discussing how this figure must be Chief Designer's carefully calculated sweet spot. Tried to offer alternate explanation (http://forum.nasaspaceflight.com/index.php?topic=26995.msg1139646#msg1139646) ;)
Nice.  Missed that...
Title: Re: SpaceX advances drive for Mars rocket via Raptor power
Post by: llanitedave on 03/12/2014 03:43 pm
The future is difficult to comprehend...
Quote
1943    "I think there is a world market for maybe five computers.", Thomas Watson, chairman of IBM.
Quote
1977    "There is no reason anyone would want a computer in their home." Ken Olson, president, chairman and founder of Digital Equipment Corp..
Quote
1981    "640k ought to be enough for anybody.", Bill Gates
Quote
1992    "Windows NT addresses 2 Gigabytes of RAM which is more than any application will ever need". Microsoft on the development of Windows NT
http://trillian.randomstuff.org.uk/~stephen/history/timeline-QUOTES.html (http://trillian.randomstuff.org.uk/~stephen/history/timeline-QUOTES.html)

My computers each have 4GB of RAM and the desktop has 2TB storage.  We are a two-person, five computer household -- not counting our iPhones, etc.

EM wants to make travel to space affordable (and go to Mars)... let us then see what happens.
The near future is *not* difficult to comprehend. Those computer memory quotes (if even accurate) were perfectly valid at the time and for at least 10 years into the future. I had to populate and install memory expansion boards into PCs in the 1980s to get them to 1 MB of system memory for my small company. It was *very* expensive back then. The 2 GB of RAM issue in the early 1990s is even valid today -- 99.99% of programs right now do not need 2 GB of address space. Back then, most computers had 4-8MB of system memory so having an address space several orders-of-magnitude higher was a perfectly valid limit. Two GB of system memory would have bankrupted you (and if you could have even afforded 2 GB of memory you would not have had enough SIMM slots on your motherboard).

The bottom line: proving those quotes wrong at the time would have bankrupted you. You wouldn't have any money left to actually use the souped up computer you created. Just like SLS (are there any 100+ mT payloads planned?).

10 years is a mere instant in technology and cultural development.
Title: Re: SpaceX advances drive for Mars rocket via Raptor power
Post by: Robotbeat on 03/12/2014 03:44 pm
A single-core, TSTO rocket in the 7 million pound class range may be needed to get full reuse for the largest military and commercial payloads with dual-launch like Ariane 5. Still doesn't justify building such a rocket by itself, but there ARE some customers. It would likely be cheaper per-flight than Falcon Heavy (though greater up front and infrastructure costs). Similar line of reasoning is why Shuttle was so big for just EELV sized payloads.
Title: Re: SpaceX advances drive for Mars rocket via Raptor power
Post by: DJPledger on 03/12/2014 03:48 pm
Do we have any data giving the chamber pressure of the 4,500 kN engine? Where did I get 69 MPa from?
69MPa is the theoretical maximum Pc possible with gas-gas LOx/LCH4. Raptor's Pc will be much lower than this with one member reckoning it to be around 20.5MPa.
Title: Re: SpaceX advances drive for Mars rocket via Raptor power
Post by: CJ on 03/13/2014 05:58 am
I remember back around the time of the Falcon Heavy announcement (this (http://shitelonsays.com/transcript/spacex-next-falcon-heavy-press-conference-2011-04-05)) there was a number of people who found it quite contradictory that SpaceX fans were cheering along with Elon's announcement of a heavy lift vehicle.. while simultaneously poopooing NASA's HLV options - as many of us have been doing for years.

Some of it was just cognitive dissonance, I'll grant that, but what a few of us said was this: there's a difference between affordable heavy lift like the Falcon Heavy and unaffordable Ares/SLS heavy lift. So long as there are customers other than NASA for the Falcon Heavy, you can imagine the price being low enough that NASA could actually afford to do something with it.

That said, this Mars monster rocket has no customers. It's commercially useless, just like Ares was and SLS is. The costs can't be shared. It can't be affordable. So far the only argument I've heard as to why this is more than just like the other heavy lift fantasies is that Elon's monster rocket will be reusable. Well, so what? Making something reusable doesn't immediately make it affordable. In fact, it typically costs more to make a launch vehicle reusable than it does to make it expendable. The only way to get cheap launch from a reusable launch vehicle is to fly it a lot, and for that you have to have a lot of customers.

Anyway, I think this needs to be said.

My primary argument against SLS is, and always has been, its price per pound to orbit. If SLS could do $500 per pound, I'd be fine with it, because at that price, it'd pay for itself with ease and be useful.   

That said, I think that *if* MCT is a launch vehicle that can beat other alternatives (including SpaceX's own) in price per pound, it's worth their while to look into.  If it's fully reusable as claimed, that's a huge step in that direction. (and if it's not reusable, I'd agree with you, it's madness because of the cost per pound).

What we seem to be looking at here is a single core rocket larger than a Saturn 5. But, S5 was three stage and not reusable, so there will be mass penalties vs. it. For a really wild ballpark, let's say that in reusable mode, the single core can do Saturn5- level payloads to LEO. Is there a market? To LEO alone, probably not. That gets us to GTO, BUT... how do you get your payload(s) to GTO and recover the upper stage? It can be done, but that's more mass penalty. S5 could do 47 tonnes through TLI, so, more (hypothetically) to GTO. Going by the GTO/TLI ratios of other US launchers, I'll guess that would be a theoretical GTO capacity of around 60 tonnes.

Let's say the Raptor9 monster, in reusable mode (and a lower ISP upper stage than S5), can only manage half that. 30 metric tons. That's still a hell of a lot. Ariane 5 can do about 8, and is looking to expand to 11.5. with the ME variant. They seem to think there's a use for that kind of capacity to GTO.

What does an Araine 5 launch cost? It's subsidized, but it's still around 200 million. So, about 25k per kilo, or $11,363 per pound to GTO.

Space X, with a fully reusable system, should be easily able to beat the Ariane 5 launch cost, so even if they only haul the same payload to GTO on a given launch, that's still a market, and a big one. (and I'll bet there are some customers who would buy the excess capacity at lower rates... much as we see in LEO now)

There we get to NRO, which runs most of America's intel birds. The photorecon ones in eccentric LEO burn through a heck of a lot of propellant (they often need to change orbit, not just maintain it. Tasking is one reason, there are others, such as doing a pass at an unpredicted time). In fact, propellant is their current design life limiter. We're talking high mass birds to LEO. The most recent ones I've seen mass range figures for are the later models of what's commonly called the KH-11, at around 20 metric tons. I don't see the newer versions being any lighter, and in fact, the NRO and Air Force were heavily involved in Shuttle design parameters, including cross-range and payload, which give a good idea of what kind of mass they had in mind for LEO back then (out of  Vandenburg.) I think this is why FH seems likely to be flying most of its missions out of Vandenburg; its high mass to LEO is tailor-made for this purpose. I also think higher mass would thus find a use for polar LEO.     

Then we get to the future possible markets; LEO and Lunar flyby tourism. Those too are mass intensive.

NASA? I'd rank them last on the potential customer list; possible, but not worth counting on. They'd go with SLS, if it's built, for reasons that have nothing to do with practicality or suitability.

So, I think it all boils down to price per pound. If MCT can bring it down below what even they can do now, they have a potential market. If not, I think they'll realize it and MCT won't be built. And as for timeframe, I'm guessing it will be a decade at best before it flies, and a lot can happen to the space market in a decade.

As for the tri-core variant and Mars applications, I think those would be ancillary capabilities; uses for (and derivatives of) a vehicle that exists for other reasons, not its fiscal reason for being. For example, launching a Mars mission by utilizing three cores at their end of their useful life would make for a cheap (relatively speaking) launch of a heck of a lot of mass (which could include paying tourists). And that's how to make Mars affordable and thus reachable; lower the cost of getting there. Otherwise, even with as much money as Elon Musk has, it's just not going to happen and he surely knows it - it's well beyond even his reach.





   

Title: Re: SpaceX advances drive for Mars rocket via Raptor power
Post by: CuddlyRocket on 03/13/2014 07:58 am
It bears repeating: There's no such thing as a rocket that's too big, only a rocket that's too expensive.

The Atlas V's addressable market is virtually everything that is launched. One of the main reasons why it doesn't launch everything is that for most of those launches there are cheaper alternatives. If you can make a big rocket that is nonetheless cheaper per launch it will succeed in the marketplace.
Title: Re: SpaceX advances drive for Mars rocket via Raptor power
Post by: cuddihy on 03/13/2014 10:38 am
If someone built a rocket that could do 30mt to GTO for a price around current Delta IV Heavy, I assure you DoD has concepts that would find the funding to start RFPs tomorrow. AF might even reconsider the case for DoD astronauts. There are good reasons to put humans near military assets if they are critical to operations.

That said, how long will it take to get there? Aren't we years away from seeing a Raptor fired for testing?

It's taken Merlin 1 10 years of iterative design&testing to get to full utility, and that had Fastrac history to lean on.
Title: Re: SpaceX advances drive for Mars rocket via Raptor power
Post by: AncientU on 03/13/2014 10:54 am
If someone built a rocket that could do 30mt to GTO for a price around current Delta IV Heavy, I assure you DoD has concepts that would find the funding to start RFPs tomorrow. AF might even reconsider the case for DoD astronauts. There are good reasons to put humans near military assets if they are critical to operations.

That said, how long will it take to get there? Aren't we years away from seeing a Raptor fired for testing?

It's taken Merlin 1 10 years of iterative design&testing to get to full utility, and that had Fastrac history to lean on.
Component testing to begin at Stennis first part of this year according to reports. Raptor has M1 'history' and T. Mueller's lead to lean on -- years, as in 2-3 maybe, but years as in decades, no.
Title: Re: SpaceX advances drive for Mars rocket via Raptor power
Post by: R7 on 03/13/2014 10:56 am
AF might even reconsider the case for DoD astronauts. There are good reasons to put humans near military assets if they are critical to operations.
You are 45+ years too late. Steady advances in sat tech rendered MOL obsolete. With digitalization the sats have enjoyed their share of the Moore's law so now MOL is even more obsolete. And GEO is not healthy place for humans ;)
Title: Re: SpaceX advances drive for Mars rocket via Raptor power
Post by: cambrianera on 03/13/2014 11:00 am
That said, how long will it take to get there? Aren't we years away from seeing a Raptor fired for testing?

It's taken Merlin 1 10 years of iterative design&testing to get to full utility, and that had Fastrac history to lean on.

Starting from zero, ten years to get an engine that is:
-cheaper than any other similar engine;
-better than any other engine in T/W;
-ISP close to the best in class (LOX-RP1 obviously).

Now SpaceX has:
-greater experience in turbomachinery;
-first class testing facilities (both their own & on lease);
-a prolific and experienced engineering group.

But still, underlining what SpaceX achieved on propulsion in a little bit more than ten years, I'm with you that a Raptor ready for firing will not be seen before at least 2-3 years.
Title: Re: SpaceX advances drive for Mars rocket via Raptor power
Post by: MP99 on 03/13/2014 11:11 am
I have a query regarding the choice of gas-gas for Raptor's engine cycle...

Merlin engines famously use pintle injectors.

Is this something that would be suitable for use in a FFSC engine? In a very large thrust chamber? I assume this choice could affect combustion efficiency. I have this mental image that gasses (which will be relatively hot, as well) might mix relatively easily - is that true?

If pintle is not suitable, I wonder if part of the work scheduled for Stennis is to investigate alternative injector arrangements?

As I understand it, pintle makes it relatively easy to throttle an engine, and everyone seems to be assuming deep throttling will be required on Raptor.

Cheers, Martin
Quite a question. There isn't much experience in gas-gas injectors. All American experience resides in AerojetRocketdyne now. But Tom Müller did work on many injector types while at TRW.
From my limited understanding, gas-gas injectors have lower pressure losses than liquid/liquid or g/l. But you need a lot more section. I estimated...

Great response, many thanks.

Cheers, Martin
Title: Re: SpaceX advances drive for Mars rocket via Raptor power
Post by: IRobot on 03/13/2014 11:16 am
That said, how long will it take to get there? Aren't we years away from seeing a Raptor fired for testing?

It's taken Merlin 1 10 years of iterative design&testing to get to full utility, and that had Fastrac history to lean on.
Hardware and software development does not follow a linear progression.
Title: Re: SpaceX advances drive for Mars rocket via Raptor power
Post by: cuddihy on 03/13/2014 02:34 pm
AF might even reconsider the case for DoD astronauts. There are good reasons to put humans near military assets if they are critical to operations.
You are 45+ years too late. Steady advances in sat tech rendered MOL obsolete. With digitalization the sats have enjoyed their share of the Moore's law so now MOL is even more obsolete. And GEO is not healthy place for humans ;)
If someone built a rocket that could do 30mt to GTO for a price around current Delta IV Heavy, I assure you DoD has concepts that would find the funding to start RFPs tomorrow. AF might even reconsider the case for DoD astronauts. There are good reasons to put humans near military assets if they are critical to operations.

That said, how long will it take to get there? Aren't we years away from seeing a Raptor fired for testing?

It's taken Merlin 1 10 years of iterative design&testing to get to full utility, and that had Fastrac history to lean on.
Component testing to begin at Stennis first part of this year according to reports. Raptor has M1 'history' and T. Mueller's lead to lean on -- years, as in 2-3 maybe, but years as in decades, no.
AF might even reconsider the case for DoD astronauts. There are good reasons to put humans near military assets if they are critical to operations.
You are 45+ years too late. Steady advances in sat tech rendered MOL obsolete. With digitalization the sats have enjoyed their share of the Moore's law so now MOL is even more obsolete. And GEO is not healthy place for humans ;)

The reasons are not technological, they are strategic and political.
Title: Re: SpaceX advances drive for Mars rocket via Raptor power
Post by: Lobo on 03/13/2014 05:22 pm
A single-core, TSTO rocket in the 7 million pound class range may be needed to get full reuse for the largest military and commercial payloads with dual-launch like Ariane 5. Still doesn't justify building such a rocket by itself, but there ARE some customers. It would likely be cheaper per-flight than Falcon Heavy (though greater up front and infrastructure costs). Similar line of reasoning is why Shuttle was so big for just EELV sized payloads.

Hmmm....that sounds a lot like what I've been speculating about on the forum.  I think that's how you build a business case for a HLV when there otherwise isn't really one.  You make it reusable, and [hopefully] cheaper to launch than an EELV-heavy class vehicle that would otherwise be needed for those bigger or dual payloads to those higher orbits, or escape.  As I think the performance on FH is starting to bear out with partial reusability vs. full reusability vs. full expendability, FH won't be lofting D4H and Ariane 5 payloads to higher orbits with much reusability.  (Outboard Boosters should be able to be reused on most payloads).
So a central core and upper stage are expended on larger payloads.  The full FH on larger payloads than that.
But if you could get 30mt to GTO for like $50M with a fully reusable HLV, vs. say $150M for a partially reusable FH, or $300M+ for a D4H (not sure what Ariane 5 prices are), then it suddenly makes it's own business case, and while is seems very overkill, it's not if fully reusable.  Just paying for fuel and pad operations and maintenance of the stages.  (hopefully the reusable upper stage is much cheaper than the Shuttle processing, or else this business model goes right out the window.  :-)  )

Those big margins for the HLV then absorb the big performance penalties for a reusable upper stage.
If NASA wants to send men to the moon, then an expendable upper stage could be used, or multiple reusable launches, depending. 
It could have that flexibility to launch two commercial satellites to GTO, or one or two large military payloads to GTO, or a large NASA planetary probe through escape (with a kick stage, so the reusable stage can make it back to Earth), or a manned lunar mission, or a manned Mars mission (smaller scale than the latter misisons).
That makes for a versitile and affordable enough HLV that it creates it's own business case.
For SpaceX, any payload larger than a fully reusable FH can launch would be moved up to this FXX-R.
Any payloads parger than a fully reusable F9R gets moved to FH-R.

As you said, if SpaceX didn't have their own plans which require HLV like going to Mars, and maybe helping to nudge out SLS to have NASA use them, then they'd probably be ok with sticking with FH and just flying fully or partially expendable as required by the mission, and still carving out market share, and avoid that investment.  But...since they'll be building it anyway, let it help pay for itself. 
Title: Re: SpaceX advances drive for Mars rocket via Raptor power
Post by: Lobo on 03/13/2014 09:50 pm
If someone built a rocket that could do 30mt to GTO for a price around current Delta IV Heavy, I assure you DoD has concepts that would find the funding to start RFPs tomorrow. AF might even reconsider the case for DoD astronauts. There are good reasons to put humans near military assets if they are critical to operations.

That said, how long will it take to get there? Aren't we years away from seeing a Raptor fired for testing?

It's taken Merlin 1 10 years of iterative design&testing to get to full utility, and that had Fastrac history to lean on.
Component testing to begin at Stennis first part of this year according to reports. Raptor has M1 'history' and T. Mueller's lead to lean on -- years, as in 2-3 maybe, but years as in decades, no.

There's a target date for the single 10m core LV to fly posted on L2.  Let's just say it's not as far out as one might think.
Title: Re: SpaceX advances drive for Mars rocket via Raptor power
Post by: QuantumG on 03/13/2014 10:09 pm
If there was a non-government market for Falcon Heavy, it'd be flying by now.

Bigger rockets are not just premature, they're fantasy.
Title: Re: SpaceX advances drive for Mars rocket via Raptor power
Post by: clongton on 03/14/2014 12:18 am
If there was a non-government market for Falcon Heavy, it'd be flying by now.

Bigger rockets are not just premature, they're fantasy.

There is a market - a market of one.

It is a mistake to think that SpaceX is building the BFR for purely commercial profits. If it were then you'd be right. Totally right!

But SpaceX is not doing that. They have their own ambitions - to go to Mars. And the plan is to do that on their own. They are not planning to do that in cooperation with NASA or any other existing space agency. It is a pure SpaceX endeavor. Sure, they will use it to launch commercially, because then they can supplement the cost of deployment. But SpaceX is going to Mars using the BFR whether or not anybody buys launch services with it or not. At least that's their plan.
Title: Re: SpaceX advances drive for Mars rocket via Raptor power
Post by: QuantumG on 03/14/2014 12:40 am
They have their own ambitions - to go to Mars. And the plan is to do that on their own. They are not planning to do that in cooperation with NASA or any other existing space agency. It is a pure SpaceX endeavor.

How did you possibly come to that conclusion?

Title: Re: SpaceX advances drive for Mars rocket via Raptor power
Post by: GalacticIntruder on 03/14/2014 01:07 am
Musk changes his mind on that topic every time he speaks. Sometimes he says he will go it alone, but he does not want to, other times he says he will do what they can and hope enough people or NASA join him. I think he waffles depending on how well he is doing on his personal finances. Definitely looking very promising so far, but we all know that could evaporate in a millisecond, with those fickle investors/traders. By 2020 he could be several times more wealthy or he could be poor again.

One thing is clear, to get to Mars you need a SHLV, like SLS Block2 or FXX. There are not too many people who have faith in the SLS program. They also have very faith in NASA to get HTM before the 2030's (if ever) and nothing very ambitious on the Elon level, ie MCT/FXX and colonies/civilians. Certainly never will be reusable and cost effective the NASA way, and thus not sustainable.

Elon will not follow others or the rules of some government, and he is ambitious. So if he wants to be on Mars in ten years, he must do it all by himself and private investors. Elon is a master of getting others to pay for his dreams, but this time, he is on his own. I can't see NASA handing over money directly for the MCT and FXX programs.
Title: Re: SpaceX advances drive for Mars rocket via Raptor power
Post by: QuantumG on 03/14/2014 01:16 am
Musk changes his mind on that topic every time he speaks.

Can you provide quotes? I've never heard him say they intend to fund a Mars mission, ever, and.. ya know, I kinda pay attention to what he says.

Quote from: GalacticIntruder
One thing is clear, to get to Mars you need a SHLV, like SLS Block2 or FXX.

That's not clear at all. In fact, if you've mastered reusability it seems like a step backwards.


Title: Re: SpaceX advances drive for Mars rocket via Raptor power
Post by: rst on 03/14/2014 03:42 am
Musk changes his mind on that topic every time he speaks. Sometimes he says he will go it alone, but he does not want to, other times he says he will do what they can and hope enough people or NASA join him. I think he waffles depending on how well he is doing on his personal finances. Definitely looking very promising so far, but we all know that could evaporate in a millisecond, with those fickle investors/traders. By 2020 he could be several times more wealthy or he could be poor again.

He's also repeatedly said that he expects some of the funding to come from the colonists themselves (at the oft-quoted $500k per head, sometimes justified by comparing it to the price of a nice house).  I'm not sure where he expects to find enough people with that kind of money to establish a self-sustaining Mars colony.  There are certainly a few --- on a planet with going on seven billion people on it, there will be a few meeting any description you like.  But by and large, people who can afford a nice house tend to buy one and stay in it.  Conversely, most of the people in past great migrations have generally left because of lousy prospects at home --- if not just being kicked or dragged out (e.g., the British prison boats to Australia, among innumerable less pleasant examples).

One place these sorts of remarks have been reported: http://news.discovery.com/space/alien-life-exoplanets/mars-colony-spacex-121126.htm
Title: Re: SpaceX advances drive for Mars rocket via Raptor power
Post by: Lobo on 03/14/2014 04:02 am

That's not clear at all. In fact, if you've mastered reusability it seems like a step backwards.

Unless it's a reusable HLV....
Title: Re: SpaceX advances drive for Mars rocket via Raptor power
Post by: dorkmo on 03/14/2014 04:11 am
at the oft-quoted $500k per head, sometimes justified by comparing it to the price of a nice house

and thats cold hard cash, i dont think any bank is guna give someone a 5% 30yr loan if theyre planning on leaving the planet.
Title: Re: SpaceX advances drive for Mars rocket via Raptor power
Post by: QuantumG on 03/14/2014 04:12 am

That's not clear at all. In fact, if you've mastered reusability it seems like a step backwards.

Unless it's a reusable HLV....

That's just excluding commercial payloads which have no need for such capacity, for no benefit. It makes no sense to build an RLV bigger than the market demand. You're just leaving money on the table that way.

.. and yeah, I just said this..
Title: Re: SpaceX advances drive for Mars rocket via Raptor power
Post by: QuantumG on 03/14/2014 04:13 am
at the oft-quoted $500k per head, sometimes justified by comparing it to the price of a nice house

and thats cold hard cash, i dont think any bank is guna give someone a 5% 30yr loan if theyre planning on leaving the planet.

So.. Mars would be entirely populated by people who can actually pay off a mortgage? Stop it, you're making me want to go.
Title: Re: SpaceX advances drive for Mars rocket via Raptor power
Post by: guckyfan on 03/14/2014 04:20 am

That's not clear at all. In fact, if you've mastered reusability it seems like a step backwards.

Unless it's a reusable HLV....

That's just excluding commercial payloads which have no need for such capacity, for no benefit. It makes no sense to build an RLV bigger than the market demand. You're just leaving money on the table that way.

.. and yeah, I just said this..

Falcon Heavy cannot lift large existing payloads in fully reusable mode. I expect Falcon X to launch at lower cost than Falcon heavy. So until other providers go fully reusable with a vehicle designed for GTO requirements and beat SpaceX Falcon X prices they will be fine launching it. Only then they would need to develop something smaller to stay competetive.

Title: Re: SpaceX advances drive for Mars rocket via Raptor power
Post by: Robotbeat on 03/14/2014 04:24 am

That's not clear at all. In fact, if you've mastered reusability it seems like a step backwards.

Unless it's a reusable HLV....

That's just excluding commercial payloads which have no need for such capacity, for no benefit. It makes no sense to build an RLV bigger than the market demand. You're just leaving money on the table that way.

.. and yeah, I just said this..
I'm not sure that's true. The "HLV" moniker is only applicable to a single-core vehicle (~100ton IMLEO) if expendable AND (this is key, here) if to LEO. Such an HLV would only be two stages (talking about initial capability here) and if it's fully reusable, its capacity would halve, down to 50 tons to LEO. And exactly because it's two stages and reusable, its GTO performance may actually be worse than the expendable Falcon Heavy, perhaps roughly equivalent to the Ariane 5 or Proton.

But it'd only be two stages, both of which could be reusable. It's POSSIBLE that it could have a (significantly) lower operational cost than an expendable Falcon Heavy (although by no means guaranteed). And if SpaceX is considering sinking the cost of development anyway, well, there's a pretty good case to be made that you'd want to switch the larger commercial comm-sats over to the single-core BFR.

You're thinking about the raw performance of this vehicle to LEO, not its usable performance to higher energy orbits after all the penalties for full reuse (and just two stages), which would be in the right range for larger commercial satellites.

EDIT:Also, if they could get enough flights on it, they could easily argue that they have a significant reliability advantage over their competitors. No one else has a two-stage rocket with engine-out capability on the first stage (and possibly just a single-engine on the upper stage...) that can put 6-15 ton payloads to GTO. Not only would it be the simplest rocket, but you could test-fly the airframe. It's a reliability benefit that's worth something. ULA (and Ariane/Airbus defense) says ultra-high reliability is worth tens of millions of dollars. But everything that puts over 5 tons to GTO has at least an extra booster or two, if not another whole stage.
Title: Re: SpaceX advances drive for Mars rocket via Raptor power
Post by: QuantumG on 03/14/2014 04:28 am
Falcon Heavy cannot lift large existing payloads in fully reusable mode.

Right now it can't lift anything, and we know nothing about its "reusable mode". What "large existing payloads" did you have in mind?

Quote from: guckyfan
I expect Falcon X to launch at lower cost than Falcon heavy.

Why? I think you're just participating in the reusable=cheaper fallacy. The economics of reuse are a lot more complicated than that.


Title: Re: SpaceX advances drive for Mars rocket via Raptor power
Post by: Robotbeat on 03/14/2014 04:48 am
Falcon Heavy cannot lift large existing payloads in fully reusable mode.

Right now it can't lift anything, and we know nothing about its "reusable mode". What "large existing payloads" did you have in mind?
...
Ariane 5 can lift over 10 tons to GTO, Delta IV Heavy can do more than that.
This satellite bus can be over 9 metric tons, fully loaded to GTO:
http://en.wikipedia.org/wiki/Alphabus
(It launched a few months ago on Ariane 5.) There are a few other satellite buses that are also larger than 6 tons.

Falcon Heavy, I think according to Elon, can only do 6 tons reusable.

You apparently don't understand the commercial satellite market very well. Do you know how many rockets are in Falcon Heavy's class (i.e. greater than Falcon 9's 4.8-5 tons to GTO) and their annual launch rate? For commercial launches, it's 15-20 per year, depending on how you count. The number of active launch vehicles that Falcon Heavy would be competing against: HIIa/b, Long March 3b/e, Proton, Ariane 5, Delta IV, and Atlas V. Without Falcon Heavy, that's about half of the commercial GTO satellite market that SpaceX can't compete in, and its MORE than half the market if you're talking about revenue. And much of that, the higher revenue stuff, can only be competed with either a largely-expendable Falcon Heavy (maybe reusing the side boosters) or fully expendable.

With a Raptor-powered vehicle, the whole thing could be reused and it'd have far fewer staging events (and far fewer engines than a Falcon Heavy).

EDIT:Also, you would be using a cheaper propellant and wouldn't have to deal with coking. Instead of 3 cores with 27 total engines with soot, you'd be talking about just a single core with fewer interfaces and with just 9 engines but with no soot, although much bigger. The operational costs are not automatically going to be cheaper for the Falcon Heavy, especially if you start throwing away cores.
Title: Re: SpaceX advances drive for Mars rocket via Raptor power
Post by: Lars_J on 03/14/2014 05:07 am
I expect Falcon X to launch at lower cost than Falcon heavy.

Why? I think you're just participating in the reusable=cheaper fallacy. The economics of reuse are a lot more complicated than that.

Of course they are. But you seem to be doing the opposite - Assuming that reuse will make it more expensive. Granted, the Shuttle evidence certainly favours that view, but SpaceX isn't trying to reuse things the Shuttle way, so we'll just have to wait and see.
Title: Re: SpaceX advances drive for Mars rocket via Raptor power
Post by: guckyfan on 03/14/2014 06:18 am
Falcon Heavy cannot lift large existing payloads in fully reusable mode.

Right now it can't lift anything, and we know nothing about its "reusable mode". What "large existing payloads" did you have in mind?

That right now it can't lift anything is getting stale, don't you think?

We have the info that it can lift 7 tons to GTO with all three boosters reusable. Add second stage reusablility we are below 5 tons, not enough for heavy comsats. Central core reuse really hurts payload capacity.

Quote from: guckyfan
I expect Falcon X to launch at lower cost than Falcon heavy.

Why? I think you're just participating in the reusable=cheaper fallacy. The economics of reuse are a lot more complicated than that.

I am just not participating in the reusable not cheaper fallacy. The economics of reuse may be complicated. But SpaceX seems very confident and they should know what they are talking about. They have tons of data from teststand runs of the Merlin engine and from Grasshopper.

If they were not that confident they would not start building the large methane vehicle (we really do need a name for it we all can use). The new launch vehicle would not make any sense if they were not confident in cheap reuse.

They may yet fail but it keeps getting more unlikely all the time.

Title: Re: SpaceX advances drive for Mars rocket via Raptor power
Post by: Dudely on 03/14/2014 12:45 pm
We know Musk has a habit of "cross-pollinating" his business ventures. Ex. Tesla is going to use solar panels purchased from Solar City to power a battery factory that will sell battery packs to Solar City (as well as go in the cars, obviously). . .

So would it be reasonable to assume that perhaps he has thought of ways to partially monetize a HLV, even the FH (though that would be off-topic)? I was reading about Bigelow and apparently they have starting building some actually hardware for tugs and habitats and other such things for moving around the lagrange points and other places in the Earth-moon system. They are apparently being designed specifically to fit in the FH fairing.

It is also likely he has backup plans for his backup plans. I, for one, will be fascinated to see which endeavors fail and what else he comes up with. People forget how much Musk has failed, which is always much more interesting!
Title: Re: SpaceX advances drive for Mars rocket via Raptor power
Post by: mfck on 03/14/2014 01:13 pm
There are obviously lessons about mass production learnt at Tesla and fed into SpaceX. I wonder when will we hear about automated assembly of stage cores.
Title: Re: SpaceX advances drive for Mars rocket via Raptor power
Post by: go4mars on 03/14/2014 01:21 pm
at the oft-quoted $500k per head, sometimes justified by comparing it to the price of a nice house

and thats cold hard cash, i dont think any bank is guna give someone a 5% 30yr loan if theyre planning on leaving the planet.
Why not?     A lot of jobs are mobile/digital.  Computer programmers, technical writers, musicians, engineers, ...

The best geo-tech I ever worked with (for several months), I never met.  He logged in from Kelowna. 

Besides; there's always credit at the Company store.  ;)
Title: Re: SpaceX advances drive for Mars rocket via Raptor power
Post by: Lobo on 03/14/2014 05:34 pm
I expect Falcon X to launch at lower cost than Falcon heavy.

Why? I think you're just participating in the reusable=cheaper fallacy. The economics of reuse are a lot more complicated than that.

Of course they are. But you seem to be doing the opposite - Assuming that reuse will make it more expensive. Granted, the Shuttle evidence certainly favours that view, but SpaceX isn't trying to reuse things the Shuttle way, so we'll just have to wait and see.

Both good points.

I think the thing to remember here is, for SpaceX, reusability -needs- to make their costs such that it makes a viable business case for a heavy sized vehicle launching EELV-heavy sized payloads to various orbits for cheaper than the competition.  Otherwise there’s no much point.
It doesn't necessarily have to start off only costing some ridiculously low price.  Let's say it's $50-$100 million per launch early on while SpaceX is figuring things out and developing a process to make it all more efficient in the future.
That's maybe about the same price as a partially reusable FH (reusable outboard boosters but expendable core and upper stage), cheaper than expendable FH, maybe half the price of Ariane 5 and the Atlas 531/541/551 LV's, and maybe 1/3 the price of D4H.
That's not a -cheap- LV, but it would be poised to be the most affordable LV in that class.  Thus instant business case.

As far as the Shuttle goes, it wasn't a bad idea, but not well implemented as we all know.  A reusable upper stage won't be manned, won't have incredibly labor intensive RS-25's, probably won't have the complex and fragile ceramic tiles (at least not in the same labor intensive way the Shuttle had), won't have external fuel piping for it's engines running through it's TPS system, won't have a complex shape to cover with TPS, etc.  It would only have a fraction of the components and systems the Shuttle had.  I imagine it would look similar to the NASA Mars DRM 5.0 biconic Aeroshell with a shuttle-like payload bay on it's side opposite the TPS system, or it will be something like Rocketplane Kistler's upper stage.  Could have an expendable PLF on top of the stage itself like in SpaceX's video showing a reusable Falcon upper stage. 

Either way, you basically have a cylinder with a TPS on it's nose and along one side.  SpaceX is already figuring out cold gas RCS systems so it'd probably use methalox residuals for it's RCS system without needing the separate hypergolic system than the Shuttle had for it's RCS/OMS system, with all the issues of reusing a toxic propellant system.

Assuming something like this, it's basically avoiding all of the issues that drove up the Shuttle's reuse costs.
And it's based on the same core and tooling that makes the booster.  Where the shuttle was a separate, limited run, custom airframe.  There was no "production line" for the Shuttle once the fleet was built up.  However, there will be a production line with 10m barrel and tank tooling, an engine production line for spares and replacements, a landing leg production area for spares and replacements, etc.  That won't but shut down after making 4 or 5 units.  After long enough, the Shuttle is 30 years old and the place that made the airframe has been shut down for over 20 years. 

Let's say the Shuttle had been basically a reusable S-1C booster and flew back to KSC, and a modified S-II stage on top with a heat shield on the nose and along one side.  The S-II with a an extension on the top with a cargo bay and crew cabin.  It would land propulsively on it's center J-2 engine, which would be a throttle able variant.
Anyone else think that something like that for STS could have been a far cheaper system to develop, and cheaper to operate?  Even given the fact it's government developed and operated which drives up costs on that fact alone, I think it would still be a fraction to develop and operate of STS. And safer as the TPS isn't sitting next to a shedding ET.

Ok, so now it's 40 years later, with current computers and technology, but basically just that concept.  Except SpaceX won't even need to have a crew on it for launching payloads, so all those crew accommodations aren't even needed.  (Although I imagine they'll have a crew version as a test bed for a later MCT.)

Reusable FXX-R upper stage would maybe look like one of these.  An alternate STS could have too:



Title: Re: SpaceX advances drive for Mars rocket via Raptor power
Post by: Chris Bergin on 03/14/2014 06:36 pm
Just so everyone knows, we are working on a second and third article surrounding Raptor....to answer anyone else who had the same question per a PM I was sent today.
Title: Re: SpaceX advances drive for Mars rocket via Raptor power
Post by: baldusi on 03/14/2014 06:51 pm
Lobo. If I had to do any referrence to the STS system is that it is not how to innovate. They decided to do everything new, make one system that did everything. And deprecate the only systems that actually worked way before finishing main development of the new system. And not happy to do that, do it for 40% of the already optimist budget.
If I wanted to do a reusable system. First I would have done something like the HL20 launched on an existing LV. Whilr I learn the necessary lesson on reusability of the craft. I would try to study a reusable first stage. Once I've learned those lessons, I'd go for an integrated system. Once that is operative, I'd try to increase size and technology.
This is a bit what SpaceX is doing. They are designing operative programs that make sense by themselves, but also teach them important operative lessons.
There's no way to hit the right design the first time. Look at Falcon, at Dragon, at Merlin, etc. Development is an iterative process and they are getting their lessons learned.
It does seem logical, then, that if they are innovating on propulsion and scale, they'll try to keep the operative lessons as close the the know F9R lessons.
Title: Re: SpaceX advances drive for Mars rocket via Raptor power
Post by: ArbitraryConstant on 03/14/2014 07:44 pm
That said, this Mars monster rocket has no customers. It's commercially useless, just like Ares was and SLS is. The costs can't be shared.
I would wager it'll be competitive against other launchers. Even if they never reuse it, even if it never multi-manifests. It'll be cheaper outright than the larger launchers from other programs, so even if its capacity is almost entirely wasted it'll be able to win bids.
Title: Re: SpaceX advances drive for Mars rocket via Raptor power
Post by: docmordrid on 03/14/2014 09:56 pm
Wouldn't the insane margins also allow for massive reserves on the sats, allowing for extended lifetimes and easier repurposing?
Title: Re: SpaceX advances drive for Mars rocket via Raptor power
Post by: QuantumG on 03/14/2014 10:45 pm
That said, this Mars monster rocket has no customers. It's commercially useless, just like Ares was and SLS is. The costs can't be shared.
I would wager it'll be competitive against other launchers. Even if they never reuse it, even if it never multi-manifests. It'll be cheaper outright than the larger launchers from other programs, so even if its capacity is almost entirely wasted it'll be able to win bids.

How?
Title: Re: SpaceX advances drive for Mars rocket via Raptor power
Post by: R7 on 03/14/2014 11:01 pm
I would wager it'll be competitive against other launchers. Even if they never reuse it, even if it never multi-manifests. It'll be cheaper outright than the larger launchers from other programs, so even if its capacity is almost entirely wasted it'll be able to win bids.
How?
Large deposit of natural Li-Al is discovered beneath SpaceX property. To celebrate this the employees stop going home.
Title: Re: SpaceX advances drive for Mars rocket via Raptor power
Post by: clongton on 03/14/2014 11:21 pm
That said, this Mars monster rocket has no customers.

AIUI it's not supposed to.
Title: Re: SpaceX advances drive for Mars rocket via Raptor power
Post by: ArbitraryConstant on 03/15/2014 05:00 am
That said, this Mars monster rocket has no customers. It's commercially useless, just like Ares was and SLS is. The costs can't be shared.
I would wager it'll be competitive against other launchers. Even if they never reuse it, even if it never multi-manifests. It'll be cheaper outright than the larger launchers from other programs, so even if its capacity is almost entirely wasted it'll be able to win bids.

How?
A Raptor-9 vehicle would be much larger and the engines extremely sophisticated by SpaceX standards, but I don't think they're going to design something they can't build economically. With Ariane 5 or others costing $200m or more, yeah I think the probability is quite high that SpaceX will be in a position to throw away a Saturn V class launcher and still come in as the lowest bid for launches towards the high end of what existing vehicles can handle.

Jim points out, as far as I know correctly, that SpaceX has all kinds of payload service and integration costs that are really hard for them to control even if the launcher itself is cheap or reusable. The corollary, and we can see this from Falcon Heavy pricing, is that their manufacturing is extraordinarily low cost. This has to be true even if they're taking a haircut on the margins for <6.4 tons to GTO. I think that means in the case of a larger core their costs will scale extremely well.
Title: Re: SpaceX advances drive for Mars rocket via Raptor power
Post by: matthewkantar on 03/15/2014 11:16 pm
NASA had to design the successor for the Hubble space telescope to come in at half the mass of the Hubble to orbit it with existing vehicles. That consumes lots of money. Lots and lots of money. The Webb will go up in a 4.6 meter fairing and weight 5 tons. How much would the Webb telescope have cost if it could have weighed 20 tons and flown in a 14 meter fairing?

 I think it might knock a billion dollars off of a nine billion dollars project, but even if it only took off a quarter of a billion it would pay for a flight on 9 Raptor LV.

Companies that spend copious amounts of money squeezing capabilities and lifetime into 5 ton satellites would jump at the chance to have lots of extra mass aloft for similar monies. I have no idea if the folks at Spacex can do it, but if you build a monster re-useable LV the world will beat a path to your door.
Title: Re: SpaceX advances drive for Mars rocket via Raptor power
Post by: QuantumG on 03/15/2014 11:27 pm
The cost of JWST has nothing to do with design decisions.

It's the result of multiple instances of management failure and the subsequent pathological application of the sunk cost fallacy.
 
Title: Re: SpaceX advances drive for Mars rocket via Raptor power
Post by: Robotbeat on 03/15/2014 11:41 pm
Yes, it does have to do with design decisions. If they had chosen a higher TRL approach, they probably would've been able to complete it with much lower costs even with the same managerial structure.
Title: Re: SpaceX advances drive for Mars rocket via Raptor power
Post by: MATTBLAK on 03/15/2014 11:46 pm
The cost of JWST has nothing to do with design decisions.

It's the result of multiple instances of management failure and the subsequent pathological application of the sunk cost fallacy.
 

It's both design decisions and management, with the latter probably being the main cause. But also; pushing the state of the art in any space telescope's design will always be expensive. There's no getting around that. Webb is rather a specialized and not 'generic' space telescope. History will record if JWST was too ambitious or not.
Title: Re: SpaceX advances drive for Mars rocket via Raptor power
Post by: ArbitraryConstant on 03/16/2014 12:11 am
Here's a question.

RD-180 and NK-33 are both used in American launchers, but there's some question to supply or domestic manufacturing of both.

Raptor is significantly better in ISP and slightly better (assuming 1mlbf is vac) in thrust than RD-180. The fuel isn't the same but it's not hard to get and it's less cryogenic than LOX.

Might there be any non-SpaceX adoption of the engine other American launchers?
Title: Re: SpaceX advances drive for Mars rocket via Raptor power
Post by: MATTBLAK on 03/16/2014 12:19 am
A Raptor powered Falcon 9 could place how big a payload to L-2? Likely something the mass of JWST I'd bet. A Falcon Heavy with Raptor upper stage should be able to place something about three times the mass of JWST at L-2. A 'single barrel' telescope somewhat like a scaled-up Spitzer would be a relatively low-cost alternative to complex, segmented mirror 'scopes like Webb. If Falcon Heavy gets a wider fairing in the 6 meter range, it's not unreasonable to expect it to be able to carry a 'scope with a monolithic mirror in the range of 5 meters diameter - more than twice the size of Hubble.
Title: Re: SpaceX advances drive for Mars rocket via Raptor power
Post by: Hyperion5 on 03/16/2014 01:02 am
That said, this Mars monster rocket has no customers.

AIUI it's not supposed to.

I suspect the publicity of launching on the first flight might prove too much for comsat makers and they might load it up with a multitude of cheap, replaceable comsats and auxiliary payloads.  Byeond that however yes, I'd have to agree that an expendable Saturn V+ class BFR would have no customers initially.  The thing is, when Spacex start reusing their Falcon Heavy rocket, they're going to vacate the top of the comsat and DoD market.  I've seen some members post simulations where it would only be able to push a 6.5 mt satellite to GTO.  Worse still, the FH would suddenly have challenges lifting BA 330s to LEO (assuming that market comes about).  They could just launch an expendable FH or only a partially reusable one, but that to me seems like a temporary solution.  A BFR able to launch 150 mt+ in an expendable launch however would have no challenges whatsoever in replacing the FH's impressive expendable launch capacity even when reused.  Provided the price was right, I see no reason why the reusable BFR couldn't fill in for the expendable FH and dominate the heavy satellite & NASA exploration markets.  Also, if Bigelow isn't talking to Spacex about launching an Olympus Module on this new rocket, they will be soon enough. 
Title: Re: SpaceX advances drive for Mars rocket via Raptor power
Post by: baldusi on 03/16/2014 01:27 am
I believe that said LV would be part of an integrated strategy. Launcher and MCT. That's why I wouldn't be surprised if they did a Red Dragon under cost. Just to get some Mars EDL experience.
Title: Re: SpaceX advances drive for Mars rocket via Raptor power
Post by: butters on 03/16/2014 02:02 am
The prospect of selling Raptor engines to ULA for expendable rockets is interesting but perhaps not very likely.

SpaceX is thinking ahead to the reusable upper stage. F9R will not be able to serve the GTO market with a reusable upper stage. FHR may have barely enough performance to GTO with a reusable upper stage, and they have to recover and process twice as many independent stages compared to the F9R. It's not difficult to image how the monolithic BFR might be more economical to operate than FH. Half the number of stages and plenty of margin for a reusable upper stage -- probably enough margin give it an integrated payload bay where the passenger cabin would be for MCT.

For SpaceX, the BFR permits full reusability with any foreseeable satellite payload.
Title: Re: SpaceX advances drive for Mars rocket via Raptor power
Post by: CuddlyRocket on 03/16/2014 06:00 am
Might there be any non-SpaceX adoption of the engine other American launchers?

That would be limited by the desire to have at least two entirely independent launch systems so that one failure doesn't ground both.
Title: Re: SpaceX advances drive for Mars rocket via Raptor power
Post by: ArbitraryConstant on 03/16/2014 06:13 am
F9R will not be able to serve the GTO market with a reusable upper stage.
I'm curious about the LEO hit.

For GTO the reusable upper stage will clearly have enormous demands placed on it. With lower staging and having to go all the way to GTO, or I guess a supersynchronous orbit... that delta-v starts looking like SSTO territory. It's tremendous for a GG hydrocarbon engine.

I'm hoping though I'm not totally confident that they'll be able to launch Dragon to LEO. Orbcomm and similar payloads could clearly still be accommodated. Even launching an orbital Grasshopper with no payload would still make my day.

Either way just with the payload hit, the Raptor-9 BFR starts to seem reasonable just for reuse margin. :)
Title: Re: SpaceX advances drive for Mars rocket via Raptor power
Post by: Robotbeat on 03/16/2014 06:55 am
Many upper stages probably could do SSTO if T/W wasn't a problem and they had vacuum Isp.
Title: Re: SpaceX advances drive for Mars rocket via Raptor power
Post by: Oli on 03/16/2014 09:08 am
The cost of JWST has nothing to do with design decisions.

It's the result of multiple instances of management failure and the subsequent pathological application of the sunk cost fallacy.
 

It's both design decisions and management, with the latter probably being the main cause. But also; pushing the state of the art in any space telescope's design will always be expensive. There's no getting around that. Webb is rather a specialized and not 'generic' space telescope. History will record if JWST was too ambitious or not.

It was too ambitious, that should be obvious by now. If the true costs would have been known, I cannot imagine the project would have been approved in that form.
Title: Re: SpaceX advances drive for Mars rocket via Raptor power
Post by: baldusi on 03/16/2014 09:36 pm
btw, I don't want to distract the thread, but the JWST specifications were all beyond the state of the art. The multi segment main mirror was driven by the active optics. The folding mechanism is simple and has little or no impact overall. Look at the operating temperature, the transfer function, the noise and sensitivity specs. The shade. Those were the issues. An open shade wouldn't have fit in a 14m fairing, either. So the 5.4m fairing only meant two hinges. The rest of the mechanisms on the mirrors are required for active optics and the required specifications. So no, it wouldn't have been cheaper.
May be an 8.4m monolithic main could have gotten some of the specs without being diffraction limited optics. But that's a whole different level of expensive, also.
So, the kind of rocket that SpaceX plans for Raptor does enable some payloads, but I don't think astronomy will be the main beneficiary. Planetary and Exploration probably will. And Heliophysics might.
Title: Re: SpaceX advances drive for Mars rocket via Raptor power
Post by: manboy on 03/16/2014 11:50 pm
btw, I don't want to distract the thread, but the JWST specifications were all beyond the state of the art. The multi segment main mirror was driven by the active optics. The folding mechanism is simple and has little or no impact overall. Look at the operating temperature, the transfer function, the noise and sensitivity specs. The shade. Those were the issues. An open shade wouldn't have fit in a 14m fairing, either. So the 5.4m fairing only meant two hinges. The rest of the mechanisms on the mirrors are required for active optics and the required specifications. So no, it wouldn't have been cheaper.
May be an 8.4m monolithic main could have gotten some of the specs without being diffraction limited optics. But that's a whole different level of expensive, also.
So, the kind of rocket that SpaceX plans for Raptor does enable some payloads, but I don't think astronomy will be the main beneficiary. Planetary and Exploration probably will. And Heliophysics might.
There probably won't be any money for a JWST successor for at least a few decades. Having said that, a larger fairing diameter would still allow for larger telescopes that would otherwise be impossible. For example the ATLAST concepts require fairings that are between 6.5 m to 10 m in diameter.

There are some other interesting telescope designs out that could be revolutionary (like OCCAM) but at the moment we can't really know how practical they will be.
Title: Re: SpaceX advances drive for Mars rocket via Raptor power
Post by: LouScheffer on 03/17/2014 12:09 am

May be an 8.4m monolithic main could have gotten some of the specs without being diffraction limited optics. But that's a whole different level of expensive, also.

A whole different level is right.  It's orders of magnitude *cheaper*  .  The Giant Magellan Telescope is buying 8 of these mirrors for $120 million. ( http://mirrorlab.as.arizona.edu/about/news/3 ) So it's 67 percent bigger, better optical quality (diffraction limited in the visible) and roughly 100 times cheaper.  But it does not fold and it's rather heavy (20t).

This is exactly the kind of tradeoff that large rockets enable.
Title: Re: SpaceX advances drive for Mars rocket via Raptor power
Post by: ArbitraryConstant on 03/17/2014 12:54 am
Many upper stages probably could do SSTO if T/W wasn't a problem and they had vacuum Isp.
I bet Centaur would beat Falcon 9 US in that contest. :)

Fewer stages and lower ISP hurts Falcon 9 disproportionately compared to others. That's not to say it's not economical as it clearly is so far, but full reusability makes it worse. Depending on the impact it may not be able to handle Dragon.

It may require the Raptor BFR to provide meaningful payloads with full reusability, especially to GTO.
Title: Re: SpaceX advances drive for Mars rocket via Raptor power
Post by: Robotbeat on 03/17/2014 12:59 am
Probably true, since Centaur has excellent mass ratio for a hydrolox stage. But kerolox is very dense, which counts for a lot if you're looking at reducing dry mass... And it's the /dry mass/ that you have to reenter in Earth's atmosphere, so that's the relevant metric, here.
Title: Re: SpaceX advances drive for Mars rocket via Raptor power
Post by: baldusi on 03/17/2014 03:27 am

May be an 8.4m monolithic main could have gotten some of the specs without being diffraction limited optics. But that's a whole different level of expensive, also.

A whole different level is right.  It's orders of magnitude *cheaper*  .  The Giant Magellan Telescope is buying 8 of these mirrors for $120 million. ( http://mirrorlab.as.arizona.edu/about/news/3 ) So it's 67 percent bigger, better optical quality (diffraction limited in the visible) and roughly 100 times cheaper.  But it does not fold and it's rather heavy (20t).

This is exactly the kind of tradeoff that large rockets enable.
I said I didn't wanted to distract the thread. But you are comparing apples to oranges. You are comparing a visible Earth based mirror to an FIR/MIR space based telescope. And you didn't even got into the optical charcteristics.
Repeat after me: mirror is 10% of mission at most. Instruments and overall complexity drive a space telescope cost.
So, to get back on thread, The BFR is interesting because it's and integrated system: LV + payload. Now we only
Title: Re: SpaceX advances drive for Mars rocket via Raptor power
Post by: cuddihy on 03/17/2014 11:51 am
I assume this is the correct thread for raptor development speculation. Thought I would lay out what I think a realistic development schedule for Raptor. I'm only focusing on test stand items. And these are total speculation based on much faster work than was done for IPD. But that was H2...

June-July 2014: methane preburner, O2 preburner development test items fired

Sep-Oct 2014: methane preburner/TPA initial assembly test fired

Dec 2014-June 2015: O2 preburner/TPA assembly test firings and development (it's hard)

Sep 2015: initial test Raptor (non flight weight) assembly and testing

Oct-Dec 2015: test Raptor firing& testing

Mar 2016: first flight weight Raptor assembled & tests

June-Sep 2016: first 3 production Raptors (Raptor 1A) tested & refined at McGregor.

Oct 2016: Raptor 1As available at low rate for attachment to a stage for integrated testing.



Title: Re: SpaceX advances drive for Mars rocket via Raptor power
Post by: john smith 19 on 03/17/2014 12:05 pm
Many upper stages probably could do SSTO if T/W wasn't a problem and they had vacuum Isp.
Well the Atlas could probably have done SSTO on the sustainer (and probably if they'd launched an Atlas III without an upper stage once they got the Russian engine on).

Historically LO2/LH2 stages have quite poor mass fractions. Look at the Saturn V 1st stage, the S1b or c. Despite not being a common bulkhead design and having the 100 tonnes Apollo payload sitting on top it's mass fraction was phenomenal and Boeing did not seem to have too many problems constructing it (they seemed to have very good stress engineers).

Musk is saying the FH booster stages will have a mass fraction of 30. That's about 3% hardware. That's close to SSTO and with Raptor might well achieve SSTO.

Note that Spacex have always been pragmatic about phasing out anything that does not help them achieve their goals. IOW they don't mind offering a range of products provided it does not complicate their inventory. So the question becomes would a single stage F9, with Raptors or Merlins offer an interesting enough package for a low cost primary payload?

Or do the economies of scale simply make it cheaper just to buy a full F9 or FH and ride mostly empty?
Title: Re: SpaceX advances drive for Mars rocket via Raptor power
Post by: GregA on 03/17/2014 12:28 pm
When I first read about the falcon and falcon 9, I then looked up falcon heavy.

Whatever I read included a picture of the standard 9 engines per core, and then had a parallel version with 1 engine per core (merlin 2s?)

Am I misremembering? That would fit the raptor engines right? If so it would seem that handling single engine failures and lower thrust reusability might have squashed that plan.
Title: Re: SpaceX advances drive for Mars rocket via Raptor power
Post by: Robotbeat on 03/17/2014 01:41 pm
Many upper stages probably could do SSTO if T/W wasn't a problem and they had vacuum Isp.
Well the Atlas could probably have done SSTO on the sustainer (and probably if they'd launched an Atlas III without an upper stage once they got the Russian engine on).

Historically LO2/LH2 stages have quite poor mass fractions. Look at the Saturn V 1st stage, the S1b or c. Despite not being a common bulkhead design and having the 100 tonnes Apollo payload sitting on top it's mass fraction was phenomenal and Boeing did not seem to have too many problems constructing it (they seemed to have very good stress engineers).

Musk is saying the FH booster stages will have a mass fraction of 30. That's about 3% hardware. That's close to SSTO and with Raptor might well achieve SSTO.

Note that Spacex have always been pragmatic about phasing out anything that does not help them achieve their goals. IOW they don't mind offering a range of products provided it does not complicate their inventory. So the question becomes would a single stage F9, with Raptors or Merlins offer an interesting enough package for a low cost primary payload?

Or do the economies of scale simply make it cheaper just to buy a full F9 or FH and ride mostly empty?
Oh, I'm confident SpaceX won't be actually /launching/ a SSTO rocket, just saying that the stage could probably produce 9km/s without a payload. I mean, 3km/s*ln(30) is 10.2km/s. For the upper stage with an Isp of 340s, it'd need a mass ratio of just 15 to get to 9km/s. That's all I was saying.
Title: Re: SpaceX advances drive for Mars rocket via Raptor power
Post by: Lars_J on 03/17/2014 03:10 pm
When I first read about the falcon and falcon 9, I then looked up falcon heavy.

Whatever I read included a picture of the standard 9 engines per core, and then had a parallel version with 1 engine per core (merlin 2s?)

Am I misremembering? That would fit the raptor engines right? If so it would seem that handling single engine failures and lower thrust reusability might have squashed that plan.

That was just an employee speculating about a F9 version powered by a single engine per core. Not official. It predated the V1.1 work.
Title: Re: SpaceX advances drive for Mars rocket via Raptor power
Post by: Lobo on 03/17/2014 05:43 pm

That's not clear at all. In fact, if you've mastered reusability it seems like a step backwards.

Unless it's a reusable HLV....

That's just excluding commercial payloads which have no need for such capacity, for no benefit. It makes no sense to build an RLV bigger than the market demand. You're just leaving money on the table that way.

.. and yeah, I just said this..

Did you not see my post above and Robotbeat's post?

The idea is it can launch the upper end of the current market demand payloads to higher orbits with full reusability, which FH will not be able to do, much less F9R.  SpaceX will have to remain with only partial reusability for all but the smaller sized payloads.

A larger LV with more margin could then get those larger birds to high orbits, and have the fuel to get the upper stage back to Earth and land. 
Now, something in this FXX size might be larger than necessary.  Something more FX size might be a better size for that if that was the only requirement.  But if SpaceX thinks they needs something FXX sized to get to Mars, then why do FX and then later FXX?  Why not go right to FXX and just have one new development?
You are still only charging for fuel and processing time per launch. And you'll be doing that regardless of the size of the LV.

Title: Re: SpaceX advances drive for Mars rocket via Raptor power
Post by: BrightLight on 03/17/2014 05:48 pm

That's not clear at all. In fact, if you've mastered reusability it seems like a step backwards.

Unless it's a reusable HLV....

That's just excluding commercial payloads which have no need for such capacity, for no benefit. It makes no sense to build an RLV bigger than the market demand. You're just leaving money on the table that way.

.. and yeah, I just said this..

Did you not see my post above and Robotbeat's post?

The idea is it can launch the upper end of the current market demand payloads to higher orbits with full reusability, which FH will not be able to do, much less F9R.  SpaceX will have to remain with only partial reusability for all but the smaller sized payloads.

A larger LV with more margin could then get those larger birds to high orbits, and have the fuel to get the upper stage back to Earth and land. 
Now, something in this FXX size might be larger than necessary.  Something more FX size might be a better size for that if that was the only requirement.  But if SpaceX thinks they needs something FXX sized to get to Mars, then why do FX and then later FXX?  Why not go right to FXX and just have one new development?
You are still only charging for fuel and processing time per launch. And you'll be doing that regardless of the size of the LV.
IMHO - the FX with the Raptor gives SpaceX very good market penetration for GEO payloads with potential for reusablity, Mars or not this is good business practice.
Title: Re: SpaceX advances drive for Mars rocket via Raptor power
Post by: Lobo on 03/17/2014 06:00 pm
Here's a question.

RD-180 and NK-33 are both used in American launchers, but there's some question to supply or domestic manufacturing of both.

Raptor is significantly better in ISP and slightly better (assuming 1mlbf is vac) in thrust than RD-180. The fuel isn't the same but it's not hard to get and it's less cryogenic than LOX.

Might there be any non-SpaceX adoption of the engine other American launchers?

I think unlikely for a few reasons.

SpaceX is a bit unique in that they make engines, as well as rockets/launch services.  Neither ULA nor OSC do that.  Offering Raptor as cheaper, domestic replacement for RD-180 or AJ26 would make it easier for ULA and OSC to compete against them in the launch market.  Seems counter productive.

Not to metion I think there'd be a considerable amount of modification to Atlas V and Antares o switch from kerolox to methalox, as well as amount a new engine that will be very different than the engines they are replacing.  As well as new infrastructure at the pads.  That would have to be traded against the economics of Raptor even if SpaceX made it available too them affordably. 

I think more likely would be AJ-1E6 or a domestic version of RD-180.  Both are AJR products now.  And I think the conversion would be much cheaper and easier.  Especially if AJR is building AJ-1E6 or RD-180US specifically for use on Atlas and/or Antares.  They'll build it to make it fit into the customer's launchers as easy as possible.
Raptor will be designed to go into FXX only.  And could be difficult to adapt into anything else.

Title: Re: SpaceX advances drive for Mars rocket via Raptor power
Post by: Lobo on 03/17/2014 06:10 pm
F9R will not be able to serve the GTO market with a reusable upper stage.
I'm curious about the LEO hit.

For GTO the reusable upper stage will clearly have enormous demands placed on it. With lower staging and having to go all the way to GTO, or I guess a supersynchronous orbit... that delta-v starts looking like SSTO territory. It's tremendous for a GG hydrocarbon engine.

I'm hoping though I'm not totally confident that they'll be able to launch Dragon to LEO. Orbcomm and similar payloads could clearly still be accommodated. Even launching an orbital Grasshopper with no payload would still make my day.

Either way just with the payload hit, the Raptor-9 BFR starts to seem reasonable just for reuse margin. :)

Bingo.

That's been my pet theory for awhile now on how SpaceX will make a "market" and "business case" for a HLV when there isn't one otherwise.  They could just bankroll it themselves just to have it for their later Mars plans, but...they are pretty clever, and I think see a potential for using it for current sized payloads, and perhaps paylaods a little larger than current which could get funding if there's a affordable LV to launch them vs. evolving a current EELV class launch just to give it an adequate launcher...which adds a lot of cost to the cost of development the payload itself.  The fully expendable FH will probably start kicking a few of those loose if they are out there waiting in the wings.  So we may see more of them come to market if there's a $150M launcher than has the capacity to launch them.  And those would be target market for a fully expendable FXX.  As well as dual launch missions.



Title: Re: SpaceX advances drive for Mars rocket via Raptor power
Post by: Lobo on 03/17/2014 06:23 pm
btw, I don't want to distract the thread, but the JWST specifications were all beyond the state of the art. The multi segment main mirror was driven by the active optics. The folding mechanism is simple and has little or no impact overall. Look at the operating temperature, the transfer function, the noise and sensitivity specs. The shade. Those were the issues. An open shade wouldn't have fit in a 14m fairing, either. So the 5.4m fairing only meant two hinges. The rest of the mechanisms on the mirrors are required for active optics and the required specifications. So no, it wouldn't have been cheaper.
May be an 8.4m monolithic main could have gotten some of the specs without being diffraction limited optics. But that's a whole different level of expensive, also.
So, the kind of rocket that SpaceX plans for Raptor does enable some payloads, but I don't think astronomy will be the main beneficiary. Planetary and Exploration probably will. And Heliophysics might.

So here's the question, any telescope over 5.4m would have to me segmented, because there's no PLF that could launch it as a monolithic, correct?
And segmented mirrors require active optics (from what little I know of telescopes), as opposed to the folding mechanisms themselves?
Meaning, I get your point that having a folding mirror might not be much of a cost factory, but is the segmented mirror itself the reason for the costs?  And if there had been an LV capabile of launching a monolithic of the same size (6.5m), then could the issues with both the segmented mirror with the active optics, as well as the folding mechanisms all have been avoided?

Per this wikipedia article, a mirror in excess of 8m is not possible without active optics.  But JWST is only 6.5m.  Could JWST have a 6.5m monolithic, and eleminate the segmented mirror, active optics, and folding mechanisms all together?

http://en.wikipedia.org/wiki/Active_optics

If so, then having a larger LV with wider PLF would have made for a much less state of the art and much less expensive telecope by default, folding mechanisms aside.

Or am I misunderstanding that?

Title: Re: SpaceX advances drive for Mars rocket via Raptor power
Post by: Lobo on 03/17/2014 06:33 pm

That's not clear at all. In fact, if you've mastered reusability it seems like a step backwards.

Unless it's a reusable HLV....

That's just excluding commercial payloads which have no need for such capacity, for no benefit. It makes no sense to build an RLV bigger than the market demand. You're just leaving money on the table that way.

.. and yeah, I just said this..

Did you not see my post above and Robotbeat's post?

The idea is it can launch the upper end of the current market demand payloads to higher orbits with full reusability, which FH will not be able to do, much less F9R.  SpaceX will have to remain with only partial reusability for all but the smaller sized payloads.

A larger LV with more margin could then get those larger birds to high orbits, and have the fuel to get the upper stage back to Earth and land. 
Now, something in this FXX size might be larger than necessary.  Something more FX size might be a better size for that if that was the only requirement.  But if SpaceX thinks they needs something FXX sized to get to Mars, then why do FX and then later FXX?  Why not go right to FXX and just have one new development?
You are still only charging for fuel and processing time per launch. And you'll be doing that regardless of the size of the LV.
IMHO - the FX with the Raptor gives SpaceX very good market penetration for GEO payloads with potential for reusablity, Mars or not this is good business practice.

Yup.  But I mean that SpaceX's Mars plans may play a factor in the size of their Raptor powered FXX.
If not for that, a smaller "FX" sized reusable LV could probably get any current or realistic future payload to GTO and get back with full reusability.  Something more in the 70-80mt to LEO range.  That would be more the size RLV QuantumG is perhaps talking about.
But they feel that's not large enough for their Mars plans, so rather tha move incrementally to the LV they ultimately want, they'll jump right to it.  And make the extra investment over an FX sized RLV for it.  Once flying it should be similar in cost to an FX sized RLV. 
FXXR will probably be oversized for even the largest NRO birds in the pipe or on the drawing board to go to GTO.   But....it's what they want for Mars, so they'll just just jump right to it.  And it'll fly with margin to spare for it's commercial and government payloads.  Maybe they'll use some propellant offload to tailor it for the specific mission.
Title: Re: SpaceX advances drive for Mars rocket via Raptor power
Post by: dorkmo on 03/17/2014 09:19 pm
Here's a question.

RD-180 and NK-33 are both used in American launchers, but there's some question to supply or domestic manufacturing of both.

...

Might there be any non-SpaceX adoption of the engine other American launchers?

I think unlikely for a few reasons.

SpaceX is a bit unique in that they make engines, as well as rockets/launch services.  Neither ULA nor OSC do that.  Offering Raptor as cheaper, domestic replacement for RD-180 or AJ26 would make it easier for ULA and OSC to compete against them in the launch market.  Seems counter productive.

...

Raptor will be designed to go into FXX only.  And could be difficult to adapt into anything else.

i'd note that telsa supplies battery packs to some other car makers.

though, other car makers own part of telsa, and as far as i know no other rocket makers own part of spacex.
Title: Re: SpaceX advances drive for Mars rocket via Raptor power
Post by: Joel on 03/17/2014 09:51 pm
Question: Is it feasible to design a large engine like the Raptor with redundancy in mind and achieve the same safety as you would get from a cluster of engines with engine-out capability? For example, have multiple smaller pre-burners instead of just one for O2 and one for CH4? And the same for other critical components.
Title: Re: SpaceX advances drive for Mars rocket via Raptor power
Post by: simonbp on 03/17/2014 09:57 pm
I seriously doubt JWST has active optics in the same way that ground telescopes have them. After unfolded, the mirrors positions (and possibly shape) are corrected through a series of calibrations and then they stay in the same place until some thermal change occurs (maybe every few days).
Active optics are 1Hz actuation of each segment, which makes no sense in JWST because it has no atmospheric turbulence/wind/gravity change (due to tilt) to counteract.

I would call them calibration optics more than active optics, although the mechanical principle is very similar.

It depends on the size and width of the mirror, but modern active optics are mainly used to keep a very large & thin mirror from slumping and deforming when it is tilted. For example, the Discovery Channel Telescope at Lowell Observatory has 4.3 m primary mirror that is only a few cm thick. Without the active optics, it would deform horribly if you pointed anywhere but zenith. But with the active optics, it stays in focus even looking down on the horizon. It's a great system, but does nothing to cancel out the atmosphere.

Now, adaptive optics are whole different can of fish that generally involves the fast actuation of the secondary or tertiary mirror in order to cancel out the atmosphere. It is very rare for adaptive optics to be used on the primary mirror, as it is much cheaper to do with a small deformable mirror.

JWST does have an active optics system (called the Active Optical System) which has three 2 Degree-of-Freedom actuators per segment, giving each segment 6 degrees of freedom for focusing the optics. While JWST doesn't have to worry about wind or strong gravity, it does have to deal with differential thermal expansion of the structure, and needs to refocus accordingly.
Title: Re: SpaceX advances drive for Mars rocket via Raptor power
Post by: Lobo on 03/17/2014 10:10 pm
So the question is, if JWST were a 6.5m monolithic, not being acted on by the Earth gravity and not being segmented, then be significantly cheaper than the current design?

Even a $500M launcher would be a bargin if the design of the telescope could then be such that a few billion were shaved off of it.
Title: Re: SpaceX advances drive for Mars rocket via Raptor power
Post by: Robotbeat on 03/17/2014 10:27 pm
So the question is, if JWST were a 6.5m monolithic, not being acted on by the Earth gravity and not being segmented, then be significantly cheaper than the current design?

Even a $500M launcher would be a bargin if the design of the telescope could then be such that a few billion were shaved off of it.
As you are well aware (but for some reason did not mention), you can order a 7.2+m diameter fairing for Atlas V from ULA if you wish.
Title: Re: SpaceX advances drive for Mars rocket via Raptor power
Post by: AncientU on 03/18/2014 12:19 am
So the question is, if JWST were a 6.5m monolithic, not being acted on by the Earth gravity and not being segmented, then be significantly cheaper than the current design?

Even a $500M launcher would be a bargin if the design of the telescope could then be such that a few billion were shaved off of it.
One of the original competitors (Lockheed-Martin IIRC) for NGST (which eventually became JWST) was a 6.5m monolithic telescope -- but the 8m segmented design was selected, and then descoped to 6.5m after 8m became too great a challenge (not sure if technical and/or cost was primary driver of descope).  At that time, early 2000s, the feasibility of a 7.2m fairing was included in the proposal.
Title: Re: SpaceX advances drive for Mars rocket via Raptor power
Post by: baldusi on 03/18/2014 01:21 am

So the question is, if JWST were a 6.5m monolithic, not being acted on by the Earth gravity and not being segmented, then be significantly cheaper than the current design?

Even a $500M launcher would be a bargin if the design of the telescope could then be such that a few billion were shaved off of it.
Active optics is a requirement that includes the wavefront sensor to keep the required precision and accutance. A monolithic mirror would actually need a bigger adaptive optic. Would simplify some, complicate another. When you have specifications like the JWST nothing is significantly cheap than the other. Did mismanagement played a role? Sure. But the ballooning budget was because it was a couple or orders of magnitude of the state of the art. And they did that for something like ten different critical technologies.
But that's besides the point. The BFR won't have big telescopes as a significant cargo. Please disregard this line of questioning.
Title: Re: SpaceX advances drive for Mars rocket via Raptor power
Post by: go4mars on 03/18/2014 01:37 am
I'm confident SpaceX won't be actually /launching/ a SSTO rocket, just saying that the stage could probably produce 9km/s without a payload. I mean, 3km/s*ln(30) is 10.2km/s.
I'm not so confident.  If I had an extra stage laying around, with a choice of scrap versus more data plus added notoriety, I'd gas the sucker up and blaze it to orbit.  Maybe with a cubesat.  Just because it's awesome.
Title: Re: SpaceX advances drive for Mars rocket via Raptor power
Post by: Carl G on 03/18/2014 02:07 am
This is NOT about JWST. This is about an engine.
Title: Re: SpaceX advances drive for Mars rocket via Raptor power
Post by: dorkmo on 03/18/2014 02:26 am
if launch prices come down with large spacex rocket, would there be any advantage to putting a large space telescope into mars or other planet orbit or elsewhere?
Title: Re: SpaceX advances drive for Mars rocket via Raptor power
Post by: baldusi on 03/18/2014 02:41 am

if launch prices come down with large spacex rocket, would there be any advantage to putting a large space telescope into mars or other planet orbit or elsewhere?
Nope, unless the NRO has an interest in said planet :-p
Again, first gas-gas for actual deployment. Biggest staged combustion ever in America. First methane powered orbital rocket. Probably first rocket to debut with reusable first stage. Potentially first system to put a men on Mars. And all you can think of is what's the biggest telescope you can fit in? You are better than this.
Title: Re: SpaceX advances drive for Mars rocket via Raptor power
Post by: baldusi on 03/18/2014 03:05 am

Question: Is it feasible to design a large engine like the Raptor with redundancy in mind and achieve the same safety as you would get from a cluster of engines with engine-out capability? For example, have multiple smaller pre-burners instead of just one for O2 and one for CH4? And the same for other critical components.
AIUI, the short answer is no. The most critical elements are the TP. Those failures are totally catastrophic. Are you going to add multiple TP? If you keep adding elements, at say, N+1, then you'd need to have redundant pipings and lots of valves to cut fluid flow before and after each element, and even to reroute in manifold. Which add points of failure and weight. Failure probability is sort of a given by element, bigger doesn't make much different. But it does increases fraticide chance. And adds complexity to handle failures. Remember that TP power balance is quite delicate. A failed preburner might not seem like such a problem, but if it's a fuel one, can your system react fast enough to avoid an oxidizer rich combustion on the MCC?
Simplicity rules in safety. Design an engine as simple as you can and test it like mad. If you want engine out, add multiple and keep them physically separated. That's the best I can think of.
Title: Re: SpaceX advances drive for Mars rocket via Raptor power
Post by: Wigles on 03/18/2014 10:16 am
Question: Is it feasible to design a large engine like the Raptor with redundancy in mind and achieve the same safety as you would get from a cluster of engines with engine-out capability? For example, have multiple smaller pre-burners instead of just one for O2 and one for CH4? And the same for other critical components.

Yes, but the development cost is likely to be prohibitive. We have done this in Aerospace in the transition from four engine for long haul overwater to enabling larger twin engine jets to do the same routes through stricter design and maintenance regimes (ETOPS and the like) which provide an end state reliability on-par with the older four engine designs.

Typically failure modes for a catastrophic consequence must have a probability less than 1x10^(-9) (I will call it E-9) or E-8 for military applications (not sure what the space standard is). In a 9 engine rocket which is designed to have enough propellant and thrust to allow engine out operations, a catastrophic condition only occurs would occur when any two engines fail. Therefore each engine can have a failure likelihood of E-5 and the likelihood of a dual engine failure is <E-9.

You could overcome this by designing, testing, and certifying the engines to have a failure likelihood of E-9 but that requires a significant increase in testing, design rigour, quality control, etc.... for each engine. 

(Yes there are large assumptions in the above, and yes I am aware that this is only a very simple systems safety analysis but it is only to explain a point.)
Title: Re: SpaceX advances drive for Mars rocket via Raptor power
Post by: Robotbeat on 03/18/2014 02:41 pm

if launch prices come down with large spacex rocket, would there be any advantage to putting a large space telescope into mars or other planet orbit or elsewhere?
Nope, unless the NRO has an interest in said planet :-p
Again, first gas-gas for actual deployment. Biggest staged combustion ever in America. First methane powered orbital rocket. Probably first rocket to debut with reusable first stage. Potentially first system to put a men on Mars. And all you can think of is what's the biggest telescope you can fit in? You are better than this.
Well, I'm sure that someday we'll have a better successor to MRO.
Title: Re: SpaceX advances drive for Mars rocket via Raptor power
Post by: Lar on 03/18/2014 06:38 pm
This is a thread about telescopes engines... Stick to telescopes engines please.

Trimmed again.
Title: Re: SpaceX advances drive for Mars rocket via Raptor power
Post by: Llian Rhydderch on 03/19/2014 03:12 am
I have a question for the more more chemistry and chemical-engineering oriented folks who are watching this thread.

The Wikipedia article on Methane (https://en.wikipedia.org/wiki/Methane#Combustion) asserts that there are a wide variety of intermediate chemicals produced in Methane/Oxygen combustion, in a complicated 19-step chemical reaction process, before resolving to the ordinary CO2 and H2O combustion products with which we are all familiar. 

Some of the intermediate products appear corrosive, or at least quite different from the alkane CH4 and 02, CO2, H2O that I had thought about in the witch's brew of hot and high pressure gasses in the rather more simple model in my head.

Quote

Methane's heat of combustion is 55.5 MJ/kg.[1] Combustion of methane is multiple step reaction. The following equations are part of the process, with the net result being:

CH4 + 2 O2 → CO2 + 2 H2O    (ΔH = −891 k J/mol (at standard conditions))

  1.  CH4+ M* → CH3 + H + M
  2.  CH4 + O2 → CH3 + HO2
  3.  CH4 + HO2 → CH3 + 2 OH
  4.  CH4 + OH → CH3 + H2O
  5.  O2 + H → O + OH
  6.  CH4 + O → CH3 + OH
  7.  CH3 + O2 → CH2O + OH
  8.  CH2O + O → CHO + OH
  9.  CH2O + OH → CHO + H2O
  10.  CH2O + H → CHO + H2
  11.  CHO + O → CO + OH
  12.  CHO + OH → CO + H2O
  13.  CHO + H → CO + H2
  14.  H2 + O → H + OH
  15.  H2 + OH → H + H2O
  16.  CO + OH → CO2 + H
  17.  H + OH + M → H2O + M*
  18.  H + H + M → H2 + M*
  19.  H + O2 + M → HO2 + M*

The species M* signifies an energetic third body, from which energy is transferred during a molecular collision. Formaldehyde (HCHO or H2CO) is an early intermediate (reaction 7). Oxidation of formaldehyde gives the formyl radical (HCO) (reactions 8, 9 & 10), which then give carbon monoxide (CO) (reactions 11, 12 & 13). Any resulting H2 oxidizes to H2O or other intermediates (reaction 14 & 15). Finally, the CO oxidizes, forming CO
2 (reaction 16). In the final stages (reactions 17, 18 & 19), energy is transferred back to other third bodies. The overall speed of reaction is a function of the concentration of the various entities during the combustion process. The higher the temperature, the greater the concentration of radical species and the more rapid the combustion process.[2]

Does any of this make Raptor Methane/Oxygen engines particularly more challenging from a design, reliability and long life point of view?  I mean in particular with respect to LOX/Kerosene or LOX/LH2 engines for orbital launch vehicles.
Title: Re: SpaceX advances drive for Mars rocket via Raptor power
Post by: 93143 on 03/19/2014 03:35 am
Not really.  All combustion reactions are like that.  The more complicated the fuel, the more intermediate reactions there are, but even hydrogen combustion has several intermediate radicals involved.

In fact, those 19 steps you list seem to be a reduced model.  The GRI-Mech 3.0 methane-air combustion model reportedly has 325 reactions involving 53 species, and kerosene would be much, much worse.  Of course, with oxygen instead of air, things should be much simpler, but a detailed model of hydrogen-oxygen combustion (the simplest possible kind) still has around 19 reactions...
Title: Re: SpaceX advances drive for Mars rocket via Raptor power
Post by: john smith 19 on 03/19/2014 08:33 am
The Wikipedia article on Methane (https://en.wikipedia.org/wiki/Methane#Combustion) asserts that there are a wide variety of intermediate chemicals produced in Methane/Oxygen combustion, in a complicated 19-step chemical reaction process, before resolving to the ordinary CO2 and H2O combustion products with which we are all familiar. 
It's time to reveal the awful truth. :o  All chemical reaction mechanisms are much more complicated that the overall equations shown in text books. However the techniques to directly see them have only existed for perhaps the last 100-150 years if that.
Quote
Some of the intermediate products appear corrosive, or at least quite different from the alkane CH4 and 02, CO2, H2O that I had thought about in the witch's brew of hot and high pressure gasses in the rather more simple model in my head.
What the list does not show is a)The concentration of those reactants and b)Their lifetime before being consumed.

Yes some of them look nasty but the example I like to give is cigarette smoke. Among its (many) constituents is the CN radical. People breath in Cyanide on a regular basis. However no one instantly drops dead because the concentration is very low (but detectable with a GCMS).
Quote
Does any of this make Raptor Methane/Oxygen engines particularly more challenging from a design, reliability and long life point of view?  I mean in particular with respect to LOX/Kerosene or LOX/LH2 engines for orbital launch vehicles.
No. O2/H2 is the simplest combustion system I'm aware of so every system is more complex relative to it. Relative to RP1/LO2 it should be simpler.
Title: Re: SpaceX advances drive for Mars rocket via Raptor power
Post by: Ben the Space Brit on 03/19/2014 08:52 am
No. O2/H2 is the simplest combustion system I'm aware of so every system is more complex relative to it. Relative to RP1/LO2 it should be simpler.

I guess it depends how you look at it. Yes, in chemical terms, it's the simplest. In engineering terms, dealing with extreme cryogens creates difficulties that offset hydrolox's simplicity and high performance through all flight modes.
Title: Re: SpaceX advances drive for Mars rocket via Raptor power
Post by: R7 on 03/19/2014 12:15 pm
The Wikipedia article on Methane (https://en.wikipedia.org/wiki/Methane#Combustion) asserts that there are a wide variety of intermediate chemicals produced in Methane/Oxygen combustion, in a complicated 19-step chemical reaction process, before resolving to the ordinary CO2 and H2O combustion products with which we are all familiar. 
It's time to reveal the awful truth. :o  All chemical reaction mechanisms are much more complicated that the overall equations shown in text books. However the techniques to directly see them have only existed for perhaps the last 100-150 years if that.
And then the more soothing truth; rocket engines work just fine despite that.  :) In practice what you tune according to the reaction rate (the more complex the chain the longer it takes to reach final products) is the characteristic chamber length L* (combustion chamber volume divided by throat area). Smaller values for hydrogen, bigger for methane.

Here's an example what RPA (http://propulsion-analysis.com/) thinks exists in the combustion gases inside notional metholox engine (10MPa, arearatio 50). Especially in the exit plane almost entirely the expected textbook species.

# Table 2. Fractions of the combustion products
#---------------------------------------------------------------------------------------------------
# Species      Injector      Injector    Nozzle inl    Nozzle inl    Nozzle thr    Nozzle thr    Nozzle exi    Nozzle exi   
#              mass fract    mole fract  mass fract    mole fract    mass fract    mole fract    mass fract    mole fract   
#---------------------------------------------------------------------------------------------------
       CO     0.2149265     0.1691100     0.2146228     0.1689158     0.2035506     0.1622033     0.1149927     0.0987688   
      CO2     0.2718559     0.1361402     0.2723361     0.1364168     0.2897638     0.1469601     0.4289486     0.2344894   
     COOH     0.0000392     0.0000192     0.0000377     0.0000184     0.0000225     0.0000112     0.0000000     0.0000000   
        H     0.0009219     0.0201571     0.0009212     0.0201477     0.0007912     0.0175208     0.0000107     0.0002554   
       H2     0.0066321     0.0725076     0.0066260     0.0724592     0.0062195     0.0688639     0.0054207     0.0646929   
      H2O     0.4023463     0.4922129     0.4025455     0.4925871     0.4115408     0.5098868     0.4504900     0.6016010   
     H2O2     0.0000474     0.0000307     0.0000458     0.0000297     0.0000281     0.0000184     0.0000000     0.0000000   
     H2CO     0.0000007     0.0000005     0.0000007     0.0000005     0.0000004     0.0000003     0.0000000     0.0000000   
      HCO     0.0000203     0.0000154     0.0000195     0.0000148     0.0000108     0.0000083     0.0000000     0.0000000   
    HCOOH     0.0000068     0.0000032     0.0000065     0.0000031     0.0000037     0.0000018     0.0000000     0.0000000   
      HO2     0.0002499     0.0001668     0.0002435     0.0001626     0.0001563     0.0001057     0.0000000     0.0000000   
        O     0.0077394     0.0106609     0.0077101     0.0106235     0.0061076     0.0085205     0.0000003     0.0000005   
       O2     0.0402029     0.0276897     0.0401281     0.0276455     0.0349045     0.0243472     0.0000027     0.0000021   
       O3     0.0000005     0.0000002     0.0000004     0.0000002     0.0000000     0.0000000     0.0000000     0.0000000   
       OH     0.0550103     0.0712855     0.0547561     0.0709750     0.0469000     0.0615515     0.0001342     0.0001898   


Title: Re: SpaceX advances drive for Mars rocket via Raptor power
Post by: Llian Rhydderch on 03/19/2014 02:33 pm
Not really.  All combustion reactions are like that.  The more complicated the fuel, the more intermediate reactions there are, but even hydrogen combustion has several intermediate radicals involved.

In fact, those 19 steps you list seem to be a reduced model.  The GRI-Mech 3.0 methane-air combustion model reportedly has 325 reactions involving 53 species, and kerosene would be much, much worse.  Of course, with oxygen instead of air, things should be much simpler, but a detailed model of hydrogen-oxygen combustion (the simplest possible kind) still has around 19 reactions...

Thanks VERY MUCH, 99143.

That was the sort of chemical reaction knowledge that I was hoping, and pretty sure, was lurking around on NSF.

Kudos to you, for enlightening me, and others who will read this.
Title: Re: SpaceX advances drive for Mars rocket via Raptor power
Post by: sugmullun on 03/31/2014 02:14 am
What would be the probable injector type of the Raptor engine?
Is there a reason that a pintle type injector couldn't work?
Are there alternatives to the plate type (SSME) and pintle (Merlin)?
Title: Re: SpaceX advances drive for Mars rocket via Raptor power
Post by: MP99 on 03/31/2014 06:09 pm
What would be the probable injector type of the Raptor engine?
Is there a reason that a pintle type injector couldn't work?
Are there alternatives to the plate type (SSME) and pintle (Merlin)?

We had a good response re this question back in Reply #173:-
http://forum.nasaspaceflight.com/index.php?topic=34197.msg1171013#msg1171013 (http://forum.nasaspaceflight.com/index.php?topic=34197.msg1171013#msg1171013)

cheers, Martin
Title: Re: SpaceX advances drive for Mars rocket via Raptor power
Post by: jimvela on 03/31/2014 10:20 pm
There's a deleted reply that asked some questions about animals and methane.

Since the reply is gone, I'll just say this as a new post:

Where biology goes, methane goes.
This is a fact, and any plans for using methane as a propellant would be wise to consider biological sources for methane and appropriate processing means to obtain sufficient methane for launches outbound from Mars.

I've often joked that I'd be a good candidate to go to Mars as if you just give me plenty of beans, I'd make a significant amount of my own propellant on the way out.  :-)p

In all seriousness, to be able to host humanity out exploring the solar system, we've got quite a bit of engineering work to be done on all of the systems to manage waste recycling and production of consumables (human or rocket)- and this could have a major impact on the formulation of propellant used for such a system.

Back to the discussion about methane combustion intermediate products...
Title: Re: SpaceX advances drive for Mars rocket via Raptor power
Post by: baldusi on 03/31/2014 10:30 pm
There's a lot of issues with ISRU in Mars. since it's Nitrogen poor, and water is only available mixed in some soils, it's not so easy to get a biological process going. Much less be as efficient as a mechanical one. The other issue is that fast cheap travel through Mars is not easy. There are no oceans, there's not enough atmosphere for planes and combustion engines lack a free oxidizer. So, wherever you put your ISRU plant, will have a very tough logistic problem to actually deliver you propellent. Specially with cryogenic CH4/O2. Only H2 would be worse. You might use the boil off for propellent, though.
Methane might be one of the easiest propellents for Mars. But ISRU is not easy by a large margin. In fact, that's probably the most critical aspect for a fully reusable MCT.
Title: Re: SpaceX advances drive for Mars rocket via Raptor power
Post by: clongton on 04/01/2014 12:46 am
Fast travel, point to point on the Martian surface can be done in the beginning by sub-orbital "hoppers". But this is not efficient and certainly mass limited. Economical point to point transport on Mars will need the development of a railroad system, MPS tbd, but a rail system none-the-less. Otherwise every new settlement will be an island unto itself. Mars will divide and conquer.
Title: Re: SpaceX advances drive for Mars rocket via Raptor power
Post by: dorkmo on 04/01/2014 01:11 am
Fast efficient travel, point to point on the Martian surface can be done in the beginning by sub-orbital "hoppers". But this is not efficient and certainly mass limited. Economical point to point transport on Mars will need the development of a railroad system, MPS tbd, but a rail system none-the-less. Otherwise every new settlement will be an island unto itself. Mars will divide and conquer.

are you talking about like a steel rail, rail road? whats mps mean?
Title: Re: SpaceX advances drive for Mars rocket via Raptor power
Post by: clongton on 04/01/2014 01:15 am
MPS = Main Power Source/Supply
Title: Re: SpaceX advances drive for Mars rocket via Raptor power
Post by: Vultur on 04/01/2014 01:35 am
There's a lot of issues with ISRU in Mars. since it's Nitrogen poor, and water is only available mixed in some soils, it's not so easy to get a biological process going.

Nitrogen poor compared to earth, yes, but there are still fairly significant amounts (about 2%) in the atmosphere. of course Mars atmosphere is thin, but it should still be extractable...

And if your product is methane, that doesn't contain nitrogen, so you probably won't need massive constant nitrogen input as it can be recycled.

EDIT: I think the methane for Mars ISRU thing is supposed to be based on the Sabatier reaction rather than biological processes IIRC.
Title: Re: SpaceX advances drive for Mars rocket via Raptor power
Post by: GregA on 04/01/2014 01:45 am
Economical point to point transport on Mars will need the development of a railroad system, MPS tbd, but a rail system none-the-less. Otherwise every new settlement will be an island unto itself. Mars will divide and conquer.

I would think that the power source for surface transport has to be Methane or Electric, to fit in with the other systems to be in use on Mars. I'm not sure what battery technology is amenable to mars and ISRU.

I'd like to think about rail vs auto-drive cars etc, but it's off topic. There isn't really a thread to discuss Mars settlement itself is there?
Title: Re: SpaceX advances drive for Mars rocket via Raptor power
Post by: Robotbeat on 04/01/2014 02:29 am
There's a lot of issues with ISRU in Mars. since it's Nitrogen poor, and water is only available mixed in some soils, it's not so easy to get a biological process going. Much less be as efficient as a mechanical one. The other issue is that fast cheap travel through Mars is not easy. There are no oceans, there's not enough atmosphere for planes and combustion engines lack a free oxidizer. So, wherever you put your ISRU plant, will have a very tough logistic problem to actually deliver you propellent. Specially with cryogenic CH4/O2. Only H2 would be worse. You might use the boil off for propellent, though.
Methane might be one of the easiest propellents for Mars. But ISRU is not easy by a large margin. In fact, that's probably the most critical aspect for a fully reusable MCT.
It's not nitrogen-poor (atmosphere is 2% nitrogen), unless you're talking about fixed nitrogen or the fact the atmosphere is so thin to begin with.

Also, water is extractible from the atmosphere, as Zubrin and others have shown. Also, it may be that there are aquifers on Mars.

And frankly, airplanes aren't an efficient way of transporting fuels on Earth, either. But Mars' atmosphere /is/ thick enough for airplanes.

I agree, though, that ISRU shouldn't be construed to be easy.
Title: Re: SpaceX advances drive for Mars rocket via Raptor power
Post by: GregA on 04/01/2014 02:40 am
ISRU shouldn't be construed to be easy.
Just easier than shipping resources from Earth...
Title: Re: SpaceX advances drive for Mars rocket via Raptor power
Post by: baldusi on 04/01/2014 01:16 pm
Let's not get into an ISRU discussion here. I just wanted to point out that developing the MCT propulsion is the easy task. And developing a fully reusable MCT is the easy part of a Mars colony. And a Mars colony is the easy of Mars conquest.
Title: Re: SpaceX advances drive for Mars rocket via Raptor power
Post by: CuddlyRocket on 04/01/2014 02:12 pm
There isn't really a thread to discuss Mars settlement itself is there?
Try the 'Missions to Mars (HSF)' or the 'Advanced Concepts' parts of the forum. Lots of threads on Mars settlements there.
Title: Re: SpaceX advances drive for Mars rocket via Raptor power
Post by: aero on 04/02/2014 06:44 pm
I have an estimate as to the mass of the 4500 kN thrust Raptor engine of 6 to 7 tonnes? Those numbers come from Alexander Ponomarenko, creator of RPA so I think they are pretty solid, but maybe a little conservative. Does anyone have a better estimate considering SpaceX's manufacturing methods?
Title: Re: SpaceX advances drive for Mars rocket via Raptor power
Post by: baldusi on 04/02/2014 08:06 pm

I have an estimate as to the mass of the 4500 kN thrust Raptor engine of 6 to 7 tonnes? Those numbers come from Alexander Ponomarenko, creator of RPA so I think they are pretty solid, but maybe a little conservative. Does anyone have a better estimate considering SpaceX's manufacturing methods?
Isn't that the weight of the RD-171M? I'd guess it would be a bit lighter. RD-170 family is usually around 95 T/W or so. RD-162 should be around that at 100%. So Raptor, with a little less pressure and more expansion than RD-170, plus a less dense propellent, but with more modern manufacturing methods should be under 6 tonnes. But that's just an educated guess.
Title: Re: SpaceX advances drive for Mars rocket via Raptor power
Post by: aero on 04/02/2014 08:39 pm

I have an estimate as to the mass of the 4500 kN thrust Raptor engine of 6 to 7 tonnes? Those numbers come from Alexander Ponomarenko, creator of RPA so I think they are pretty solid, but maybe a little conservative. Does anyone have a better estimate considering SpaceX's manufacturing methods?
Isn't that the weight of the RD-171M? I'd guess it would be a bit lighter. RD-170 family is usually around 95 T/W or so. RD-162 should be around that at 100%. So Raptor, with a little less pressure and more expansion than RD-170, plus a less dense propellent, but with more modern manufacturing methods should be under 6 tonnes. But that's just an educated guess.

If they are still targeting T/W ratio of 100:1, that puts the mass at ~4.6 tonnes. I guess that's why I asked.
Title: Re: SpaceX advances drive for Mars rocket via Raptor power
Post by: Marslauncher on 04/21/2014 10:00 pm
Looks like SpaceX have more ability to test the larger engines now.


(https://pbs.twimg.com/media/BlxsPB3IUAAIYnq.jpg)
Stennis Space Center
‏@NASAStennis
@SpaceX held a ribbon cutting ceremony today at SSC for a new testing partnership. pic.twitter.com/g2pZFXGFAv
Title: Re: SpaceX advances drive for Mars rocket via Raptor power
Post by: rst on 04/21/2014 10:51 pm
Looks like SpaceX have more ability to test the larger engines now.

More Raptor- than Merlin-related.  The press release says that this is about the previously announced agreement to use Stennis for testing Raptor engine components; the actual news is that test stand renovations to support the Raptor component tests are now complete.

The release:  http://mseigs.com/nasa-spacex-cut-ribbon-to-launch-testing-partnership/

So, I'd expect Merlin testing to stay at McGregor for the foreseeable future.
Title: Re: SpaceX advances drive for Mars rocket via Raptor power
Post by: AncientU on 04/21/2014 11:15 pm
Looks like SpaceX have more ability to test the larger engines now.

More Raptor- than Dragon-related.  The press release says that this is about the previously announced agreement to use Stennis for testing Raptor engine components; the actual news is that test stand renovations to support the Raptor component tests are now complete.

The release:  http://mseigs.com/nasa-spacex-cut-ribbon-to-launch-testing-partnership/

So, I'd expect Merlin Dragon testing to stay at McGregor for the foreseeable future.
Timing is interesting:
Quote
Since the fall, Stennis has performed necessary maintenance to prepare the test stand and completed equipment modifications needed to accommodate Raptor components.
 
With preparations complete, the ribbon-cutting ceremony paves the way for testing which is scheduled to begin within a month.
Means that they may have power-pack or turbo-pump(s) built and ready for testing. (That was quick!)

Edit: moved, thanks for making it easy. ++Lar (thanks Lar)
Title: Re: SpaceX advances drive for Mars rocket via Raptor power
Post by: docmordrid on 04/22/2014 02:12 am
Does that mean, if all goes well, we may see a Raptor on the stand in 1-2 years?

That could rattle a few windows, and maybe a few head-in-sand politicians.
Title: Re: SpaceX advances drive for Mars rocket via Raptor power
Post by: baldusi on 04/22/2014 02:24 am

Does that mean, if all goes well, we may see a Raptor on the stand in 1-2 years?

That could rattle a few windows, and maybe a few head-in-sand politicians.
If I understood correctly, they'll be testing elements. Probably the preburners at first. Then the powerpack. The stand is too small for a full sized Raptor.
Title: Re: SpaceX advances drive for Mars rocket via Raptor power
Post by: docmordrid on 04/22/2014 02:51 am
Didn't mean this stand but a stand.

Also, I would think preburners could be tested at McGregor.  IIRC there was a post that USAF types had been there to check out methane related stuff, so if correct  they're doing somerhing there.
Title: Re: SpaceX advances drive for Mars rocket via Raptor power
Post by: meekGee on 04/22/2014 02:53 am
Means that they may have power-pack or turbo-pump(s) built and ready for testing. (That was quick!)

If you count from the time of the public announcement, then yes.  But in the same manner, Grasshopper showed up very quickly after the announcement of the intent to RTLS - but the reality is that there was easily a year of work on RTLS before it was announced.

Probably even more so with Raptor. The peak work on Merlin was probably when the 1D was announced, and after that people started getting more idle/bored - depending of course on their job title. Elon is not the kind of CEO that will lay off the propulsion team just in order to re-hire a different one 12 months later - as I've seen done in large aerospace companies.

It might even be that the formal announcement of Raptor had to wait until the Stennis deal was closed.
Title: Re: SpaceX advances drive for Mars rocket via Raptor power
Post by: Llian Rhydderch on 04/22/2014 03:09 am

Probably even more so with Raptor. The peak work on Merlin was probably when the 1D was announced, and after that people started getting more idle/bored - depending of course on their job title. Elon is not the kind of CEO that will lay off the propulsion team just in order to re-hire a different one 12 months later - as I've seen done in large aerospace companies.

It might even be that the formal announcement of Raptor had to wait until the Stennis deal was closed.

Definitely.  SpaceX has been working on Raptor concepts (originally LOX/LH2 of course) since 2009, with a small team publicly announced to be working on it since 2011.  Much more information about Raptor-as-a-LOX/methane-engine was made available in late 2012, when it became public that the company was moving in a methane-fueled direction.  So yes, they've had a fair bit of development work on Raptor before they ever announced the Stennis deal in fall 2013.
Title: Re: SpaceX advances drive for Mars rocket via Raptor power
Post by: rst on 04/22/2014 03:24 am
It might even be that the formal announcement of Raptor had to wait until the Stennis deal was closed.

... or, contrariwise, that they couldn't do that deal without announcing something about what they were testing.  Even if they would have otherwise preferred to keep it quiet, as they had while the whole thing was in house.
Title: Re: SpaceX advances drive for Mars rocket via Raptor power
Post by: cuddihy on 04/22/2014 03:17 pm

Does that mean, if all goes well, we may see a Raptor on the stand in 1-2 years?

That could rattle a few windows, and maybe a few head-in-sand politicians.
If I understood correctly, they'll be testing elements. Probably the preburners at first. Then the powerpack. The stand is too small for a full sized Raptor.

But for a FFSC, the powerpack IS full-sized. It's full-flow, right?

So I guess you maybe only do half at a time?
Title: Re: SpaceX advances drive for Mars rocket via Raptor power
Post by: baldusi on 04/22/2014 05:33 pm

Does that mean, if all goes well, we may see a Raptor on the stand in 1-2 years?

That could rattle a few windows, and maybe a few head-in-sand politicians.
If I understood correctly, they'll be testing elements. Probably the preburners at first. Then the powerpack. The stand is too small for a full sized Raptor.

But for a FFSC, the powerpack IS full-sized. It's full-flow, right?

So I guess you maybe only do half at a time?
The power pack doesn't include the injector. So it's pretty much two isolated systems in the FFSC cycle, but only if you don't have any expanding cycle embedded (like the SSME low pressure fuel pump).
But for preburner testing, you only need the propellent in liquid form, but you do need it at the correct pressure. My guess is that it will need to get a steady 30MPa or so and flow 320 kg/s of CH4 and 1,100kg/s of LOX. Those must have some serious cryo pumping capability.
Title: Re: SpaceX advances drive for Mars rocket via Raptor power
Post by: Llian Rhydderch on 04/22/2014 05:38 pm

Does that mean, if all goes well, we may see a Raptor on the stand in 1-2 years?

That could rattle a few windows, and maybe a few head-in-sand politicians.
If I understood correctly, they'll be testing elements. Probably the preburners at first. Then the powerpack. The stand is too small for a full sized Raptor.

In rocket engine schematics, what is a "powerpack"?  I'm familiar with combustion chambers, preburners, turbines and turbopumps, ...; but can't get my head around a powerpack.
Title: Re: SpaceX advances drive for Mars rocket via Raptor power
Post by: Llian Rhydderch on 04/22/2014 05:51 pm
I found this schematic of a "Full-flow staged combustion rocket cycle" on Wikipedia, here (https://en.wikipedia.org/wiki/Staged_combustion_cycle).

(https://upload.wikimedia.org/wikipedia/commons/1/1d/Full_flow_staged_rocket_cycle.png)

From discussion earlier on this thread, I get the impression that this is not the right schematic for the full-flow gas-gas type of staged combustion that the Raptor will be using.  Besides that, it doesn't label the preburners which are a critically important part of what is going on, methinks, in the Raptor FFSC engine.  (I suspect, but am not sure, that the preburners are the small light pink rectangles on the inside of the two turbines in the schematic.)

Might one of the more technical rocket scientists here be willing to sketch up a schematic for the gas-gas full-flow staged combustion cycle that Raptor will be using, based on the publicly-released information?  How do those of you who understand rocket combustion cycles picture the Raptor cycle being different from this diagram?



Title: Re: SpaceX advances drive for Mars rocket via Raptor power
Post by: Jim on 04/22/2014 06:19 pm

In rocket engine schematics, what is a "powerpack"?  I'm familiar with combustion chambers, preburners, turbines and turbopumps, ...; but can't get my head around a powerpack.

The moving parts.  The parts that change a pressure fed thruster into a pump fed engine.  Everything above the combustion chamber and nozzle in the diagram above
Title: Re: SpaceX advances drive for Mars rocket via Raptor power
Post by: AnalogMan on 04/22/2014 07:33 pm
I found this schematic of a "Full-flow staged combustion rocket cycle" on Wikipedia, here (https://en.wikipedia.org/wiki/Staged_combustion_cycle).

[...]

From discussion earlier on this thread, I get the impression that this is not the right schematic for the full-flow gas-gas type of staged combustion that the Raptor will be using.  Besides that, it doesn't label the preburners which are a critically important part of what is going on, methinks, in the Raptor FFSC engine.  (I suspect, but am not sure, that the preburners are the small light pink rectangles on the inside of the two turbines in the schematic.)

I think that schematic is correct but, as you say, does not label the pre-burners.  Here is an alternative diagram of a FFSC cycle where the pre-burners are shown more clearly (only fuel or oxidiser rich gaseous exhaust products from them enter the injector head of the main combustion chamber - hence the 'gas-gas' bit).
Title: Re: SpaceX advances drive for Mars rocket via Raptor power
Post by: baldusi on 04/22/2014 08:05 pm
Both schematics are sort of correct. You don't always use all the fuel as cooling mass. And you have a lot more valves and such. Which is important to what a powerpack is.
A powerpack everything from the main Fuel and Oxidizer valve upto just before the injector. As Jim said, preburners, turbines, pumps, but also main valves, throttling valves and such. Testing a powerpack is important because you can validate and solve problems in the turbopump before worring about combustion instabilities on the main combustion chamber. But it's pretty difficult if you don't have some alternate pump system. And I simply don't know how would you test a powerpack in an expander cycle. I mean, you could, but you'd need to make an ad hoc heat exchanger and apply some heat source.
And I'm making this point because the alternative fuel for expanders when not using H2, is CH4. Thus, I seriously suspect that some energy will be extracted out of the cooling loop. But that's just my guess. I heard one that the RD-0162 does it, though. But since I don't read Russian, I haven't been able to exactly pin point where nor how.
Title: Re: SpaceX advances drive for Mars rocket via Raptor power
Post by: docmordrid on 04/23/2014 12:27 am
This AP story says the first thing up at Stennis is an injector.

Could they dev pumps and preburners that large at McGregor?

http://www.sacbee.com/2014/04/22/6343028/spacex-to-test-methane-rocket.html

Quote
>
"We're no stranger to commercial testing," Stennis Director Rick Gilbrech said at Monday's ceremony.

"We've been in the commercial market for over a decade. We're very pleased to welcome Space X as a partner and commercial customer."

He said the company will start with a very fundamental test program — a single Raptor injector element.

The E2 stand, said Space X President and COO Gwynne Shotwell, is "one of the most capable high pressure test stands on the planet."
>
Title: Re: SpaceX advances drive for Mars rocket via Raptor power
Post by: sublimemarsupial on 04/23/2014 01:15 am
This AP story says the first thing up at Stennis is an injector.

Could they dev pumps and preburners that large at McGregor?

http://www.sacbee.com/2014/04/22/6343028/spacex-to-test-methane-rocket.html

Quote
>
"We're no stranger to commercial testing," Stennis Director Rick Gilbrech said at Monday's ceremony.

"We've been in the commercial market for over a decade. We're very pleased to welcome Space X as a partner and commercial customer."

He said the company will start with a very fundamental test program — a single Raptor injector element.

The E2 stand, said Space X President and COO Gwynne Shotwell, is "one of the most capable high pressure test stands on the planet."
>

Of importance, its a single injector element, not the whole injector, so its a much smaller scale (SSME had 264 individual injector elements that made up the whole injector). This is almost definitely the first component they've tested, the pumps and and preburners will come later.

On another note, this is a pretty clear indication that Raptor is face injected, not a pintle, which means even less heritage with Merlin.
Title: Re: SpaceX advances drive for Mars rocket via Raptor power
Post by: JBF on 04/23/2014 01:54 am
Deleted due to being wrong.
Title: Re: SpaceX advances drive for Mars rocket via Raptor power
Post by: Lars_J on 04/23/2014 02:25 am
The F-1 was not a pintle injection engine - unless the definition has changed.
Title: Re: SpaceX advances drive for Mars rocket via Raptor power
Post by: sublimemarsupial on 04/23/2014 02:31 am
This AP story says the first thing up at Stennis is an injector.

Could they dev pumps and preburners that large at McGregor?

http://www.sacbee.com/2014/04/22/6343028/spacex-to-test-methane-rocket.html

Quote
>
"We're no stranger to commercial testing," Stennis Director Rick Gilbrech said at Monday's ceremony.

"We've been in the commercial market for over a decade. We're very pleased to welcome Space X as a partner and commercial customer."

He said the company will start with a very fundamental test program — a single Raptor injector element.

The E2 stand, said Space X President and COO Gwynne Shotwell, is "one of the most capable high pressure test stands on the planet."
>

Of importance, its a single injector element, not the whole injector, so its a much smaller scale (SSME had 264 individual injector elements that made up the whole injector). This is almost definitely the first component they've tested, the pumps and and preburners will come later.

On another note, this is a pretty clear indication that Raptor is face injected, not a pintle, which means even less heritage with Merlin.

Not necessarily. A large pintle injector could be composed of several elements.  See this picture of the F-1 Injector.

A "Pintle Injector" as it was developed by TRW and used by SpaceX in Merlin has only one element - one large post in the center of the engine, with one propellent flowing down the center and then redirected out 180 degrees (towards the chamber walls) and the other propellent flowing around the outside of the post in a cylindrical sheet, such that the two streams intersect and mix. See the attached image for a visualization of the combustion chamber flow pattern.

The F1 injector  was a stereotypical face injector, just like the SSME, being a cluster of individual injector elements. Historically, face injected engines have had much more severe problems with combustion instabilities than pintle engines, so it makes sense that SpaceX would start small (with a single element), and build up to to full injector, studying the stability at each step.

See here for a great summary of pintle injectors:
http://smartdata.usbid.com/datasheets/usbid/2001/2001-q1/pintleenginepaperaiaafinal.pdf
Title: Re: SpaceX advances drive for Mars rocket via Raptor power
Post by: baldusi on 04/23/2014 02:33 am

Not necessarily. A large pintle injector could be composed of several elements.  See this picture of the F-1 Injector.
A pintle injector is like your car's engine valves. Just with one inside the other. So they use a single element. The whole point of the great stability of pintle injectors, that's a bit like a torus. If you put more than one, it would become a very complicated issue. But a gas-gas injector might simply mean a scaled down demonstrator.
Title: Re: SpaceX advances drive for Mars rocket via Raptor power
Post by: JBF on 04/23/2014 10:35 am
My mistake, that's what I get for posting late at night.
Title: Re: SpaceX advances drive for Mars rocket via Raptor power
Post by: Elmar Moelzer on 04/23/2014 01:15 pm
Any reason whey they would abandon the pintle injector? From all I know about it (which is admittedly not that much), it has nothing but advantages over the traditional approach. Does it have to do with the properties of methane compared to RP1?
Title: Re: SpaceX advances drive for Mars rocket via Raptor power
Post by: ArbitraryConstant on 04/23/2014 02:19 pm
Any reason whey they would abandon the pintle injector? From all I know about it (which is admittedly not that much), it has nothing but advantages over the traditional approach. Does it have to do with the properties of methane compared to RP1?
Properties of none of the propellants in Raptor being liquid when they go into the combustion chamber because they put them all through the preburners.
Title: Re: SpaceX advances drive for Mars rocket via Raptor power
Post by: AncientU on 04/23/2014 02:33 pm
Any reason whey they would abandon the pintle injector? From all I know about it (which is admittedly not that much), it has nothing but advantages over the traditional approach. Does it have to do with the properties of methane compared to RP1?
Tom Mueller's track record with Pintle injectors is relevant here.
Quote
Mr. Mueller has a track record as one of the world's foremost rocket engine designers and is responsible for building and managing an elite propulsion development group at SpaceX. Before being recruited to SpaceX, Mr. Mueller spent 14 years at TRW where he ran the Propulsion and Combustion Products Department, responsible for all liquid rocket engine activities.

During his career at TRW, he was the lead engineer for development of the 650,000 lbf thrust LOX/hydrogen engine, which was successfully hot fired at NASA Stennis in the summer of 2000. He has a broad range of rocket engine design, development and testing experience, including all common liquid propellants and many advanced propellants, ranging in thrust from 5 lbf to 650,000 lbf.

From TRW-Built Pintle Rocket Engine Promises to Lower Launch Costs:

The 650,000-pound thrust Low Cost Pintle Engine (LCPE), one of the largest liquid rocket engines built since Saturn F-1 engines powered Apollo program flights in the 1970s, was designed as a simple, easy-to-manufacture, low-cost engine. The LCPE has parts made from common steel alloys using standard industrial fabrication techniques, employs ablative cooling techniques instead of more expensive regenerative cooling, and features the least complex type of rocket propellant injector -- a single element coaxial pintle injector.
http://forum.nasaspaceflight.com/index.php?topic=29035.msg912275#msg912275

And...
Quote
There has never been a flight failure of a pintle injector engine. Moreover, there has never been an instance of combustion instability in a pintle engine during any ground or flight operations, despite scaling over a range of 50,000:1 in thrust and 250:1 in chamber pressure and operation with 25 different propellant combinations, including LOX/LH2 and F2/hydrazine.
http://arc.aiaa.org/doi/pdf/10.2514/6.2000-3871

This seems to be where they are headed.
Title: Re: SpaceX advances drive for Mars rocket via Raptor power
Post by: Elmar Moelzer on 04/23/2014 02:35 pm
Properties of none of the propellants in Raptor being liquid when they go into the combustion chamber because they put them all through the preburners.
I guess a pintle does not allow to disperse and direct the gaseous fuel as well as a network of injectors?
Title: Re: SpaceX advances drive for Mars rocket via Raptor power
Post by: Elmar Moelzer on 04/23/2014 02:39 pm
Any reason whey they would abandon the pintle injector? From all I know about it (which is admittedly not that much), it has nothing but advantages over the traditional approach. Does it have to do with the properties of methane compared to RP1?
Tom Mueller's track record with Pintle injectors is relevant here.
Quote
Mr. Mueller has a track record as one of the world's foremost rocket engine designers and is responsible for building and managing an elite propulsion development group at SpaceX. Before being recruited to SpaceX, Mr. Mueller spent 14 years at TRW where he ran the Propulsion and Combustion Products Department, responsible for all liquid rocket engine activities.

During his career at TRW, he was the lead engineer for development of the 650,000 lbf thrust LOX/hydrogen engine, which was successfully hot fired at NASA Stennis in the summer of 2000. He has a broad range of rocket engine design, development and testing experience, including all common liquid propellants and many advanced propellants, ranging in thrust from 5 lbf to 650,000 lbf.

From TRW-Built Pintle Rocket Engine Promises to Lower Launch Costs:

The 650,000-pound thrust Low Cost Pintle Engine (LCPE), one of the largest liquid rocket engines built since Saturn F-1 engines powered Apollo program flights in the 1970s, was designed as a simple, easy-to-manufacture, low-cost engine. The LCPE has parts made from common steel alloys using standard industrial fabrication techniques, employs ablative cooling techniques instead of more expensive regenerative cooling, and features the least complex type of rocket propellant injector -- a single element coaxial pintle injector.
http://forum.nasaspaceflight.com/index.php?topic=29035.msg912275#msg912275

And...
Quote
There has never been a flight failure of a pintle injector engine. Moreover, there has never been an instance of combustion instability in a pintle engine during any ground or flight operations, despite scaling over a range of 50,000:1 in thrust and 250:1 in chamber pressure and operation with 25 different propellant combinations, including LOX/LH2 and F2/hydrazine.
http://arc.aiaa.org/doi/pdf/10.2514/6.2000-3871

This seems to be where they are headed.
I am fully aware of Tom Mueller's experience with pintle injector engines and their advantages. Hence my surprise about the statement that they are allegedly abandoning this successful concept for the Raptor engines. Arbitrary Constants explanation seems to make sense though.
Title: Re: SpaceX advances drive for Mars rocket via Raptor power
Post by: eriblo on 04/23/2014 03:29 pm
Any reason whey they would abandon the pintle injector? From all I know about it (which is admittedly not that much), it has nothing but advantages over the traditional approach. Does it have to do with the properties of methane compared to RP1?
Properties of none of the propellants in Raptor being liquid when they go into the combustion chamber because they put them all through the preburners.
Pintle injectors have been proven to work with at least one propellant in a gaseous phase (methane actually) and in this case both will be super-critical with a density of perhaps 1/10th the liquid one. I (and Elmar I guess) wonder if there is any fundamental problem with this or if it's just a case of the pros/cons shifting and perhaps making an other configuration more favorable?
Title: Re: SpaceX advances drive for Mars rocket via Raptor power
Post by: prime8 on 04/23/2014 06:59 pm
Quote
There has never been a flight failure of a pintle injector engine.
http://arc.aiaa.org/doi/pdf/10.2514/6.2000-3871

CRS-1?
Title: Re: SpaceX advances drive for Mars rocket via Raptor power
Post by: Jdeshetler on 04/23/2014 07:20 pm
I tried to search the SpaceX threads regarding the methane liquid in tanks before being converted to gas state but can't find anything specific. 

Was the methane liquid converted to gas state by the heater unit before entering powerplant? 

And what is the temp of methane liquid in the tank and what is the temp of methane gas before it enter the powerplant?
Title: Re: SpaceX advances drive for Mars rocket via Raptor power
Post by: AncientU on 04/23/2014 07:36 pm
Quote
There has never been a flight failure of a pintle injector engine.
http://arc.aiaa.org/doi/pdf/10.2514/6.2000-3871

CRS-1?
Good point!  The article predated that event by a decade, so CRS-1 didn't enter their argument -- yet it was something of an amazing statement which is why I included it.  (Note: I will not get sucked into the black hole of discussing if CRS-1 was an engine, or piping, or whatever failure or pressure release or explosion... let's please not go there)
Title: Re: SpaceX advances drive for Mars rocket via Raptor power
Post by: go4mars on 04/24/2014 12:45 am
Falcon 1 flight 3 had a (gaseous?) thrust transient through pintle injector. 
Title: Re: SpaceX advances drive for Mars rocket via Raptor power
Post by: TrueBlueWitt on 04/24/2014 01:16 am
Pintle might be cheaper. However.. How much of a factor is engine cost if they plan full reusability?
Title: Re: SpaceX advances drive for Mars rocket via Raptor power
Post by: baldusi on 04/24/2014 01:30 am

I tried to search the SpaceX threads regarding the methane liquid in tanks before being converted to gas state but can't find anything specific. 

Was the methane liquid converted to gas state by the heater unit before entering powerplant? 

And what is the temp of methane liquid in the tank and what is the temp of methane gas before it enter the powerplant?
I think you are thinking about an expander cycle, where the liquid methane that cools the engine is heated to drive the turbopumps. There have been experiments done with American (RL10) and Russian engines. But no production. And the expander cycle is thrust limited. One small detail, in the expander cycle the fuel is heated beyond the supercritical point. Thus, it doesn't evaporates, but slowly changes its properties from liquid to gaseous.
In the Raptor case, a preburner is used to generate gas. This is achieved by adding a tiny bit of oxidizer and burning it to hot gas. The thrust level is way beyond what can be achieved by an expander. But the expander cycle can be added to drive something small, like a low pressure pump to avoid cavitation.
Title: Re: SpaceX advances drive for Mars rocket via Raptor power
Post by: Hyperion5 on 04/24/2014 04:00 am

I tried to search the SpaceX threads regarding the methane liquid in tanks before being converted to gas state but can't find anything specific. 

Was the methane liquid converted to gas state by the heater unit before entering powerplant? 

And what is the temp of methane liquid in the tank and what is the temp of methane gas before it enter the powerplant?
I think you are thinking about an expander cycle, where the liquid methane that cools the engine is heated to drive the turbopumps. There have been experiments done with American (RL10) and Russian engines. But no production. And the expander cycle is thrust limited. One small detail, in the expander cycle the fuel is heated beyond the supercritical point. Thus, it doesn't evaporates, but slowly changes its properties from liquid to gaseous.
In the Raptor case, a preburner is used to generate gas. This is achieved by adding a tiny bit of oxidizer and burning it to hot gas. The thrust level is way beyond what can be achieved by an expander. But the expander cycle can be added to drive something small, like a low pressure pump to avoid cavitation.

Speaking of expander-cycle, if I remember the translated publications on the RD-0162/0164 family correctly, wasn't there some part of those engines that used an expander cycle?  From what I remember reading, the engine features a staged combustion setup for its oxidizer but uses a sort of expander cycle for its liquid methane.  Now maybe I'm wrong, but I think it would be really interesting for our members to go over the RD-0164 and the Raptor combustion cycles compared to one another.  Perhaps then we could understand the differing approaches taken by the Russians and Spacex to methalox engines and the advantages and disadvantages of both approaches. 

I'm guessing, from the stats on the RD-0162, that a 100 t/w ratio on both the RD-0164 and Raptor would be very likely.  However that presumes reusability.  The Russians claim they can get a methalox engine up to ~130 t/w ratio but not do so very often.  If Spacex were to push a Raptor like the Russians claim you can push an SC methalox engine "beyond nominal", how much more thrust could they get before it wouldn't be so reusable?  Could they push t/w ratio as high as 120:1? 
Title: Re: SpaceX advances drive for Mars rocket via Raptor power
Post by: AncientU on 04/24/2014 01:56 pm
In testing a new engine like Raptor, can we expect that an entire engine or full power pack was built, then disassembled to do component and sub-system tests (parallel approach)? Or would the approach be to build a component, test it, and then move to the next component (serial approach)?  Modern Cad systems allow an awful lot of testing and simulation/modeling before metal is cut, so wondering what approach SpaceX is most likely taking.
Title: Re: SpaceX advances drive for Mars rocket via Raptor power
Post by: baldusi on 04/24/2014 03:57 pm
The whole engine might be designed (at PDR level or so). But now they need to validate the results of the simulation. And the correct way is to do a very exhaustive approach. You first test the physical properties of materials (like oxidizer rich resistance, tensile strength at temperature, etc.), then you test a component. First you test that it flows like it should, then that it can handle the pressure, then heat and pressure, etc. Then you test your ignition methods. And only then you test a component like the preburner or injector.
Title: Re: SpaceX advances drive for Mars rocket via Raptor power
Post by: RedLineTrain on 04/24/2014 04:30 pm
Don't know if this has been mentioned otherwise, but this article from Spaceref is a little more specific than the AP article.  Also, the article states that Raptor will be used for future versions of Falcon Heavy.  Don't know what to make of that.

Quote
SpaceX will test Raptor injectors and combustion chambers during the initial phase at E-2 Cell 1. According to SpaceX they are still in the very early stages of the Raptor engine development program and this initial test phase will last 12 to 24 months with larger components to be tested afterwards presumably at their rocket engine development facility in McGregor, Texas.

http://spaceref.biz/company/spacex-set-to-test-raptor-engine-components-at-nasa-stennis.html
Title: Re: SpaceX advances drive for Mars rocket via Raptor power
Post by: AncientU on 04/24/2014 04:42 pm
Don't know if this has been mentioned otherwise, but this article from Spaceref is a little more specific than the AP article.  Also, the article states that Raptor will be used for future versions of Falcon Heavy.  Don't know what to make of that.

Quote
SpaceX will test Raptor injectors and combustion chambers during the initial phase at E-2 Cell 1. According to SpaceX they are still in the very early stages of the Raptor engine development program and this initial test phase will last 12 to 24 months with larger components to be tested afterwards presumably at their rocket engine development facility in McGregor, Texas.

http://spaceref.biz/company/spacex-set-to-test-raptor-engine-components-at-nasa-stennis.html
Good catch.  There has been an incredible amount of speculation on this forum as to whether the Raptor (or, more properly, a member of the Raptor family of engines) is still intended as a high-energy upper stage engine -- which I believe is how it was originally introduced -- or if it is now 'just' for the BFR.  I believe the latter is the consensus view, though I wish both would happen.  Certainly the million pound force in vacuum version (six M1Ds worth) wouldn't work on the FH, so I expect the article is just quoting old 'news.'
Title: Re: SpaceX advances drive for Mars rocket via Raptor power
Post by: baldusi on 04/24/2014 05:03 pm
I still believe that they want to characterize the gas-gas flow on scaled down components. Once they validate their model they'll scale those up.
Title: Re: SpaceX advances drive for Mars rocket via Raptor power
Post by: AncientU on 04/24/2014 05:20 pm
I still believe that they want to characterize the gas-gas flow on scaled down components. Once they validate their model they'll scale those up.
That would be great -- 1/4th or 1/5th scale, please.  But seriously, what are the components that would be most sensitive to the gas-gas flow conditions?  Only Injector element(s)?
Title: Re: SpaceX advances drive for Mars rocket via Raptor power
Post by: baldusi on 04/24/2014 06:31 pm
I still believe that they want to characterize the gas-gas flow on scaled down components. Once they validate their model they'll scale those up.
That would be great -- 1/4th or 1/5th scale, please.  But seriously, what are the components that would be most sensitive to the gas-gas flow conditions?  Only Injector element(s)?
The two biggest technological risks should be Oxidizer Rich subsystem and Gas-Gas 1Mlbf Thrust Chamber. E-2 Cell 1 could do O2, N2 and H2 in both liquid and gaseous state. The mods were to add CH4 (both liquid and gaseous). But it's rated to a top of 100klbf, which is an order of magnitude less than 1Mblf. But if that is vacuum, we are talking 1/10th to 1/8th or so for maximum size.
My guess, is that this is previous or parallel to the preburners. Because you don't need the gaseous system for that. And that's probably why they've chosen this particular stand.
Title: Re: SpaceX advances drive for Mars rocket via Raptor power
Post by: Llian Rhydderch on 04/24/2014 06:49 pm
I still believe that they want to characterize the gas-gas flow on scaled down components. Once they validate their model they'll scale those up.
That would be great -- 1/4th or 1/5th scale, please.  But seriously, what are the components that would be most sensitive to the gas-gas flow conditions?  Only Injector element(s)?
The two biggest technological risks should be Oxidizer Rich subsystem and Gas-Gas 1Mlbf Thrust Chamber. E-2 Cell 1 could do O2, N2 and H2 in both liquid and gaseous state. The mods were to add CH4 (both liquid and gaseous). But it's rated to a top of 100klbf, which is an order of magnitude less than 1Mblf. But if that is vacuum, we are talking 1/10th to 1/8th or so for maximum size.
My guess, is that this is previous or parallel to the preburners. Because you don't need the gaseous system for that. And that's probably why they've chosen this particular stand.

Thanks, baldusi.  I really appreciate what you've been adding to our knowledge of Raptor and rocket engine design over the past month since your Raptor article was published.

One comment I don't understand is "But if that is vacuum, we are talking 1/10th to 1/8th or so for maximum size."  Could you elaborate on that thought?
Title: Re: SpaceX advances drive for Mars rocket via Raptor power
Post by: baldusi on 04/24/2014 07:50 pm
I still believe that they want to characterize the gas-gas flow on scaled down components. Once they validate their model they'll scale those up.
That would be great -- 1/4th or 1/5th scale, please.  But seriously, what are the components that would be most sensitive to the gas-gas flow conditions?  Only Injector element(s)?
The two biggest technological risks should be Oxidizer Rich subsystem and Gas-Gas 1Mlbf Thrust Chamber. E-2 Cell 1 could do O2, N2 and H2 in both liquid and gaseous state. The mods were to add CH4 (both liquid and gaseous). But it's rated to a top of 100klbf, which is an order of magnitude less than 1Mblf. But if that is vacuum, we are talking 1/10th to 1/8th or so for maximum size.
My guess, is that this is previous or parallel to the preburners. Because you don't need the gaseous system for that. And that's probably why they've chosen this particular stand.

Thanks, baldusi.  I really appreciate what you've been adding to our knowledge of Raptor and rocket engine design over the past month since your Raptor article was published.

One comment I don't understand is "But if that is vacuum, we are talking 1/10th to 1/8th or so for maximum size."  Could you elaborate on that thought?
Oh, I was talking about maximum scale. 100klbf is the maximum thrust. But this is clearly sea level thrust. If Raptor is 1Mlbf at vacuum, should be something like 850klbf at sea level, thus a 100klbf scale model would be about 1/8th. Of course that they could do it smaller and we should take this as an upper bound.
The fact with pintle is that scaling is not that easy. I mean, there's a picture on the Indian development thread that shows them testing a single injector element. Since you usually have a hundred or more of those, you can do that on a really small scale. But you have a single one on a pintle. Thus, I don't know how much would they gain from working on a 25klbf one. BTW, a 100klbf might perfectly be used for an CH4/LOX upper stage on the Falcon 9. But I don't think that's their current line of development.
Title: Re: SpaceX advances drive for Mars rocket via Raptor power
Post by: cuddihy on 04/24/2014 10:52 pm

Speaking of expander-cycle, if I remember the translated publications on the RD-0162/0164 family correctly, wasn't there some part of those engines that used an expander cycle?  From what I remember reading, the engine features a staged combustion setup for its oxidizer but uses a sort of expander cycle for its liquid methane.  Now maybe I'm wrong, but I think it would be really interesting for our members to go over the RD-0164 and the Raptor combustion cycles compared to one another.  Perhaps then we could understand the differing approaches taken by the Russians and Spacex to methalox engines and the advantages and disadvantages of both approaches. 

I'm guessing, from the stats on the RD-0162, that a 100 t/w ratio on both the RD- and Raptor would be very likely.  However that presumes reusability.  The Russians claim they can get a methalox engine up to ~130 t/w ratio but not do so very often.  If Spacex were to push a Raptor like the Russians claim you can push an SC methalox engine "beyond nominal", how much more thrust could they get before it wouldn't be so reusable?  Could they push t/w ratio as high as 120:1? 

From what I've seen, RD-0162 is dual-expander cycle , methane heated via nozzle, lox via cumbustion chamber.
Title: Re: SpaceX advances drive for Mars rocket via Raptor power
Post by: cuddihy on 04/24/2014 10:54 pm
I remain convinced they have to do a smaller methalox engine than Raptor for OMS & landing... But who knows.
Title: Re: SpaceX advances drive for Mars rocket via Raptor power
Post by: Ben the Space Brit on 04/25/2014 04:38 pm
I remain convinced they have to do a smaller methalox engine than Raptor for OMS & landing... But who knows.

Yes I am a great fan of a Merlin-1m (improved U/S performance for F9 and FH) and Kestrel-M (BEO Dragon MPS).
Title: Re: SpaceX advances drive for Mars rocket via Raptor power
Post by: baldusi on 04/25/2014 06:36 pm
I remain convinced they have to do a smaller methalox engine than Raptor for OMS & landing... But who knows.

Yes I am a great fan of a Merlin-1m (improved U/S performance for F9 and FH) and Kestrel-M (BEO Dragon MPS).
A CH4 Merlin wouldn't add much performance and might, in fact, lose it. Among other thing it would need a 30% extra tanking, which might be an issue on pmf with very little isp won.
Now, a full staged mini Raptor, that would be another thing entirely. And I see how they are getting experience on composites (interstage and vac nozzle). LNG composite tanks are the norm. So the most difficult part would be doing the LOX tank. Common bulkhead is almost free in that propellant combo. A composite CH4/LOX upper stage with a full flow engine would be quite an amazing combination. It would increase the Falcon 9 high energy performance from Atlas V401 to 431, or even higher.
Why do I ask about this line? Because it would be the cheapest possible way to develop that technology. Known first vehicle and fairing, same avionics and interfaces, the smallest tank and cheapest stage. And it would help a MCT immensely. Out of autoclave composites are cheaper than Al-Li, and require less tooling. And the pmf goes even higher, which is a very important characteristic for an upper stage.
But, as I said it, for all I know, they are not worried about that... yet. First they have to figure out how to actually return an upper stage with a meaningful payload capacity.
Regarding Kestrel, it was a pressure fed RP-1/LOX engine. In the right thrust level, but the wrong propellant for long missions. I would go with a HAN based propellant.
Title: Re: SpaceX advances drive for Mars rocket via Raptor power
Post by: DJPledger on 04/25/2014 06:42 pm
I remain convinced they have to do a smaller methalox engine than Raptor for OMS & landing... But who knows.

Yes I am a great fan of a Merlin-1m (improved U/S performance for F9 and FH) and Kestrel-M (BEO Dragon MPS).
A CH4 Merlin wouldn't add much performance and might, in fact, lose it. Among other thing it would need a 30% extra tanking, which might be an issue on pmf with very little isp won.
Now, a full staged mini Raptor, that would be another thing entirely. And I see how they are getting experience on composites (interstage and vac nozzle). LNG composite tanks are the norm. So the most difficult part would be doing the LOX tank. Common bulkhead is almost free in that propellant combo. A composite CH4/LOX upper stage with a full flow engine would be quite an amazing combination. It would increase the Falcon 9 high energy performance from Atlas V401 to 431, or even higher.
Why do I ask about this line? Because it would be the cheapest possible way to develop that technology. Known first vehicle and fairing, same avionics and interfaces, the smallest tank and cheapest stage. And it would help a MCT immensely. Out of autoclave composites are cheaper than Al-Li, and require less tooling. And the pmf goes even higher, which is a very important characteristic for an upper stage.
But, as I said it, for all I know, they are not worried about that... yet. First they have to figure out how to actually return an upper stage with a meaningful payload capacity.
Regarding Kestrel, it was a pressure fed RP-1/LOX engine. In the right thrust level, but the wrong propellant for long missions. I would go with a HAN based propellant.
Gwynne Shotwell explicitly said on The Space Show recently that SpaceX are only working on the full size Raptor and that no smaller versions of it will be dev. and she said that it is for SHLV for Mars launches. However knowing SpaceX they could change their plans in the future and may decide to dev. a smaller version of Raptor to improve F9 and FH US performance.
Title: Re: SpaceX advances drive for Mars rocket via Raptor power
Post by: Zed_Noir on 04/25/2014 06:57 pm
A CH4 Merlin wouldn't add much performance and might, in fact, lose it. Among other thing it would need a 30% extra tanking, which might be an issue on pmf with very little isp won.
Now, a full staged mini Raptor, that would be another thing entirely. And I see how they are getting experience on composites (interstage and vac nozzle). LNG composite tanks are the norm. So the most difficult part would be doing the LOX tank. Common bulkhead is almost free in that propellant combo. A composite CH4/LOX upper stage with a full flow engine would be quite an amazing combination. It would increase the Falcon 9 high energy performance from Atlas V401 to 431, or even higher.
Why do I ask about this line? Because it would be the cheapest possible way to develop that technology. Known first vehicle and fairing, same avionics and interfaces, the smallest tank and cheapest stage. And it would help a MCT immensely. Out of autoclave composites are cheaper than Al-Li, and require less tooling. And the pmf goes even higher, which is a very important characteristic for an upper stage.
But, as I said it, for all I know, they are not worried about that... yet. First they have to figure out how to actually return an upper stage with a meaningful payload capacity.
Regarding Kestrel, it was a pressure fed RP-1/LOX engine. In the right thrust level, but the wrong propellant for long missions. I would go with a HAN based propellant.

Just how many times can the composite structures be reuse versus the Al- Li structures SpaceX is using currently?
Title: Re: SpaceX advances drive for Mars rocket via Raptor power
Post by: baldusi on 04/25/2014 09:17 pm
A CH4 Merlin wouldn't add much performance and might, in fact, lose it. Among other thing it would need a 30% extra tanking, which might be an issue on pmf with very little isp won.
Now, a full staged mini Raptor, that would be another thing entirely. And I see how they are getting experience on composites (interstage and vac nozzle). LNG composite tanks are the norm. So the most difficult part would be doing the LOX tank. Common bulkhead is almost free in that propellant combo. A composite CH4/LOX upper stage with a full flow engine would be quite an amazing combination. It would increase the Falcon 9 high energy performance from Atlas V401 to 431, or even higher.
Why do I ask about this line? Because it would be the cheapest possible way to develop that technology. Known first vehicle and fairing, same avionics and interfaces, the smallest tank and cheapest stage. And it would help a MCT immensely. Out of autoclave composites are cheaper than Al-Li, and require less tooling. And the pmf goes even higher, which is a very important characteristic for an upper stage.
But, as I said it, for all I know, they are not worried about that... yet. First they have to figure out how to actually return an upper stage with a meaningful payload capacity.
Regarding Kestrel, it was a pressure fed RP-1/LOX engine. In the right thrust level, but the wrong propellant for long missions. I would go with a HAN based propellant.

Just how many times can the composite structures be reuse versus the Al- Li structures SpaceX is using currently?
Difficult to say. But LNG tanks are used on cars, buses and ships. There's a lot of experience on those. From the Orion experience, the actual problem of composites vs aluminum are basically three:
1) Non Destructive Inspection for internal failures.
2) Fragility to manufacturing and integration accidents.
3) Difficulty in integrating and perforations.
The last one is not such a problem. The second is not as bad for an upper stage vs a capsule. And the first might be an issue. But re-usability might even improve if the materials have better resistance to heat and strength.
Title: Re: SpaceX advances drive for Mars rocket via Raptor power
Post by: cuddihy on 04/25/2014 10:08 pm

 And I see how they are getting experience on composites (interstage and vac nozzle). LNG composite tanks are the norm. So the most difficult part would be doing the LOX tank. Common bulkhead is almost free in that propellant combo. A composite CH4/LOX upper stage with a full flow engine would be quite an amazing combination.

Where? Most tanks I'm familiar with are metal w/ composite wrapped for strength.
Title: Re: SpaceX advances drive for Mars rocket via Raptor power
Post by: Hyperion5 on 04/26/2014 05:43 pm

 And I see how they are getting experience on composites (interstage and vac nozzle). LNG composite tanks are the norm. So the most difficult part would be doing the LOX tank. Common bulkhead is almost free in that propellant combo. A composite CH4/LOX upper stage with a full flow engine would be quite an amazing combination.

Where? Most tanks I'm familiar with are metal w/ composite wrapped for strength.

What about using AL-2050 and avoiding composites altogether? 

http://www.nasaspaceflight.com/2013/02/sls-new-buckling-standards-drops-super-light-alloy/

Quote
Information also notes that the SBKF project has also been doing preliminary work on a new alloy. AL-2050 adds magnesium for an Al-Mg-Li mix, and “is already used extensively in several commercial aircraft”. This promises plates and orthogrids three times thicker than Al-2195 – up to six inches – with weight savings of as much as 20-30 percent.

If you can save the same amount of mass using something relatively familiar to Spacex's engineers, why would you bother with using composites?  I seem to recall that issues with composites caused more than a few delays on several modern airliners (like the 787 and A380) and causes plenty of repair headaches to boot.  If you want a genuinely reusable rocket, then it should be easy to repair and detect structural problems that need to be repaired.  This is why I think composites should have a limited application in any future Spacex rocket. 
Title: Re: SpaceX advances drive for Mars rocket via Raptor power
Post by: Hauerg on 04/26/2014 05:47 pm
Would SpaceX like to use composites on future Mars vehicles? If not, then they will not go this route of building experience that they will not use on Mars.
IIRC.
Title: Re: SpaceX advances drive for Mars rocket via Raptor power
Post by: daveklingler on 04/27/2014 09:28 pm
If you can save the same amount of mass using something relatively familiar to Spacex's engineers, why would you bother with using composites?  I seem to recall that issues with composites caused more than a few delays on several modern airliners (like the 787 and A380) and causes plenty of repair headaches to boot.  If you want a genuinely reusable rocket, then it should be easy to repair and detect structural problems that need to be repaired.  This is why I think composites should have a limited application in any future Spacex rocket.

The old rule of thumb is that carbon, executed correctly, will provide at least 30% weight savings over aluminum.  Filament winding, newer, finer fabrics and nanotube-reinforced epoxies can sometimes provide an additional 20-30% by saving layers.  Granted, Boeing is going through quite a learning curve with the 787, but the significant point is that they felt that there were very good reasons for them to go through it, and for Airbus.

Aviation is a conservative industry, often decades behind other industries in the materials they use, and commercial launchers are even more conservative for the reason that there's just very little reason to innovate.  I'm unsure how a rocket that flies, say, once a week would compare to an airplane that flies most of the day, most of the year, in terms of material fatigue.  My inclination, especially with liquid rockets, would be to say that the airplane sees far more punishment.
Title: Re: SpaceX advances drive for Mars rocket via Raptor power
Post by: Occupymars on 04/29/2014 11:36 pm
Just heard on the Spaceshow that Jeff Thornburg, Spacex's Principal Propulsion Engineer will be talking about Raptor at the International Space Development Conference (ISDC) which will be held between may 14-18  8)
Title: Re: SpaceX advances drive for Mars rocket via Raptor power
Post by: Occupymars on 04/30/2014 12:21 am
Just heard on the Spaceshow that Jeff Thornburg, Spacex's Principal Propulsion Engineer will be talking about Raptor at the International Space Development Conference (ISDC) which will be held between may 14-18  8)
The bad news is that apparently none of the conference will be live streamed or put up on youtube but alot of the conference will be recorded and then burned on dvd's for sale if people want to inquire about them.
If that video is put up on L2 I would join in a heartbeat ;)
Title: Re: SpaceX advances drive for Mars rocket via Raptor power
Post by: docmordrid on 04/30/2014 01:06 am
10:00 AM on Saturday May 17

"Raptor High Performance Rocket Engine"
Title: Re: SpaceX advances drive for Mars rocket via Raptor power
Post by: Halidon on 04/30/2014 01:30 am
10:00 AM on Saturday May 17

"Raptor High Performance Rocket Engine"
Anyone interested in wearing a wire?
Title: Re: SpaceX advances drive for Mars rocket via Raptor power
Post by: Mongo62 on 04/30/2014 01:41 am
10:00 AM on Saturday May 17

"Raptor High Performance Rocket Engine"

Will this be open to the (admission-paying) public, or will only industry big shots be invited?

(Not that these admission details are likely to be known yet, but if it's possible for the general public to attend, I would hope that somebody on NSF is there.)
Title: Re: SpaceX advances drive for Mars rocket via Raptor power
Post by: docmordrid on 04/30/2014 02:16 am
It's in LA at the Sheraton.Gateway

https://www.nss.org/cgi-bin/register/tdregister?$Origin=ISDC14 (https://www.nss.org/cgi-bin/register/tdregister?$Origin=ISDC14)
Title: Re: SpaceX advances drive for Mars rocket via Raptor power
Post by: baldusi on 04/30/2014 02:32 am
By getting a membership I can get a copy of that conference? I couldn't find a link to buy previous ones.
Title: Re: SpaceX advances drive for Mars rocket via Raptor power
Post by: Jdeshetler on 04/30/2014 04:24 am
10:00 AM on Saturday May 17

"Raptor High Performance Rocket Engine"
Anyone interested in wearing a wire?

Or "Ray Ban" Google Glasses? 8)
Title: Re: SpaceX advances drive for Mars rocket via Raptor power
Post by: beancounter on 04/30/2014 02:11 pm

 And I see how they are getting experience on composites (interstage and vac nozzle). LNG composite tanks are the norm. So the most difficult part would be doing the LOX tank. Common bulkhead is almost free in that propellant combo. A composite CH4/LOX upper stage with a full flow engine would be quite an amazing combination.

Where? Most tanks I'm familiar with are metal w/ composite wrapped for strength.

What about using AL-2050 and avoiding composites altogether? 

http://www.nasaspaceflight.com/2013/02/sls-new-buckling-standards-drops-super-light-alloy/

Quote
Information also notes that the SBKF project has also been doing preliminary work on a new alloy. AL-2050 adds magnesium for an Al-Mg-Li mix, and “is already used extensively in several commercial aircraft”. This promises plates and orthogrids three times thicker than Al-2195 – up to six inches – with weight savings of as much as 20-30 percent.

If you can save the same amount of mass using something relatively familiar to Spacex's engineers, why would you bother with using composites?  I seem to recall that issues with composites caused more than a few delays on several modern airliners (like the 787 and A380) and causes plenty of repair headaches to boot.  If you want a genuinely reusable rocket, then it should be easy to repair and detect structural problems that need to be repaired.  This is why I think composites should have a limited application in any future Spacex rocket.

No metal fatigue with composites.
Title: Re: SpaceX advances drive for Mars rocket via Raptor power
Post by: Lars_J on 04/30/2014 04:29 pm
Composites are not a golden solution that will solve everything. They have different failure modes than metal, but they can fail too.
Title: Re: SpaceX advances drive for Mars rocket via Raptor power
Post by: baldusi on 04/30/2014 06:40 pm
Composites are not a golden solution that will solve everything. They have different failure modes than metal, but they can fail too.
So true. What's more important, there are at least 80 years of aluminum in airplanes and 50 in spacecrafts. Structural composites on planes is new, and zero experience in spacecrafts and launch vehicles. Thus, the understanding of failure modes, fatigue, crack propagation, etc., is very limited. We assume it will be superior, but there are a lot of lessons to be learned. As said before, the Orion pressure vessel experience was that once you take into consideration the lack of simple non destructive inspection, the fragility for integration accidents, and the difficulty of repairs, then there was simply no saving. It had an advantage in radiation shielding (less secondaries), thou. But if you look at the three problems together, you'll notice that those are mostly lack of experience and technical and manufacturing development. I'm pretty sure that by 2025 or so, all the experience on the aircraft industry will reduce or even solve most of those problems.
Title: Re: SpaceX advances drive for Mars rocket via Raptor power
Post by: deltaV on 04/30/2014 07:33 pm
Structural composites on planes is new, and zero experience in spacecrafts and launch vehicles.

That's news to SpaceX: Falcon 9 uses composite interstages and fairings.
Title: Re: SpaceX advances drive for Mars rocket via Raptor power
Post by: Elmar Moelzer on 04/30/2014 08:37 pm
I think that it is prudent to use an incremental approach as SpaceX does. Maybe once they have reached a routine with the current version of the F9 and there are no more bugfixes, they will go and start optimizing to get more performance out of it. Its just like it is in software development. First you make sure it runs, then you fix all the bugs, then you optimize as much as possible and then... then you start all over again ;)
Title: Re: SpaceX advances drive for Mars rocket via Raptor power
Post by: ImUtrecht on 05/01/2014 01:10 am
SpaceX uses a lot of composites and they are increasing the use.
The landinglegs for F9R for example.
There is a lot of new developement on this field
Title: Re: SpaceX advances drive for Mars rocket via Raptor power
Post by: beancounter on 05/01/2014 01:55 pm
Composites are not a golden solution that will solve everything. They have different failure modes than metal, but they can fail too.
Didn't say that.  Just that they don't have fatigue failure modes like metal.
Title: Re: SpaceX advances drive for Mars rocket via Raptor power
Post by: baldusi on 05/01/2014 06:52 pm

Structural composites on planes is new, and zero experience in spacecrafts and launch vehicles.

That's news to SpaceX: Falcon 9 uses composite interstages and fairings.
Yes, my sentence didn't parse right. Structural composites on planes is new, composite main tanks (which are structural in rockets) have zero experience.
Title: Re: SpaceX advances drive for Mars rocket via Raptor power
Post by: wannamoonbase on 05/01/2014 06:57 pm
I think that it is prudent to use an incremental approach as SpaceX does. Maybe once they have reached a routine with the current version of the F9 and there are no more bugfixes, they will go and start optimizing to get more performance out of it. Its just like it is in software development. First you make sure it runs, then you fix all the bugs, then you optimize as much as possible and then... then you start all over again ;)

Flight rate, they need more flights and flight time on hardware.

But agree that minor changes and evolving make sense.

I admire what SpaceX has accomplished and their future goals.  However, I remain optimistically skeptic about the finances of the company until they are getting a paying payload into orbit more often.  They need to start making some $$$ off of the costs they have invested to date.
Title: Re: SpaceX advances drive for Mars rocket via Raptor power
Post by: Zed_Noir on 05/01/2014 10:06 pm
I admire what SpaceX has accomplished and their future goals.  However, I remain optimistically skeptic about the finances of the company until they are getting a paying payload into orbit more often.  They need to start making some $$$ off of the costs they have invested to date.

SpaceX don't need to show a profit. The main shareholder is happy with breaking even.  ;)
Title: Re: SpaceX advances drive for Mars rocket via Raptor power
Post by: QuantumG on 05/01/2014 10:28 pm
I admire what SpaceX has accomplished and their future goals.  However, I remain optimistically skeptic about the finances of the company until they are getting a paying payload into orbit more often.  They need to start making some $$$ off of the costs they have invested to date.

SpaceX don't need to show a profit. The main shareholder is happy with breaking even.  ;)

Not true. Elon wants SpaceX to achieve things that it currently doesn't have the funding to achieve. The best way to do that is to grow the treasure chest.
Title: Re: SpaceX advances drive for Mars rocket via Raptor power
Post by: ImUtrecht on 05/01/2014 10:42 pm
Composites are not a golden solution that will solve everything. They have different failure modes than metal, but they can fail too.
So true. What's more important, there are at least 80 years of aluminum in airplanes and 50 in spacecrafts. Structural composites on planes is new, and zero experience in spacecrafts and launch vehicles. Thus, the understanding of failure modes, fatigue, crack propagation, etc., is very limited. We assume it will be superior, but there are a lot of lessons to be learned. As said before, the Orion pressure vessel experience was that once you take into consideration the lack of simple non destructive inspection, the fragility for integration accidents, and the difficulty of repairs, then there was simply no saving. It had an advantage in radiation shielding (less secondaries), thou. But if you look at the three problems together, you'll notice that those are mostly lack of experience and technical and manufacturing development. I'm pretty sure that by 2025 or so, all the experience on the aircraft industry will reduce or even solve most of those problems.

Structural composites were for example used on the Mars rover and in a lot of other spacecraft.
The Fokker F27 had mayor parts of it wings glued.
Mayor parts of the Airbus 380 were done with composites.
It is superior and there are already a lot of lessons learned.
The understanding of failure modes is quite well known nowadays and it is easyer to repair.
It is/was the conservatisme of the industry that has stopped more use.
SpaceX does not have that problem and they are more and more integrating composites in F9.
The certification of this is an ongoing process.
It is also one of the reasons why the payload of the FH went up.
There is a new generation of composites in developement that will push the bounderies again and SpaceX will take advantage of that.

Title: Re: SpaceX advances drive for Mars rocket via Raptor power
Post by: Occupymars on 05/01/2014 11:20 pm
I admire what SpaceX has accomplished and their future goals.  However, I remain optimistically skeptic about the finances of the company until they are getting a paying payload into orbit more often.  They need to start making some $$$ off of the costs they have invested to date.

SpaceX don't need to show a profit. The main shareholder is happy with breaking even.  ;)
Yeah and if the company is growing very fast then profit's aren't really a big deal I mean if Spacex were to go public how much would it be worth now? At least a couple of billion and probably a few more with the impact Elon has on share prices.
Also if they only get the three cargo launches off this year then they may well be in the "red".
The average salary of an engineer in California is 92000$, so if you round that off to 100000$ and times that by the number of employee's you get 100000$X3000= 300 million. Three cargo launches a year for 400 million may put them in the red and nearly all the commercial launches after that could be pure gravy.
Title: Re: SpaceX advances drive for Mars rocket via Raptor power
Post by: CJ on 05/02/2014 12:12 am
Yeah and if the company is growing very fast then profit's aren't really a big deal I mean if Spacex were to go public how much would it be worth now? At least a couple of billion and probably a few more with the impact Elon has on share prices.
Also if they only get the three cargo launches off this year then they may well be in the "red".
The average salary of an engineer in California is 92000$, so if you round that off to 100000$ and times that by the number of employee's you get 100000$X3000= 300 million. Three cargo launches a year for 400 million may put them in the red and nearly all the commercial launches after that could be pure gravy.

Reading the above, I think it's possible that you typed "red" when you meant "black". ("In the red" means running at a loss, IE, red ink.)  :)

As for companies running at a loss, I recall Amazon running at a loss year after year. It was a long time before they showed a profit. Same for a lot of other startups. But, if you've got the backing and can arrange it so borrowing costs don't eat you alive, it can be done - hang in until the profits start. One way, and indeed the easiest way, to do that is to have an owner with deep pockets. My guess; SpaceX's payroll isn't as high as you estimate, due to not everyone there being engineers. I'll further guess that four launches a year would be past the breakeven point.

But, fiscal issues are very real, and this gets me back to Raptor. I'm very perplexed by reports that someone (Can't recall whom) at SpaceX's claimed it would be only for Mars launches. That really makes no sense to me. "Primarily" I could accept, but not "only". It just makes no fiscal sense; why wouldn't they accept business for it? Sure, it's huge, but it'd be ideal for launching high-mass payloads, such as, say, a space station, or a really large Geo communications platform that just isn't feasible to launch today (for example, one requiring a lot of power and thus large solar arrays, such as to do direct broadcast). At the very least, they could defray the development cost with some commercial launches, and commercial launches with it would be viable even if using only some of its capacity; at the cost per pound to orbit they'd have to have to make this viable for Mars, it'd by default also have some commercial utility. 

I may be wrong, as well as swimming against the tide, but it seems to me that the best way to make Mars missions cheaper is to mitigate your costs by making money where you can - the way airlines do by letting their slack capacity be used for air cargo, for example.

On the other hand, SpaceX may have something else in mind; they have surely thought this through, and of course they know far more about their plans than I ever could.
 
Title: Re: SpaceX advances drive for Mars rocket via Raptor power
Post by: Zed_Noir on 05/02/2014 12:29 am
I admire what SpaceX has accomplished and their future goals.  However, I remain optimistically skeptic about the finances of the company until they are getting a paying payload into orbit more often.  They need to start making some $$$ off of the costs they have invested to date.

SpaceX don't need to show a profit. The main shareholder is happy with breaking even.  ;)

Not true. Elon wants SpaceX to achieve things that it currently doesn't have the funding to achieve. The best way to do that is to grow the treasure chest.

Re-investing for company growth and not making a profit for ROI is what I meant.
Title: Re: SpaceX advances drive for Mars rocket via Raptor power
Post by: wannamoonbase on 05/02/2014 12:43 am
I admire what SpaceX has accomplished and their future goals.  However, I remain optimistically skeptic about the finances of the company until they are getting a paying payload into orbit more often.  They need to start making some $$$ off of the costs they have invested to date.

SpaceX don't need to show a profit. The main shareholder is happy with breaking even.  ;)
Yeah and if the company is growing very fast then profit's aren't really a big deal I mean if Spacex were to go public how much would it be worth now? At least a couple of billion and probably a few more with the impact Elon has on share prices.
Also if they only get the three cargo launches off this year then they may well be in the "red".
The average salary of an engineer in California is 92000$, so if you round that off to 100000$ and times that by the number of employee's you get 100000$X3000= 300 million. Three cargo launches a year for 400 million may put them in the red and nearly all the commercial launches after that could be pure gravy.

Firstly: The burdened cost of an employee far exceeds salary itself.  Health, bennies, stock options, payroll taxes, office overhead.

Second, plant equipment, parts and materials. 

There are a lot of costs in running any business beyond employees. 

Like I said, SpaceX has done great things! but they need revenue to pay thier way.  And yes profit matters.  Even if Elon and other investors are happy to reinvest 100% of profits! the more profit you make the quicker you can get to building the BFR. 

Compounding this is the size of the global launch market.  If SpaceX can capture 100% of the current global market at thier market price how much is that in billions?  Especially as their goal is to lower costs. 

In short profit matters, you can't just engineer away forever without limits.
Title: Re: SpaceX advances drive for Mars rocket via Raptor power
Post by: Vultur on 05/02/2014 05:57 am
I'm very perplexed by reports that someone (Can't recall whom) at SpaceX's claimed it would be only for Mars launches. That really makes no sense to me. "Primarily" I could accept, but not "only". It just makes no fiscal sense; why wouldn't they accept business for it?

I believe someone else suggested on this forum that what that really means is that they're designing it for Mars only (not taking other possible uses into account in the design process, staying focused on Mars) not necessarily that they'd never sell launches of the rocket for any other purpose.

Quote
Sure, it's huge, but it'd be ideal for launching high-mass payloads, such as, say, a space station, or a really large Geo communications platform that just isn't feasible to launch today (for example, one requiring a lot of power and thus large solar arrays, such as to do direct broadcast).

Maybe space-based solar power, too, if reusability can lower costs enough.
Title: Re: SpaceX advances drive for Mars rocket via Raptor power
Post by: CuddlyRocket on 05/02/2014 05:58 am
I'm very perplexed by reports that someone (Can't recall whom) at SpaceX's claimed [Raptor] would be only for Mars launches. That really makes no sense to me. "Primarily" I could accept, but not "only". It just makes no fiscal sense; why wouldn't they accept business for it?

I think they mean by this that the design is governed purely by its envisaged use for Mars launches. No tweaking is taking place because of considerations of wider use. No making it slightly less optimum for Mars launches because that would open up a wider market.

Once they've designed and built the thing, then if someone else wants to buy one for other uses, why not?
Title: Re: SpaceX advances drive for Mars rocket via Raptor power
Post by: MP99 on 05/02/2014 10:50 am
But, fiscal issues are very real, and this gets me back to Raptor. I'm very perplexed by reports that someone (Can't recall whom) at SpaceX's claimed it would be only for Mars launches.

Shotwell, Space Show interview.

Cheers, Martin
Title: Re: SpaceX advances drive for Mars rocket via Raptor power
Post by: su27k on 05/02/2014 01:32 pm
But, fiscal issues are very real, and this gets me back to Raptor. I'm very perplexed by reports that someone (Can't recall whom) at SpaceX's claimed it would be only for Mars launches.

Shotwell, Space Show interview.

Cheers, Martin

She could be trying very hard to avoid the impression that Raptor/MCT is a competitor to SLS.
Title: Re: SpaceX advances drive for Mars rocket via Raptor power
Post by: CJ on 05/02/2014 08:52 pm
I'm very perplexed by reports that someone (Can't recall whom) at SpaceX's claimed it would be only for Mars launches. That really makes no sense to me. "Primarily" I could accept, but not "only". It just makes no fiscal sense; why wouldn't they accept business for it?

I believe someone else suggested on this forum that what that really means is that they're designing it for Mars only (not taking other possible uses into account in the design process, staying focused on Mars) not necessarily that they'd never sell launches of the rocket for any other purpose.

Quote
Sure, it's huge, but it'd be ideal for launching high-mass payloads, such as, say, a space station, or a really large Geo communications platform that just isn't feasible to launch today (for example, one requiring a lot of power and thus large solar arrays, such as to do direct broadcast).

Maybe space-based solar power, too, if reusability can lower costs enough.

Hrmmm. Designing it so it's optimized for Mars does fit... and it actually wouldn't necessarily harm their LEO and GEO prospects.
The example that comes to mind is the F-15 fighter. The design philosophy was "not one pound for air to ground", because they wanted it to be the best air-to-air fighter it could be. But... in spite of that design philosophy (or perhaps because of it) we now have the F-15 E, which is superb in both air-to-air and air-to-ground roles.

A solar power sat would be interesting, though I'm a bit skeptical; the radiation environment is such that you'd need gallium-arsenide cells, which are very expensive. My personal hunch is that with current tech, a case can't be made for a solar power sat to beam power to earth cheaper than generating it here. But... it might be very viable to build one to supply power to other satellites in Geo, as the cost dynamics are a lot different. There are all sorts of possibilities in GEO, or in other orbits, that low cost-per-pound would open up.

The reported thrust of Raptor (apparently over a million foot-pounds!!) is astounding. That's getting close to the Saturn 5's F-1, at 1.5 million - and the S5 first stage used 5 of them. Assuming current interpretations are correct, the Raptor-powered first stage will use 9, so considerably more thrust (and thus higher gross takeoff mass) than S5. Also, the F-1 wasn't great on ISP at 264. That's big, very big. And if they do a heavy version, 3 cores... I think they'll need to measure the launches on the Richter scale. :)

And @Martin, thanks for the source (Shotwell comments). Interesting... but as for SpaceX official comments regarding future plans, the more I think about it, the more I'm inclined to take them with a grain of salt. The reason is that, as with most any complex endeavor, things can change. I'm not suggesting they are lying, only that if things look like they should be done differently when the times comes, SpaceX is quite capable of disregarding past statements and adapting. And that IMHO is a good thing. (An example... they originally went with insulating the first stage to survive entry, but that didn't work, so they changed plans and did something else.)   

One thing I'd like to ask, and hope someone knows; has the possibility of a direct-ascent launch profile been discussed on the forums anywhere (Either for GEO or for earth-escape) in context of Raptor and the BFR? I know that, in contrast to going to LEO first, you get more gravity losses, but... how do the numbers work out for direct ascent when factoring in reusability (are the fuel costs less than for boostback? Direct ascent negates to downrange velocity issue, and that's a Delta/v savings.). I'm chagrined to admit that I can't figure out how to calculate the fuel needs (and thus payload impact) of grav losses for direct ascent profile vs. boostback from a LEO ascent profile.   
 
 

 
Title: Re: SpaceX advances drive for Mars rocket via Raptor power
Post by: CuddlyRocket on 05/03/2014 07:36 am
[Gwynne Shotwell] could be trying very hard to avoid the impression that Raptor/MCT is a competitor to SLS.

You might very well be right there! If so, it's a stance they'll maintain until they've built their BFR; then they'll be arguing to be allowed to compete for the payloads!

Maybe space-based solar power, too, if reusability can lower costs enough.

A solar power sat would be interesting, though I'm a bit skeptical; the radiation environment is such that you'd need gallium-arsenide cells, which are very expensive. My personal hunch is that with current tech, a case can't be made for a solar power sat to beam power to earth cheaper than generating it here.

Your hunch is spot on. You get more Earth-based, even 24-hr, electricity with Earth-based photovoltaics than orbital, and at much less risk and money up-front! The relative difference has even been increasing for some time; but as far as I know, no-one's done a study with reusability taken into account.

Quote
One thing I'd like to ask, and hope someone knows; has the possibility of a direct-ascent launch profile been discussed on the forums anywhere (Either for GEO or for earth-escape) in context of Raptor and the BFR? I know that, in contrast to going to LEO first, you get more gravity losses, but... how do the numbers work out for direct ascent when factoring in reusability (are the fuel costs less than for boostback? Direct ascent negates to downrange velocity issue, and that's a Delta/v savings.). I'm chagrined to admit that I can't figure out how to calculate the fuel needs (and thus payload impact) of grav losses for direct ascent profile vs. boostback from a LEO ascent profile. 

Yep. Check the early pages of the MCT speculation thread or in the Missions to Mars (HSF) sub-forum. As far as I can recall, direct launch requires less delta-v; the purpose of going to LEO first is to refuel, thereby allowing more payload with smaller launchers. But I'm not an expert either!
Title: Re: SpaceX advances drive for Mars rocket via Raptor power
Post by: MP99 on 05/03/2014 10:16 am
And @Martin, thanks for the source (Shotwell comments). Interesting... but as for SpaceX official comments regarding future plans, the more I think about it, the more I'm inclined to take them with a grain of salt. The reason is that, as with most any complex endeavor, things can change. I'm not suggesting they are lying, only that if things look like they should be done differently when the times comes, SpaceX is quite capable of disregarding past statements and adapting. And that IMHO is a good thing. (An example... they originally went with insulating the first stage to survive entry, but that didn't work, so they changed plans and did something else.)   

NP.

And agree with that 100%.

Cheers, Martin
Title: Re: SpaceX advances drive for Mars rocket via Raptor power
Post by: Mongo62 on 05/03/2014 11:46 am
Maybe space-based solar power, too, if reusability can lower costs enough.

A solar power sat would be interesting, though I'm a bit skeptical; the radiation environment is such that you'd need gallium-arsenide cells, which are very expensive. My personal hunch is that with current tech, a case can't be made for a solar power sat to beam power to earth cheaper than generating it here.

Your hunch is spot on. You get more Earth-based, even 24-hr, electricity with Earth-based photovoltaics than orbital, and at much less risk and money up-front! The relative difference has even been increasing for some time; but as far as I know, no-one's done a study with reusability taken into account.

I would think that solar thermal power generation, perhaps using a Sterling cycle, would be more mass-effective than photovoltaic, mainly because the concentration mirrors could be made nearly arbitrarily thin. And since there would be no solar cells to degrade, the radiation environment would be far less of an issue.

This might be considered OT, but if SpaceX succeeds with their cost-to-orbit goals, I would not be surprised if space-based solar thermal electricity generation suddenly becomes financially competitive -- and a lot more carbon-friendly. So it's not really OT in my opinion, since space-based power generation could provide a major increase in demand for BFR-sized launch services, in addition to Mars colonization.
Title: Re: SpaceX advances drive for Mars rocket via Raptor power
Post by: docmordrid on 05/03/2014 12:02 pm
JAXA recently unveiled their roadmap to a 1GW solar power satellote system. Long IEEE Spectrum writeup

http://spectrum.ieee.org/green-tech/solar/how-japan-plans-to-build-an-orbital-solar-farm
Title: Re: SpaceX advances drive for Mars rocket via Raptor power
Post by: rst on 05/03/2014 01:38 pm
This might be considered OT, but if SpaceX succeeds with their cost-to-orbit goals, I would not be surprised if space-based solar thermal electricity generation suddenly becomes financially competitive -- and a lot more carbon-friendly. So it's not really OT in my opinion, since space-based power generation could provide a major increase in demand for BFR-sized launch services, in addition to Mars colonization.

Just as a reminder:  Elon hates solar power satellites.  I'm not sure he hates them enough to turn down money from someone else who has funding for them, but, well ... here's one public statement:

Quote
While Musk loves electric cars and spaceflight, there’s one thing he hates: space solar power. "You’d have to convert photon to electron to photon back to electron. What’s the conversion rate?" he says, getting riled up for the first time during his talk. "Stab that bloody thing in the heart!"

This particular objection doesn't have much to do with your Stirling-cycle idea, and even on its own, it doesn't quite stand without further elaboration.  (The photon-to-electron-to-photon conversion in the powersats effectively shifts their frequency to a wavelength where the atmosphere aborbs less; you've got to figure that into the aggregate system efficiency as well.)  But he's certainly not brimming with enthusiasm.

http://www.popularmechanics.com/how-to/blog/elon-musk-on-spacex-tesla-and-why-space-solar-power-must-die-13386162
Title: Re: SpaceX advances drive for Mars rocket via Raptor power
Post by: ncb1397 on 05/03/2014 02:19 pm
We already get plenty of space based solar power beamed to earth on a regular basis. No need to reinvent the sun.
Title: Re: SpaceX advances drive for Mars rocket via Raptor power
Post by: AncientU on 05/03/2014 02:46 pm
[Gwynne Shotwell] could be trying very hard to avoid the impression that Raptor/MCT is a competitor to SLS.

You might very well be right there! If so, it's a stance they'll maintain until they've built their BFR; then they'll be arguing to be allowed to compete for the payloads!

I think they'll simply sell a couple BFR flights per year to NASA so that NASA can actually afford to build some payloads and maybe --- wait for it --- explore.  The cost advantage of their BFR over SLS will make the EELV advantage look modest.
Title: Re: SpaceX advances drive for Mars rocket via Raptor power
Post by: Mongo62 on 05/03/2014 03:40 pm
We already get plenty of space based solar power beamed to earth on a regular basis. No need to reinvent the sun.

You mean, other than the fact that Earth based direct solar power is:

1. only available for half the day
2. available for less than that when allowing for cloud cover
3. available at much lower solar power density than in space, around 50% at best (high noon with the Sun directly overhead) dropping to near zero when the Sun is near the horizon
4. with photovoltaic elements subject to weather-related degradation over time (space photovoltaic also degrades over time due to radiation, but not space thermal)
5. with a limit in combined power density that is considerably lower than is theoretically possible with microwave transmission, hence requiring more surface area on Earth to acquire than a microwave rectenna with the same power output
Title: Re: SpaceX advances drive for Mars rocket via Raptor power
Post by: Chris Bergin on 05/03/2014 03:41 pm
That's all smashing stuff lads, but how's about we concentrate on Raptor? :)
Title: Re: SpaceX advances drive for Mars rocket via Raptor power
Post by: ImUtrecht on 05/10/2014 08:32 am
Chamberpressure of Raptor could be around 50 Mpa ?
Title: Re: SpaceX advances drive for Mars rocket via Raptor power
Post by: baldusi on 05/10/2014 01:50 pm

Chamberpressure of Raptor could be around 50 Mpa ?
My first calculation was 20.5MPa with an expansion ratio of 45:1. O/F 3.5.
Title: Re: SpaceX advances drive for Mars rocket via Raptor power
Post by: upjin on 05/11/2014 11:01 pm
This might be considered OT, but if SpaceX succeeds with their cost-to-orbit goals, I would not be surprised if space-based solar thermal electricity generation suddenly becomes financially competitive -- and a lot more carbon-friendly. So it's not really OT in my opinion, since space-based power generation could provide a major increase in demand for BFR-sized launch services, in addition to Mars colonization.

Just as a reminder:  Elon hates solar power satellites.  I'm not sure he hates them enough to turn down money from someone else who has funding for them, but, well ... here's one public statement:

Quote
While Musk loves electric cars and spaceflight, there’s one thing he hates: space solar power. "You’d have to convert photon to electron to photon back to electron. What’s the conversion rate?" he says, getting riled up for the first time during his talk. "Stab that bloody thing in the heart!"

This particular objection doesn't have much to do with your Stirling-cycle idea, and even on its own, it doesn't quite stand without further elaboration.  (The photon-to-electron-to-photon conversion in the powersats effectively shifts their frequency to a wavelength where the atmosphere aborbs less; you've got to figure that into the aggregate system efficiency as well.)  But he's certainly not brimming with enthusiasm.

http://www.popularmechanics.com/how-to/blog/elon-musk-on-spacex-tesla-and-why-space-solar-power-must-die-13386162

Excellent point.  Elon, for a Mars colony, will be looking for the best sources to get power and sustain growth.

It's not just a question of getting to Mars.  He wants to stay there.
Title: Re: SpaceX advances drive for Mars rocket via Raptor power
Post by: ImUtrecht on 05/13/2014 09:47 pm

Chamberpressure of Raptor could be around 50 Mpa ?
My first calculation was 20.5MPa with an expansion ratio of 45:1. O/F 3.5.

But that would be lower than the RD-180 that has 26.17MPa.
I thought that with full flow staged combustion higher pressures were possibele.
The expansion rate is higher then RD-180
I think they will use hydrostatic bearings for reusability and higher pressures.
Soon we will know more and i am quite curious to find out.
Thanks for your input Baldusi.

Question: first calculation for how much thrust? One million or 1,6 million lbf ?

Title: Re: SpaceX advances drive for Mars rocket via Raptor power
Post by: baldusi on 05/14/2014 03:13 am
The isp calculations weren't affected by the thrust level in the basic software I used. Regarding the chamber pressure, with full flow you can do high pressure or lower the turbine temperature. And 20.5MPa is nothing to sneeze at. SSME has that chamber pressure. The NK-33 has 14.5. And the amazing design for the RD-0164, 17.5MPa. So 20.5MPa would put it right up there with the big boys. The RL10 is just 4.5MPa.
Title: Re: SpaceX advances drive for Mars rocket via Raptor power
Post by: MP99 on 05/14/2014 08:30 am

Chamberpressure of Raptor could be around 50 Mpa ?
My first calculation was 20.5MPa with an expansion ratio of 45:1. O/F 3.5.

But that would be lower than the RD-180 that has 26.17MPa.
I thought that with full flow staged combustion higher pressures were possibele.
The expansion rate is higher then RD-180
I think they will use hydrostatic bearings for reusability and higher pressures.
Soon we will know more and i am quite curious to find out.
Thanks for your input Baldusi.

Question: first calculation for how much thrust? One million or 1,6 million lbf ?

BTW, there are no prizes for making difficult engineering challenges for yourself.

A lower chamber pressure should make the engine easier to design, and leave margins for multiple reuses. Remember the failure of M1C engine on one of the F9 v1.0 flights, and that will have been at lower pressure than this.

Cheers, Martin
Title: Re: SpaceX advances drive for Mars rocket via Raptor power
Post by: meekGee on 05/15/2014 05:55 am
A bit of evening kremlinology.

Does anyone remember which conferences SpaceX used to make significant reveals at, in the past?

To those not from the U.S.:

ISDC (http://isdc.nss.org/2014) is the more "enthusiastic" venue.  Anything from suborbital to Mars.
The Space Symposium (http://www.spacesymposium.org) is where the fat cats are.  100% what they call business.
Joint Propulsion Conference (http://www.aiaa.org/EventDetail.aspx?id=18582) is where the tech is.  Not just rockets.

All three conferences are in the very near future.

As far as I can tell Elon is skipping the Space Symposium (Can you imagine the dinner tables if he were there?), and has an engineer (Jeff Thornburg) make a Raptor reveal at ISDC.  EDIT: In addition to his talk, that is.

Message?
Title: Re: SpaceX advances drive for Mars rocket via Raptor power
Post by: Llian Rhydderch on 05/15/2014 06:02 am
A bit of evening kremlinology.

Does anyone remember which conferences SpaceX used to make significant reveals at, in the past?

To those not from the U.S.:

ISDC is the more "enthusiastic" venue.  Anything from suborbital to Mars.
The Space Symposium is where the fat cats are.  100% what they call business.
Joint Propulsion Conference is where the tech is.  Not just rockets.

As far as I can tell Elon is skipping the Space Symposium (Can you imagine the dinner tables if he were there?), and has an engineer (Jeff Thornburg) make a Raptor reveal at ISDC.

Message?

"First they ignore you, then they laugh at you, then they fight you, then you [ignore them]."

(I've slightly paraphrased Mahatma Gandhi's famous words to make them most applicable to Lars' question.)
Title: Re: SpaceX advances drive for Mars rocket via Raptor power
Post by: docmordrid on 05/15/2014 06:10 am
Message? Fat cat meetings are for if you want to sell them something. Is there any indication SpaceX wants to sell Raptors? BFR's?

ISTM that Musk sees himself, and SpaceX, as more akin to the newspace advocacy groups than the button down groups. He'll gravitate there and to press events where SpaceX is the focus.
Title: Re: SpaceX advances drive for Mars rocket via Raptor power
Post by: meekGee on 05/15/2014 06:18 am
It's not just that Musk is skipping the SS.  It's that in the entire agenda there are only two SpaceX appearances.

Shotwell vs. Gass on a panel (plus 4 other people nobody will care about), and something sponsored by SpaceX's VP for Government sales.   And SpaceX wants to sell them stuff.

Of course Musk is not the fat-cat type, and of course he has to talk at ISDC.  But a technical talk about the engine?  ISDC is not that kind of conference.


There's something about the mentality of a follower that wants to be "as good as the leader", and the mentality of a leader that just takes it for granted he's in front.  I think SpaceX outgrew the "I want to be a grown up" phase.

Never mind the award dinners - they'll sell their rockets even without trying to one-up Boeing in the size of the booth.

...

I'm trying to dig up past agendas to get a feel for a trend.  It's easier with ISDC than it is with SS.
Title: Re: SpaceX advances drive for Mars rocket via Raptor power
Post by: fregate on 05/20/2014 10:03 am
SpaceX advances drive for Mars rocket via Raptor power (http://www.nasaspaceflight.com/2014/03/spacex-advances-drive-mars-rocket-raptor-power/) article on NSF
Alejandro, a slightly off-topic note: black & white photo does not show Korolev and Glushko. It is a snapshot from a Soviet fiction movie "Taming of the Fire" (1972)  ;) It also has an amazing SOUNDTRACK
imdb link (http://www.imdb.com/title/tt0069434/)
wikipedia  (http://en.wikipedia.org/wiki/Taming_of_the_Fire)
Title: Re: SpaceX advances drive for Mars rocket via Raptor power
Post by: baldusi on 05/20/2014 01:52 pm
I thought that it was them young, I had heard about the movie but never seen it. But the one that put the pictures was Chris. I will PM him. Thanks fregate!
Title: Re: SpaceX advances drive for Mars rocket via Raptor power
Post by: Chris Bergin on 05/20/2014 01:59 pm
SpaceX advances drive for Mars rocket via Raptor power (http://www.nasaspaceflight.com/2014/03/spacex-advances-drive-mars-rocket-raptor-power/) article on NSF
Alejandro, a slightly off-topic note: black & white photo does not show Korolev and Glushko. It is a snapshot from a Soviet fiction movie "Taming of the Fire" (1972)  ;) It also has an amazing SOUNDTRACK
imdb link (http://www.imdb.com/title/tt0069434/)
wikipedia  (http://en.wikipedia.org/wiki/Taming_of_the_Fire)

Oh that's my fault. I add the images and links in all articles.

Shame, as it's a great photo! ;D

I'll remove it, but if anyone has a good image that would be a good replacement, please add it to the thread and Pm me.... :)
Title: Re: SpaceX advances drive for Mars rocket via Raptor power
Post by: pospa on 05/20/2014 06:43 pm
I'll remove it, but if anyone has a good image that would be a good replacement, please add it to the thread and Pm me.... :)

Not the best quality picture, but this is one of very small number I found where both Valentin Glushko (second from left) and Sergey Korolyev (third from left) are visible together.

(http://vivovoco.astronet.ru/VV/JOURNAL/NATURE/09_05/KOR-4.JPG)

For more pics of them google : Сергей Павлович Королев and Валентин Глушко
Title: Re: SpaceX advances drive for Mars rocket via Raptor power
Post by: llanitedave on 05/21/2014 01:35 am
Not a happy looking group!
Title: Re: SpaceX advances drive for Mars rocket via Raptor power
Post by: Llian Rhydderch on 05/21/2014 04:46 am
Not a happy looking group!

They're not unhappy, they're Russian.   ;)
Title: Re: SpaceX advances drive for Mars rocket via Raptor power
Post by: pospa on 05/21/2014 06:59 am
Not a happy looking group!
They're not unhappy, they're Russian.   ;)

Also picture taken in the coldest time of the Cold War. :)

But seriously as you might know there was a lot of competition and nagative relationships between soviet design bureaus during the Moon Race. There was no "Russian NASA" or Roscosmos as today which would ensure the unity and clear giudeline for the R&D institutes and space manufacturers. Which was one of the reasons why Russinans failed at that time.
That's why those men on the picture do not look very happy - they were mostly competitors, not friends.

See http://en.wikipedia.org/wiki/Soviet_space_program#Internal_competition
Title: Re: SpaceX advances drive for Mars rocket via Raptor power
Post by: Ben the Space Brit on 05/21/2014 11:12 am
Regarding Raptor, should we consider Raptor-VAC to be the main engine for MCT or just the MPS for a dual-mode upper stage on a BFR? Everything I've seen so far seems to suggest that the BFR's upper stage and payload will be integrated but I can't see how a chemical engine, any chemical engine, could do the Mars transit in 90 days as Musk advocates. IMHO, the MCT needs its own high-impulse/thrust engine (possibly nuclear-electric or LCH4-burning nuclear-plasma, ) and the Raptor will just be the propulsion of the launch vehicle for ETO or any cis-lunar missions for which SpaceX gets a contract.

Not a happy looking group!

I'm genuinely surprised that they convinced Glushko and Korolev to sit together! The two of them despised each other on such a profound level that they couldn't even be allowed into the same room together without an argument breaking out!
Title: Re: SpaceX advances drive for Mars rocket via Raptor power
Post by: Sohl on 05/21/2014 05:19 pm
Not the best quality picture, but this is one of very small number I found where both Valentin Glushko (second from left) and Sergey Korolyev (third from left) are visible together.
For more pics of them google : Сергей Павлович Королев and Валентин Глушко

Not saying it is, but this this photo sure looks "photoshopped" or the old-time equivalent.  Head positions and focus of the faces compared to bodies seems a bit off, at least on a few of these gentlemen   ???
Title: Re: SpaceX advances drive for Mars rocket via Raptor power
Post by: Proponent on 05/21/2014 08:42 pm
SpaceX advances drive for Mars rocket via Raptor power (http://www.nasaspaceflight.com/2014/03/spacex-advances-drive-mars-rocket-raptor-power/) article on NSF
Alejandro, a slightly off-topic note: black & white photo does not show Korolev and Glushko. It is a snapshot from a Soviet fiction movie "Taming of the Fire" (1972)  ;) It also has an amazing SOUNDTRACK
imdb link (http://www.imdb.com/title/tt0069434/)
wikipedia  (http://en.wikipedia.org/wiki/Taming_of_the_Fire)

This is OT, but the movie is available on YouTube (see this post (http://forum.nasaspaceflight.com/index.php?topic=32617.msg1084829#msg1084829)).
Title: Re: SpaceX advances drive for Mars rocket via Raptor power
Post by: aero on 07/06/2014 05:56 am
SpaceX had their ribbon cutting back in April, 3 months ago now. They indicated they would be testing a single injector first.

Do we have any more news?
Title: Re: SpaceX advances drive for Mars rocket via Raptor power
Post by: baldusi on 07/06/2014 01:11 pm
After the legal actions, Raptor's designer suspended all presentations. My guess is that we won't see any news nor press release for a while.
Title: Re: SpaceX advances drive for Mars rocket via Raptor power
Post by: docmordrid on 07/06/2014 04:54 pm
Mueller gave a presentation to the late May propulsion conference in Cologne, Germany, the only account of which I've seen was an article in the June 9  Aviation Week about AR1 and Raptor.

Downside: it's behind a paywall.

Updated Raptor specs, but I won't repeat them due to said paywall. Little info about the progress at Stennis that isn't public though.

Title: Re: SpaceX advances drive for Mars rocket via Raptor power
Post by: king1999 on 07/06/2014 05:00 pm
After the legal actions, Raptor's designer suspended all presentations. My guess is that we won't see any news nor press release for a while.
What legal actions?
Title: Re: SpaceX advances drive for Mars rocket via Raptor power
Post by: docmordrid on 07/06/2014 05:06 pm
The USAF lawsuit.

IMO, they don't want the SLS crowd getting their feathers ruffled while the USAF suit is going on too.
Title: Re: SpaceX advances drive for Mars rocket via Raptor power
Post by: edkyle99 on 07/06/2014 05:53 pm
IMO, they don't want the SLS crowd getting their feathers ruffled while the USAF suit is going on too.
What does Space Launch System have to do with any of this?

 - Ed Kyle
Title: Re: SpaceX advances drive for Mars rocket via Raptor power
Post by: Mongo62 on 07/06/2014 06:32 pm
What does Space Launch System have to do with any of this?
Presumably, the BFR implied by the currently projected performance numbers for Raptor would put it into direct competition with SLS. In fact, it would massively outperform SLS, at what is assumed would be a much lower cost per kg to LEO, especially if reusability is considered. Spacex might not wish to draw attention to this embarrassing (to Congress) potential issue by publicly disclosing the Raptor numbers at this time.
Title: Re: SpaceX advances drive for Mars rocket via Raptor power
Post by: docmordrid on 07/06/2014 06:38 pm
IMO, they don't want the SLS crowd getting their feathers ruffled while the USAF suit is going on too.
What does Space Launch System have to do with any of this?

 - Ed Kyle
They're already in conflict with the USAF (block buy) and Shelby (CC). Putting too much info abput a potential SLS competitor in the public domain could start a third conflict. 

Ask Germany about 3 front wars.

As it is now BFR doesn't seem "real" to most of those congresscritters not following it closely. No need to change that by giving Shelby more to be paranoid over.
Title: Re: SpaceX advances drive for Mars rocket via Raptor power
Post by: sublimemarsupial on 07/06/2014 06:38 pm
What does Space Launch System have to do with any of this?
Presumably, the BFR implied by the currently projected performance numbers for Raptor would put it into direct competition with SLS. In fact, it would massively outperform SLS, at what is assumed would be a much lower cost per kg to LEO, especially if reusability is considered. Spacex might not wish to draw attention to this embarrassing (to Congress) potential issue by publicly disclosing the Raptor numbers at this time.

I think the rollback in public exposure for Raptor is more due to the recent RD-180 turmoil than anything else. If there is a competition for a new American hydrocrabon boost engine, I'm sure SpaceX would at least consider submitting Raptor or a Raptor derivative engine in order to get funding for development instead of having to foot the bill themselves. Anything they put out publicly gives their competition an advantage. SLS may be a tiny secondary concern, but I can't see it being the driving factor in keeping Raptor private.
Title: Re: SpaceX advances drive for Mars rocket via Raptor power
Post by: docmordrid on 07/06/2014 06:41 pm
What does Space Launch System have to do with any of this?
Presumably, the BFR implied by the currently projected performance numbers for Raptor would put it into direct competition with SLS. In fact, it would massively outperform SLS, at what is assumed would be a much lower cost per kg to LEO, especially if reusability is considered. Spacex might not wish to draw attention to this embarrassing (to Congress) potential issue by publicly disclosing the Raptor numbers at this time.

I think the rollback in public exposure for Raptor is more due to the recent RD-180 turmoil than anything else. If there is a competition for a new American hydrocrabon boost engine, I'm sure SpaceX would at least consider submitting Raptor or a Raptor derivative engine in order to get funding for development instead of having to foot the bill themselves. Anything they put out publicly gives their competition an advantage. SLS may be a tiny secondary concern, but I can't see it being the driving factor in keeping Raptor private.

That too, meaning the engine competition. But I'd still be wary of it being a  4th front. 
Title: Re: SpaceX advances drive for Mars rocket via Raptor power
Post by: Burninate on 07/06/2014 10:09 pm
Mueller gave a presentation to the late May propulsion conference in Cologne, Germany, the only account of which I've seen was an article in the June 9  Aviation Week about AR1 and Raptor.

Downside: it's behind a paywall.

Updated Raptor specs, but I won't repeat them due to said paywall. Little info about the progress at Stennis that isn't public though.

A paywall is not designed to stifle discussion and bury numeric facts, excerpts should be acceptable.

Quote
SpaceX is developing the Raptor as a reusable engine for a heavy-lift Mars vehicle, the first stage of which will feature 705 metric tons of thrust, making it "slightly larger than the Apollo F-1 engine," Tom Mueller, SpaceX vice president of propulsion development, said during a space propulsion conference last month in Cologne, Germany.  The vacuum version is targetting 840 metric tons of thrust with 380 sec. of specific impulse.  The company is testing subscale components using the E-2 test stand at NASA's Stennis Space Center in Missisippi, says Stennis spokeswoman Rebecca Strecker.

Quote
Mueller said many people ask why the company switched to methane for its Mars rocket.  With reusability in mind, SpaceX's cost studies revealed that "by far the most cost-effective propellant to use is methane," he said, which would be easier than hydrogen to manufacture on Mars.
- "AR1 vs. Raptor: New rocket program will likely pit kerosene against methane".  Amy Butler & Amy Svitak, Aviation Week & Space Technology, Juny 9 2014. p33

705mtf implies that used on the BFR, this will create a 14Mlbf / 62.7MN first stage using 9 engines.

edit:Thanks baldusi
Title: Re: SpaceX advances drive for Mars rocket via Raptor power
Post by: baldusi on 07/06/2014 11:39 pm

705mtf is a 14Mlbf / 6.27MN first stage at 9 cores.
62MN
Title: Re: SpaceX advances drive for Mars rocket via Raptor power
Post by: Vultur on 07/07/2014 01:33 am
I think the 705 metric tons is a single engine not a stage. metric ton = 2204 pounds so about 1,550,000 pounds thrust. That has to be a single engine otherwise it wouldn't be "slightly larger than the Apollo F-1 engine", it would be way smaller.

Of course metric tons aren't really a unit of thrust/force...
Title: Re: SpaceX advances drive for Mars rocket via Raptor power
Post by: aero on 07/07/2014 02:59 am
I think the 705 metric tons is a single engine not a stage. metric ton = 2204 pounds so about 1,550,000 pounds thrust. That has to be a single engine otherwise it wouldn't be "slightly larger than the Apollo F-1 engine", it would be way smaller.

Of course metric tons aren't really a unit of thrust/force...

Yea, something is fishy. Last winter when Mueller talked about the Raptor, he gave 4,500 kN as the engine thrust. Then I thought I read here somewhere, someone attributing a 6,500 kN comment to Elon.

And they already have the Falcon 9 advertised with sea level thrust of 5,885kN (5.885 MN) or 1,323,000 lbf. That is 600 metric tonnes force. So at 705 metric tonnes force for the core, the engine is not "slightly larger than an F-1" but instead, "slightly larger than a Merlin 1 D."

Something is fishy. Maybe it's aviation leak?
Title: Re: SpaceX advances drive for Mars rocket via Raptor power
Post by: Mongo62 on 07/07/2014 03:11 am
705 metric tons SL thrust is per engine. Elon Musk has said that the first stage would develop about 15 million pounds of thrust. 705 metric tons times 9 is almost exactly 14 million pounds, which is reasonably close to Elon's 15 million pounds.
Title: Re: SpaceX advances drive for Mars rocket via Raptor power
Post by: Roy_H on 07/07/2014 05:40 am
Every once  in a while someone suggests that SpaceX should propose the Raptor as a replacement for ULA's RD-180 engines for the Atlas 5.There is no point. The primary reason to develop a replacement engine, is to have a US version, AND have diversity of choice. The government does not want to be dependent on any one design and certainly not any one source. That's why they supported both Boeing and Lockheed. Boeing doesn't appear to be promoting their Delta series, as most government flights are with Atlas. If Boeing decided to get out of the launch rocket business, then there would be only Lockheed and SpaceX to provide different competing designs.

I would think that methane/oxygen would be significantly easier to store in space (for fuel depot or extended trips) than hydrogen/oxygen. Liquid H2 must be kept at a much lower temperature than LOX and best kept physically separated for long storage. OTOH liquid CH4/O2 can be kept at the same temperature and have two tanks with common bulkhead.
Title: Re: SpaceX advances drive for Mars rocket via Raptor power
Post by: MP99 on 07/07/2014 07:08 am


And they already have the Falcon 9 advertised with sea level thrust of 5,885kN (5.885 MN) or 1,323,000 lbf. That is 600 metric tonnes force. So at 705 metric tonnes force for the core, the engine is not "slightly larger than an F-1" but instead, "slightly larger than a Merlin 1 D."

I think you meant" slightly larger than *nine* Merlin 1 Ds".

Cheers, Martin
Title: Re: SpaceX advances drive for Mars rocket via Raptor power
Post by: Nathan2go on 07/07/2014 07:53 am
...I would think that methane/oxygen would be significantly easier to store in space...
This strikes me as the most important issue.

It is seldom discussed, but the launch windows for flights to Mars only occur every two years.  Building a special rocket (with related infrastructure) which only launches once or twice every two years will be impractical, no matter what that rocket is.

So when the rocket is re-usable, each Mars mission should be broken down into multiple smaller launches, which will sit in Earth orbit (for many months) until the departure window opens.  As Roy says, H2 is terrible for long term storage of an Earth-departure-stage, even kerosene/oxygen has the problem of kerosene freezing at LOx temperatures, but methane/oxygen seems ok, and will be much cheaper than the hypergolic Super Draco fuel (used in the Dragon capsule).

The other trick to make a viable Mars rocket is to use a multi-core version of a rocket that is designed to serve the Earth orbit market.

As to the initial size of a Mars exploration rocket, I think it makes sense to size the basic core to match the largest Earth orbit payload that is anticipated to have a reasonable flight rate (double the F9's 5 ton to GTO?), and build the Mars program around a 3-core version of that.  Assuming the Falcon 9 loses 30-50% of its payload when it is made fully reusable, that suggests a Falcon X should have around 3x-4x the mass and thrust; so 25 tons to LEO for 1 core, 100 tons for 3 cores (Saturn V class).

The colonization idea is nice for long term, but I think exploration with smaller rockets must come first (likely with government funding).  So 3-4 Raptor engines, plus a center Merlin-derived engine for landing might be a better choice (the reusable upper stage could use a single Raptor plus 4 Super-Draco-derived landing engines); a smaller rocket would be built in a cheaper factory, etc.
Title: Re: SpaceX advances drive for Mars rocket via Raptor power
Post by: aero on 07/07/2014 05:07 pm


And they already have the Falcon 9 advertised with sea level thrust of 5,885kN (5.885 MN) or 1,323,000 lbf. That is 600 metric tonnes force. So at 705 metric tonnes force for the core, the engine is not "slightly larger than an F-1" but instead, "slightly larger than a Merlin 1 D."

I think you meant" slightly larger than *nine* Merlin 1 Ds".

Cheers, Martin

No. I meant what I wrote - poking fun at the Ave. Week quote.

But I agree with the consensus that the thrust of 705 metric tons is per engine, and slightly greater than "9 Merlin 1 Ds" or one Falcon 9. I wish we had some Isp numbers for the basic stage 1 engine though.
Title: Re: SpaceX advances drive for Mars rocket via Raptor power
Post by: Excession on 07/07/2014 07:44 pm
But I agree with the consensus that the thrust of 705 metric tons is per engine, and slightly greater than "9 Merlin 1 Ds" or one Falcon 9. I wish we had some Isp numbers for the basic stage 1 engine though.

Well, if the mass flow of the two versions is the same, then the difference in thrust would be caused by the difference in exhaust velocity. That implies a sea-level Isp of 380*(705/840)= ~319 seconds, which seems... implausibly low for a staged-combustion methane engine.
Title: Re: SpaceX advances drive for Mars rocket via Raptor power
Post by: aero on 07/07/2014 08:27 pm
But I agree with the consensus that the thrust of 705 metric tons is per engine, and slightly greater than "9 Merlin 1 Ds" or one Falcon 9. I wish we had some Isp numbers for the basic stage 1 engine though.

Well, if the mass flow of the two versions is the same, then the difference in thrust would be caused by the difference in exhaust velocity. That implies a sea-level Isp of 380*(705/840)= ~319 seconds, which seems... implausibly low for a staged-combustion methane engine.

Mass flow is probably the same, but the problem is the different nozzles on the engine for those two thrust values. The stage 1 nozzle gives sl thrust/sl Isp and vac thrust/vac Isp for the sl nozzle, while the vac nozzle gives vac thrust and vac Isp for the stage 2 nozzle. The vac nozzle doesn't have a sl Isp.
Title: Re: SpaceX advances drive for Mars rocket via Raptor power
Post by: DJPledger on 07/07/2014 08:44 pm
But I agree with the consensus that the thrust of 705 metric tons is per engine, and slightly greater than "9 Merlin 1 Ds" or one Falcon 9. I wish we had some Isp numbers for the basic stage 1 engine though.

Well, if the mass flow of the two versions is the same, then the difference in thrust would be caused by the difference in exhaust velocity. That implies a sea-level Isp of 380*(705/840)= ~319 seconds, which seems... implausibly low for a staged-combustion methane engine.
Calculated Raptor SL Isp indicates that the thrust figures are for the block 1 Raptor with a very conservative (for a FFSC LOx/LCH4 engine) Pc of around ~20MPa. Raptor will likely get a block 2 upgrade achieved mainly by increasing Pc a few years after the first one is launched. The block 2 Raptor may push north of 10MN thrust at SL with a significantly better SL Isp of likely around 330-335 seconds.

SpaceX appears to have dropped the tri-core BFR from their Mars plans so they will need the block 2 Raptor to deliver 100 metric tonnes to Mars in a single launch. Raptor thrust figures also indicate that they are going with a 15m dia. core so that 9 Raptors can fit under it without the need for engine fairings which would otherwise get in the way of the landing legs.
Title: Re: SpaceX advances drive for Mars rocket via Raptor power
Post by: jsgirald on 07/07/2014 08:54 pm

SpaceX appears to have dropped the tri-core BFR from their Mars plans so they will need the block 2 Raptor to deliver 100 metric tonnes to Mars in a single launch. Raptor thrust figures also indicate that they are going with a 15m dia. core so that 9 Raptors can fit under it without the need for engine fairings which would otherwise get in the way of the landing legs.

Is it possible to launch from Earth and land a ship the size of a shuttle orbiter in Mars in a single push? Without refuelling in LEO?

Regarding the landing gear, they might use nacelles a la Dragon v2 on their MCT. Thus, the ship might use the bottom not just to have a strong heatshield, it might even land on it with only minimal legs deployed from the sides like F9R (just to prevent toppling). This strong base might even double as a radiation shield, but I'm digressing ...  ;)
Title: Re: SpaceX advances drive for Mars rocket via Raptor power
Post by: docmordrid on 07/07/2014 08:56 pm
But I agree with the consensus that the thrust of 705 metric tons is per engine, and slightly greater than "9 Merlin 1 Ds" or one Falcon 9. I wish we had some Isp numbers for the basic stage 1 engine though.

Well, if the mass flow of the two versions is the same, then the difference in thrust would be caused by the difference in exhaust velocity. That implies a sea-level Isp of 380*(705/840)= ~319 seconds, which seems... implausibly low for a staged-combustion methane engine.
Calculated Raptor SL Isp indicates that the thrust figures are for the block 1 Raptor with a very conservative (for a FFSC LOx/LCH4 engine) Pc of around ~20MPa. Raptor will likely get a block 2 upgrade achieved mainly by increasing Pc a few years after the first one is launched. The block 2 Raptor may push north of 10MN thrust at SL with a significantly better SL Isp of likely around 330-335 seconds.

SpaceX appears to have dropped the tri-core BFR from their Mars plans so they will need the block 2 Raptor to deliver 100 metric tonnes to Mars in a single launch. Raptor thrust figures also indicate that they are going with a 15m dia. core so that 9 Raptors can fit under it without the need for engine fairings which would otherwise get in the way of the landing legs.
And if true, that explains the comment about making Saturn V look small. Even at the same height a 10.1m vs a 15m is visually like comparing Miguel Cotto vs Vladimir Klitschko.
Title: Re: SpaceX advances drive for Mars rocket via Raptor power
Post by: Llian Rhydderch on 07/07/2014 09:39 pm
...I would think that methane/oxygen would be significantly easier to store in space...
This strikes me as the most important issue.

It is seldom discussed, but the launch windows for flights to Mars only occur every two years.  Building a special rocket (with related infrastructure) which only launches once or twice every two years will be impractical, no matter what that rocket is.

So when the rocket is re-usable, each Mars mission should be broken down into multiple smaller launches, which will sit in Earth orbit (for many months) until the departure window opens.  As Roy says, H2 is terrible for long term storage of an Earth-departure-stage, even kerosene/oxygen has the problem of kerosene freezing at LOx temperatures, but methane/oxygen seems ok, and will be much cheaper than the hypergolic Super Draco fuel (used in the Dragon capsule).

The other trick to make a viable Mars rocket is to use a multi-core version of a rocket that is designed to serve the Earth orbit market.

As to the initial size of a Mars exploration rocket, I think it makes sense to size the basic core to match the largest Earth orbit payload that is anticipated to have a reasonable flight rate (double the F9's 5 ton to GTO?), and build the Mars program around a 3-core version of that.  Assuming the Falcon 9 loses 30-50% of its payload when it is made fully reusable, that suggests a Falcon X should have around 3x-4x the mass and thrust; so 25 tons to LEO for 1 core, 100 tons for 3 cores (Saturn V class).

The colonization idea is nice for long term, but I think exploration with smaller rockets must come first (likely with government funding).  So 3-4 Raptor engines, plus a center Merlin-derived engine for landing might be a better choice (the reusable upper stage could use a single Raptor plus 4 Super-Draco-derived landing engines); a smaller rocket would be built in a cheaper factory, etc.

Welcome to the forum, Nathan.  That was a thoughtful first post!

On your substantive suggestions, I'm with you on the value of more-launches-that-are-less-constrained-by-Mars-synode-departure-windows while storing the LOX/Methane in on-orbit depots for later (less constrained by weather, range availability, overflights, ship traffic, launch site availability, etc.) Earth-orbit departure windows.  Folks on this forum have pointed out before that Musk has never said anything about propellant depots.  True, not publically at least; but there have often been public "reveals" in recent years of things SpaceX has been working on privately for some time.  So I, for one, will not be surprised if they tell us at some future point that their Mars MCT mission architecture includes the use of propellant depots. 

I'm currently agnostic on the fewer engine and smaller engine methalox SpaceX rockets question.
Title: Re: SpaceX advances drive for Mars rocket via Raptor power
Post by: Llian Rhydderch on 07/07/2014 10:32 pm

SpaceX appears to have dropped the tri-core BFR from their Mars plans so they will need the block 2 Raptor to deliver 100 metric tonnes to Mars in a single launch. Raptor thrust figures also indicate that they are going with a 15m dia. core so that 9 Raptors can fit under it without the need for engine fairings which would otherwise get in the way of the landing legs.

I'm not sure where this info is coming from.  Do we have a source for it?

The original article by baldusi which founded this thread (http://www.nasaspaceflight.com/2014/03/spacex-advances-drive-mars-rocket-raptor-power/) indicated nine Raptor engines would be used on the MCT launch vehicle, on either one or three cores.

I'm personally agnostic, and don't really care which vehicle design SpaceX uses to solve the rocket equation for getting its large payloads to Mars.  But I would like to know if SpaceX has publically revealed any info on the MCT being only a single core, or if that might be the result of rocketeer speculations based on various bits of non-public knowledge. 
Title: Re: SpaceX advances drive for Mars rocket via Raptor power
Post by: baldusi on 07/08/2014 01:02 am
The AW article is newer information than the one that the article was based of. Regarding the rest of the post I won't comment due to L2 rules on information dissemination. I can only say that there's some amazing insight and renderings on possible evolution of the MCT project.
Title: Re: SpaceX advances drive for Mars rocket via Raptor power
Post by: Nathan2go on 07/08/2014 03:26 am
Welcome to the forum, Nathan.
Thanks.

... but there have often been public "reveals" in recent years of things SpaceX has been working on privately for some time.
Yes, speaking of reveals, the graphic of the SpaceX rocket family (which I assume comes from SpaceX) hints at a problem with the claim that F9 and F9h will be reusable.  The drawing of the Falcon X shows a second stage which is about half as big as the first stage.  This is consistent with the Kistler  K1 (http://www.astronautix.com/lvs/kislerk1.htm), in which the stages separate at only Mach 4, and the first stage flies back to the launch site, and the second stage flies to LEO (the stages use similar kerosene engines, 3 on the first and one on the second); it would have put a payload of 1.2% of its launch mass in orbit (compared to 2.6% for expendable F9). 

The problem is that the F9 and F9h have small upper stages, which implies a small payload, assuming the first stages must fly back to the launch site, as a low staging velocity is required.  I would assume this means the Falcon X single-core will be fully reusable, with the first stage returning to the launch site; and the F9 must have an at-sea booster recovery to have a commercially interesting payload.  The F9h could have the side boosters flyback, but the center core would be recovered at sea or expended.

The K1's 3:1 thrust ratio between the first and second stage also helps to explain why 4 or 5 core boosters are not part of the plan, and why even a 3-core booster for MCT is not shown (i.e. the center core could not fly back to the launch site, and its awkwardly shaped to return from orbit).
Title: Re: SpaceX advances drive for Mars rocket via Raptor power
Post by: manboy on 07/08/2014 06:17 am
Mueller gave a presentation to the late May propulsion conference in Cologne, Germany, the only account of which I've seen was an article in the June 9  Aviation Week about AR1 and Raptor.

Downside: it's behind a paywall.

Updated Raptor specs, but I won't repeat them due to said paywall. Little info about the progress at Stennis that isn't public though.

A paywall is not designed to stifle discussion and bury numeric facts, excerpts should be acceptable.

Quote
SpaceX is developing the Raptor as a reusable engine for a heavy-lift Mars vehicle, the first stage of which will feature 705 metric tons of thrust, making it "slightly larger than the Apollo F-1 engine," Tom Mueller, SpaceX vice president of propulsion development, said during a space propulsion conference last month in Cologne, Germany.  The vacuum version is targetting 840 metric tons of thrust with 380 sec. of specific impulse.  The company is testing subscale components using the E-2 test stand at NASA's Stennis Space Center in Missisippi, says Stennis spokeswoman Rebecca Strecker.

Quote
Mueller said many people ask why the company switched to methane for its Mars rocket.  With reusability in mind, SpaceX's cost studies revealed that "by far the most cost-effective propellant to use is methane," he said, which would be easier than hydrogen to manufacture on Mars.
- "AR1 vs. Raptor: New rocket program will likely pit kerosene against methane".  Amy Butler & Amy Svitak, Aviation Week & Space Technology, Juny 9 2014. p33

705mtf implies that used on the BFR, this will create a 14Mlbf / 62.7MN first stage using 9 engines.

edit:Thanks baldusi
ULA has now posted the article, I'm guessing there was a month-long exclusivity agreement.

Quote
Aerojet Rocketdyne, SpaceX Square Off For New Engine Work
Aviation Week & Space Technology    06/09/2014
Authors: Amy Butler and Amy Svitak

As unusually strong and swift legislative support for funding a new U.S. rocket engine program continues to gain momentum, the battle lines for designs are being drawn between the two likely bidders, Aerojet Rocket-dyne and SpaceX.

Aerojet Rocketdyne, sticking with liquid oxygen/kerosene fuel, is targeting a cost of $20-25 million per “ship set” of two new AR1 engines, says Scott Seymour, president and CEO of parent GenCorp. SpaceX is shifting toward methane and has not provided a price for its Raptor engine. Both companies say their designs will be efficient and low-cost.

Including legacy systems and risk-reduction projects, Aerojet Rocketdyne has spent roughly $300 million working on technologies that will feed into the AR1, Seymour tells Aviation Week. The effort to build a liquid oxygen/kerosene propulsion system would require about four years from contract award and cost $800 million to $1 billion. Each engine would produce 500,000 lb. of thrust to meet the ship set’s target of 1 million lb. of thrust. The units could be mated to scale performance, Seymour notes.

Such an engine is being considered for the United Launch Alliance’s (ULA) Atlas V as well as Orbital Science Corp.’s Antares and possibly SpaceX’s Falcon 9 v1.1.

The development price is roughly the same as the cost to establish U.S. coproduction of the RD-180 engine, which is manufactured in Russia and sold to the ULA for the Atlas V.

“We certainly believe [the AR1 will be] on a par with—if not better than—the performance of the RD-180. We also believe it is going to be more affordable,” Seymour says. “With each launch vehicle having its own engine, trying to get any kind of economic buy quantity has been a struggle for us. We really believe that with the AR1 approach, we have a multitude of applications for the engine.”

The Falcon 9v1.1 is powered by SpaceX’s own Merlin 1D engine, but Seymour says he hopes the AR1 is competitive enough in pricing to earn a place even on the Falcon. SpaceX President Gwynne Shotwell, however, does not seem optimistic about that prospect. “It would be very unusual for us to buy a critical piece of our strategy and our technology from somebody else,” she said last week.

The ULA would not release the per-unit cost of the RD-180 for the Atlas V.

The AR1 is intended to mate with multiple boosters, helping to increase the production volume. The intent is to bring “engines in the space industry more toward the model of aircraft engines. . . . The destination for those engines are any multitude of aircraft applications.”

Eventually, Seymour says this engine could be a foundation for NASA’s Space Launch System rocket that could launch spacecraft to Mars, though he did not give details on that development path.

Despite the tight fiscal environment in Washington, momentum for a new hydrocarbon engine has grown substantially in recent weeks due largely to lawmakers’ aversion to continue buying Russian-made engines in light of Russia’s annexation of Crimea and threats to cut off RD-180 supply.

SpaceX is developing the Raptor as a reusable engine for a heavy-lift Mars vehicle, the first stage of which will feature 705 metric tons of thrust, making it “slightly larger than the Apollo F-1 engine,” Tom Mueller, SpaceX vice president of propulsion development, said during a space propulsion conference last month in Cologne, Germany. The vacuum version is targeting 840 metric tons of thrust with 380 sec. of specific impulse. The company is testing subscale components using the E-2 test stand at NASA’s Stennis Space Center in Mississippi, says Stennis spokeswoman Rebecca Strecker.

Seymour says the AR1 could be reusable but provided no design details. Though the AR1 and Raptor offer notionally similar thrust, it is not possible to compare their specific impulse performance; Seymour did not provide that specification for AR1.

Mueller said many people ask why the company switched to methane for its Mars rocket. With reusability in mind, SpaceX’s cost studies revealed that “by far the most cost-effective propellant to use is methane,” he said, which would be easier than hydrogen to manufacture on Mars.

Since the fall, Stennis has performed maintenance to prepare the test stand for Raptor and completed equipment modifications to accommodate components. Strecker would not say how much funding NASA contributed to the effort, but Shotwell says the NASA and Mississippi Development Authority investments helped pay for infrastructure improvements to the test stand that are not specific to SpaceX testing.

Given time to set up a program, an award is possible in fiscal 2016.

http://ula.lonebuffalo.com/story.cfm?story_id=7398139
Title: Re: SpaceX advances drive for Mars rocket via Raptor power
Post by: Burninate on 07/08/2014 08:26 am

SpaceX appears to have dropped the tri-core BFR from their Mars plans so they will need the block 2 Raptor to deliver 100 metric tonnes to Mars in a single launch. Raptor thrust figures also indicate that they are going with a 15m dia. core so that 9 Raptors can fit under it without the need for engine fairings which would otherwise get in the way of the landing legs.

I'm not sure where this info is coming from.  Do we have a source for it?

The original article by baldusi which founded this thread (http://www.nasaspaceflight.com/2014/03/spacex-advances-drive-mars-rocket-raptor-power/) indicated nine Raptor engines would be used on the MCT launch vehicle, on either one or three cores.

I'm personally agnostic, and don't really care which vehicle design SpaceX uses to solve the rocket equation for getting its large payloads to Mars.  But I would like to know if SpaceX has publically revealed any info on the MCT being only a single core, or if that might be the result of rocketeer speculations based on various bits of non-public knowledge.

In February, Tom Mueller released info indicating 1Mlbf per Raptor, 9 Raptors per core, but then the anomaly: 100 tons to Mars.  This payload to MTO was just a little bit too optimistic with those precise numbers, and the expected Isp of the engine.  Later Gwynn Shotwell said something about a 150mT to LEO vehicle (which we have heard nothing further on).  The combination of the two comments led to speculation about three cores.

Lately though, Musk has said it will definitely be"around 15Mlbf" for the Mars rocket, which dismisses a triple-core.

This new info clarifies that a single core is in play.  We're not certain if they're still targetting 100 tons to MTO as the simple there-and-back mission plan Musk initially had for MCT, or if they've shifted to more advanced paradigms.  A single launch, single core of the current size would provide in that neighborhood with an LEO->MTO burn, though.
Title: Re: SpaceX advances drive for Mars rocket via Raptor power
Post by: jsgirald on 07/08/2014 09:26 am

Lately though, Musk has said it will definitely be"around 15Mlbf" for the Mars rocket, which dismisses a triple-core.


My bet is two BFR acting as side boosters and MCT acting as a central core / second stage. Just a hunch though ...
Title: Re: SpaceX advances drive for Mars rocket via Raptor power
Post by: go4mars on 07/08/2014 01:17 pm

Lately though, Musk has said it will definitely be"around 15Mlbf" for the Mars rocket, which dismisses a triple-core.


My bet is two BFR acting as side boosters and MCT acting as a central core / second stage. Just a hunch though ...
Why only 2?
Title: Re: SpaceX advances drive for Mars rocket via Raptor power
Post by: jsgirald on 07/08/2014 03:35 pm

Lately though, Musk has said it will definitely be"around 15Mlbf" for the Mars rocket, which dismisses a triple-core.


My bet is two BFR acting as side boosters and MCT acting as a central core / second stage. Just a hunch though ...
Why only 2?

As I said, there isn't a retionale behind it (I'm a software developer not a rocket scientist!). It's just that I did some calculations with the published estimates in this forum and a TSTO system seemed to give the minimal necessary push to orbit. I think MCT will integrate the second stage, will refuel in orbit, and then will do the Mars burn, crossfeeding might be possible as well.

I see the vehicle itself similar to a payload fairing in shape, only with two 'wings' with engines arranged a bit like the Soyuz boosters. Cargo will be placed at the base accessed by a ramp for ease of operation when loading/unloading  on Mars (a bit like military transport planes). Actually it could land on the bottom, with four legs (F9R style) deploying just to keep it upright.

With 4 engines per 'wing' plus 2 boosters, arranged at 90 degrees from the 'wings' it's 26 engines at launch. The whole assembly wouldn't look too different from a Space Shuttle, only more massive.


Note: See MCT thread http://forum.nasaspaceflight.com/index.php?topic=33494.msg1223846#msg1223846
Title: Re: SpaceX advances drive for Mars rocket via Raptor power
Post by: MP99 on 07/09/2014 06:50 am


The problem is that the F9 and F9h have small upper stages, which implies a small payload, assuming the first stages must fly back to the launch site, as a low staging velocity is required.  I would assume this means the Falcon X single-core will be fully reusable, with the first stage returning to the launch site; and the F9 must have an at-sea booster recovery to have a commercially interesting payload.  The F9h could have the side boosters flyback, but the center core would be recovered at sea or expended.

850 klb prop on F9 first stage, 200 klb on second stage.

Cheers, Martin
Title: Re: SpaceX advances drive for Mars rocket via Raptor power
Post by: aero on 07/10/2014 05:42 am
Has anyone noticed anything strange with the new numbers for the Raptor?

Looking at the vacuum engine (T = 840 tonnes, Isp=380) I calculate an mdot ~2210.5 kg/s. Then looking at the sea level thrust (T = 705 tonnes) with that mdot, I calculate sea level Isp ~ 319 seconds. While much better than the Merlins, it doesn't seem nearly as good as it should be.
Title: Re: SpaceX advances drive for Mars rocket via Raptor power
Post by: sdsds on 07/10/2014 06:32 am
Has anyone noticed anything strange with the new numbers for the Raptor?

I wonder if it's a question of the expansion ratio. With an mdot value and a guess at the combustion product mix is it possible to estimate the diameter of the throat? Maybe it's so large that when the engines are clustered they will have to be pretty substantially under-expanded, even for sea level?
Title: Re: SpaceX advances drive for Mars rocket via Raptor power
Post by: aero on 07/10/2014 06:46 am
Has anyone noticed anything strange with the new numbers for the Raptor?

I wonder if it's a question of the expansion ratio. With an mdot value and a guess at the combustion product mix is it possible to estimate the diameter of the throat? Maybe it's so large that when the engines are clustered they will have to be pretty substantially under-expanded, even for sea level?

Sure, throat area can be determined, just iterate this equation here -
https://www.grc.nasa.gov/www/k-12/airplane/mflchk.html (https://www.grc.nasa.gov/www/k-12/airplane/mflchk.html)
until mdot matches.

Don't use the calculator on that page though, it only works for air.

No, the throat diameter is like 30 to 40 cm so there is plenty of space for the first stage nozzles.
Title: Re: SpaceX advances drive for Mars rocket via Raptor power
Post by: aero on 07/10/2014 08:29 pm
Has anyone noticed anything strange with the new numbers for the Raptor?

I wonder if it's a question of the expansion ratio. With an mdot value and a guess at the combustion product mix is it possible to estimate the diameter of the throat? Maybe it's so large that when the engines are clustered they will have to be pretty substantially under-expanded, even for sea level?

Sure, throat area can be determined, just iterate this equation here -
https://www.grc.nasa.gov/www/k-12/airplane/mflchk.html (https://www.grc.nasa.gov/www/k-12/airplane/mflchk.html)
until mdot matches.

Don't use the calculator on that page though, it only works for air.

No, the throat diameter is like 30 to 40 cm so there is plenty of space for the first stage nozzles.

Well, maybe there is plenty of space for the first stage nozzles, how about the stage 2? I've matched the performance of the June 9-th numbers, here is what I calculated.

mdot = 2210.53 kg/s, which includes the tank pressurization prop estimated at 4.24 kg/s.
Pc = 13 MPa
A* =  0.19136991 m^2, (Dia = 0.49362 m)
Area ratio = 20 sl booster engine and 350 stage 2 engine
Ae = 3.827 m^ sl booster, (Dia = 2.208 m) and 67 m^2 (Dia =9.235 m) for the stage 2 engine
Isp = 320 s at sea level, 338 vac and 380.16 for stage 2 engine

With these parameters the thrusts match those announced. I am only disappointed that the chamber pressure is that low. For some reason I was expecting much higher pressure but 13 MPa is a 34% increase over the Merlin D 1 so I guess it is reasonable.

Question: Will those nozzles fit the BFR octaweb with sufficient space for gimbaling? How is the fit of Stage 2 in the inner stage?
Title: Re: SpaceX advances drive for Mars rocket via Raptor power
Post by: baldusi on 07/11/2014 12:06 am
I would expect more like a 20MPa Pc and expansion of 45 for SL and 180 for the vac version.
Title: Re: SpaceX advances drive for Mars rocket via Raptor power
Post by: aero on 07/11/2014 01:40 am
I would expect more like a 20MPa Pc and expansion of 45 for SL and 180 for the vac version.

That's about where I started, but that won't mesh with the thrusts numbers and the >380 s Vacuum Isp given in the "Ave Week" article. The seemingly poor numbers I gave do have the merit of matching them. I can't match them with Pc = 20 MPa, how do you do it?

These numbers do re-enforce the thought that there will be a block 2 Raptor in the relatively near future, at least in my mind.
Title: Re: SpaceX advances drive for Mars rocket via Raptor power
Post by: getitdoneinspace on 07/11/2014 10:04 pm
The AW article is newer information than the one that the article was based of. Regarding the rest of the post I won't comment due to L2 rules on information dissemination. I can only say that there's some amazing insight and renderings on possible evolution of the MCT project.

Can you provide the link to that L2 information you are referencing? So much information out there.
Title: Re: SpaceX advances drive for Mars rocket via Raptor power
Post by: malu5531 on 07/12/2014 09:33 am
A paywall is not designed to stifle discussion and bury numeric facts, excerpts should be acceptable.

Quote
SpaceX is developing the Raptor as a reusable engine for a heavy-lift Mars vehicle, the first stage of which will feature 705 metric tons of thrust, making it "slightly larger than the Apollo F-1 engine," Tom Mueller, SpaceX vice president of propulsion development, said during a space propulsion conference last month in Cologne, Germany.  The vacuum version is targetting 840 metric tons of thrust with 380 sec. of specific impulse.  The company is testing subscale components using the E-2 test stand at NASA's Stennis Space Center in Missisippi, says Stennis spokeswoman Rebecca Strecker.

Awesome information!

Has anyone noticed anything strange with the new numbers for the Raptor?

I wonder if it's a question of the expansion ratio. With an mdot value and a guess at the combustion product mix is it possible to estimate the diameter of the throat? Maybe it's so large that when the engines are clustered they will have to be pretty substantially under-expanded, even for sea level?

Sure, throat area can be determined, just iterate this equation here -
https://www.grc.nasa.gov/www/k-12/airplane/mflchk.html (https://www.grc.nasa.gov/www/k-12/airplane/mflchk.html)
until mdot matches.

Don't use the calculator on that page though, it only works for air.

No, the throat diameter is like 30 to 40 cm so there is plenty of space for the first stage nozzles.

Well, maybe there is plenty of space for the first stage nozzles, how about the stage 2? I've matched the performance of the June 9-th numbers, here is what I calculated.

mdot = 2210.53 kg/s, which includes the tank pressurization prop estimated at 4.24 kg/s.
Pc = 13 MPa
A* =  0.19136991 m^2, (Dia = 0.49362 m)
Area ratio = 20 sl booster engine and 350 stage 2 engine
Ae = 3.827 m^ sl booster, (Dia = 2.208 m) and 67 m^2 (Dia =9.235 m) for the stage 2 engine
Isp = 320 s at sea level, 338 vac and 380.16 for stage 2 engine

With these parameters the thrusts match those announced. I am only disappointed that the chamber pressure is that low. For some reason I was expecting much higher pressure but 13 MPa is a 34% increase over the Merlin D 1 so I guess it is reasonable.

Question: Will those nozzles fit the BFR octaweb with sufficient space for gimbaling? How is the fit of Stage 2 in the inner stage?

I've made new calculations (https://docs.google.com/a/infidyne.com/spreadsheet/ccc?key=0Av6Zu8Wm_3cqdHFEVmYzd1FQRi1JeTZMajdYMURxRmc#gid=2) (follow my calculations in the spreadsheet). With my assumptions I get these specs for Raptor:

RaptorRaptor Vac
Fuel flow kg/s2200 kg/s2200 kg/s
Thrust, SL, klbf1554 klbf
Thrust, Vac, klbf1737 klbf1850 klbf
Isp, SL, s320
Isp, Vac, s358381
Chamber pressure, Mpa20 Mpa20 Mpa
Nozzle diameter, m3.22m8.32m
Throat Area, m^20.205330.20533
Pressure exhaust, bar0.420.04

Rationale for low Pe; better performance overall as atmosphere diminish fast during ascent

Given this engine, I calculate (https://docs.google.com/a/infidyne.com/spreadsheet/ccc?key=0Av6Zu8Wm_3cqdHFEVmYzd1FQRi1JeTZMajdYMURxRmc#gid=3) a nine raptor fully reusable rocket to be capable of ~200mT to LEO (200x200x26°).
Title: Re: SpaceX advances drive for Mars rocket via Raptor power
Post by: aero on 07/12/2014 10:17 pm
@malu5531
Thanks for posting your spread sheet. I did find a misplaced "(" on my throat area calculation and now I can match your numbers. Surprisingly, my thrust and Isp numbers didn't change very much. That is, 14 MPa chamber pressure is still a valid candidate. But now my booster nozzle is larger, 2.376 m diameter so I doubt the octaweb would fit under a 10 meter tank. But then, your nozzles at 3.22 m diameter wouldn't fit either.

I wonder if someone has calculated the maximum nozzle diameter that might fit under a 10, 12, 15 meter diameter stage.
Title: Re: SpaceX advances drive for Mars rocket via Raptor power
Post by: Tass on 07/13/2014 11:56 am
@malu5531
Thanks for posting your spread sheet. I did find a misplaced "(" on my throat area calculation and now I can match your numbers. Surprisingly, my thrust and Isp numbers didn't change very much. That is, 14 MPa chamber pressure is still a valid candidate. But now my booster nozzle is larger, 2.376 m diameter so I doubt the octaweb would fit under a 10 meter tank. But then, your nozzles at 3.22 m diameter wouldn't fit either.

I wonder if someone has calculated the maximum nozzle diameter that might fit under a 10, 12, 15 meter diameter stage.

I hadn't, but it is simple trigonometry.

Dst > 3.62 Dnz

Being close to this limit of course means that only the central engine will have any room to gimbal.
Title: Re: SpaceX advances drive for Mars rocket via Raptor power
Post by: TrueBlueWitt on 07/13/2014 12:51 pm
@malu5531
Thanks for posting your spread sheet. I did find a misplaced "(" on my throat area calculation and now I can match your numbers. Surprisingly, my thrust and Isp numbers didn't change very much. That is, 14 MPa chamber pressure is still a valid candidate. But now my booster nozzle is larger, 2.376 m diameter so I doubt the octaweb would fit under a 10 meter tank. But then, your nozzles at 3.22 m diameter wouldn't fit either.

I wonder if someone has calculated the maximum nozzle diameter that might fit under a 10, 12, 15 meter diameter stage.

From a post of mine about a month back


As for Nozzle diameter question:
I found this cool calculator for circles in circles. 
http://www.engineeringtoolbox.com/smaller-circles-in-larger-circle-d_1849.html

Engine Nozzle diameter vs core size
(for 9 engines completely under the core)

Nozzle diameter   Minimum Core Size
       2.7m*                  10m                 *2.7m is maximum nozzle for 10m Core
      3.23m                   12m
      3.66m                   13.5m

Nozzle diameter(thrust level) may end up dictating the core diameter.
Title: Re: SpaceX advances drive for Mars rocket via Raptor power
Post by: baldusi on 07/13/2014 03:07 pm

Nozzle diameter(thrust level) may end up dictating the core diameter.
Or the other way around.
Title: Re: SpaceX advances drive for Mars rocket via Raptor power
Post by: aero on 07/13/2014 04:00 pm

Nozzle diameter(thrust level) may end up dictating the core diameter.
Or the other way around.

I'm thinking along those same lines. Chamber pressure strongly drives nozzle diameter through the nozzle exit pressure and area ratio, and throat diameter is a direct function of mass flow. For these powerful Raptor engine concepts, mass flow, hence throat and exit diameters are large so the nozzle is either very inefficiently under expanded or nozzle diameter is large.

And by "large" exit diameter, I mean to large to fit 9 of them under the 10 meter stage. So who among us thinks that SpaceX will build the tooling and manufacture 10 meter diameter stages that prevent them from increasing engine efficiency, not to mention engine power beyond the first concept? And if they go bigger than 10 meters, I wonder what size they will choose?
Title: Re: SpaceX advances drive for Mars rocket via Raptor power
Post by: Roy_H on 07/13/2014 04:18 pm
10m dia. produces a very tall and skinny rocket, given the huge fuel load this will require. I think 10m was just a first pass estimate, and analysis since has shown that 13m to 15m would be much more reasonable from the fuel mass to rocket mass ratio. i.e. fat tanks are more mass efficient than long skinny ones. Aerodynamic resistance at 15m is not an issue. A 10m dia. rocket of this capacity would be by far the tallest rocket ever made and require a very high service tower. There seem to be zero reasons to stay with that original estimate.
 
Title: Re: SpaceX advances drive for Mars rocket via Raptor power
Post by: Nathan2go on 07/14/2014 03:33 am
Yes, speaking of reveals, the graphic of the SpaceX rocket family (which I assume comes from SpaceX) hints at a problem with the claim that F9 and F9h will be reusable.  The drawing of the Falcon X shows a second stage which is about half as big as the first stage.  This is consistent with the Kistler  K1 (http://www.astronautix.com/lvs/kislerk1.htm), in which the stages separate at only Mach 4, and the first stage flies back to the launch site, and the second stage flies to LEO (the stages use similar kerosene engines, 3 on the first and one on the second); it would have put a payload of 1.2% of its launch mass in orbit (compared to 2.6% for expendable F9). 

The problem is that the F9 and F9h have small upper stages, which implies a small payload, assuming the first stages must fly back to the launch site, as a low staging velocity is required.
I've looked at the numbers in more detail, and now I think that the current F9 upper stage (200 klbs per Martin) is well suited for fly-back booster operation.  This is based on a staging velocity of around Mach 6.5.

Running the calculations with methane/O2 engines (Isp=380 s) makes the upper stage want to be a little bigger (around 250 k lbs), so that may explain some of the apparent tanks size ratios in the Falcon X drawing.

Another theory is that the upper stage in the drawing is really sized for the Falcon X heavy.  With all three cores flying back to the launch site, a nearly triple-sized upper stage would be required.

Or it could be that they had intended to use a hydrogen upper stage (at the time the drawing was made).  This would have also boosted the performance of the Earth departure stage, and also reduced the penalty for fly-back operation of the hydrocarbon first stage; plus, carrying hydrogen to Mar (to avoid the need for water collection) would mean the launch pad has to have hydrogen plumbing anyway.
(http://www.nasaspaceflight.com/wp-content/uploads/2014/03/Z8.jpg)
Title: Re: SpaceX advances drive for Mars rocket via Raptor power
Post by: Torbjorn Larsson, OM on 07/14/2014 09:27 am
10m dia. produces a very tall and skinny rocket, given the huge fuel load this will require. I think 10m was just a first pass estimate, and analysis since has shown that 13m to 15m would be much more reasonable from the fuel mass to rocket mass ratio. i.e. fat tanks are more mass efficient than long skinny ones. Aerodynamic resistance at 15m is not an issue. A 10m dia. rocket of this capacity would be by far the tallest rocket ever made and require a very high service tower. There seem to be zero reasons to stay with that original estimate.

I looked at a naive scaling of the updated Red Dragon Mars landing technology as presented by NASA recently. While a 10 m heat shield for braking may be doable (on Vastitas Borealis), a 15 m one is both a more suitable scaling of V2 given the MCT mass estimates and should be able to put an MCT down most anywhere on Mars. (If you stay away from 5+ km topography obstacles.)

If the Raptor engine generation is targeted for MCT vehicles, the largest core size should fit a 15 m-ish diameter craft.
Title: Re: SpaceX advances drive for Mars rocket via Raptor power
Post by: RanulfC on 07/14/2014 03:18 pm

Nozzle diameter(thrust level) may end up dictating the core diameter.
Or the other way around.

Anyone considered that they may go a step further and simply go with a "plug-cluster" nozzle set up similar to Firefly systems?
http://www.fireflyspace.com/vehicles/firefly-a

It would actually help solve reentry and stability issues though without a "central" throttable engine it would mean some seriously deep-throttling for the rest of the engines

Randy
Title: Re: SpaceX advances drive for Mars rocket via Raptor power
Post by: Robotbeat on 07/14/2014 08:27 pm
10m dia. produces a very tall and skinny rocket, given the huge fuel load this will require. I think 10m was just a first pass estimate, and analysis since has shown that 13m to 15m would be much more reasonable from the fuel mass to rocket mass ratio. i.e. fat tanks are more mass efficient than long skinny ones. Aerodynamic resistance at 15m is not an issue. A 10m dia. rocket of this capacity would be by far the tallest rocket ever made and require a very high service tower. There seem to be zero reasons to stay with that original estimate.

I looked at a naive scaling of the updated Red Dragon Mars landing technology as presented by NASA recently. While a 10 m heat shield for braking may be doable (on Vastitas Borealis), a 15 m one is both a more suitable scaling of V2 given the MCT mass estimates and should be able to put an MCT down most anywhere on Mars. (If you stay away from 5+ km topography obstacles.)

If the Raptor engine generation is targeted for MCT vehicles, the largest core size should fit a 15 m-ish diameter craft.
I think we should make peace with the fact that flights will be to some low-altitude locations. It makes a lot of things much easier.
Title: Re: SpaceX advances drive for Mars rocket via Raptor power
Post by: aero on 07/21/2014 08:17 pm
I'm hoping for some feed-back for a sanity check.

I configured my simulation for a Raptor BFR using 20 MPa chamber pressure with nozzles giving Isp's of 320.49, 359.1 and 381.92. I used 5% payload to orbit in expendable mode and came up with some stage masses for what I will name a Raptor 9-2. Are these masses reasonable?

Raptor engine sl thrust = 705 tonnes,
Raptor engine T/W = 100,
Lift-Off T/W = 1.186
Stage 1 mass, inc. 9 engines = 290 tonnes,
Diameter = 15 - 16 meters
Stage 2 mass, inc. 2 engines =75.25 tonnes,
Minimum Diameter = 16 meter,
Fairing mass = 8 tonnes
MECO =177 s, Prop remaining = 0.38 kg  :)
SECO =297 s, Prop remaining = 1019 kg

I used 2 engines on stage 2 because the payload is just to large for a single Raptor to push to orbit from MECO. Well, one engine can give it a good go but it takes nearly 600 seconds burn time which adds over 1,000 m/s gravity drag. Using two engines keeps the gravity drag close to 1,500 m/s, similar to the Falcon 9 gravity drag.

My question is this: Are these  stage masses reasonable?

Title: Re: SpaceX advances drive for Mars rocket via Raptor power
Post by: baldusi on 07/21/2014 09:00 pm
I don't want to deduct the propellent masses. Could you add them?
I would be a bit more conservative with the engine T/W (90 to 95), and whole stack T/W is usually >1.2, probably in the 1.25~1.35 range.
I ignore the fairing size, but if it is a 16m fairing I seriously doubt less than 20 tonnes, and probably above 30.
You should assume at least 1.5% of fuel left. Remember that some part is used for pressurization, some is left on the pipes and you do want to avoid cavitation on because of lack of head pressure.
Regarding your US T/W, what sort of ascent profile you used to get 1000m/s of gravity losses on the second stage? Probably once you increase the overall Stack T/W, this problem will go away.
Title: Re: SpaceX advances drive for Mars rocket via Raptor power
Post by: Hyperion5 on 07/21/2014 09:41 pm
I would be a bit more conservative with the engine T/W (90 to 95), and whole stack T/W is usually >1.2, probably in the 1.25~1.35 range.

Sounds rather more conservative than it needs to be, Baldusi.  We have examples of BFRs like the Saturn V that could have taken off with t/w ratios around 1.2.  The Falcon 9 meanwhile has a mere 1.186 t/w ratio.  To be cautious I think a 1.2 t/w ratio is just fine.  No need to go higher, as all you'll be doing is losing payload to orbit while barely making the rocket more engine-out resistant.  Also, we have examples of Russian SC methalox engines under design with t/w ratios of 97 (RD-0162) and 100 (RD-0164).  Those engines can also use extra turbine power and push thrust 33-20% higher (RD-0162 vs. RD-0164).  That in turn means t/w ratios of higher than 120 are possible.  The only catch is the engine has a lot more stress put on it, thus curtailing its reusability.  So if in doubt, go with a t/w ratio of 100. 

I ignore the fairing size, but if it is a 16m fairing I seriously doubt less than 20 tonnes, and probably above 30.
You should assume at least 1.5% of fuel left. Remember that some part is used for pressurization, some is left on the pipes and you do want to avoid cavitation on because of lack of head pressure.

Just bear in mind, Aero, that when launching an MCT you only need an aeroshell.  Such an aeroshell could be as little as couple tonnes in mass.  Perhaps even lower, depending on how you design it.  As for the fairing, 20 tonnes is not unreasonable if it's composite.  I wouldn't go lower than that unless it's a really short 16 m fairing. 

Title: Re: SpaceX advances drive for Mars rocket via Raptor power
Post by: aero on 07/21/2014 09:46 pm
I don't want to deduct the propellent masses. Could you add them?
I would be a bit more conservative with the engine T/W (90 to 95), and whole stack T/W is usually >1.2, probably in the 1.25~1.35 range.
I ignore the fairing size, but if it is a 16m fairing I seriously doubt less than 20 tonnes, and probably above 30.
You should assume at least 1.5% of fuel left. Remember that some part is used for pressurization, some is left on the pipes and you do want to avoid cavitation on because of lack of head pressure.
Regarding your US T/W, what sort of ascent profile you used to get 1000m/s of gravity losses on the second stage? Probably once you increase the overall Stack T/W, this problem will go away.

Thanks.

For the above,
S1 Prop mass = 3,442,013 kg
S2 Prop Mass = 1,255,715 kg.

As for the US ascent profile, currently I have MECO at:
Vz = 857.82 m/s   Vz = 1,901.18 m/s   Velocity = 2,085.75 m/s   Alt = 72,835.27 m    down range = 83,288.98 m

From MECO I targeted 185 km altitude at 7.792 km/s Vx. I can't give the real numbers of the single engine US trajectory as they were superseded by the twin engine US. As I recall it was thrusting at about 45 degrees, gradually decreasing toward horizontal at orbital velocity. The 5% GLOW payload is pretty massive in the above case and 600 seconds is a long burn time so S2 gravity drag adds up.

I used such low values for MECO in anticipation of S1 recovery.

As for the Lift-Off T/W, I think that is the same as the Falcon 9 with a 13,150 kg payload. In the above case, the GLOW certainly does include payload, but I don't think the Falcon 9 numbers on the SpaceX web page does.

 Edit: Just reading back over the thread, I found a typo. Vz = 857.82 m/s   Vx = 1,901.18 m/s

Title: Re: SpaceX advances drive for Mars rocket via Raptor power
Post by: aero on 07/21/2014 10:23 pm
Thanks for the input! Once I make some changes we'll see what comes up.

I deliberately avoided posting the payload mass until now. Without any changes, the payload is 267,420.15 kg to a 185 km, near circular orbit. Is that enough for a fully loaded and fueled MCT?

I think that launching an MCT will not require such a massive fairing, but it will require an additional inner stage that goes all the way to orbit. Any comments on its mass or whatnot?

Also, I think I will need to reduce the S2 nozzle expansion ratio hence the S2 Isp. That's because the nozzle diameter is currently 7.945 meters with an expansion ratio of 240.  Two of those really won't fit within a 16 meter diameter inner stage and I don't even want to think about a bigger single engine nozzle. Inner stage mass would eat the performance alive, IMO.


Title: Re: SpaceX advances drive for Mars rocket via Raptor power
Post by: baldusi on 07/22/2014 03:23 am
Aero, how did you chose the first stage / second stage, I get a feel the second stage is too big. But I usually optimize for higher energy. The point that makes some noise is that upper stage has better pmf than the first stage, even with two engines.
Title: Re: SpaceX advances drive for Mars rocket via Raptor power
Post by: Hyperion5 on 07/22/2014 04:29 am

The 5% GLOW payload is pretty massive in the above case and 600 seconds is a long burn time so S2 gravity drag adds up.

Having seen more than a few methalox rockets simulated, I can assure you 5% of GLOW to orbit is pretty typical.  At least it is with engines that have this kind of Isp & a ~100 t/w ratio.  Generally, as you scale down to EELV masses, the payload % of GLOW should decline to around 4.5%.  If however you were to scale up your BFR further and chop one of the SII engines off, things improve.  You might even be able to get payload to orbit to almost 5.5% of GLOW.  Of course that depends on ditching the 2nd SII engine.  As Dmitry always tells me, adding a 2nd engine up top does nothing to help lift more payload to orbit.  It would however allow you to claim the record for most powerful upper stage ever built. 
Title: Re: SpaceX advances drive for Mars rocket via Raptor power
Post by: aero on 07/22/2014 04:42 am
Aero, how did you chose the first stage / second stage, I get a feel the second stage is too big. But I usually optimize for higher energy. The point that makes some noise is that upper stage has better pmf than the first stage, even with two engines.

My choice was intended as a first guess to be refined after discussions here. I simply used the rocket equation and estimated staging velocity at 2 km/s with 1.5 km/s gravity drag, total delta V = 3500 m/s to MECO.
MR = exp (delta u / (Isp * g0) ) so GLOW and MR gives S1 Prop used and stack mass at MECO. (Of course a higher staging velocity would give more S1 prop and a larger first stage.)

Estimating the S1 dry mass gives what I call the S2 stack mass. Using the rocket equation again with delta V = 5700 km/s gives S2 Prop used and S2 stack mass at SECO. Use payload = 5% of GLOW and fairing mass gives mass available for S2 dry.

As you can read, its pretty crude but it is an approach doesn't require in depth knowledge of material strengths and all the other details that real designers must consider.

I plugged these numbers into my simulation integrator and only needed to shave 10 tonnes from S1 dry mass, everything else worked to orbit. And as it happens, part of that shaved 10 tonnes should show up as S1 Prop margin once I revisit it.
Title: Re: SpaceX advances drive for Mars rocket via Raptor power
Post by: aero on 07/22/2014 05:05 am

Quote
As Dmitry always tells me, adding a 2nd engine up top does nothing to help lift more payload to orbit.  It would however allow you to claim the record for most powerful upper stage ever built. 

Dmitry is making an unstated assumption. That is, assuming that the altitude and velocity at MECO plus the thrust of the single engine is enough to hold S2 out of the atmosphere for the S2 burn down range. Were I to change my MECO conditions to a higher altitude and/or velocity a single S2 engine could be made to work as allocating more of the delta V, hence GLOW to S1 would reduce the S2 Prop mass.

I chose my initial configuration to accommodate S1 recovery but I don't like a twin engine S2 either.
Title: Re: SpaceX advances drive for Mars rocket via Raptor power
Post by: aero on 07/22/2014 06:44 am
I guess I'll go ahead and switch some delta V to S1 from S2 to see what is needed in order to remove the second S2 engine. I guess, if I am trying to mimic the Falcon 9, that I want only ~375 seconds of S2 Prop.
Title: Re: SpaceX advances drive for Mars rocket via Raptor power
Post by: baldusi on 07/22/2014 04:59 pm
I guess I'll go ahead and switch some delta V to S1 from S2 to see what is needed in order to remove the second S2 engine. I guess, if I am trying to mimic the Falcon 9, that I want only ~375 seconds of S2 Prop.
Please consider that pmf of S1 is very difficult to keep above 95% (F9 is rumored 96.6%). The best pmf S2 that I know of is the Centaur and is 90% or so. This masses include propulsion. If you add propellant to achieve your desired delta-v, is kind of a self-fulfilling prophecy. You should first state your pmf that you expect to achieve. Then you have to trade S1/S2 mass proportion until you get your best performance.
Title: Re: SpaceX advances drive for Mars rocket via Raptor power
Post by: solartear on 07/22/2014 08:16 pm
I guess I'll go ahead and switch some delta V to S1 from S2 to see what is needed in order to remove the second S2 engine. I guess, if I am trying to mimic the Falcon 9, that I want only ~375 seconds of S2 Prop.
Please consider that pmf of S1 is very difficult to keep above 95% (F9 is rumored 96.6%). The best pmf S2 that I know of is the Centaur and is 90% or so. This masses include propulsion. If you add propellant to achieve your desired delta-v, is kind of a self-fulfilling prophecy. You should first state your pmf that you expect to achieve. Then you have to trade S1/S2 mass proportion until you get your best performance.

http://www.spaceflight101.com/falcon-9-v11.html lists the F9 S2 as 94.8%.  We should expect SpaceX to get at least that for the Raptor powered upperstage. Yes? Or would the stage combustion and safety margins prevent it?
Title: Re: SpaceX advances drive for Mars rocket via Raptor power
Post by: Owlon on 07/22/2014 08:22 pm
I guess I'll go ahead and switch some delta V to S1 from S2 to see what is needed in order to remove the second S2 engine. I guess, if I am trying to mimic the Falcon 9, that I want only ~375 seconds of S2 Prop.
Please consider that pmf of S1 is very difficult to keep above 95% (F9 is rumored 96.6%). The best pmf S2 that I know of is the Centaur and is 90% or so. This masses include propulsion. If you add propellant to achieve your desired delta-v, is kind of a self-fulfilling prophecy. You should first state your pmf that you expect to achieve. Then you have to trade S1/S2 mass proportion until you get your best performance.

http://www.spaceflight101.com/falcon-9-v11.html lists the F9 S2 as 94.8%.  We should expect SpaceX to get at least that for the Raptor powered upperstage. Yes? Or would the stage combustion and safety margins prevent it?

About 95% sounds right for the numbers I've heard on the F9 second stage. All other things held equal, your average kerosene stage should have a better mass fraction than a methane stage should have a better mass fraction than a hydrogen stage, simply due to the propellant density.
Title: Re: SpaceX advances drive for Mars rocket via Raptor power
Post by: baldusi on 07/22/2014 09:46 pm
I've never seen a 95% second stage. Let's remember that all are estimations since SpaceX has not disclosed the actual fuel nor dry masses of either stage.
Just to put some examples:
Zenit-2 S2 90.46%
Proton-M S2 93.46%
Delta II S2 86.34%
Soyuz-2B I-Blok 91.52%
Ariane 5 EPS 80.00%
Dnepr S2 89.36%
Long March S2 4C 92.30%
And I've not included a single H2 stage, and many are huge hypergolics (which are more volume efficient than RP1/LOX) . But if the second stage has a pmf of 95%, the first stage can't have a 91.5%. Use 95%/92.5% (S1/S2) for normal or 96%/94% for optimist.

Regarding the T/W, I remember that the original GLOW of Falcon 9 v1.1 was 480tonnes. Since the possible 15% increase in thrust of Merlin 1D would bring the T/W 1.36.
Title: Re: SpaceX advances drive for Mars rocket via Raptor power
Post by: Robotbeat on 07/23/2014 12:05 am
SpaceX is using better alloys and better computer-aided design and machine tools than have ever been available except for some of the very latest rockets. The thrust/weight ratio for their (first stage) Merlin 1D is record-breaking. They're partially pressure-stabilized. It shouldn't be that surprising to hear they can get record or near-record pmf for the upper stage.

Also, methane/oxygen pmf is improved somewhat with propellant densification which they very well may end up using since we've already heard hints.
Title: Re: SpaceX advances drive for Mars rocket via Raptor power
Post by: aero on 07/23/2014 12:19 am
I've never seen a 95% second stage. Let's remember that all are estimations since SpaceX has not disclosed the actual fuel nor dry masses of either stage.
Just to put some examples:
Zenit-2 S2 90.46%
Proton-M S2 93.46%
Delta II S2 86.34%
Soyuz-2B I-Blok 91.52%
Ariane 5 EPS 80.00%
Dnepr S2 89.36%
Long March S2 4C 92.30%
And I've not included a single H2 stage, and many are huge hypergolics (which are more volume efficient than RP1/LOX) . But if the second stage has a pmf of 95%, the first stage can't have a 91.5%. Use 95%/92.5% (S1/S2) for normal or 96%/94% for optimist.

Regarding the T/W, I remember that the original GLOW of Falcon 9 v1.1 was 480tonnes. Since the possible 15% increase in thrust of Merlin 1D would bring the T/W 1.36.

If I'm calculating pmf correctly, I have S1/S2 pmf = 92/94 in my first cut example.

http://www.spacex.com/falcon9 (http://www.spacex.com/falcon9)

As for the GLOW, the SpaceX web site gives 505,846kg but considered evaluation makes me think that that number does not include the payload. I can calculate lift-off T/W with or without a payload but we should agree on the correct method for valid communication of the rocket's capability. The same web page gives lift-off thrust as 5,885kN. It doesn't make much sense to me to ignore the payload mass on lift-off. For example, a fireworks sky rocket has a good T/W, but strap a brick on it for payload and it won't do so well.

And I don't understand the relationship between S1 and S2 pmf. The definition of propellant mass fraction is
pmf =usable prop/(usable prop+ dry mass). That is for the stage, not the rocket. Propellant mass fraction is a measure of the structural efficiency of the stage so S1 pmf doesn't relate to S2 pmf?http://ntrs.nasa.gov/archive/nasa/casi.ntrs.nasa.gov/20090037584.pdf (http://ntrs.nasa.gov/archive/nasa/casi.ntrs.nasa.gov/20090037584.pdf)
Title: Re: SpaceX advances drive for Mars rocket via Raptor power
Post by: Hyperion5 on 07/23/2014 05:00 am
I've never seen a 95% second stage. Let's remember that all are estimations since SpaceX has not disclosed the actual fuel nor dry masses of either stage.
Just to put some examples:
Zenit-2 S2 90.46%
Proton-M S2 93.46%
Delta II S2 86.34%
Soyuz-2B I-Blok 91.52%
Ariane 5 EPS 80.00%
Dnepr S2 89.36%
Long March S2 4C 92.30%
And I've not included a single H2 stage, and many are huge hypergolics (which are more volume efficient than RP1/LOX) . But if the second stage has a pmf of 95%, the first stage can't have a 91.5%. Use 95%/92.5% (S1/S2) for normal or 96%/94% for optimist.

Now wait just a minute.  You're comparing Spacex's conceptual monster's PMF to such "monsters" as the Zenit-2, the Long March S2, the Dnepr S2, Proton-M and even the Soyuz-2B?  :o Surely it has occurred to you, Baldusi, that the rockets you're mentioning are just a "tad" small compared to a record-setting BFR?  If we're going to give examples to Aero, let's make sure we compare his work to the historical "king of rockets", the Saturn V.  The Saturn V was no slouch even compared to modern rockets.  It used common bulkheads on both of its hydrolox upper stages.  Here's the PMF figures for each stage:

S-IC(first stage): 94.09%
S-II(second stage): 92.04%
S-IVB(third stage): 88.91%

Calculated using the following page: http://www.astronautix.com/lvs/saturnv.htm

So my advice, Aero, is to use the S-II as your benchmark.  Basically there is no way you should allow the SII on the BFR you're testing to fall below that PMF figure (92.04%).  If you really want to max out performance on this stage, I'd gun for a equal PMF on both the SI & SII like Dmitry did way back before he was in L2.  Realistically you could probably get the PMF figures on both stages up to 92.5% at least.  I'd be very surprised if you didn't top 5% of GLOW as payload to orbit.  Make sure you chop off the second SII engine if you do it though. 

Regarding the T/W, I remember that the original GLOW of Falcon 9 v1.1 was 480tonnes. Since the possible 15% increase in thrust of Merlin 1D would bring the T/W 1.36.

165 klbf is actually only 12.2% more thrust than 147 klbf of thrust, Baldusi.  We might as well make sure we nail that detail at least. 
Title: Re: SpaceX advances drive for Mars rocket via Raptor power
Post by: baldusi on 07/23/2014 01:07 pm
Here are two issues wrt pmf. The first is to have realistic pmf, the second is the relationship between S1 and S2. A methalox stage should be worse than RP-1/LOX but better than an H2/LOX. Methalox is, after al, some 30% more volumetric than RP-1/LOX combo, and the CH4 tanks require more insulation than the RP-1 ones. When I mentioned Centaur, you said that I shouldn't compare to hydrolox. And then it became very difficult to find actual propelland and dry masses for non hydrolox upper stage. Sure, many sites have estimation. But actual data from the rocket's user guides, is not so simple. Thus, that was the best, relatively modern sample that I could get. Soyuz-2 and Proton-M have been modernized and shaved some upper stage mass during the 2000s. But the fact is that the proposed upper stage was to have two engines with nozzle extensions. That's gonna have to weight. Yet, after looking at the Saturn V numbers (which I did but didn't posted because it was an hydrolox) I was convinced that 92.5% was relatively easy and thus should be the base assumption. I even conceded that on those sizes 94% could be feasible, but probably with a single engine.
Regarding the S1/S2 pmf, first stages are always more mass efficient than the upper stages (at least when both expendables). First stages are usually not height limited, have bigger scale, have shorter mission times, don't have to transfer more stresses than they generate and many other things. Thus, if you assume a pmf of 92% or 93%, then S1 should be in the 95% to 96%. When expendable.
Title: Re: SpaceX advances drive for Mars rocket via Raptor power
Post by: aero on 07/23/2014 04:35 pm
OK. Now I've one (for now) more question before I get cracking on revisions. That has to do with the prop used to pressurize the tanks. I am currently adding an amount to mdot for pressurization, reducing Isp accordingly. That way the prop for pressurization is used up, but that is not quite right because the prop used for tank pressurization does not go overboard. I'll find a fix but my question is:

"What is a realistic mass flow of prop to pressurize the tanks?"

For the SSME, external tank pressurization took 0.7 lbs/s H2 and ~1.2 lbs/s LOX. That flow replaced the ~ 500 kg/s prop consumed. I think those are per engine numbers? Using this as a start, I can directly scale the LOX to match the Raptor ~ 2200 kg/s mdot, but LH2 is quite different from methane. I'm not sure I even know where to start scaling that to the Raptor consumptions.
Title: Re: SpaceX advances drive for Mars rocket via Raptor power
Post by: baldusi on 07/23/2014 06:44 pm
OK. Now I've one (for now) more question before I get cracking on revisions. That has to do with the prop used to pressurize the tanks. I am currently adding an amount to mdot for pressurization, reducing Isp accordingly. That way the prop for pressurization is used up, but that is not quite right because the prop used for tank pressurization does not go overboard. I'll find a fix but my question is:

"What is a realistic mass flow of prop to pressurize the tanks?"

For the SSME, external tank pressurization took 0.7 lbs/s H2 and ~1.2 lbs/s LOX. That flow replaced the ~ 500 kg/s prop consumed. I think those are per engine numbers? Using this as a start, I can directly scale the LOX to match the Raptor ~ 2200 kg/s mdot, but LH2 is quite different from methane. I'm not sure I even know where to start scaling that to the Raptor consumptions.
First, it depends on how do you pressurize. The most likely way, is to actually heat a bit of the incoming liquid state element. If they have a LP TP, or the first stage of a many stages TP, you run a bit of it through a heat exchanger until it is in gaseous state and run in it to the re-pressurization pipe.
Using some of the output of the preburner is not a good idea. Specially with a SC engine. Raptor's Full Flow might be different, but I still believe that the heat exchanger would be easier and more reliable.
But since you want to know the mass, it's relatively simple. Once you know the mass of element that you are actually burning, you have to replace it with the same volume of gas. If we assume a 500K/3.5Bar (temperature from Russian papers talking about 300C or so and pressure from Falcon 9 v1.0 tank pressure) gas, you can easily get the amount of mass needed per mass burned. From there you can get the proportion of fuel that will be needed just to keep the tank pressurized. Then you can add 0.5% to 1% of mass for shutdown margin, keeping head pressure, etc. With that you'll have a very reasonable estimation of propellant mass.
Please remember to do the calculations for each element (CH4 and O2).
BTW, from here (http://www.peacesoftware.de/einigewerte/calc_methan.php5): CH4 @ 500K/3.5Bar: 0.00135075(tonne/m³) vs 0.42262(tonne/m³) @ (111K/1.0Bar), which means that you'll need about 0.3% of fuel for pressurization.
From here (http://yeroc.us/calculators/gas-density.php): O2 @ 500K/3.5Bar: 0.0026939(tonne/m³) vs 1.141(tonne/m³) @ (91K/1.0Bar), which means that you'll need about 0.236% of oxidizer for pressurization.
In both cases I'm assuming they'll heat to (300C/573K) but then it will be cooling during the mission, and that's why I keep the 73K of margin.
Title: Re: SpaceX advances drive for Mars rocket via Raptor power
Post by: aero on 07/23/2014 07:43 pm
Thanks baldusi, you worked the hard part for me! And I like that gas calculator.
Title: Re: SpaceX advances drive for Mars rocket via Raptor power
Post by: MP99 on 07/24/2014 09:12 am
Note that He systems also benefit from being heated, for same reason.

As for high temp autogenous pressurisation, does this have a benefit for lowering boiloff during coast on u/s post SECO-1?

High temp gas will cool, while also boiling off some liquid. My intuition says the net pressure once the system reaches equilibrium will be lower than it would be if pressured with cooler gas. And that provides some "headroom" for liquid to boil during coast before pressures get high enough to need to expel gas.

Thoughts?

Cheers, Martin
Title: Re: SpaceX advances drive for Mars rocket via Raptor power
Post by: aero on 07/25/2014 06:22 pm
It occurred to me while struggling to model the Raptor BFR and coming up short on prop, that the BFR first stage and probably the second stage will never leave the vicinity of Earth. So why am I using gaseous prop to pressurize the tanks? Wouldn't a helium system work better without wasting prop that has been carried to MECO and SECO? And the vehicles will return to Earth so there will be no shortage of helium.

It makes sense to avoid helium in a vehicle that will go to Mars but the BFR won't, so where did I get the idea that the BFR will avoid helium?

How much mass would a helium pressurization system entail? I can say that total mass of prop needed to pressurize the near empty  tanks of the BFR is about  9,038.36 kg (S1) and 2,935.04 kg (S2) while equal pressurization using He would mass about 1,262.80 kg (S1) and 410.07 kg (S2). That is not very much mass relative to the payload to orbit of the BFR, but still, the mass savings for the stage 2 pressurization gases equates to over two tonnes of payload to orbit, not to mention additional impulse obtained from burning that prop for orbit insertion which is just over one second of engine burn at full throttle.

So my question is, "Why am I using prop to pressurize the tanks?"
   
Title: Re: SpaceX advances drive for Mars rocket via Raptor power
Post by: sublimemarsupial on 07/25/2014 06:35 pm
So my question is, "Why am I using prop to pressurize the tanks?"

Commonality? Elon has said that at least the MCT will use autogenous pressurization. Given SpaceX's current MO, if you consider the MCT to be a combined third stage and crew vehicle, it would make sense that all the stages will share a common architecture, if not the same tooling, just as F9 S1 and S2 do.

Also, any autogenous pressurization system will use heat exchangers built into the engines to provide the gaseous propellents for pressurization, and if SpaceX plans to make Raptor mostly common between the stages (just like Merlin), they'll already have those heat exchangers available on the first stage engines, why not use them.
Title: Re: SpaceX advances drive for Mars rocket via Raptor power
Post by: aero on 07/25/2014 06:45 pm
So my question is, "Why am I using prop to pressurize the tanks?"

Commonality? Elon has said that at least the MCT will use autogenous pressurization. Given SpaceX's current MO, if you consider the MCT to be a combined third stage and crew vehicle, it would make sense that all the stages will share a common architecture, if not the same tooling, just as F9 S1 and S2 do.

Also, any autogenous pressurization system will use heat exchangers built into the engines to provide the gaseous propellents for pressurization, and if SpaceX plans to make Raptor mostly common between the stages (just like Merlin), they'll already have those heat exchangers available on the first stage engines, why not use them.

Hmm - "Commonality." But SpaceX has a helium pressurization system in place on the Falcon 9 and FH so the "commonality" argument cuts both ways.
Title: Re: SpaceX advances drive for Mars rocket via Raptor power
Post by: Mongo62 on 07/25/2014 06:50 pm
I also thought that SpaceX wants to move away from helium because of the obvious leak problems we have seen with it. One less source of scrubs and other launch delays.
Title: Re: SpaceX advances drive for Mars rocket via Raptor power
Post by: aero on 07/25/2014 07:01 pm
I also thought that SpaceX wants to move away from helium because of the obvious leak problems we have seen with it. One less source of scrubs and other launch delays.

I too would like to see SpaceX solve their helium system problems but others have solved it in the past haven't they? If so, then it is a problem with a solution not requiring the abandonment of helium.

In any case, do we have anything definitive that says that helium will not be used on the BFR?
Title: Re: SpaceX advances drive for Mars rocket via Raptor power
Post by: Mongo62 on 07/25/2014 07:20 pm
I too would like to see SpaceX solve their helium system problems but others have solved it in the past haven't they? If so, then it is a problem with a solution not requiring the abandonment of helium.

In any case, do we have anything definitive that says that helium will not be used on the BFR?

Elon has talked about autogenous pressurization on the MCT vehicle, but nothing so far as I know about the BFR itself. However, if the MCT is considered the "third stage" of the BFR, then commonality suggests that the first two stages might be autogenously pressurized as well:

http://shitelonsays.com/transcript/spacex-dragon-2-unveil-qa-2014-05-29

"Well yeah, so here I'll give you a little bit of a tidbit on the Mars vehicle which will be methane powered. Mars vehicle will be autogenously pressurized with methane and oxygen. So instead of helium pressurization - there's no helium on Mars. So, we'll gasify the liquid oxygen and liquid methane to pressurize their respective tanks. Looking forward to that."
Title: Re: SpaceX advances drive for Mars rocket via Raptor power
Post by: MP99 on 07/25/2014 09:04 pm


It occurred to me while struggling to model the Raptor BFR and coming up short on prop, that the BFR first stage and probably the second stage will never leave the vicinity of Earth. So why am I using gaseous prop to pressurize the tanks? Wouldn't a helium system work better without wasting prop that has been carried to MECO and SECO? And the vehicles will return to Earth so there will be no shortage of helium.

Well, He's not cheap, so there's a small cost saving. And anything that stops consuming He is good.

But, an out-there speculation...

Assume S1 will land similarly to F9 S1, on a single main engine.

Given Raptor is a clean-sheet design, how about the chance that it might land burning pure gas input, rather than the liquid? There could be a big thrust hit, but lower thrust may actually be an advantage in this role. Can even burn multiple engines if necessary.

The landing stage can support it's own weight + u/s + payload under gravity, so it doesn't need much pressure to maintain integrity when landing.

Basically, I'm suggesting a vapak system, but with an auxiliary inlet that's above residual prop levels, to guarantee gas intake for that burn. Maybe using regenerative cooling to help with the boiling of liquid to guarantee production of gasses. Reminder that sub-cooled prop with autogenous pressurisation will require a *very substantial* prop-boiling subsystem, which might make this work.

Reminder, an out-there speculation...

Cheers, Martin
Title: Re: SpaceX advances drive for Mars rocket via Raptor power
Post by: aero on 07/25/2014 10:17 pm
I believe the Raptor is planned to be a gas/gas full flow staged combustion engine.
That is, it compresses the liquid props then gasifies them prior to injection into the chamber. But as it uses part of the liquid fuel for regenerative cooling of the chamber/nozzle, I suspect that using gaseous prop from the tanks is a non-starter. Even a very short and cool burn would probably damage the engines and the re-use potential.
Title: Re: SpaceX advances drive for Mars rocket via Raptor power
Post by: baldusi on 07/26/2014 01:44 am

I believe the Raptor is planned to be a gas/gas full flow staged combustion engine.
That is, it compresses the liquid props then gasifies them prior to injection into the chamber. But as it uses part of the liquid fuel for regenerative cooling of the chamber/nozzle, I suspect that using gaseous prop from the tanks is a non-starter. Even a very short and cool burn would probably damage the engines and the re-use potential.
You really can't use a gas like that. You need high pressure at the main injector. For that you need the turbopump to increase pressure. But the pumps are designed liquid, not gas. And then the preburners are designed to take liquids. Plus the turbines are thermal machines that still need the temperature differential of the preburner. In short, you don't want gas. In fact, you need enough head pressure to avoid cavitation, even that amount of bubbles can destroy the turbopumps.
Title: Re: SpaceX advances drive for Mars rocket via Raptor power
Post by: baldusi on 07/26/2014 01:49 am

It occurred to me while struggling to model the Raptor BFR and coming up short on prop, that the BFR first stage and probably the second stage will never leave the vicinity of Earth. So why am I using gaseous prop to pressurize the tanks? Wouldn't a helium system work better without wasting prop that has been carried to MECO and SECO? And the vehicles will return to Earth so there will be no shortage of helium.

It makes sense to avoid helium in a vehicle that will go to Mars but the BFR won't, so where did I get the idea that the BFR will avoid helium?

How much mass would a helium pressurization system entail? I can say that total mass of prop needed to pressurize the near empty  tanks of the BFR is about  9,038.36 kg (S1) and 2,935.04 kg (S2) while equal pressurization using He would mass about 1,262.80 kg (S1) and 410.07 kg (S2). That is not very much mass relative to the payload to orbit of the BFR, but still, the mass savings for the stage 2 pressurization gases equates to over two tonnes of payload to orbit, not to mention additional impulse obtained from burning that prop for orbit insertion which is just over one second of engine burn at full throttle.

So my question is, "Why am I using prop to pressurize the tanks?"
At a certain point, simplicity is more important than performance. Autopressurization will probably be less complex and more reliable than an He system. Normally engineers want to minimize dry mass to minimize development cost. But with MCT they can do a 10% bigger rocket and eat the performance difference and win on the operations side.
Title: Re: SpaceX advances drive for Mars rocket via Raptor power
Post by: aero on 07/26/2014 03:44 am

It occurred to me while struggling to model the Raptor BFR and coming up short on prop, that the BFR first stage and probably the second stage will never leave the vicinity of Earth. So why am I using gaseous prop to pressurize the tanks? Wouldn't a helium system work better without wasting prop that has been carried to MECO and SECO? And the vehicles will return to Earth so there will be no shortage of helium.

It makes sense to avoid helium in a vehicle that will go to Mars but the BFR won't, so where did I get the idea that the BFR will avoid helium?

How much mass would a helium pressurization system entail? I can say that total mass of prop needed to pressurize the near empty  tanks of the BFR is about  9,038.36 kg (S1) and 2,935.04 kg (S2) while equal pressurization using He would mass about 1,262.80 kg (S1) and 410.07 kg (S2). That is not very much mass relative to the payload to orbit of the BFR, but still, the mass savings for the stage 2 pressurization gases equates to over two tonnes of payload to orbit, not to mention additional impulse obtained from burning that prop for orbit insertion which is just over one second of engine burn at full throttle.

So my question is, "Why am I using prop to pressurize the tanks?"
At a certain point, simplicity is more important than performance. Autopressurization will probably be less complex and more reliable than an He system. Normally engineers want to minimize dry mass to minimize development cost. But with MCT they can do a 10% bigger rocket and eat the performance difference and win on the operations side.

Well that's fair enough. At 267 tonnes to LEO, what is another 2 or 3 tonnes? And that brings up some results I have obtained. I am modeling an auto pressurization system using oxygen and methane gas. No conclusions, just some numbers.

I did manage to achieve a 5% payload with both versions of my BFR, the twin engine S2 that I posted before and finally, the single engine S2. The problem I was having getting the single engine second stage to orbit boiled down to not allowing enough delta V for gravity losses. Second stage gravity loss is not so much, compared to the first stage losses but if the design doesn't allow enough prop to overcome the second stage losses, the rocket still doesn't work! The single engine second stage incurs over 170 m/s more gravity loss than the twin engine stage 2. As I wrote above, no conclusions but some numbers.

For brevity, let me name the BFR that uses a twin engine stage 2 the Raptor 9-2, or 9-2 and the single engine stage 2 BFR the Raptor 9-1 or 9-1 in the following. The propellant mass fractions and dry masses:

Rocket      S1 pmf     S2 pmf      S1 dry mass    S2 dry mass
9-1        0.95990     0.95443     163,543.92     44,754.05
9-2        0.93986     0.94214     229,761.35     71,791.39


Consider that the Raptor engines likely masses 7.05 tonnes or more each, and the prop tanks of the rocket will mass between 50 and 70 tonnes, depending on the fineness ratio and lots of other stuff. I can break it down by stage if needed but indications are that either rocket could be built.

I speculate that the final design will settle around 12 to 13 meters diameter, and a total length of prop tanks (including both stages) of near 50 meters. Of course the rocket will be a lot taller than that with the engines, the inner stage holding that big stage 2 engine, then of course the payload. How tall, I couldn't guess at this point. Maybe someone can give an educated guess for the lengths of the stage engines and thrust structures. Engine nozzle diameters that I have now are 3.242 meters and 8.880 meters. Of course the Raptor 9-2 S2 engine nozzles are smaller. In fact if the rocket diameter is 12 to 13 meters, then they would be on the order of 5 to 5.5 meters diameter with a corresponding Isp like 374 seconds.

I need to read a bedtime story to my boy now, maybe edit later.
Title: Re: SpaceX advances drive for Mars rocket via Raptor power
Post by: Joel on 07/26/2014 09:06 am
So my question is, "Why am I using prop to pressurize the tanks?"
At a certain point, simplicity is more important than performance. Autopressurization will probably be less complex and more reliable than an He system. Normally engineers want to minimize dry mass to minimize development cost. But with MCT they can do a 10% bigger rocket and eat the performance difference and win on the operations side.

2000 kg of He equals about 8000 liters liquid He or about 240.000 USD at today's prices, cf.  http://www.reuters.com/article/2013/09/19/us-helium-shortage-analysis-idUSBRE98I0AN20130919 (http://www.reuters.com/article/2013/09/19/us-helium-shortage-analysis-idUSBRE98I0AN20130919). I don't know how significant that is. But then there is also the handling issues, sourcing on Mars etc.
Title: Re: SpaceX advances drive for Mars rocket via Raptor power
Post by: baldusi on 07/26/2014 01:35 pm

So my question is, "Why am I using prop to pressurize the tanks?"
At a certain point, simplicity is more important than performance. Autopressurization will probably be less complex and more reliable than an He system. Normally engineers want to minimize dry mass to minimize development cost. But with MCT they can do a 10% bigger rocket and eat the performance difference and win on the operations side.

2000 kg of He equals about 8000 liters liquid He or about 240.000 USD at today's prices, cf.  http://www.reuters.com/article/2013/09/19/us-helium-shortage-analysis-idUSBRE98I0AN20130919 (http://www.reuters.com/article/2013/09/19/us-helium-shortage-analysis-idUSBRE98I0AN20130919). I don't know how significant that is. But then there is also the handling issues, sourcing on Mars etc.
Of course. The most probable issue is QA, and operations cost. The He on the total propellant cost might not be that much. But manufacturing, quality assurance and operative cost might well be two couples of orders of magnitude bigger. Besides, if SpaceX want to be as close to gas and go, what is more simpler than auto-pressurization? No bottles, much simpler regulators, one less fluid on the pad, a lot of very leak sensitive piping and regulation system disappears.
Title: Re: SpaceX advances drive for Mars rocket via Raptor power
Post by: aero on 07/28/2014 04:53 am
A question - How much would it hurt to use separate helium tanks for methane and LOX He pressurization?

We keep hearing that there is no helium on Mars, but that is not so. Once the MCT lands, there could be a LOX tank and a methane fuel tank full of relatively low pressure He, just exactly as much as is needed in fact. They'd only need to pump it back into the He storage tanks and use it again. I wouldn't want to mix it up although it would probably be OK. Still, oxygen and methane fumes mixed in with high pressure He storage sounds bad. That's the reason for the question about separate tanks.

I used the rocket equation to calculate the payload penalty to LEO for using prop for autopressurization, the penalty is about 5 tonnes to LEO (I used Total delta V = 9,670 m/s.) I don't know what masses or the delta V from LEO to Mars surface but I guess it would be another 4 tonnes or so. (7 km/s from 185 km Earth circular orbit to Mars surface?)

Anyway, an additional 9-10 tonnes on the surface of Mars might be worth some trouble. Then again, maybe the Raptor powered BFR and MCT has all the capabilities wanted to send the MTC to Mars.

Edit: Another question - Is 270 tonnes to LEO enough for the MCT? It's only about half the size of the space station. :)
Title: Re: SpaceX advances drive for Mars rocket via Raptor power
Post by: guckyfan on 07/28/2014 06:38 am

Edit: Another question - Is 270 tonnes to LEO enough for the MCT? It's only about half the size of the space station. :)

Even not considering the reuse penalty it is nowhere near enough unless they use a very much smaller payload MCT than announced. That's why I concluded a long time ago they cannot do it without refuelling in LEO.
Title: Re: SpaceX advances drive for Mars rocket via Raptor power
Post by: baldusi on 07/28/2014 03:05 pm
A question - How much would it hurt to use separate helium tanks for methane and LOX He pressurization?

We keep hearing that there is no helium on Mars, but that is not so. Once the MCT lands, there could be a LOX tank and a methane fuel tank full of relatively low pressure He, just exactly as much as is needed in fact. They'd only need to pump it back into the He storage tanks and use it again. I wouldn't want to mix it up although it would probably be OK. Still, oxygen and methane fumes mixed in with high pressure He storage sounds bad. That's the reason for the question about separate tanks.

I used the rocket equation to calculate the payload penalty to LEO for using prop for autopressurization, the penalty is about 5 tonnes to LEO (I used Total delta V = 9,670 m/s.) I don't know what masses or the delta V from LEO to Mars surface but I guess it would be another 4 tonnes or so. (7 km/s from 185 km Earth circular orbit to Mars surface?)

Anyway, an additional 9-10 tonnes on the surface of Mars might be worth some trouble. Then again, maybe the Raptor powered BFR and MCT has all the capabilities wanted to send the MTC to Mars.

Edit: Another question - Is 270 tonnes to LEO enough for the MCT? It's only about half the size of the space station. :)
First, consider that He is even smaller than the H molecule (because it has two H atoms). So it's the most difficult gas to contain. This means avoiding leaks through every single pipe, valve, regulator and seat. And to actually store it you need to take it to about 4K (yes, just 4K above absolute zero).
Thus, the issue is not having the He, but avoiding that it leaks through the year long mission. And if you have a leak, you're done and your rocket will stay whenever you are.
This is what I mean about trading "performance" for reliability and simplicity. You need 10 more tonnes on Mars, increase the size of the vehicle by 10% and be done with it. Simplicity and reliability rule.
The reason that you end up with those systems is mostly when you have an existing design and you want to add performance, or your design margin is used up and you need to reach a certain level. But long term reliability and cost are achieved by simplicity.
Title: Re: SpaceX advances drive for Mars rocket via Raptor power
Post by: aero on 07/28/2014 06:57 pm
Ok, Ok enough. I'm convinced. Musk's solution using auto pressurization correct. 

One year (or more) is a very long time to contain He and no other gasses work significantly better than auto pressurization. Since I have the code in place I tried nitrogen and argon instead of He but those gasses are to massive, and cost performance over auto pressurization. Neon does provide about 1000 kg additional payload to LEO but so what? One tonne isn't enough to bother with a completely new, untried subsystem IMO.

Its auto pressurization, final answer.

Next I'll look at the reuse penalty, when I get back to looking at the BFR. But perhaps before that someone would comment on the viability of one engine verses two engines on Stage 2. For the single engine version the dry masses (posted on the previous page) look marginal to me. Two engines look much better to me and although I won't know until I see the numbers, I speculate that the lower staging altitude and velocity allowed by the twin engine upper stage will reduce the reuse penalty significantly for stage 1 and should have little or no effect on stage 2 reuse.
Title: Re: SpaceX advances drive for Mars rocket via Raptor power
Post by: baldusi on 07/28/2014 11:12 pm
Remember that a second engine means more mass, and thus the pmf of the stage decreases. Also, once you're orbital the T/W doesn't matters for cryogenic engines.
Title: Re: SpaceX advances drive for Mars rocket via Raptor power
Post by: aero on 07/29/2014 12:29 am
Remember that a second engine means more mass, and thus the pmf of the stage decreases. Also, once you're orbital the T/W doesn't matters for cryogenic engines.

Yes - but as I posted before and repeat here, I think the mass is available, especially compared to the single engine design. And the key is the "once you're orbital" part. Hopefully I can get some guidance to improve the single stage 2 engine BFR but as it stands now, it really struggles to get to orbit. Maybe I should post more detail, and will if asked. I just want to avoid a wall of text that everyone will ignore.

Quote
For brevity, let me name the BFR that uses a twin engine stage 2 the Raptor 9-2, or 9-2 and the single engine stage 2 BFR the Raptor 9-1 or 9-1 in the following. The propellant mass fractions and dry masses:

Rocket      S1 pmf     S2 pmf      S1 dry mass    S2 dry mass
9-1        0.95990     0.95443     163,543.92     44,754.05
9-2        0.93986     0.94214     229,761.35     71,791.39
Title: Re: SpaceX advances drive for Mars rocket via Raptor power
Post by: Coastal Ron on 07/29/2014 02:51 am
A question - How much would it hurt to use separate helium tanks for methane and LOX He pressurization?

We keep hearing that there is no helium on Mars, but that is not so. Once the MCT lands, there could be a LOX tank and a methane fuel tank full of relatively low pressure He, just exactly as much as is needed in fact. They'd only need to pump it back into the He storage tanks and use it again. I wouldn't want to mix it up although it would probably be OK. Still, oxygen and methane fumes mixed in with high pressure He storage sounds bad. That's the reason for the question about separate tanks.

A friend is a rebreather diver and he talks about how he mixes the gases in their tanks (including helium) and then let's them settle for a day or so to mix on their own.

I would assume the same would happen over time with helium pressurization systems, that the helium would mix with the oxygen and methane.  If you pump in more oxygen and methane that would mean that there wouldn't really be any helium left for pressurization since it would have been absorbed into the leftover oxygen and methane.

That would be a disadvantage for using helium in an application where you are refueling.
Title: Re: SpaceX advances drive for Mars rocket via Raptor power
Post by: MP99 on 07/29/2014 08:17 am
Remember that a second engine means more mass, and thus the pmf of the stage decreases. Also, once you're orbital the T/W doesn't matters for cryogenic engines.

T/W is less important, but it does still add to the gross dV required if it drops too low. (And, of course, that's on the wrong end of an exponential relationship to prop load.)

It was on the edge of biting with DIRECT's Lunar architecture - ~200t IMLEO with 100 klb thrust. [Edit: call it T/W of 0.2.]

But, if we're talking about one Raptor or two, that's absolutely correct. [Edit: but a 1 mlbf engine pushing 100t through TMI would have a terminal T/W over 4g (before you take throttling into account). It will get even higher for later phases of the flight.]

Cheers, Martin
Title: Re: SpaceX advances drive for Mars rocket via Raptor power
Post by: aero on 07/29/2014 04:46 pm
Well, I did a check. The T/W of the single Raptor engine S2 at ignition is 0.67 which seems enough compared to the Falcon 9 stage 2 at ignition which is 0.73. The difference is that the Falcon 9 burns off prop fast enough that it reaches T/W =1 at 93 seconds while the Raptor takes 183 seconds to reach T/W = 1. In both cases the S2 has some upward velocity imparted by the first stage but without an upward thrust component from S2, that upward velocity is bled off by gravity. Of course both S2's supply the needed upward thrust component, it's just that with the Raptor that component is a larger percent of total thrust for a much longer time. That adds about 175 m/s of gravity loss to the Raptor trajectory.

Of course it could be pilot error, too. I'll try some different trajectories.

Edit add: Note that even at burn-out (SECO) the Raptor only reaches a T/W = 2.6 or 2.6 g's acceleration.
Title: Re: SpaceX advances drive for Mars rocket via Raptor power
Post by: baldusi on 07/29/2014 07:14 pm

Quote
For brevity, let me name the BFR that uses a twin engine stage 2 the Raptor 9-2, or 9-2 and the single engine stage 2 BFR the Raptor 9-1 or 9-1 in the following. The propellant mass fractions and dry masses:

Rocket      S1 pmf     S2 pmf      S1 dry mass    S2 dry mass
9-1        0.95990     0.95443     163,543.92     44,754.05
9-2        0.93986     0.94214     229,761.35     71,791.39
Why do you have such a lower pmf on the S1 for 9-2? That would imply a much lower tank volume. If we assume a T/W of 100 on the engines, that's 63tonnes just on engines. Plus octaweb and piping it might well be around 80 tonnes or so. Thus, you have about 83 tonnes of tank in 9-1 but 149 tonnes of tank on the 9-2. I don't believe the structural requirements would be so terrible on the 9-2 case. What are the propellant masses, btw?

Well, I did a check. The T/W of the single Raptor engine S2 at ignition is 0.67 which seems enough compared to the Falcon 9 stage 2 at ignition which is 0.73. The difference is that the Falcon 9 burns off prop fast enough that it reaches T/W =1 at 93 seconds while the Raptor takes 183 seconds to reach T/W = 1. In both cases the S2 has some upward velocity imparted by the first stage but without an upward thrust component from S2, that upward velocity is bled off by gravity. Of course both S2's supply the needed upward thrust component, it's just that with the Raptor that component is a larger percent of total thrust for a much longer time. That adds about 175 m/s of gravity loss to the Raptor trajectory.

Of course it could be pilot error, too. I'll try some different trajectories.

Edit add: Note that even at burn-out (SECO) the Raptor only reaches a T/W = 2.6 or 2.6 g's acceleration.
Well, it's mighty difficult to find the T/W of a two stage RP-1/LOX rocket. The Falcon 1 was 0.68 and Soyuz-2.1v Block-I is 1.15, but its flown usually with a Volga stage, so if it is in fact a two stage rocket is quite debatable. Zenit 2SL S2 is 1.11, but again, most of the time is flown as a three stage rocket.
For comparison, Centaur has a 0.44 for normal missions and .88 for dual engine. The DIVUS 4m is 0.47 and the 5m DIVUS is 0.37. The Saturn IVB was 0.91. Antares Castor 30B is 2.38, but that's a solid.
So I believe that somewhere around the 0.75+/-0.10 is more than fine. I would love to see your trajectory rule. It's normal that 80% of the velocity be done by the upper stage (S1 eats most of gravity and all aero losses). You can trade altitude to get more horizontal velocity (i.e. a more steeper S1 trajectory). This is particularly true for recoverable first stages, that I understand that is not this case. I hope that you find my comments useful.
Title: Re: SpaceX advances drive for Mars rocket via Raptor power
Post by: aero on 07/30/2014 04:52 pm
I was able to make a small change that improved things quite a lot for the single engine stage 2. Now the S2 pmf is 0.93471 and dry mass is 64,365.50 kg which is consistent with the twin engine version dry mass, 71,791.39 kg.

I've attached curves showing the altitude and velocity of the stage 2, and also the ballistic path of the stage from MECO. This is just the trajectory with stage 2 mdot = 0. The horizontal axis units are time from nominal S2 ignition.

My only concern at the moment is that the relatively high velocity at staging (over the Falcon 9 and the Raptor 9-2) will add difficulty for recovery. And by the way, that is the reason for the lower pmf on the S1 for 9-2. The 9-2 S2 performance is enough that I could probably make the pmf on the S1 for 9-2 even lower but I will look at that when I look at recovery.
Title: Re: SpaceX advances drive for Mars rocket via Raptor power
Post by: baldusi on 07/30/2014 06:14 pm
So, your S1 pmf wasn't the stage pmf but the necessary fuel consumption to achieve your performance? In other words, a stage with a pmf of 95% but with 2% of fuel reserves?
In any case, in expendable mode, you shouldn't care about staging speed. May be drop zones, but not staging velocity.
Title: Re: SpaceX advances drive for Mars rocket via Raptor power
Post by: aero on 07/30/2014 07:33 pm
So, your S1 pmf wasn't the stage pmf but the necessary fuel consumption to achieve your performance? In other words, a stage with a pmf of 95% but with 2% of fuel reserves?
In any case, in expendable mode, you shouldn't care about staging speed. May be drop zones, but not staging velocity.

Pretty much.

While I am treating with expendable mode, I really don't care about it. The BFR will be designed from the start to be reusable so now that I have baseline performance in expendable mode I will start looking at recovery. I speculate that only the first stage will need recovery prop and that the S2 will use heat shield and landing engines. These considerations may change staging speed and the pmf values for both stages.
Title: Re: SpaceX advances drive for Mars rocket via Raptor power
Post by: baldusi on 07/30/2014 09:01 pm
So, your S1 pmf wasn't the stage pmf but the necessary fuel consumption to achieve your performance? In other words, a stage with a pmf of 95% but with 2% of fuel reserves?
In any case, in expendable mode, you shouldn't care about staging speed. May be drop zones, but not staging velocity.

Pretty much.

While I am treating with expendable mode, I really don't care about it. The BFR will be designed from the start to be reusable so now that I have baseline performance in expendable mode I will start looking at recovery. I speculate that only the first stage will need recovery prop and that the S2 will use heat shield and landing engines. These considerations may change staging speed and the pmf values for both stages.
May be conceptually it would be easier to state dry mass and propellant reserves separately. It is a cleaner presentation and you state clearly what's the structural margin and what is the propellant needed for reusability.
Title: Re: SpaceX advances drive for Mars rocket via Raptor power
Post by: Chris Bergin on 10/16/2014 01:01 pm
As noted on a thread I've removed, there's been a copyright breach of NSF content by Brian Wang at @nextbigfuture - I do not want to see them get promoted on here for it (despite the thread pointing out it's a copyright breach).

I would urge everyone to point out they have breached NSF's copyright, as I have, by tweeting such messages to them (without being rude).

Most of you have tweeter accounts, to I want to see some community pressure put on this issue! Don't sit on your hands, support NSF. It's the short end of a long stick if we just shrug our shoulders when other sites think our content is free to use any way they wish without any accreditation.
Title: Re: SpaceX advances drive for Mars rocket via Raptor power
Post by: Chris Bergin on 10/16/2014 04:33 pm
Well done everyone. That's worked!
Title: Re: SpaceX advances drive for Mars rocket via Raptor power
Post by: LouScheffer on 10/16/2014 05:21 pm
Ok, Ok enough. I'm convinced. Musk's solution using auto pressurization correct. 

One year (or more) is a very long time to contain He and no other gasses work significantly better than auto pressurization. Since I have the code in place I tried nitrogen and argon instead of He but those gasses are to massive, and cost performance over auto pressurization.
How about using hydrogen to pressurize the methane?  It's half the weight of helium, and potentially available on Mars. Then neon for the oxygen tank? You could get this from the Mars atmosphere, as well.
Title: Re: SpaceX advances drive for Mars rocket via Raptor power
Post by: Robotbeat on 10/16/2014 05:45 pm
Just use warmed methane and oxygen. Don't make it more complicated than it needs to be.
Title: Re: SpaceX advances drive for Mars rocket via Raptor power
Post by: Hyperion5 on 10/16/2014 06:06 pm
Ok, Ok enough. I'm convinced. Musk's solution using auto pressurization correct. 

One year (or more) is a very long time to contain He and no other gasses work significantly better than auto pressurization. Since I have the code in place I tried nitrogen and argon instead of He but those gasses are to massive, and cost performance over auto pressurization.
How about using hydrogen to pressurize the methane?  It's half the weight of helium, and potentially available on Mars. Then neon for the oxygen tank? You could get this from the Mars atmosphere, as well.

Dmitry_V_home has looked into this, and found that the performance difference for hydrogen pressurization of the methane tanks is of negligible difference for performance versus using gaseous methane.  He thus recommended using gaseous methane for tank pressurization over hydrogen, and he didn't even consider Neon for pressurizing the oxygen tanks.  Most likely he didn't because it didn't seem a logical gas to use for such a task when you can just use gaseous oxygen. 
Title: Re: SpaceX advances drive for Mars rocket via Raptor power
Post by: Nindalf on 10/16/2014 07:22 pm
Yeah, neon's a bad combination of too hard to get and not good enough (the boiling point's good and low at 27K, but the atomic mass is 20, compared to a molecular mass of 28 for nitrogen and 32 for oxygen).  On Earth neon is more expensive than helium (which is generated in the Earth's interior by alpha decay processes), and on Mars it's going to be basically unavailable (though you might find helium while drilling for water, methane, and other valuables).  Maybe you were thinking of argon, which is plentiful on both Earth and Mars, but it offers no advantage at all over oxygen self-pressurization or compressed nitrogen (the atomic mass is 40, and the boiling point is similar to oxygen's or nitrogen's).

Basically, there's little point in considering anything other than helium (for performance) or nitrogen (for abundance) if you're using separately tanked pressurant.
Title: Re: SpaceX advances drive for Mars rocket via Raptor power
Post by: go4mars on 01/06/2015 07:52 pm
So Stennis seems to make more sense given the reduced presumable scale of raptor.

Is the reduction related to RD-180 replacement funding?  I seem to vaguely recall an airforce request for proposals about 5 years ago in this ballpark (or slightly smaller?)
Or independently-
Thrust to weight or height or failure redundancy or mass producibility or rocket scalability of many smaller ones versus fewer larger ones?  For low-flow plume cushion during rentry?  Better stoichiometric combustion?
Or for versatility (moon & lower g landings/maneuvers)? 
Use on Bigelow units? 

Anyone have some general pros and cons of megaclustering? Like on UR700M?
Title: Re: SpaceX advances drive for Mars rocket via Raptor power
Post by: dglow on 01/06/2015 08:08 pm
So Stennis seems to make more sense given the reduced presumable scale of raptor.

Is the reduction related to RD-180 replacement funding?  I seem to vaguely recall an airforce request for proposals about 5 years ago in this ballpark (or slightly smaller?)
Or independently-
Thrust to weight or height or failure redundancy or mass producibility or rocket scalability of many smaller ones versus fewer larger ones?  For low-flow plume cushion during rentry?  Better stoichiometric combustion?
Or for versatility (moon & lower g landings/maneuvers)? 
Use on Bigelow units? 

Anyone have some general pros and cons of megaclustering? Like on UR700M?


Or for versatility (moon & lower g landings/maneuvers)

^ This. Landing on Mars.
Title: Re: SpaceX advances drive for Mars rocket via Raptor power
Post by: spacenut on 03/02/2015 04:52 pm
Does anyone know what is happening here?  Wikipedia said they upgraded the metholox engine to 1 million lbs thrust and speculation is for a 10m rocket with 9 of these engines for 9 million lbs thrust.  This update said February 2015.  Also does anyone have a time frame for this to come about?  Would it be before SLS is ready?

Title: Re: SpaceX advances drive for Mars rocket via Raptor power
Post by: gongora on 03/02/2015 05:35 pm
SpaceX isn't going to develop a new rocket, build a new factory and launch site for it, and test/fly it before SLS flies.
Title: Re: SpaceX advances drive for Mars rocket via Raptor power
Post by: BobHk on 03/02/2015 05:52 pm
Does anyone know what is happening here?  Wikipedia said they upgraded the metholox engine to 1 million lbs thrust and speculation is for a 10m rocket with 9 of these engines for 9 million lbs thrust.  This update said February 2015.  Also does anyone have a time frame for this to come about?  Would it be before SLS is ready?

In a recent reddit appearance Musk said they're downsizing Raptor to 500,000 lbf

I don't bet against SpaceX producing anything as quickly as they want to. 
Title: Re: SpaceX advances drive for Mars rocket via Raptor power
Post by: BobHk on 03/02/2015 05:53 pm
SpaceX isn't going to develop a new rocket, build a new factory and launch site for it, and test/fly it before SLS flies.

I'll take that bet. 

And SLS might, 'might' fly twice.  And not before 2018 if its even fully funded throughout its dev/life cycle.

Title: Re: SpaceX advances drive for Mars rocket via Raptor power
Post by: gongora on 03/02/2015 06:01 pm
In that Reddit talk Elon said that optimizing thrust to weight led to a surprisingly low number.  Now we need to see if they're actually going to optimize the engine thrust to weight, or if any other factors alter the size of the final engine design.
Title: Re: SpaceX advances drive for Mars rocket via Raptor power
Post by: Brovane on 03/02/2015 06:27 pm
Does anyone know what is happening here?  Wikipedia said they upgraded the metholox engine to 1 million lbs thrust and speculation is for a 10m rocket with 9 of these engines for 9 million lbs thrust.  This update said February 2015.  Also does anyone have a time frame for this to come about?  Would it be before SLS is ready?

In a recent reddit appearance Musk said they're downsizing Raptor to 500,000 lbf

I don't bet against SpaceX producing anything as quickly as they want to.

Two 500,000 lbf Raptors could be a replacement for the RD-180 on the Atlas-V. 
Title: Re: SpaceX advances drive for Mars rocket via Raptor power
Post by: Lars-J on 03/02/2015 06:36 pm
Does anyone know what is happening here?  Wikipedia said they upgraded the metholox engine to 1 million lbs thrust and speculation is for a 10m rocket with 9 of these engines for 9 million lbs thrust.  This update said February 2015.  Also does anyone have a time frame for this to come about?  Would it be before SLS is ready?

In a recent reddit appearance Musk said they're downsizing Raptor to 500,000 lbf

I don't bet against SpaceX producing anything as quickly as they want to.

Two 500,000 lbf Raptors could be a replacement for the RD-180 on the Atlas-V.

I guess you missed the BE-4 announcement. ;)
Title: Re: SpaceX advances drive for Mars rocket via Raptor power
Post by: Brovane on 03/02/2015 06:42 pm
Does anyone know what is happening here?  Wikipedia said they upgraded the metholox engine to 1 million lbs thrust and speculation is for a 10m rocket with 9 of these engines for 9 million lbs thrust.  This update said February 2015.  Also does anyone have a time frame for this to come about?  Would it be before SLS is ready?

In a recent reddit appearance Musk said they're downsizing Raptor to 500,000 lbf

I don't bet against SpaceX producing anything as quickly as they want to.

Two 500,000 lbf Raptors could be a replacement for the RD-180 on the Atlas-V.

I guess you missed the BE-4 announcement. ;)

Well so did the US govt.  ;)  Congress want's to pay for the development of a US engine to replace the RD-180, regardless of the BE-4.  Maybe SpaceX should put in a proposal for this govt contract.  Get the US govt to pay for the development of the Raptor Engine.
Title: Re: SpaceX advances drive for Mars rocket via Raptor power
Post by: Lobo on 03/02/2015 07:30 pm
SpaceX isn't going to develop a new rocket, build a new factory and launch site for it, and test/fly it before SLS flies.

I'll take that bet. 

And SLS might, 'might' fly twice.  And not before 2018 if its even fully funded throughout its dev/life cycle.


If SLS does fly in 2018, BFR will not fly before that.  They need a pad, a new facility with wider tooling, and a fully working engine prior to that.  That won't happen in the next 3-4 years.  If the first SLS launch is pushed back to 2020 or 2021 or something, then it's possible. 
So I agree with Gongora here.

However, I agree that once BFR is flying or perhaps even when it's late into development and looking "inevitable" with metal being bent and Raptor firing properly...that SLS main supporting argument that it's the only LV with that capacity, and that capacity is necessary for BLEO HSF pretty much goes away.  Then I think it'll be cancelled after just a few launches as Musk will go into full salesman mode and offer it's services to NASA for some very attractive pricing to help facilitate SLS's demise.  Without SLS, NASA BLEO HSF will pretty much be locked into SpaceX.  That's worth offering launch services at a large bargin to get that locked in.  And that can be used to help fund MCT then.
 
Title: Re: SpaceX advances drive for Mars rocket via Raptor power
Post by: MP99 on 03/02/2015 07:33 pm
Does anyone know what is happening here?  Wikipedia said they upgraded the metholox engine to 1 million lbs thrust and speculation is for a 10m rocket with 9 of these engines for 9 million lbs thrust.  This update said February 2015.  Also does anyone have a time frame for this to come about?  Would it be before SLS is ready?

In a recent reddit appearance Musk said they're downsizing Raptor to 500,000 lbf

I don't bet against SpaceX producing anything as quickly as they want to.

Two 500,000 lbf Raptors could be a replacement for the RD-180 on the Atlas-V.

I guess you missed the BE-4 announcement. ;)

Off-the-wall thought - SpaceX take up BE-4 instead of developing Raptor.

cheers, Martin
Title: Re: SpaceX advances drive for Mars rocket via Raptor power
Post by: PahTo on 03/02/2015 07:40 pm

Off-the-wall thought - SpaceX take up BE-4 instead of developing Raptor.

cheers, Martin

I suspect that won't happen given the purported rivalry between Bezos and Musk.  More likely Musk wants to build a better methane engine sooner.  But given ULA involvement (by no mistake, a-hem) the BE-4 looks to have the inside track for earlier production.
Title: Re: SpaceX advances drive for Mars rocket via Raptor power
Post by: kch on 03/02/2015 07:49 pm

Without SLS, NASA BLEO HSF will pretty much be locked into SpaceX. 

... which is pretty much where NASA LEO HSF is now with regard to the Russians -- why would they make *that* mistake again?  That's more than enough reason to continue SLS, even if SpaceX gave them a dozen free BFR flights.  No more "barrels and ankles" situations, thank-you-very-much!
Title: Re: SpaceX advances drive for Mars rocket via Raptor power
Post by: symbios on 03/02/2015 07:54 pm

Without SLS, NASA BLEO HSF will pretty much be locked into SpaceX. 

... which is pretty much where NASA LEO HSF is now with regard to the Russians -- why would they make *that* mistake again?  That's more than enough reason to continue SLS, even if SpaceX gave them a dozen free BFR flights.  No more "barrels and ankles" situations, thank-you-very-much!

So you are saying that the Geopolitical situation between SpaceX and America is going to deteriorate because of Elon Musks overwhelming ambition to conquer other nations? And this will cause Elon Musk to tell America to find a trampoline? Yea that will happen... [/sarcasm]
Title: Re: SpaceX advances drive for Mars rocket via Raptor power
Post by: kch on 03/02/2015 08:13 pm

Without SLS, NASA BLEO HSF will pretty much be locked into SpaceX. 

... which is pretty much where NASA LEO HSF is now with regard to the Russians -- why would they make *that* mistake again?  That's more than enough reason to continue SLS, even if SpaceX gave them a dozen free BFR flights.  No more "barrels and ankles" situations, thank-you-very-much!

So you are saying that the Geopolitical situation between SpaceX and America is going to deteriorate because of Elon Musks overwhelming ambition to conquer other nations? And this will cause Elon Musk to tell America to find a trampoline? Yea that will happen... [/sarcasm]

LMAO ... no.  Nice try, but no.  Once NASA is "over a barrel" (wrt Russia, or SpaceX, or *any* potential-monopoly supplier), the price goes up ("to help fund MCT," in this case), and there ain't JS they can do about it (in the short term).  I would hope they've learned *that* lesson!
Title: Re: SpaceX advances drive for Mars rocket via Raptor power
Post by: mfck on 03/02/2015 08:18 pm

Without SLS, NASA BLEO HSF will pretty much be locked into SpaceX. 

... which is pretty much where NASA LEO HSF is now with regard to the Russians -- why would they make *that* mistake again?  That's more than enough reason to continue SLS, even if SpaceX gave them a dozen free BFR flights.  No more "barrels and ankles" situations, thank-you-very-much!

So you are saying that the Geopolitical situation between SpaceX and America is going to deteriorate because of Elon Musks overwhelming ambition to conquer other nations? And this will cause Elon Musk to tell America to find a trampoline? Yea that will happen... [/sarcasm]

LMAO ... no.  Nice try, but no.  Once NASA is "over a barrel" (wrt Russia, or SpaceX, or *any* potential-monopoly supplier), the price goes up ("to help fund MCT," in this case), and there ain't JS they can do about it (in the short term).  I would hope they've learned *that* lesson!
What gives you that hope? Prior conduct?
Title: Re: SpaceX advances drive for Mars rocket via Raptor power
Post by: mme on 03/02/2015 08:23 pm
...
Off-the-wall thought - SpaceX take up BE-4 instead of developing Raptor.

cheers, Martin
I think that will happen shortly after they discover unicorns dancing in the flame trench...

For reasons I don't know or understand, Bezos has teamed up with ULA in the past to impede SpaceX's progress (like trying to lease 39-A while ULA plans to reduce the numbers of pads it uses and BO doesn't have an LV.)  SpaceX won't be betting their business on anything from BO.
Title: Re: SpaceX advances drive for Mars rocket via Raptor power
Post by: kch on 03/02/2015 08:34 pm

Without SLS, NASA BLEO HSF will pretty much be locked into SpaceX. 

... which is pretty much where NASA LEO HSF is now with regard to the Russians -- why would they make *that* mistake again?  That's more than enough reason to continue SLS, even if SpaceX gave them a dozen free BFR flights.  No more "barrels and ankles" situations, thank-you-very-much!

So you are saying that the Geopolitical situation between SpaceX and America is going to deteriorate because of Elon Musks overwhelming ambition to conquer other nations? And this will cause Elon Musk to tell America to find a trampoline? Yea that will happen... [/sarcasm]

LMAO ... no.  Nice try, but no.  Once NASA is "over a barrel" (wrt Russia, or SpaceX, or *any* potential-monopoly supplier), the price goes up ("to help fund MCT," in this case), and there ain't JS they can do about it (in the short term).  I would hope they've learned *that* lesson!

What gives you that hope? Prior conduct?

Relentless optimism in the face of reality, I guess -- I'm easily encouraged (some would say 'incorriged') by any glimmer of intelligence that dares show itself.  With any luck, they've learned something ... but is it the right thing?  We shall see.
Title: Re: SpaceX advances drive for Mars rocket via Raptor power
Post by: meekGee on 03/02/2015 09:21 pm

Without SLS, NASA BLEO HSF will pretty much be locked into SpaceX. 

... which is pretty much where NASA LEO HSF is now with regard to the Russians -- why would they make *that* mistake again?  That's more than enough reason to continue SLS, even if SpaceX gave them a dozen free BFR flights.  No more "barrels and ankles" situations, thank-you-very-much!

So you are saying that the Geopolitical situation between SpaceX and America is going to deteriorate because of Elon Musks overwhelming ambition to conquer other nations? And this will cause Elon Musk to tell America to find a trampoline? Yea that will happen... [/sarcasm]

LMAO ... no.  Nice try, but no.  Once NASA is "over a barrel" (wrt Russia, or SpaceX, or *any* potential-monopoly supplier), the price goes up....

... up higher even than NASA's own SLS pricing?  That's a lot of up.
Title: Re: SpaceX advances drive for Mars rocket via Raptor power
Post by: Lobo on 03/02/2015 09:51 pm

Without SLS, NASA BLEO HSF will pretty much be locked into SpaceX. 

... which is pretty much where NASA LEO HSF is now with regard to the Russians -- why would they make *that* mistake again?  That's more than enough reason to continue SLS, even if SpaceX gave them a dozen free BFR flights.  No more "barrels and ankles" situations, thank-you-very-much!

So you are saying that the Geopolitical situation between SpaceX and America is going to deteriorate because of Elon Musks overwhelming ambition to conquer other nations? And this will cause Elon Musk to tell America to find a trampoline? Yea that will happen... [/sarcasm]

LMAO ... no.  Nice try, but no.  Once NASA is "over a barrel" (wrt Russia, or SpaceX, or *any* potential-monopoly supplier), the price goes up ("to help fund MCT," in this case), and there ain't JS they can do about it (in the short term).  I would hope they've learned *that* lesson!

???

Ummm....this doesn't make any sense to me.

How would NASA be any more "over a barrel" Depending on SpaceX than they are now with Boeing building the core, AJR building RS-25's, and ATK building the boosters?  A problem with any one of them and SLS is as grounded as BFR would be if there was a problem with SpaceX. 

And there is no comparison of any American company, SpaceX, Boeing or otherwise compared to Russia.  American companies are subject to American law.  They are compelled by the force of the US government to fullfill their contracts, where Russia is not. 

NASA is no more "over a barrel" with SpaceX than they are with any US Contractor, as they don't actually build rockets directly as an agency.  And even if they did they'd be "Over a barrel" with regard to their suppliers.  If they can't get alloy or other components, they can't build anything. 

So this comparision is not valid.
Title: Re: SpaceX advances drive for Mars rocket via Raptor power
Post by: symbios on 03/02/2015 09:53 pm
Yea, what was the estimated price tag of a launch of the SLS again? Above a billion?

From what I have gathered the BFR will come well below 500 million for a launch maybe even closer to 200 or below.

SpaceX wants to drive the price down for access to space. Until they do something to counter their stated policy I will go with that they do not work like old space/classic big corporate america. This to me means that they do not try to extort every penny the can and then some...

Volume is the key, and you do not get volume by a to high a price... If NASA can afford to do two missions instead of one because of low launch prices that will spread the cost and enable a lower price and maybe a even higher launch cadence.
Title: Re: SpaceX advances drive for Mars rocket via Raptor power
Post by: sghill on 03/02/2015 10:00 pm

SpaceX wants to drive the price down for access to space. Until they do something to counter their stated policy I will go with that they do not work like old space/classic big corporate america. This to me means that they do not try to extort every penny the can and then some...

"Corporate America" does not operate like "old space."  The two are very different for -IMHO- very valid balanced scorecard reasons, and it is a straw man argument to equate the two.

What does any of this current discussion have to do with Raptor engines again? :)

Title: Re: SpaceX advances drive for Mars rocket via Raptor power
Post by: TomH on 03/02/2015 10:18 pm
However, I agree that once BFR is flying or perhaps even when it's late into development and looking "inevitable" with metal being bent and Raptor firing properly...that SLS main supporting argument that it's the only LV with that capacity, and that capacity is necessary for BLEO HSF pretty much goes away.  Then I think it'll be cancelled after just a few launches...

One would think so. But then again there's that little cadre of senators holding committee chairmanships. I think your scenario will happen if they're retired by then. If they all pull a Strom Thurmond and stay until they're centenarians, SLS may well continue receiving its welfare payments.
Title: Re: SpaceX advances drive for Mars rocket via Raptor power
Post by: CuddlyRocket on 03/02/2015 11:05 pm
Off-the-wall thought - SpaceX take up BE-4 instead of developing Raptor.

cheers, Martin

No. Mars.
Title: Re: SpaceX advances drive for Mars rocket via Raptor power
Post by: Lobo on 03/03/2015 12:32 am
However, I agree that once BFR is flying or perhaps even when it's late into development and looking "inevitable" with metal being bent and Raptor firing properly...that SLS main supporting argument that it's the only LV with that capacity, and that capacity is necessary for BLEO HSF pretty much goes away.  Then I think it'll be cancelled after just a few launches...

One would think so. But then again there's that little cadre of senators holding committee chairmanships. I think your scenario will happen if they're retired by then. If they all pull a Strom Thurmond and stay until they're centenarians, SLS may well continue receiving its welfare payments.

You have a point, but I think if those fossils are still there then, their hold won't be enough.  Questions will be asked that currently can be explained away by saying, "There's no LV that can come close to what SLS (or Ares V SDHLV) can do, and near 130mt to LEO is what's necessary for going to BLEO destinations with astronauts.  Multiple launch missions with smaller LV's introduces unacceptable level of LOM risk with their complexity.  A single LV of this class is necessary for a safe and robust exploration future...etc. etc.".

You can disagree with that assessment, but the fact is there is no other system that can do what SLS will and it's a he said/she said argument on whether that is -really- needed.  But "conventional wisdom" says it is and so that's the view you have to dislodge.
A BFR advocate will be able to say, "Yes, you are quite right.  Fortuantely now there is a lower cost alternative with the capacity equal (or in excess) of SLS.  With the money saved from it we can launch more payloads and have more missions and do more exploration.  NASA is relieved from having to maintain the overhead of a HLV themselves, etc. etc".

It'll be man-rated, so that argument is out.  And while cancelling SLS will mean cutting jobs in certain places, it'll mean creating new jobs in other places to support BFR.  So there will be those who'll fight those fighting to keep SLS.

Finally, NASA itself could be an X-factor.  I think there will be those who think they have a better shot of walking on MArs with SpaceX than with SLS, and will start saying so to Congress.  At the end of the day...NASA really would like to have their astros be the first to walk on Mars and worry that their current trajectory puts them in the same holding pattern they've been in for the last decade.

So we'll see.  But I think the fossils days will be numbered at that point, IMHO.

Title: Re: SpaceX advances drive for Mars rocket via Raptor power
Post by: Owlon on 03/03/2015 01:21 am
Wouldn't it be ironic if SpaceX's Raptor-powered rocket led to SLS being cancelled, which led to the same bigger-is-better logic being applied to, say, a 500 ton to LEO NASA rocket that costs even more?
Title: Re: SpaceX advances drive for Mars rocket via Raptor power
Post by: su27k on 03/03/2015 01:54 am
Two 500,000 lbf Raptors could be a replacement for the RD-180 on the Atlas-V.

I guess you missed the BE-4 announcement. ;)

Off-the-wall thought - SpaceX take up BE-4 instead of developing Raptor.

cheers, Martin

More off-the-wall thought: Re-engine SLS core stage using BE-4. (Did someone do the math about this before?)
Title: Re: SpaceX advances drive for Mars rocket via Raptor power
Post by: Brovane on 03/03/2015 02:26 am
Does anyone know what is happening here?  Wikipedia said they upgraded the metholox engine to 1 million lbs thrust and speculation is for a 10m rocket with 9 of these engines for 9 million lbs thrust.  This update said February 2015.  Also does anyone have a time frame for this to come about?  Would it be before SLS is ready?

In a recent reddit appearance Musk said they're downsizing Raptor to 500,000 lbf

I don't bet against SpaceX producing anything as quickly as they want to.

Two 500,000 lbf Raptors could be a replacement for the RD-180 on the Atlas-V.

I guess you missed the BE-4 announcement. ;)

Off-the-wall thought - SpaceX take up BE-4 instead of developing Raptor.

cheers, Martin

Or SpaceX gets the USAF contract to develop a new engine that Congress wants in addition to the BE-4.   The USAF pays to finish the development of a Raptor engine in the range of 500-600k lbf.  SpaceX gets one part of the US govt to pay to develop the engine for it's BFR and it can then have a rival HLV to NASA's SLS. 
Title: Re: SpaceX advances drive for Mars rocket via Raptor power
Post by: Norm38 on 03/03/2015 02:52 am
Wouldn't it be ironic if SpaceX's Raptor-powered rocket led to SLS being cancelled, which led to the same bigger-is-better logic being applied to, say, a 500 ton to LEO NASA rocket that costs even more?

I would hope that NASA has learned the lesson of runaway scope creep by now.  And working with a contractor is a two-way street.  NASA can ask for anything, doesn't mean that SpaceX has to go along with it.  I don't think SpaceX is interested in getting bogged down with some boondoggle that they can't sell to anyone else and use for anything else.

If 500 ton to LEO happens, it'll happen due to true need.  Such as so many launches of 100 ton class rockets are happening, docking payloads in LEO, that it's more efficient to launch more highly integrated and functional 500 ton blocks. 

So for the next decade, no.
Title: Re: SpaceX advances drive for Mars rocket via Raptor power
Post by: kch on 03/03/2015 03:27 am

Without SLS, NASA BLEO HSF will pretty much be locked into SpaceX. 

... which is pretty much where NASA LEO HSF is now with regard to the Russians -- why would they make *that* mistake again?  That's more than enough reason to continue SLS, even if SpaceX gave them a dozen free BFR flights.  No more "barrels and ankles" situations, thank-you-very-much!

So you are saying that the Geopolitical situation between SpaceX and America is going to deteriorate because of Elon Musks overwhelming ambition to conquer other nations? And this will cause Elon Musk to tell America to find a trampoline? Yea that will happen... [/sarcasm]

LMAO ... no.  Nice try, but no.  Once NASA is "over a barrel" (wrt Russia, or SpaceX, or *any* potential-monopoly supplier), the price goes up....

... up higher even than NASA's own SLS pricing?  That's a lot of up.

Yes, it is.  For comparison: 

* what was the price of a Soyuz seat just before the Shuttles stopped flying?
* what is the price of a Soyuz seat now?

That's been a fair bit of up, too, has it not?
Title: Re: SpaceX advances drive for Mars rocket via Raptor power
Post by: Robotbeat on 03/03/2015 03:29 am
There are laws preventing ripping off the government. Doesn't mean costs don't grow, but it will not exceed SLS.
Title: Re: SpaceX advances drive for Mars rocket via Raptor power
Post by: kch on 03/03/2015 03:37 am
There are laws preventing ripping off the government. Doesn't mean costs don't grow, but it will not exceed SLS.

Very glad to hear that.  :)
Title: Re: SpaceX advances drive for Mars rocket via Raptor power
Post by: meekGee on 03/03/2015 06:18 am
The one thing to bring into consideration is that unlike all the other scenarios, SpaceX's own plans are much larger than any that the government has in mind.

If NASA says "never mind SLS, we'll fly with BFR" it won't make much difference to BFR, financially.  However, SpaceX will be more than happy to gain from NASA's other resources, and given SpaceX's plan, there's a large multiplier there.

So it's in their interest to serve as the heavy lift provider for NASA, and not in their interest to jack up pricing the minute they can. They are not a near-sighted company.
Title: Re: SpaceX advances drive for Mars rocket via Raptor power
Post by: The Amazing Catstronaut on 03/03/2015 07:42 am
The one thing to bring into consideration is that unlike all the other scenarios, SpaceX's own plans are much larger than any that the government has in mind.

If NASA says "never mind SLS, we'll fly with BFR" it won't make much difference to BFR, financially.  However, SpaceX will be more than happy to gain from NASA's other resources, and given SpaceX's plan, there's a large multiplier there.

So it's in their interest to serve as the heavy lift provider for NASA, and not in their interest to jack up pricing the minute they can. They are not a near-sighted company.

Agreed. In addition, it's always been in their ethos to try and appear to be as transparent a contractor as possible in the past - I'm not sure they'd mess around with that when conducting a project as high risk as BFR is.
Title: Re: SpaceX advances drive for Mars rocket via Raptor power
Post by: baldusi on 03/03/2015 01:28 pm
It's all in the contracting. If you get a Not To Exceed pricing contract for the next 20 years, like the OSP, or NLS II, then it's not that bed. The danger is on the re-negotiation.
On the other hand, the real cost of BEO won't be the launchers, but the payload. And the 3B/yr of SLS infrastructure could pay for a lot of mission.
Regarding the Raptor, the 230tnf reusable CH4/LOX seems to be the choice of Blue Origin (BE-4) and KBKhA and RSc Progress (RD-0162/4) have the same size and propellant. The BE-4 is ORSC, and so is the RD-0162/4, but they also use the expander cycle on the CH4 side, so it's actually a gas-gas injector.
Raptor, being full staged, should probably have the best performance, or ridiculous reusability. But nothing that they make can't be sort of replicated with the other two engines. And that's where it gets interesting. If SpaceX can solve the economic reusability problem of Mars transport, ULA/BO and KBKhA/RSC Progress could also do it in less than a decade (six to seven years if propulsion is a known quantity and money flows). And that's the point where SLS or any NASA owned SHLV had no meaning.
Title: Re: SpaceX advances drive for Mars rocket via Raptor power
Post by: starsilk on 03/03/2015 01:36 pm
Or SpaceX gets the USAF contract to develop a new engine that Congress wants in addition to the BE-4.   The USAF pays to finish the development of a Raptor engine in the range of 500-600k lbf.  SpaceX gets one part of the US govt to pay to develop the engine for it's BFR and it can then have a rival HLV to NASA's SLS.

Ahh. Perhaps that is the deal that seems to have occurred regarding the block buy... leave it alone and USAF will fund raptor development.
Title: Re: SpaceX advances drive for Mars rocket via Raptor power
Post by: FinalFrontier on 03/03/2015 01:37 pm
Potentially worth noting here. MCT (unless I am mistaken) which we often refer to as BFR is (as designed I think) more powerful than SLS. Even with the advanced booster, an extra RS25 (5 engine core) and a j2x upper stage (which is shelved at present) I believe SLS even in Block 3 territory only gets up around what, 150 mt? maybe? If the numbers are right on BFR it likely would be that powerful in its block one design. Engine improvements, iterative design improvements, could make it even stronger. And its not hard to see this actually, BFR as a design is much better than SLS and less complex purely from a technical standpoint. The single biggest advantage is the methane fuel supply instead of LH2. Methane is extremely energetic as a fuel, there is a massive surplus of it worldwide at present (gas wells are shut in due to over production) so its very VERY cheap to get, compared to LH2 which is quite expansive, and it should have more reaction mass per kg for a from sea level launch. Therefore you can, in theory, get more power out of a methane engine than both RP1 and LH2. For in vacuum flight, and this depends highly on engine design, its theoretically possible to get a greater ISP out of it than a comparable LH2 engine, purely due to the reason that some of your engine and tank-age components do not need to be quite as hardy when dealing with liquid methane, due to temperature constraints. Correct me if I am wrong but I believe LH2 is significantly colder than liquid methane.

In any case much of this is either in the design or theoretical realm right now as none of these things have been tried yet, let alone for a full flow stage combustion configuration, I don't believe anyone has ever tried that with a methalox engine. But the potential gains here are enormous, I think you can easily make something more powerful than most of the SLS designs in your first go around and potentially more reliable as well, and I am a shuttle and shuttle hardware lover saying that.
Title: Re: SpaceX advances drive for Mars rocket via Raptor power
Post by: dglow on 03/03/2015 02:00 pm
And its not hard to see this actually, BFR as a design is much better than SLS and less complex purely from a technical standpoint. The single biggest advantage is the methane fuel supply instead of LH2.

BFR's biggest advantage will be reuse and, therefore, flight rate.
The choice of fuel is most important to MCT – the part that travels to Mars – since it enables refuel and return (and therefore reuse, flight rate).
Title: Re: SpaceX advances drive for Mars rocket via Raptor power
Post by: S.Paulissen on 03/03/2015 02:18 pm
Potentially worth noting here. MCT (unless I am mistaken) which we often refer to as BFR is (as designed I think) more powerful than SLS. Even with the advanced booster, an extra RS25 (5 engine core) and a j2x upper stage (which is shelved at present) I believe SLS even in Block 3 territory only gets up around what, 150 mt? maybe? If the numbers are right on BFR it likely would be that powerful in its block one design. Engine improvements, iterative design improvements, could make it even stronger. And its not hard to see this actually, BFR as a design is much better than SLS and less complex purely from a technical standpoint. The single biggest advantage is the methane fuel supply instead of LH2. Methane is extremely energetic as a fuel, there is a massive surplus of it worldwide at present (gas wells are shut in due to over production) so its very VERY cheap to get, compared to LH2 which is quite expansive, and it should have more reaction mass per kg for a from sea level launch. Therefore you can, in theory, get more power out of a methane engine than both RP1 and LH2. For in vacuum flight, and this depends highly on engine design, its theoretically possible to get a greater ISP out of it than a comparable LH2 engine, purely due to the reason that some of your engine and tank-age components do not need to be quite as hardy when dealing with liquid methane, due to temperature constraints. Correct me if I am wrong but I believe LH2 is significantly colder than liquid methane.

In any case much of this is either in the design or theoretical realm right now as none of these things have been tried yet, let alone for a full flow stage combustion configuration, I don't believe anyone has ever tried that with a methalox engine. But the potential gains here are enormous, I think you can easily make something more powerful than most of the SLS designs in your first go around and potentially more reliable as well, and I am a shuttle and shuttle hardware lover saying that.

The cost of the fuel itself is a rounding error in the cost of launch of such a large rocket.  Also,you're also confusing natural gas and methane.  Natural gas is what comes out of the ground and it's not pure methane, it needs to be processed to be methane.  The cost savings come from ease of ground handling, not the cost of the fuel. 

You then state that you have more reaction mass per kilogram, which is incorrect as, mass is mass, there is no way to make 1kg less than 1kg in a chemical reaction.  Perhaps you meant with increased tankage mass for the less dense hydrogen fuel that you mention a little later?  Please clarify.

If you build an engine poorly you could get worse ISP out of an ion motor than an Estes model rocket motor.  I'm unsure of the point you're trying to make.  The upper bound is dictated by reactant chemical energy, which is higher with LH2 than with CH4.  If you're talking impulse density factoring in tankage it's a muddier topic.  I don't mean to pick on you, I just hope you'll write with a little more specificity in the future so I, and others, aren't tempted to tear into you for inaccuracies.  :)

The only full flow engine demonstrated was the RD-280 and managed 301s ISP from hypergols.  AJR was working on the powerhead but I don't know if they ever had a working model.
Title: Re: SpaceX advances drive for Mars rocket via Raptor power
Post by: FinalFrontier on 03/03/2015 03:37 pm
Quote
The cost of the fuel itself is a rounding error in the cost of launch of such a large rocket.  Also,you're also confusing natural gas and methane.  Natural gas is what comes out of the ground and it's not pure methane, it needs to be processed to be methane.  The cost savings come from ease of ground handling, not the cost of the fuel. 
Minimal processing (if any) when compared to cracking needed to get sufficient quantities of  hydrogen for LH2. Not sure about this for raptor itself, but it is likely possible to build an engine that runs on simple liquefied natural gas or liqueifed petroleum gas. Thats another topic though.  Also (forgot this in my post), yes re-usability is a huge advantage.
Quote
You then state that you have more reaction mass per kilogram, which is incorrect as, mass is mass, there is no way to make 1kg less than 1kg in a chemical reaction.  Perhaps you meant with increased tankage mass for the less dense hydrogen fuel that you mention a little later?  Please clarify.
Correct I am wrong. Meant more btu/thermal equivalent energy per mass.However, even on that I am not sure off the top of my head if hydrogen has a higher upper bound per btu/mass equivalent than CH4 as you state later on. I will check on this because I am curious now. It would sort of surprise me but maybe it shouldn't. But wrt tankage yes  that is correct, you see possible improvements due to not needing tanks as large/complex as for LH2 due to density (and temperatures).
Quote
If you build an engine poorly you could get worse ISP out of an ion motor than an Estes model rocket motor.  I'm unsure of the point you're trying to make.  The upper bound is dictated by reactant chemical energy, which is higher with LH2 than with CH4.  If you're talking impulse density factoring in tankage it's a muddier topic.  I don't mean to pick on you, I just hope you'll write with a little more specificity in the future so I, and others, aren't tempted to tear into you for inaccuracies.
Reactant energy may be higher with LH2 however I was referring to both tankage AND to the mass of the engine itself. May be apples to oranges but consider the mass of an RS25 and the fact that to operate this engine must use two turbopumps for each component (LOX and LH2) where as a comparable methalox may function properly with unified pumps. Other components such as injectors ect, may save mass by virtue of the fuel the engine is designed for. Make your engine lighter you see performance improvements. But it is a muddy topic, however my general point is this particular engine is likely to more shall we say "optimize-able" as is the vehicle as compared to an LH2 core vehicle (at least wrt sea level launches).
Quote
The only full flow engine demonstrated was the RD-280 and managed 301s ISP from hypergols.  AJR was working on the power-head but I don't know if they ever had a working model.
True but this was hypergolics. My point was, not sure of any previous full flow design for methalox.

Title: Re: SpaceX advances drive for Mars rocket via Raptor power
Post by: spacenut on 03/03/2015 03:45 pm
This is what I think may happen.  SpaceX builds an 8m core rocket with about 5-5.5 million lb thrust which can deliver about 75 tons to LEO (next step up from F9H + wider loads).  A three core heavy version of the 8m rocket might deliver 200+ tons to LEO.  This trumps SLS and gives a smaller more usable single core rocket for deep space probes greater than F9H can deliver. 

Now he might build a 25 engine 10m core to do it all at once.  I think it would be more flexible with the smaller core.   
Title: Re: SpaceX advances drive for Mars rocket via Raptor power
Post by: FinalFrontier on 03/03/2015 03:52 pm
This is what I think may happen.  SpaceX builds an 8m core rocket with about 5-5.5 million lb thrust which can deliver about 75 tons to LEO (next step up from F9H + wider loads).  A three core heavy version of the 8m rocket might deliver 200+ tons to LEO.  This trumps SLS and gives a smaller more usable single core rocket for deep space probes greater than F9H can deliver. 

Now he might build a 25 engine 10m core to do it all at once.  I think it would be more flexible with the smaller core.   

Worth noting several people did impromptu calculations based on some of the available known specifications of raptor (as currently designed) on a 10M core vehicle and came up with "roughly" this:
10M core first stage return (partially reusable): 128mt-LEO Block 1 variant single core
10M core first stage expendable (no boost back): 150mt-LEO Block 1 variant single core.
This is worth noting, though remember these are very rough estimates because this would make even the first variant of this vehicle more powerful than most of the SLS variants let alone the Block 1 currently in development, ostensibly for much lower cost. And remember, this is only a single core. A  "ultra heavy" configuration using three 10 meter core vehicle in a FH style config would be significantly more powerful and, ostensibly, would not require major new design/production effort.

But this is all speculation. WRT the numbers if you want to learn more see L2.
Title: Re: SpaceX advances drive for Mars rocket via Raptor power
Post by: spacenut on 03/03/2015 03:56 pm
How many of the metholox engines would this 10m core need?  The specs on the engine keep changing.  I've heard 660,000 lbs thrust recently?  I read that on another forum, but can't remember. 
Title: Re: SpaceX advances drive for Mars rocket via Raptor power
Post by: philw1776 on 03/03/2015 04:42 pm
ElonMusk on Reddit 1 month ago
"Thrust to weight is optimizing for a surprisingly low thrust level, even when accounting for the added mass of plumbing and structure for many engines. Looks like a little over 230 metric tons (~500 klbf) of thrust per engine, but we will have a lot of them :)
"
I'm looking up the definition of "a lot" right now  ;)
Title: Re: SpaceX advances drive for Mars rocket via Raptor power
Post by: TomH on 03/03/2015 04:44 pm
There are no set specs yet. The most recent thing I'm aware of is 500k lb variant has best T/W. That being said, they have not committed to any particular set of specs publicly.
Title: Re: SpaceX advances drive for Mars rocket via Raptor power
Post by: Lar on 03/03/2015 08:26 pm
What does any of this current discussion have to do with Raptor engines again? :)

Not too much. And this was over a page back... let's try to bring it around and some of the wilder SLS and BO stuff should go elsewhere, ok?
Title: Re: SpaceX advances drive for Mars rocket via Raptor power
Post by: TomH on 03/03/2015 08:54 pm
However, I agree that once BFR is flying or perhaps even when it's late into development and looking "inevitable" with metal being bent and Raptor firing properly...that SLS main supporting argument that it's the only LV with that capacity, and that capacity is necessary for BLEO HSF pretty much goes away.  Then I think it'll be cancelled after just a few launches...

One would think so. But then again there's that little cadre of senators holding committee chairmanships. I think your scenario will happen if they're retired by then. If they all pull a Strom Thurmond and stay until they're centenarians, SLS may well continue receiving its welfare payments.

You have a point, but I think if those fossils are still there then, their hold won't be enough.  Questions will be asked that currently can be explained away by saying, "There's no LV that can come close to what SLS (or Ares V SDHLV) can do, and near 130mt to LEO is what's necessary for going to BLEO destinations with astronauts.  Multiple launch missions with smaller LV's introduces unacceptable level of LOM risk with their complexity.  A single LV of this class is necessary for a safe and robust exploration future...etc. etc.".

You can disagree with that assessment, but the fact is there is no other system that can do what SLS will and it's a he said/she said argument on whether that is -really- needed.  But "conventional wisdom" says it is and so that's the view you have to dislodge.
A BFR advocate will be able to say, "Yes, you are quite right.  Fortuantely now there is a lower cost alternative with the capacity equal (or in excess) of SLS.  With the money saved from it we can launch more payloads and have more missions and do more exploration.  NASA is relieved from having to maintain the overhead of a HLV themselves, etc. etc".

It'll be man-rated, so that argument is out.  And while cancelling SLS will mean cutting jobs in certain places, it'll mean creating new jobs in other places to support BFR.  So there will be those who'll fight those fighting to keep SLS.

Finally, NASA itself could be an X-factor.  I think there will be those who think they have a better shot of walking on MArs with SpaceX than with SLS, and will start saying so to Congress.  At the end of the day...NASA really would like to have their astros be the first to walk on Mars and worry that their current trajectory puts them in the same holding pattern they've been in for the last decade.

So we'll see.  But I think the fossils days will be numbered at that point, IMHO.

Another thing they may do is say, "Oh, BFR could fail, so it's gotta have a backup!" Just like that endless drone, "We can't rely on a single engine supplier for F-35, we need to play it safe and have a backup engine." When that supplier spends millions on lobbyists and other PR, it can be difficult to stop the inertia of the steamroller.
Title: Re: SpaceX advances drive for Mars rocket via Raptor power
Post by: spacenut on 03/03/2015 09:22 pm
F9H on SpaceX's website says it cost $85million for a launch.  50 tons a launch.  Say a 600 ton Mars transfer vehicle assembly in LEO for 12 launches at $1 billion, 20 million.  SLS will cost what $1 billion each launch minimum for only 100 tons and would require 6 launches.  SpaceX is already half the launch cost.  In space assembly will add to the price, but it can't be that much, depends on how much is automated. 

I assume the BFR would cost about half SLS to launch.  Let's go to Mars instead of building big expensive rockets only being launched once a year
Title: Re: SpaceX advances drive for Mars rocket via Raptor power
Post by: Lar on 03/03/2015 09:24 pm
Let's go to Mars instead of building big expensive rockets only being launched once a year
Really, let's not go there on this thread. I'd really appreciate it if you all can self moderate, thanks.

Title: Re: SpaceX advances drive for Mars rocket via Raptor power
Post by: Lobo on 03/03/2015 09:38 pm
The one thing to bring into consideration is that unlike all the other scenarios, SpaceX's own plans are much larger than any that the government has in mind.

If NASA says "never mind SLS, we'll fly with BFR" it won't make much difference to BFR, financially.  However, SpaceX will be more than happy to gain from NASA's other resources, and given SpaceX's plan, there's a large multiplier there.

So it's in their interest to serve as the heavy lift provider for NASA, and not in their interest to jack up pricing the minute they can. They are not a near-sighted company.

I disagree.  I think NASA getting on board is important (if not critical) for BFR.  NASA cancelling SLS and signing a contract with SpaceX for say, $330M/launch (as an example.)  $1B per year if 3 NASA launches per year (as an example).  That's a lot of money coming in to SpaceX that would be very useful to develop MCT and possibly a block 2 BFR (if Block 1 isn't the full size they want for their colonization plans).  Having those NASA payloads will help with production rates, pad launch rates (the more you do the better you get at it) as well as profits for other required developments.

If NASA does not get on board, and SpaceX really just goes it alone completely independant from any NASA contracts as some around here think is the plan, They'll need to fund both BFR and BFR's pad and infrastructure out of just Falcon profits (which aren't all that high)...and then MCT...and then associated equipment like rovers and space suits and large Sabatier ractors (to make the methane on Mars) large power sources for operating for long periods of time on Mars, etc.  These are all life critical developments and won't be cheap.  Now that's a LOT of money needed by SpaceX from just their Falcon profits if NASA isn't invovled.

However, if NASA gets involved, suddenly that SLS money comes to SpaceX.  It also could mean that SpaceX could skip a lot of equipment development by contracting the first Mars missions to NASA, as NASA would then need to develop those things.  That could be a big boon to SpaceX to help then move on to MCT's development.

So while BFR will be developed with or without NASA, subsequent Mars hardware developments could be difficult after that without NASA.   Which is why I have a hunch Elon is fully planning to take out SLS, get NASA on board with BFR and his Mars plans (because they really want to go to MArs too), and use that to help fund his long term goals.  It would a lot ot help facilitate his larger MArs colony goals.
Title: Re: SpaceX advances drive for Mars rocket via Raptor power
Post by: Coastal Ron on 03/03/2015 10:07 pm
However, if NASA gets involved, suddenly that SLS money comes to SpaceX.

No.  The budget for the SLS is for the SLS.  If the SLS goes away then the money goes too.  There is nothing stopping Congress from increasing NASA's budget except for an acknowledged need to increase it, with or without the SLS or any other program.

Quote
It also could mean that SpaceX could skip a lot of equipment development by contracting the first Mars missions to NASA, as NASA would then need to develop those things.  That could be a big boon to SpaceX to help then move on to MCT's development.

Elon Musk has made statements regarding hoping to work with NASA on going to Mars (I forget the exact statements), and I don't think he is planning on going to Mars without others helping out.  NASA would be a big boon even if they don't contribute much monetarily since a lot of what they can contribute is knowledge - and more importantly, validation.  Saying NASA is your partner makes it easier to get smaller contributors.

Quote
So while BFR will be developed with or without NASA, subsequent Mars hardware developments could be difficult after that without NASA.   Which is why I have a hunch Elon is fully planning to take out SLS, get NASA on board with BFR and his Mars plans (because they really want to go to MArs too), and use that to help fund his long term goals.  It would a lot ot help facilitate his larger MArs colony goals.

I don't think it is an explicit plan for Musk to "take out" the SLS.  Musk is building the vehicle that is most appropriate for the plan Musk has in mind, regardless what anyone else in the world is doing.

Besides, the way NASA's budget is being managed there is no hope for the SLS anyways, since there are no missions or payloads that are being funded to use the SLS.  It will die on it's own for lack of need.  And about the time that happens the attention on leaving Earth will naturally turn to Musk and SpaceX, because no one else will be working on leaving LEO at that point.  Free bonus for Musk, and he won't have to do anything.

Of course there is still no guarantee that our politicians in the future will want to spend taxpayer money on sending people to Mars, so let's not think this is a done deal.  So far our politicians have resisted doing that, and I have yet to see a reason for them to change their minds - with or without Elon Musk.
Title: Re: SpaceX advances drive for Mars rocket via Raptor power
Post by: wes_wilson on 03/03/2015 10:38 pm
So while BFR will be developed with or without NASA, subsequent Mars hardware developments could be difficult after that without NASA.   Which is why I have a hunch Elon is fully planning to take out SLS, get NASA on board with BFR and his Mars plans (because they really want to go to MArs too), and use that to help fund his long term goals.  It would a lot ot help facilitate his larger MArs colony goals.

If you have a colony on Mars that depends, at least for awhile, on a steady stream of supplies from Earth; there is value in having both BFR & SLS as a risk mitigation strategy in case of issues with the launcher.

I don't disagree with your reasoning but I think there may be factors beyond the economic that argue for having SLS around for awhile.
Title: Re: SpaceX advances drive for Mars rocket via Raptor power
Post by: Lars-J on 03/03/2015 11:29 pm
However, if NASA gets involved, suddenly that SLS money comes to SpaceX.

No.  The budget for the SLS is for the SLS.  If the SLS goes away then the money goes too.  There is nothing stopping Congress from increasing NASA's budget except for an acknowledged need to increase it, with or without the SLS or any other program.

While I agree with much of you sentiment, the statements that "The budget for the SLS is for the SLS" and "If the SLS goes away then the money goes too" are *FALSE*.

There is no "SLS line item" or anything like that in a budget. Just like there wasn't for Constellation. It got cancelled - and lo and behold - a new project was found for the contractors and NASA centers. When/if SLS goes away, the people that have a stake in it in Congress are not going to suddenly decide that they aren't interested in securing funding to the contractors or space centers in their district anymore. They will continue to receive funds for whatever new project arises.
Title: Re: SpaceX advances drive for Mars rocket via Raptor power
Post by: FinalFrontier on 03/04/2015 02:37 am
Proposed simple solution. Hear me out if possible
Keep SLS. In the near future, add budget to NASA for a commercial BEO program. Think COTSDEV/CCDEV but for BEO. It worked for LEO why won't it now work for BEO especially with at least one company developing a mars vehicle anyway? Use the same lessons learned and same model, incremental steps, development goals, ect.

THAT, IMHO, is how NASA could be an "ideal" boon to commercial BEO thoughts and still keep its own funding, goals, and relevance. And two HLV's are better than one. I would take this any day over one or none. Funding increases would be minimal at best. Once (if) JWST launches, SLS gets more into production, ect, you can take cost savings from these sorts of elephants and use them to create such a program. Or merely build it on as an extension of the existing commercial program.

All you really need is to convince Congress to take a reasonable balanced approach instead of "lets cancel this in favor of doing this now", something that never gets you anywhere. It also would help to have a POTUS that isn't dead set on redoing absolutely everything the last guy had going. Continuity is not always a bad thing.

Anyway, my two cents on the blended idea here. To get back on topic:
1. When/where does spacex plan to install LCH4 handling facilites
2. Where would MCT likely launch from
3. When is raptor being test fired for the first time?
Things I am curious about.
Title: Re: SpaceX advances drive for Mars rocket via Raptor power
Post by: su27k on 03/04/2015 04:28 am
Proposed simple solution. Hear me out if possible
Keep SLS. In the near future, add budget to NASA for a commercial BEO program.

All space problem can be solved by adding more budget to NASA, if only it's that simple...

I hope SpaceX is not counting on NASA BLEO program to close the business case for BFR and Raptor, that would be a serious mistake.
Title: Re: SpaceX advances drive for Mars rocket via Raptor power
Post by: macpacheco on 03/04/2015 05:46 am
Very interesting speculation if the settlement to USAF block buy arbitration was SpaceX backs off and gets funding to build raptor. Not the honest politically correct solution I was hoping for, but wouldn't raptor development perhaps constitute at least 1/3 of the total cost to make the upscale F9R like Raptor rocket ?
Even a basic 9+1 Raptor rocket should be able to drop large GEO birds 500m/s or closer to GEO.
The closer a launch solution can drop a GEO bird to GEO, the more incentives are to go electric which reduces payload costs or allow for a much more capable payload. This will revolutionize the GEO market.
Don't fixate too much on Mars. Elon will get there, but he's not in as much of a hurry as many here are.
He wants to do it as sustainable as possible. That would mandate using rockets that are used for GEO/LEO/MEO missions too.
Title: Re: SpaceX advances drive for Mars rocket via Raptor power
Post by: Owlon on 03/04/2015 07:11 am
Very interesting speculation if the settlement to USAF block buy arbitration was SpaceX backs off and gets funding to build raptor. Not the honest politically correct solution I was hoping for, but wouldn't raptor development perhaps constitute at least 1/3 of the total cost to make the upscale F9R like Raptor rocket ?
Even a basic 9+1 Raptor rocket should be able to drop large GEO birds 500m/s or closer to GEO.
The closer a launch solution can drop a GEO bird to GEO, the more incentives are to go electric which reduces payload costs or allow for a much more capable payload. This will revolutionize the GEO market.
Don't fixate too much on Mars. Elon will get there, but he's not in as much of a hurry as many here are.
He wants to do it as sustainable as possible. That would mandate using rockets that are used for GEO/LEO/MEO missions too.

I'm pretty sure that sort of quid pro quo (drop the lawsuit in exchange for Raptor funding) is illegal for the federal government. The engine funding contract would have to be competed.
Title: Re: SpaceX advances drive for Mars rocket via Raptor power
Post by: The Amazing Catstronaut on 03/04/2015 07:36 am
Potentially worth noting here. MCT (unless I am mistaken) which we often refer to as BFR is (as designed I think) more powerful than SLS.

A small correction: MCT is the Mars Colonial Transport. It's effectively the capsule/apartment building/Battlestar/Pressure vessel mounted on the top of the BFR (big frackin' rocket). The MTC is the payload + Transfer + ISRU + return stage + lander Mars SSTO, whilst the BFR is the booster that pushes the MTC up to the thermosphere. Imagine a D2 mounted on top of an F9, then add steroids.

You've got the correct idea, but the MTC and BFR aren't the same craft. Just that the first depends on the former and both are symbiotic components of the same system.
Title: Re: SpaceX advances drive for Mars rocket via Raptor power
Post by: The Amazing Catstronaut on 03/04/2015 07:42 am

I hope SpaceX is not counting on NASA BLEO program to close the business case for BFR and Raptor, that would be a serious mistake.

Elon has suggested in past interviews (possibly at the MIT one, I don't quite remember), that he wouldn't be discouraged if BFR received support from the private sector only (ex: probably just SpaceX), but that the process would be slower, and that less would get done in more time.
Title: Re: SpaceX advances drive for Mars rocket via Raptor power
Post by: macpacheco on 03/04/2015 07:55 am
Very interesting speculation if the settlement to USAF block buy arbitration was SpaceX backs off and gets funding to build raptor. Not the honest politically correct solution I was hoping for, but wouldn't raptor development perhaps constitute at least 1/3 of the total cost to make the upscale F9R like Raptor rocket ?
Even a basic 9+1 Raptor rocket should be able to drop large GEO birds 500m/s or closer to GEO.
The closer a launch solution can drop a GEO bird to GEO, the more incentives are to go electric which reduces payload costs or allow for a much more capable payload. This will revolutionize the GEO market.
Don't fixate too much on Mars. Elon will get there, but he's not in as much of a hurry as many here are.
He wants to do it as sustainable as possible. That would mandate using rockets that are used for GEO/LEO/MEO missions too.

I'm pretty sure that sort of quid pro quo (drop the lawsuit in exchange for Raptor funding) is illegal for the federal government. The engine funding contract would have to be competed.
There are so many things that are illegal but done anyways. Many ways to skirt the law. Anyhow, I think SpaceX could afford to underbid on such a competition, since they will build raptor anyways.
I sincerely hope that speculation is wrong anyways. However until F9R certification is declared, and the first F9R DoD certified payload is awarded I don't know what to really think.
Hopefully F9R will achieve total 13 GEO launches still in 2015, which would allow SpaceX to request certification under the 13 launch rule which as I understand is very quick (I actually heard turn over the data and get immediately certified).
Title: Re: SpaceX advances drive for Mars rocket via Raptor power
Post by: spacenut on 03/04/2015 01:24 pm
I'm sorry if I was out of line with my comments.  However, they landed on the moon on my 16th birthday.  They were to use Saturn V with several launches to assemble a Mars ship in orbit and go to Mars by 1986.  It never happened.  I just want to see us go to Mars in my lifetime.  Been waiting a long time.  So it looks like SpaceX gives me hope to get there since the government and NASA can't stay focused on a goal. 

Back to the Raptor, it looks like it will take 18 on a 10m core to do the 128 tons to LEO if it is a 500k lb thrust engine.  Hope it will be a 1 million lb thrust engine so they can use 9 like the Falcon 9 since they will already have experience with that configuration. 
Title: Re: SpaceX advances drive for Mars rocket via Raptor power
Post by: TomH on 03/04/2015 03:51 pm
I'm sorry if I was out of line with my comments.  However, they landed on the moon on my 16th birthday.  They were to use Saturn V with several launches to assemble a Mars ship in orbit and go to Mars by 1986.  It never happened.  I just want to see us go to Mars in my lifetime.  Been waiting a long time.  So it looks like SpaceX gives me hope to get there since the government and NASA can't stay focused on a goal. 

Back to the Raptor, it looks like it will take 18 on a 10m core to do the 128 tons to LEO if it is a 500k lb thrust engine.  Hope it will be a 1 million lb thrust engine so they can use 9 like the Falcon 9 since they will already have experience with that configuration.

I understand your Mars sentiment, you are just a few days older than I. As for the engine configuration, I'm not sure that matters. Having more engines of less thrust could give better control for landing.
Title: Re: SpaceX advances drive for Mars rocket via Raptor power
Post by: philw1776 on 03/04/2015 07:09 pm
I'm sorry if I was out of line with my comments.  However, they landed on the moon on my 16th birthday.  They were to use Saturn V with several launches to assemble a Mars ship in orbit and go to Mars by 1986.  It never happened.  I just want to see us go to Mars in my lifetime.  Been waiting a long time.  So it looks like SpaceX gives me hope to get there since the government and NASA can't stay focused on a goal. 

Back to the Raptor, it looks like it will take 18 on a 10m core to do the 128 tons to LEO if it is a 500k lb thrust engine.  Hope it will be a 1 million lb thrust engine so they can use 9 like the Falcon 9 since they will already have experience with that configuration.

Been waiting equally long for Mars.

Your hope is in vain as Elon has said he's abandoned the large Raptor design for the smaller ~500K LB thrust design which means that BFR in his own words will have "lots of engines".

Think of this F9H has 27 engines so why can't BFR have "lots of engines"?  They will "have experience" with lots of engines.
Title: Re: SpaceX advances drive for Mars rocket via Raptor power
Post by: Lars-J on 03/04/2015 07:16 pm
I'm sorry if I was out of line with my comments.  However, they landed on the moon on my 16th birthday.  They were to use Saturn V with several launches to assemble a Mars ship in orbit and go to Mars by 1986.  It never happened.  I just want to see us go to Mars in my lifetime.  Been waiting a long time.  So it looks like SpaceX gives me hope to get there since the government and NASA can't stay focused on a goal. 

Back to the Raptor, it looks like it will take 18 on a 10m core to do the 128 tons to LEO if it is a 500k lb thrust engine.  Hope it will be a 1 million lb thrust engine so they can use 9 like the Falcon 9 since they will already have experience with that configuration.

Been waiting equally long for Mars.

Your hope is in vain as Elon has said he's abandoned the large Raptor design for the smaller ~500K LB thrust design which means that BFR in his own words will have "lots of engines".

Think of this F9H has 27 engines so why can't BFR have "lots of engines"?  They will "have experience" with lots of engines.

Hope is not completely lost for a 1 million lb thrust engine. Merlin has now in its latest M1D iteration has more than doubled the thrust of of the original Merlin 1A.  :)
Title: Re: SpaceX advances drive for Mars rocket via Raptor power
Post by: philw1776 on 03/04/2015 07:21 pm
It would be unreasonable to think that Raptor Mark One would NOT evolve as SX's culture is to build a robust Mark One and then add continuous improvement.  But then you're down the infinite loop of MCT Mark One vs MCT evolved with 100 people & screaming kids and teenagers aboard.
Title: Re: SpaceX advances drive for Mars rocket via Raptor power
Post by: Brovane on 03/04/2015 07:31 pm
I'm pretty sure that sort of quid pro quo (drop the lawsuit in exchange for Raptor funding) is illegal for the federal government. The engine funding contract would have to be competed.

As long as you write the Bid request appropriately, nothing illegal will happen but the appropriate bidder will  be selected.   
Title: Re: SpaceX advances drive for Mars rocket via Raptor power
Post by: Lobo on 03/04/2015 09:50 pm
However, if NASA gets involved, suddenly that SLS money comes to SpaceX.

No.  The budget for the SLS is for the SLS.  If the SLS goes away then the money goes too.  There is nothing stopping Congress from increasing NASA's budget except for an acknowledged need to increase it, with or without the SLS or any other program.


Probably a poor choice of words by me.  But the money not being spent for SLS, or any subsequent NASA operated LV, would most likely be voted on by Congress to be reallocated to payloads/launch services.  The parts of NASA's current budget that pay for probes and EELV launch services.  I've not really educated myself on the particulars of NASA's budget system, but I'd think those areas could get the moneies previously allocated to SLS.  And that would be used to buy launches from SpaceX.
Title: Re: SpaceX advances drive for Mars rocket via Raptor power
Post by: Lobo on 03/04/2015 09:57 pm
I don't think it is an explicit plan for Musk to "take out" the SLS.  Musk is building the vehicle that is most appropriate for the plan Musk has in mind, regardless what anyone else in the world is doing.

Besides, the way NASA's budget is being managed there is no hope for the SLS anyways, since there are no missions or payloads that are being funded to use the SLS.  It will die on it's own for lack of need.  And about the time that happens the attention on leaving Earth will naturally turn to Musk and SpaceX, because no one else will be working on leaving LEO at that point.  Free bonus for Musk, and he won't have to do anything.

Of course there is still no guarantee that our politicians in the future will want to spend taxpayer money on sending people to Mars, so let's not think this is a done deal.  So far our politicians have resisted doing that, and I have yet to see a reason for them to change their minds - with or without Elon Musk.

Again, poor choice of words.  Yes, Musk is designing BFR for his purposes, but as that will happen to parallel SLS capabilities and SLS is under a lot of budget and political problems, I'm sure the thought of "helping to speed along SLS's demise" by drawing attention to it isn't lost on him.  He may completely stay out of it and hope SLS's dies on it's own, but once he's got something flying or getting close to it, I'm betting that we start to see Elon the salesman come out in full display to help it die a little faster.
Title: Re: SpaceX advances drive for Mars rocket via Raptor power
Post by: MP99 on 03/05/2015 12:30 am
F9H on SpaceX's website...

There is no rocket on SpaceX's website called "F9H".

... says it cost $85million for a launch.  50 tons a launch.

SpaceX charge more than that for a 50t launch.

Cheers, Martin
Title: Re: SpaceX advances drive for Mars rocket via Raptor power
Post by: Robotbeat on 03/05/2015 01:59 am
Thoughts:
1) NASA and SpaceX are natural partners. Both see Mars as the ultimate destination (even a lot of buy-in from the planetary science community, although there's significant grumbling about Mars missions taking all the opportunities) even if there's some disagreement about Moon-first or whatever. Ultimately, the vast majority of people at NASA would be incredibly thrilled if SpaceX succeeds. There is, however, significant skepticism still (which is absolutely warranted, let's be honest! their plans ARE crazy).

2) I'm no SLS fan, but SLS may actually end up a boon to Musk's Mars plans since SLS supporters are working tirelessly to create payloads which justify SLS. If BFR flies before SLS's inevitable cancellation (which WILL happen eventually... if after 0 flights, 2 flights, 10 flights, or 20 flights), then there will be a list of payloads which many at NASA (and in Congress!) will have spent a good decade justifying which only BFR could fly (and at a good price, too!). Each of those payloads will also have built up their own little constituency by then, too.

3) And still, NASA is interested in new, high power hydrocarbon engines. I think there might be some funding for this which SpaceX could utilize for Raptor. And NASA especially likes methane engines due to the whole Mars ISRU angle.

4) Playing off of #3, there are lots of little opportunities like this if SpaceX really does start doing all they say. Red Dragon is one example. Mars telecomm (with science package) orbiter(s) is another. Longer term, you have Mars surface ISRU which is pretty essential for a ma'ammed* Mars mission so is very much of interest to NASA. Continuing, the whole MCT architecture basically solves 95% of the problems NASA would have with a manned* Mars mission and also enables lunar missions. It'd be ridiculous to say NASA wouldn't be hugely interested in these things if SpaceX were actually capable of them (we hope they will be capable of them, but currently they're still plans).

5) For those who say that SLS money (or Orion money or whatever) is ONLY for SLS and would disappear if cancelled, etc, remember this: you could make much the same argument about any NASA program, so how in the heck does SpaceX (or, say, Orbital, etc) receive payment for any of its services at all? The argument that the status quo cannot change is destroyed by the fact that it HAS changed. CRS exists where it didn't before, and NASA's funding was not increased, so the money came from somewhere. That's no guarantee, but it does show it is possible. (it's also not a 1-to-1 thing, neither should it be.)

6) A lot of SLS supporters honestly believe it's the best way because they still don't think SpaceX's plans are credible and they don't think orbital assembly or refueling is credible using EELV-class vehicles. If SpaceX is successful, they will win over some of these people.

7) In order to accomplish all these things, SpaceX's footprint will have to expand. Correspondingly, so will their political support. SpaceX has already hired a LOT of employees. They are no longer the upstart challenging the Goliath aerospace players. Soon, SpaceX will be the Goliath. With significant and expanding presence in (politically important states) California, Texas, and Florida, SpaceX will command plenty of bipartisan support if they continue their successes.

*Human spaceflight? Crewed spaceflight? Bah, I'm switching off between ma'ammed spaceflight and manned spaceflight. Because I want to.
Title: Re: SpaceX advances drive for Mars rocket via Raptor power
Post by: Mariusuiram on 03/05/2015 02:22 am
While I think its unlikely that anything in the AF settlement was directly related to the potential for funding Raptor, there are plenty of ways that could happen without illegal, corrupt quid pro quo agreements. Possibly just verbal commitments.

I think its very likely that AF may plan to interview Aerojet or ATK during the preparation of the RFP. As people have said, these RFP's arent written in a vacuum. My guess is that how the RFP is written will determine whether SpaceX participates. What rights will AF have over the engine? Would they have a right of first refusal on engines produced? Would they require it be available for purchase to all US launch providers? Could they restrict other users if SpaceX considered moving to a "wet-lease" business model?

A topic of the settlement could easily be (and not illegally so) that SpaceX will be consulted during the drafting of the RFP and AF will make an effort to take their feedback into consideration. This could all be informal, but the AF could easily make some effort to ensure the language opens the RFP to as many bidders as possible.

I still expect the restrictions / limitations on the engine will make it impractical for SpaceX. The whole point of funding a new US-made engine is to maintain the US launch market. If no one else could use the engine other than SpaceX, it kind of defeats the purpose. Of course, maybe SpaceX calls the bluff. SpaceX's cost advantage isnt just their engines. Let ULA and others have an option to buy Raptors. Its a whole extra revenue stream and shouldn't really impact their competitiveness.
Title: Re: SpaceX advances drive for Mars rocket via Raptor power
Post by: spacenut on 03/05/2015 02:43 am
I double checked the SpaceX website.  I was wrong about F9H, it was Falcon Heavy.

Now, the website DID say:  2016 Standard Pricing.  FH $85 million for LEO 28.5 degrees, 53,000 kilograms (53 metric tons) and GTO 27 degrees, 21,200 kilograms (21.2 metric tons). 

I know this is for the rocket only, and the cost of payload, tracking, etc, would have to be added in, but hey, that is lower than anyone else. 
Title: Re: SpaceX advances drive for Mars rocket via Raptor power
Post by: Robotbeat on 03/05/2015 02:46 am
$85m is for much less than 21 tons to GTO. Look again!

But regardless, BFR would be fully reusable. If it isn't much less than half an SLS launch, then SpaceX has some serious issues.
Title: Re: SpaceX advances drive for Mars rocket via Raptor power
Post by: RanulfC on 03/05/2015 07:24 pm
There are laws preventing ripping off the government. Doesn't mean costs don't grow, but it will not exceed SLS.

Very glad to hear that.  :)

Unless of course the government authorizes you to rip them off :)

Randy
Title: Re: SpaceX advances drive for Mars rocket via Raptor power
Post by: RanulfC on 03/05/2015 07:35 pm
Well so did the US govt.  ;)  Congress want's to pay for the development of a US engine to replace the RD-180, regardless of the BE-4.  Maybe SpaceX should put in a proposal for this govt contract.  Get the US govt to pay for the development of the Raptor Engine.

Uhm last I looked both the BE-4 and Raptor were methane/lox engines while the RD-180 and Congress' suggested replacement were supposed to be RP1/lox.

Randy
Title: Re: SpaceX advances drive for Mars rocket via Raptor power
Post by: TomH on 03/05/2015 07:50 pm
Well so did the US govt.  ;)  Congress want's to pay for the development of a US engine to replace the RD-180, regardless of the BE-4.  Maybe SpaceX should put in a proposal for this govt contract.  Get the US govt to pay for the development of the Raptor Engine.

Uhm last I looked both the BE-4 and Raptor were methane/lox engines while the RD-180 and Congress' suggested replacement were supposed to be RP1/lox.

Randy

I think the term used is hydrocarbon. RP-1 contains numerous hydrocarbons. Natural gas contains numerous hydrocarbons as well, along with other substances. Ninety-five percent of natural gas is methane (CH4), which is a hydrocarbon. Methalox qualifies.
Title: Re: SpaceX advances drive for Mars rocket via Raptor power
Post by: TomH on 03/05/2015 08:18 pm
Your hope is in vain as Elon has said he's abandoned the large Raptor design for the smaller ~500K LB thrust design which means that BFR in his own words will have "lots of engines".

I believe he tweeted that the 500K lb design had the most optimal T/W. He also used the words "lots of engines." I do not remember that he ever actually stated that 500k lb had been settled upon, however. It is entirely possible that from 500k lb upwards, the T/W decreases at a logarithmic rate. I.E. perhaps 750k lb may have a T/W that is 1% less efficient than 500K, but 1M lb is 5% less efficient. T/W is only one factor among many to be considered when they look at the trades. There may be advantages with regards to trades on other factors that make it worth swallowing that 1% on the 750k design. (These numbers are made up, but with the purpose of illustrating that the math involved may follow quadratic functions as opposed to linear functions.)
Title: Re: SpaceX advances drive for Mars rocket via Raptor power
Post by: somepitch on 03/05/2015 08:35 pm
Your hope is in vain as Elon has said he's abandoned the large Raptor design for the smaller ~500K LB thrust design which means that BFR in his own words will have "lots of engines".

I believe he tweeted that the 500K lb design had the most optimal T/W. He also used the words "lots of engines." I do not remember that he ever actually stated that 500k lb had been settled upon, however. It is entirely possible that from 500k lb upwards, the T/W decreases at a logarithmic rate. I.E. perhaps 750k lb may have a T/W that is 1% less efficient than 500K, but 1M lb is 5% less efficient. T/W is only one factor among many to be considered when they look at the trades. There may be advantages with regards to trades on other factors that make it worth swallowing that 1% on the 750k design. (These numbers are made up, but with the purpose of illustrating that the math involved may follow quadratic functions as opposed to linear functions.)

It was in his Reddit IAMA - full quote below:

Q. Has the Raptor engine changed in its target thrust since the last number we have officially heard of 1.55Mlbf SL thrust?

Elon Musk: Thrust to weight is optimizing for a surprisingly low thrust level, even when accounting for the added mass of plumbing and structure for many engines. Looks like a little over 230 metric tons (~500 klbf) of thrust per engine, but we will have a lot of them :)
Title: Re: SpaceX advances drive for Mars rocket via Raptor power
Post by: RanulfC on 03/05/2015 08:38 pm
Well so did the US govt.  ;)  Congress want's to pay for the development of a US engine to replace the RD-180, regardless of the BE-4.  Maybe SpaceX should put in a proposal for this govt contract.  Get the US govt to pay for the development of the Raptor Engine.

Uhm last I looked both the BE-4 and Raptor were methane/lox engines while the RD-180 and Congress' suggested replacement were supposed to be RP1/lox.

Randy

I think the term used is hydrocarbon. RP-1 contains numerous hydrocarbons. Natural gas contains numerous hydrocarbons as well, along with other substances. Ninety-five percent of natural gas is methane (CH4), which is a hydrocarbon. Methalox qualifies.

Thanks. Wasn't sure. (Of course while methalox qualifies so do a lot of other "hydrocarbon" fuels so... :) )

Randy
Title: Re: SpaceX advances drive for Mars rocket via Raptor power
Post by: TomH on 03/05/2015 08:45 pm
Your hope is in vain as Elon has said he's abandoned the large Raptor design for the smaller ~500K LB thrust design which means that BFR in his own words will have "lots of engines".

I believe he tweeted that the 500K lb design had the most optimal T/W. He also used the words "lots of engines." I do not remember that he ever actually stated that 500k lb had been settled upon, however. It is entirely possible that from 500k lb upwards, the T/W decreases at a logarithmic rate. I.E. perhaps 750k lb may have a T/W that is 1% less efficient than 500K, but 1M lb is 5% less efficient. T/W is only one factor among many to be considered when they look at the trades. There may be advantages with regards to trades on other factors that make it worth swallowing that 1% on the 750k design. (These numbers are made up, but with the purpose of illustrating that the math involved may follow quadratic functions as opposed to linear functions.)

It was in his Reddit IAMA - full quote below:

Q. Has the Raptor engine changed in its target thrust since the last number we have officially heard of 1.55Mlbf SL thrust?

Elon Musk: Thrust to weight is optimizing for a surprisingly low thrust level, even when accounting for the added mass of plumbing and structure for many engines. Looks like a little over 230 metric tons (~500 klbf) of thrust per engine, but we will have a lot of them :)

Exactly. You still are not parsing the sentence correctly. He said the T/W is optimizing at 500klbf. In other words, that is where you get the best T/W in isolation with no other factors considered. He did NOT say that is the thrust they have committed to use.
Title: Re: SpaceX advances drive for Mars rocket via Raptor power
Post by: somepitch on 03/05/2015 08:47 pm
Your hope is in vain as Elon has said he's abandoned the large Raptor design for the smaller ~500K LB thrust design which means that BFR in his own words will have "lots of engines".

I believe he tweeted that the 500K lb design had the most optimal T/W. He also used the words "lots of engines." I do not remember that he ever actually stated that 500k lb had been settled upon, however. It is entirely possible that from 500k lb upwards, the T/W decreases at a logarithmic rate. I.E. perhaps 750k lb may have a T/W that is 1% less efficient than 500K, but 1M lb is 5% less efficient. T/W is only one factor among many to be considered when they look at the trades. There may be advantages with regards to trades on other factors that make it worth swallowing that 1% on the 750k design. (These numbers are made up, but with the purpose of illustrating that the math involved may follow quadratic functions as opposed to linear functions.)

It was in his Reddit IAMA - full quote below:

Q. Has the Raptor engine changed in its target thrust since the last number we have officially heard of 1.55Mlbf SL thrust?

Elon Musk: Thrust to weight is optimizing for a surprisingly low thrust level, even when accounting for the added mass of plumbing and structure for many engines. Looks like a little over 230 metric tons (~500 klbf) of thrust per engine, but we will have a lot of them :)

Exactly. You still are not parsing the sentence correctly. He said the T/W is optimizing at 500klbf. In other words, that is where you get the best T/W in isolation with no other factors considered. He did NOT say that is the thrust they have committed to use.

I'm not parsing anything correctly or incorrectly... I simply copied and pasted his own words for reference!
Title: Re: SpaceX advances drive for Mars rocket via Raptor power
Post by: guckyfan on 03/05/2015 08:54 pm
He did say we will have many of them. That sure sounds to me like he committed to the low value. That does not mean exactly this value is set in stone and won't change any more. But it is what they are going for at the moment.
Title: Re: SpaceX advances drive for Mars rocket via Raptor power
Post by: TomH on 03/05/2015 09:10 pm
He did say we will have many of them. That sure sounds to me like he committed to the low value. That does not mean exactly this value is set in stone and won't change any more. But it is what they are going for at the moment.

I think he was implying tha value may be low. As for saying 500k is what they are going for, he simply did not say that with absolute clarity.
Title: Re: SpaceX advances drive for Mars rocket via Raptor power
Post by: Mariusuiram on 03/06/2015 04:10 am
He did say we will have many of them. That sure sounds to me like he committed to the low value. That does not mean exactly this value is set in stone and won't change any more. But it is what they are going for at the moment.

I think he was implying tha value may be low. As for saying 500k is what they are going for, he simply did not say that with absolute clarity.

Agreed. We can reasonably assume that they are no longer looking at 1.5 mil lbf monsters, but all he is providing is a starting point. And this was also from an off-the-cuff Q&A. They may have 4 different numbers depending on what they are optimizing and thats the one done most recently and fresh in his mind for the Q&A.

The conclusion, sadly, seems to be a whole lot of wait-and-see  :(
Title: Re: SpaceX advances drive for Mars rocket via Raptor power
Post by: Owlon on 03/06/2015 04:58 am
To the people who keep saying the 500klb number is just the engine optimized in isolation and that the ideal number may be higher when accounting for other things, he very clearly said exactly the opposite of that in the only quote we have about the new lower thrust level.

Quote from: Elon Musk
Thrust to weight is optimizing for a surprisingly low thrust level, even when accounting for the added mass of plumbing and structure for many engines. Looks like a little over 230 metric tons (~500 klbf) of thrust per engine, but we will have a lot of them

That's not to say that the number won't change as they get deeper into engine development, simply that they're definitely looking at more than just the engine T/W when they say that's ideal.
Title: Re: SpaceX advances drive for Mars rocket via Raptor power
Post by: Coastal Ron on 03/06/2015 05:41 am
There is no "SLS line item" or anything like that in a budget. Just like there wasn't for Constellation.

As I'm writing this I'm looking at the "FY 2016 PRESIDENT’S BUDGET REQUEST SUMMARY" for NASA, and within the the Exploration section, Exploration Systems Development sub-section, there is a line item for "Space Launch System".  So yes, there is an SLS line item.  There is one for the Orion/MPCV too.  And yes there was a line item for the Constellation program.

Quote
It got cancelled - and lo and behold - a new project was found for the contractors and NASA centers. When/if SLS goes away, the people that have a stake in it in Congress are not going to suddenly decide that they aren't interested in securing funding to the contractors or space centers in their district anymore. They will continue to receive funds for whatever new project arises.

This is a completely separate point from what I was talking about, and yes, and a cancellation of the SLS and Orion would be resisted mightily.  But it's hard to predict what the politics of the day will be, and it really depends on what "vision" takes hold in the minds of the powers that be at that moment in history.

But since you mentioned it, if it's decided that we really can't afford to support a no-less-than-every-12-months SLS flight schedule due to the overall cost it requires (SLS + missions and payloads costs), then how much more can the SLS and Orion/MPCV shrink?

Derate the 70mT SLS and you end up with what the Falcon Heavy can handle, which should be flying frequently by the time the next President is weighing their options.  And by that time SpaceX should have announced their plans for the Raptor powered BFR, and the handful of politicians that actually care about money in Congress will be able to point to the private sector and ask "why does the government need to have it's own rocket?"

Now if Elon Musk is ready for that question, he will have already been floating his plans for going to Mars and suggesting different options for how NASA could ride along.  He could suggest it as a public-private venture, where he takes most of the risk.  Could happen.  Might not.  We'll have to wait and see.  But if it did...
Title: Re: SpaceX advances drive for Mars rocket via Raptor power
Post by: TomH on 03/06/2015 03:46 pm
To the people who keep saying the 500klb number is just the engine optimized in isolation and that the ideal number may be higher when accounting for other things, he very clearly said exactly the opposite of that in the only quote we have about the new lower thrust level.

Quote from: Elon Musk
Thrust to weight is optimizing for a surprisingly low thrust level, even when accounting for the added mass of plumbing and structure for many engines. Looks like a little over 230 metric tons (~500 klbf) of thrust per engine, but we will have a lot of them

That's not to say that the number won't change as they get deeper into engine development, simply that they're definitely looking at more than just the engine T/W when they say that's ideal.

Nope, that is a dependent clause and is subordinate to the independent clause. You do not understand the rules of grammar and syntax. When the sentence is correctly parsed and diagrammed, it does not say with absolute certainty that it is the engine they will use. You are assuming an inference that was not implied with absolute certainty.
Title: Re: SpaceX advances drive for Mars rocket via Raptor power
Post by: Sohl on 03/06/2015 05:02 pm
Nope, that is a dependent clause and is subordinate to the independent clause. You do not understand the rules of grammar and syntax. When the sentence is correctly parsed and diagrammed, it does not say with absolute certainty that it is the engine they will use. You are assuming an inference that was not implied with absolute certainty.

Logically, you have a point, but why would Elon say what he said?  A very reasonable assumption is to manage public expectations.  Elon might have been aware some people were speculating on one million lbs of thrust or more, and wanted expectations to come back down a bit.  So I'm with guckyfan and others who think the Raptor when introduced will be a lot closer to 500K than 1M lbs thrust each.
Title: Re: SpaceX advances drive for Mars rocket via Raptor power
Post by: TomH on 03/06/2015 07:35 pm
And I also think that. But the key word is think. The point is that it is not absolutely certain that it will be exactly 500k.
Title: Re: SpaceX advances drive for Mars rocket via Raptor power
Post by: dror on 03/06/2015 07:40 pm
Nope, that is a dependent clause and is subordinate to the independent clause. You do not understand the rules of grammar and syntax. When the sentence is correctly parsed and diagrammed, it does not say with absolute certainty that it is the engine they will use. You are assuming an inference that was not implied with absolute certainty.

Logically, you have a point, but why would Elon say what he said?  A very reasonable assumption is to manage public expectations.  Elon might have been aware some people were speculating on one million lbs of thrust or more, and wanted expectations to come back down a bit.  So I'm with guckyfan and others who think the Raptor when introduced will be a lot closer to 500K than 1M lbs thrust each.

Let's hope it will be 750 klbf and than you could all say "I told you so" 😉
Title: Re: SpaceX advances drive for Mars rocket via Raptor power
Post by: philw1776 on 03/06/2015 08:25 pm
Parse away Musk's Reddit comment as you will but it should be obvious to any development engineer that absolute numbers so early in the development phase are not to be taken as laws of physics nor were they represented as such by Musk or posters here.  That said, it is clear that the early 2015 design point envisions LOTS of lower thrust engines than the ~F-1 monster first mentioned in early 2014.

If and I doubt it, Musk really reveals the MCT architecture later this year as he'd stated, I'm sure that the actual first flight hardware will have lots of differences and not just the subtle ones so well ferreted out by the curious membership here.
Title: Re: SpaceX advances drive for Mars rocket via Raptor power
Post by: Lars-J on 03/06/2015 08:31 pm

I have a hard time believing Elon would let Blue/ULA BE4 engine to have more thrust than Raptor.  Musk is either just managing expectations or he has a road map, like Merlin, where they tweak it for more over time. I would love to see the 750klbf SL version myself.

I seriously doubt that they are deciding on the optimal engine thrust using the "mine is bigger than yours" philosophy.
Title: Re: SpaceX advances drive for Mars rocket via Raptor power
Post by: BobHk on 03/07/2015 08:13 pm
Whatever they decide it'll be running at less than max when first used.  Say 500-550 with max at over 600.  It seems to be their M.o.  Dropping back down to that range manages expectations and also realistically addresses throttling:  if they're not going to have an engine with massive throttling and they have to use a lot of them (for the hill climb) then burning one on landing, like the F9R, while the rest are off (or some iteration thereof) makes sense.  The 500-550 range also allows them to compete with BO for contracts that have been floated.  Whether or not its exactly 550 or 500 or 505 is immaterial at this point.  Its (500 something) the last best 'idea' mentioned by Musk of what the target is, nothing more.

I look forward to meeting our ~500klb Raptor Overlords.
Title: Re: SpaceX advances drive for Mars rocket via Raptor power
Post by: RotoSequence on 03/17/2015 12:54 am
It looks like SpaceX will be talking about Raptor's development tomorrow at the GPU Technology Conference:
 (https://registration.gputechconf.com/form/session-listing&doSearch=true&queryInput=&topic_selector=Supercomputing&type_selector=none)
Quote
S5398 - GPUs to Mars: Full-Scale Simulation of SpaceX's Mars Rocket Engine

Day: Tuesday, 03/17
Time: 15:00 - 15:50
Location: Room LL21A

Stephen Jones Lead Software Engineer, SpaceX
Adam Lichtl Director of Research, SpaceX

SpaceX is designing a new, methane-fueled engine powerful enough to lift the equipment and personnel needed to colonize Mars. A vital aspect of this effort involves the creation of a multi-physics code to accurately model a running rocket engine. The scale and complexity of turbulent non-premixed combustion has so far made it impractical to simulate, even on today's largest supercomputers. We present a novel approach using wavelets on GPUs, capable of capturing physics down to the finest turbulent scales.

Level: All
Type: Talk
Tags: Manufacturing; Computational Physics; Supercomputing; Developer - Algorithms
Title: Re: SpaceX advances drive for Mars rocket via Raptor power
Post by: Robotbeat on 03/17/2015 03:00 am
Good luck! Simulating a rocket engine like that is not a simple task.
Title: Re: SpaceX advances drive for Mars rocket via Raptor power
Post by: Semmel on 03/17/2015 08:41 am
Very interesting. From experience with computer science talks, the first 10% might be interesting background information about the application and the rest details on the computer science task. So there might be some publically unknown info in there, but I wouldnt expect ground breaking information.

I would like to see a video stream of the talk though.
Title: Re: SpaceX advances drive for Mars rocket via Raptor power
Post by: abaddon on 03/17/2015 01:42 pm
SpaceX needs to be careful, this type of work is bordering on "Science".
Title: Re: SpaceX advances drive for Mars rocket via Raptor power
Post by: newpylong on 03/17/2015 06:26 pm
Jeff Foust ‏@jeff_foust  2h2 hours ago
Shotwell: vehicle architecture that will use the Raptor (large LOX/CH4) engine still in work, so engine performance TBD. #satshow
Title: Re: SpaceX advances drive for Mars rocket via Raptor power
Post by: philw1776 on 03/17/2015 06:39 pm
Jeff Foust ‏@jeff_foust  2h2 hours ago
Shotwell: vehicle architecture that will use the Raptor (large LOX/CH4) engine still in work, so engine performance TBD. #satshow

Makes SO much sense.
You don't completely design an engine (thrust, etc.) and later design your transportation system especially when you have explicit mission target objectives for your transportation system.
They likely consider, pick a design point, re-evaluate based on feasibility, cost, etc. then iterate.
Title: Re: SpaceX advances drive for Mars rocket via Raptor power
Post by: douglas100 on 03/17/2015 07:01 pm
That's interesting. I was under the impression that Raptor performance had been more or less tied down.  As you say, if the architecture is still being worked on, then it makes sense to keep Raptor's performance "fluid" in the meantime.
Title: Re: SpaceX advances drive for Mars rocket via Raptor power
Post by: BobHk on 03/18/2015 09:19 pm
Could this be an image of Raptor?  offhand anyone know?

first slide down the page

from

http://www.slashgear.com/simulating-spacexs-mars-rocket-engine-on-a-virtual-grid-18374078/

Title: Re: SpaceX advances drive for Mars rocket via Raptor power
Post by: DanielW on 03/18/2015 09:24 pm
Could this be an image of Raptor?  offhand anyone know?

first slide down the page

from

http://www.slashgear.com/simulating-spacexs-mars-rocket-engine-on-a-virtual-grid-18374078/ (http://Raptor?)

I believe that is a Merlin. Note the gas generator exhaust. They probably used that to demonstrate their methods that they will then use on the Raptor.
Title: Re: SpaceX advances drive for Mars rocket via Raptor power
Post by: guckyfan on 03/18/2015 09:25 pm
Could this be an image of Raptor?  offhand anyone know?

The engine bell looks strange to me.

http://cdn.slashgear.com/wp-content/uploads/2015/03/IMG_1508slashgear_.jpg
Title: Re: SpaceX advances drive for Mars rocket via Raptor power
Post by: BobHk on 03/18/2015 09:35 pm
From the same link, spacex simulation videos of raptor engine and capsules

https://www.youtube.com/watch?feature=player_embedded&v=n8JqbooVvjA

https://www.youtube.com/watch?feature=player_embedded&v=ZQCLrtgfRis
Title: Re: SpaceX advances drive for Mars rocket via Raptor power
Post by: DanielW on 03/18/2015 09:47 pm
I would have loved to be at that talk. I am immensely curious about the grid they are using. It seems to have a maximum grid size instead of being say a full octtree or quadtree. Also they seem to be using non-square regions. I also wonder if they change the quantization in the time-domain as well.
Title: Re: SpaceX advances drive for Mars rocket via Raptor power
Post by: docmordrid on 03/18/2015 09:59 pm
The above  SlashGear link was dead from here, but this one  works

Link.... (http://www.slashgear.com/simulating-spacexs-mars-rocket-engine-on-a-virtual-grid-18374078/)
Title: Re: SpaceX advances drive for Mars rocket via Raptor power
Post by: Lars-J on 03/18/2015 11:23 pm

Could this be an image of Raptor?  offhand anyone know?

first slide down the page

from

http://www.slashgear.com/simulating-spacexs-mars-rocket-engine-on-a-virtual-grid-18374078/

It looks like a Merlin 1D engine. (Same model as shown in Elon's "3d printing/prototyping engines" video released last year)
Title: Re: SpaceX advances drive for Mars rocket via Raptor power
Post by: AncientU on 03/18/2015 11:42 pm
Could this be an image of Raptor?  offhand anyone know?

first slide down the page

from

http://www.slashgear.com/simulating-spacexs-mars-rocket-engine-on-a-virtual-grid-18374078/

Quote
All of this information means a massive number of output points on a scale. Lots of data to process. At 1kB of data per point, SpaceX has Yottabytes of data.

*A Yottabyte is equal to one SEPTILLION (10 to the 24th power) bytes. That's a vast amount of data.

Using Wavelet Compression, SpaceX reduces the number of points - points of data - that they need at any given time. Transform Output, it's called, is used to show the points which show greatest change.

Yottabytes... yikes!  (A terabyte of terabytes?)
And we were definitively told they only do "trial and error."
Title: Re: SpaceX advances drive for Mars rocket via Raptor power
Post by: Port on 03/18/2015 11:45 pm
SpaceX needs to be careful, this type of work is bordering on "Science".

and where's the problem with that?

i think what they've done with this adaptive grid could be of major use for a HUGE variety fields where simulation of multidimensional fluiddynamics was simply impractical or not possible to use
Title: Re: SpaceX advances drive for Mars rocket via Raptor power
Post by: BobHk on 03/19/2015 01:40 am
Could this be an image of Raptor?  offhand anyone know?

first slide down the page

from

http://www.slashgear.com/simulating-spacexs-mars-rocket-engine-on-a-virtual-grid-18374078/

Quote
All of this information means a massive number of output points on a scale. Lots of data to process. At 1kB of data per point, SpaceX has Yottabytes of data.

*A Yottabyte is equal to one SEPTILLION (10 to the 24th power) bytes. That's a vast amount of data.

Using Wavelet Compression, SpaceX reduces the number of points - points of data - that they need at any given time. Transform Output, it's called, is used to show the points which show greatest change.

Yottabytes... yikes!  (A terabyte of terabytes?)
And we were definitively told they only do "trial and error."

Someone in a meeting must have pointed out pure trial and error in a Mars mission was likely to kill the participants.
Title: Re: SpaceX advances drive for Mars rocket via Raptor power
Post by: Robotbeat on 03/19/2015 02:08 am
From the same link, spacex simulation videos of raptor engine and capsules

https://www.youtube.com/watch?feature=player_embedded&v=n8JqbooVvjA

https://www.youtube.com/watch?feature=player_embedded&v=ZQCLrtgfRis
Wow, near the end of that last one looks like our first glimpse of the MCT from SpaceX!
EDIT: Um, Self, that just looks like Dragon 2. Chill.
Title: Re: SpaceX advances drive for Mars rocket via Raptor power
Post by: meekGee on 03/19/2015 02:29 am
Could this be an image of Raptor?  offhand anyone know?

first slide down the page

from

http://www.slashgear.com/simulating-spacexs-mars-rocket-engine-on-a-virtual-grid-18374078/

Quote
All of this information means a massive number of output points on a scale. Lots of data to process. At 1kB of data per point, SpaceX has Yottabytes of data.

*A Yottabyte is equal to one SEPTILLION (10 to the 24th power) bytes. That's a vast amount of data.

Using Wavelet Compression, SpaceX reduces the number of points - points of data - that they need at any given time. Transform Output, it's called, is used to show the points which show greatest change.

Yottabytes... yikes!  (A terabyte of terabytes?)
And we were definitively told they only do "trial and error."

I never took the "they don't do analysis" comment seriously, but what's absolutely awesome to me is the direct connect between people that do things like wavelet compression (and I remember wavelets from school and I couldn't keep up with it back then) and people who figure out how to weld the feet of a rocket on a rolling barge in a rough sea, for real.

Things flow full circle really quickly when your design generations are 2 years long and every generation is a leap beyond the previous one.
Title: Re: SpaceX advances drive for Mars rocket via Raptor power
Post by: deltaV on 03/19/2015 02:49 am
The entire world wide web is only a couple of zettabytes, one factor of a thousand below yottabyte: http://en.wikipedia.org/wiki/Zettabyte . It's unlikely that SpaceX has a hundred times more storage space than the rest of humanity put together. The idea that SpaceX is handling yottabytes is ludicrous.
Title: Re: SpaceX advances drive for Mars rocket via Raptor power
Post by: llanitedave on 03/19/2015 03:36 am
I would have loved to be at that talk. I am immensely curious about the grid they are using. It seems to have a maximum grid size instead of being say a full octtree or quadtree. Also they seem to be using non-square regions. I also wonder if they change the quantization in the time-domain as well.


The approach seems to be similar to gravitational n-body simulations of star clusters and galaxies, where they can average background regions when they need to, and detail them for individual stars when necessary.


http://www.cs.cmu.edu/~scandal/alg/nbody.html (http://www.cs.cmu.edu/~scandal/alg/nbody.html)
Title: Re: SpaceX advances drive for Mars rocket via Raptor power
Post by: Mariusuiram on 03/19/2015 04:20 am
The entire world wide web is only a couple of zettabytes, one factor of a thousand below yottabyte: http://en.wikipedia.org/wiki/Zettabyte . It's unlikely that SpaceX has a hundred times more storage space than the rest of humanity put together. The idea that SpaceX is handling yottabytes is ludicrous.

It would be ludicrous and thats why they are presenting a novel approach at a GPU conference. This is the problem with shrinking quote chains where information is lost until there are misunderstandings (or possibly articles misquoting SpaceX)

I think SpaceX is explaining how trying to simulate engine exhaust on a grid generates yottabytes of data for the detail necessary. Their solution is to use "wavelet compression" and focus on points where the greatest change is occurring to reduce the data requirement.

So they are using a novel technique to get the detail needed to simulate their engine exhaust without the need to manage a scale of data that would be impossible.

At least thats my interpretation without actually knowing much about the programming involved.
Title: Re: SpaceX advances drive for Mars rocket via Raptor power
Post by: AdrianW on 03/19/2015 05:50 am
SpaceX needs to be careful, this type of work is bordering on "Science".

and where's the problem with that?

It was a reference to a well known poster's comment in another thread, claiming that "[SpaceX] aren't `studying` or doing basic science, they are doing trial and error vs analyzing or ground testing."
Title: Re: SpaceX advances drive for Mars rocket via Raptor power
Post by: Robotbeat on 03/19/2015 11:00 am
Yeah this is a grid optimization scheme. If your temperature or pressure etc. gradient is very small then you don't have to put very many points in that area but if it's large you can jam it packed full of data points and capture all the relevant detail that is needed.
Title: Re: SpaceX advances drive for Mars rocket via Raptor power
Post by: GalacticIntruder on 03/19/2015 04:05 pm
If anyone is looking for their talk, here it is:

http://on-demand.gputechconf.com/gtc/2015/video/S5398.html (http://on-demand.gputechconf.com/gtc/2015/video/S5398.html)
Title: Re: SpaceX advances drive for Mars rocket via Raptor power
Post by: mlindner on 03/19/2015 04:22 pm
I would have loved to be at that talk. I am immensely curious about the grid they are using. It seems to have a maximum grid size instead of being say a full octtree or quadtree. Also they seem to be using non-square regions. I also wonder if they change the quantization in the time-domain as well.


The approach seems to be similar to gravitational n-body simulations of star clusters and galaxies, where they can average background regions when they need to, and detail them for individual stars when necessary.


http://www.cs.cmu.edu/~scandal/alg/nbody.html (http://www.cs.cmu.edu/~scandal/alg/nbody.html)

To be specific they're doing something called Adaptive Mesh Refinement, but they're doing it on a GPU as opposed to a CPU, which is harder. http://en.wikipedia.org/wiki/Adaptive_mesh_refinement
Title: Re: SpaceX advances drive for Mars rocket via Raptor power
Post by: mlindner on 03/19/2015 04:36 pm
The entire world wide web is only a couple of zettabytes, one factor of a thousand below yottabyte: http://en.wikipedia.org/wiki/Zettabyte . It's unlikely that SpaceX has a hundred times more storage space than the rest of humanity put together. The idea that SpaceX is handling yottabytes is ludicrous.

To be clear, after watching the above video. Yottabytes is how many data points they would have if they did not use Adaptive Mesh Refinement in their CFD simulations, but they do, so they have vastly less actual data. But the data they have would be AS IF they had yottabytes of data. Slashdot just screwed up and went for a sensational line.
Title: Re: SpaceX advances drive for Mars rocket via Raptor power
Post by: S.Paulissen on 03/19/2015 04:54 pm
This type of solution is at work in a lot of newer computation technologies.  I'm happy to see them use it to make rockets cheaper.

The basic premise as I understand it is that they treat the problem more like a search engine than a simulation.  Before anyone tries to lynch me for saying that let me finish.  In a classical search type problem you're sifting through the mountains of 'useless' data to find the 'useful' data.  This is essentially the same thing, it simulates a rough grid of points, searches through it to find where the useful data is, re-renders in finer detail, searches in that, renders further and iterates that until you've the amount of detail you need, where you need it.

This is also being used on voxel rendering.

http://www.euclideon.com/
Title: Re: SpaceX advances drive for Mars rocket via Raptor power
Post by: lele on 03/19/2015 05:22 pm
Now that's pretty pictures!

If their simulations realistically represent engine behavior, I have no words strong enough to say how it's impressive. (I know a few things about computer simulations)
Title: Re: SpaceX advances drive for Mars rocket via Raptor power
Post by: meekGee on 03/19/2015 05:58 pm
This type of solution is at work in a lot of newer computation technologies.  I'm happy to see them use it to make rockets cheaper.

The basic premise as I understand it is that they treat the problem more like a search engine than a simulation.  Before anyone tries to lynch me for saying that let me finish.  In a classical search type problem you're sifting through the mountains of 'useless' data to find the 'useful' data.  This is essentially the same thing, it simulates a rough grid of points, searches through it to find where the useful data is, re-renders in finer detail, searches in that, renders further and iterates that until you've the amount of detail you need, where you need it.

This is also being used on voxel rendering.

http://www.euclideon.com/

Never a timelier line.
Title: Re: SpaceX advances drive for Mars rocket via Raptor power
Post by: AdrianW on 03/19/2015 06:09 pm
The basic premise as I understand it is that they treat the problem more like a search engine than a simulation.
No, they don't: They're treating the problem very much like a simulation, not like a search engine. Adaptive mesh refinement is not a new technique in simulation, and it has nothing to do with search engines.

Quote
In a classical search type problem you're sifting through the mountains of 'useless' data to find the 'useful' data.  This is essentially the same thing, it simulates a rough grid of points, searches through it to find where the useful data is, re-renders in finer detail, searches in that, renders further and iterates that until you've the amount of detail you need, where you need it.
What you're describing has nothing in common with what "search engines" do. In fact, it isn't even a "search problem", as the term is understood in computer science.
Title: Re: SpaceX advances drive for Mars rocket via Raptor power
Post by: Port on 03/19/2015 06:51 pm
I wonder, surely you would need to calculate this in double-precision - which is REALLY slow on a GPU (factor 8 or so) - ESPECIALLY on nvidia GPU's (which is funny since it's been hosted by nvidia :D)

with the next gen of GPU's being able to calculate mixed-precision much much faster this could seriously take off in terms of speed IMO

the whole few seconds of speed-distribution inside the raptor engine where calculated on a single gpu over the weekend, which is super impressive but think what a multi-gpu with enhanced double/mixed precision capabilities would be able to accoplish here, we're talking about realtime-cfd O_o

but i guess back to topic here :D
Title: Re: SpaceX advances drive for Mars rocket via Raptor power
Post by: mlindner on 03/19/2015 07:06 pm
I wonder, surely you would need to calculate this in double-precision - which is REALLY slow on a GPU (factor 8 or so) - ESPECIALLY on nvidia GPU's (which is funny since it's been hosted by nvidia :D)

with the next gen of GPU's being able to calculate mixed-precision much much faster this could seriously take off in terms of speed IMO

the whole few seconds of speed-distribution inside the raptor engine where calculated on a single gpu over the weekend, which is super impressive but think what a multi-gpu with enhanced double/mixed precision capabilities would be able to accoplish here, we're talking about realtime-cfd O_o

but i guess back to topic here :D

Also note that, that looked like a 2D simulation of an engine rather than a 3D one. That would run quite a bit quicker I would think. They're also not simulating there any of the turbine assemblies which I would also think would run quite a bit slower.
Title: Re: SpaceX advances drive for Mars rocket via Raptor power
Post by: guckyfan on 03/19/2015 07:21 pm

Also note that, that looked like a 2D simulation of an engine rather than a 3D one. That would run quite a bit quicker I would think. They're also not simulating there any of the turbine assemblies which I would also think would run quite a bit slower.

They were talking about simulating LOX/Methane combustion down to the molecular level, taking about (80?) different intermediate chemicals reactions into consideration. I think simulating just flow of fluids should be significantly easier.
Title: Re: SpaceX advances drive for Mars rocket via Raptor power
Post by: AdrianW on 03/19/2015 07:22 pm
I wonder, surely you would need to calculate this in double-precision - which is REALLY slow on a GPU (factor 8 or so) - ESPECIALLY on nvidia GPU's (which is funny since it's been hosted by nvidia :D)
You're probably thinking of consumer GPUs. For the high performance computing models (e.g., the "Tesla" brand of Nvidia), it's about a factor of 3 for the newer cards, and a factor of 2 for the older cards (e.g., the C2070). This is about what you find in desktop/server CPUs as well: The DP throughput is half that of the SP throughput, because the silicon for a DP multiplication can be used for two parallel SP multiplications without too much difficulty.
Title: Re: SpaceX advances drive for Mars rocket via Raptor power
Post by: Port on 03/19/2015 08:04 pm

Also note that, that looked like a 2D simulation of an engine rather than a 3D one. That would run quite a bit quicker I would think. They're also not simulating there any of the turbine assemblies which I would also think would run quite a bit slower.

They were talking about simulating LOX/Methane combustion down to the molecular level, taking about (80?) different intermediate chemicals reactions into consideration. I think simulating just flow of fluids should be significantly easier.

with the 2d: it's rotation-symmetrical so there's no need for a full-fledged 3d model if you're doing it right - at least thats what i thought

~230 intermediate reactions :)


You're probably thinking of consumer GPUs. For the high performance computing models (e.g., the "Tesla" brand of Nvidia), it's about a factor of 3 for the newer cards, and a factor of 2 for the older cards (e.g., the C2070). This is about what you find in desktop/server CPUs as well: The DP throughput is half that of the SP throughput, because the silicon for a DP multiplication can be used for two parallel SP multiplications without too much difficulty.

yeah well.. the kepler based tesla (there's no maxwell-tesla aviable yet afaik) gets arround 1 TFLOP dp (the dual-gpu card around 1,8), a 295x2 gets 2,67 TFLOPS (so a r9 290x around 1,3) done, of course without ECC which might be a deciding factor in such simulations i guess?
just saying that ever since 3 generations nvidias dp-performance is seriously bad compared to amd/ati's cards, funny enough on the consumer side things look the very opposite way (some might argues against that, but that's just my opinion ;))

(According to this article (german)  (http://www.golem.de/news/quadro-m6000-nvidias-neue-profi-grafikkarte-fuer-4k-bietet-eine-backplate-1503-113062.html) the new quadro M6k will have just 1/32 of the performance for double calculations, leading to just 0,22 TFLOPs which is INSANELY low)

takeaway should be: with the next generations of gpu's coming out in the next 1-1,5 years the should be a significant boost for this kind of application (not to mention optimizing it for parallel-computing on multiple gpu's) - thanks to the - still very steadily climbing progress of - moore's law :) (which still as a lot of headroom for gpu's because current designs are still 28nm withouth finfet-tech, which is ancient compared to what intel does)
Title: Re: SpaceX advances drive for Mars rocket via Raptor power
Post by: Semmel on 03/19/2015 08:50 pm
The grid looks fun to do. The idea is not new. Its used in computer graphics for collisions  and z-buffer (buzzword: oct-tree), I myself used a similar idea to run a clustering algorithm (finding structure in data) to speed up calculation from O(n^2) to O(n log n). I too used a decision making algorithm based on an estimation of the maximal gradient within one cell. If the gradient was too strong, the cell was subdivided. And thats essentially whats happening within the engine simulation as well. The fact that they implemented it on a GPU is impressive but not magic either. I like it. Well established technology used in the right and simple combination often gives the best results. In software or otherwise.
Title: Re: SpaceX advances drive for Mars rocket via Raptor power
Post by: Robotbeat on 03/19/2015 10:37 pm
It does look like a more robust/scalable adaptive grid implementation than I've seen in my work, but it's true it's a fairly common practice.

But doing it in a GP-GPU should help lower the cost of computation a lot. 1TFLOP (dual precision) in a single PCI-E slot is pretty awesome, on the right motherboard combos can give you 5 TFlop per U, so 3 or for racks could give you a petaflop of theoretical performance.

...but I do wonder if this adaptive grid method is as-amenable to parallelization as other such methods.
Title: Re: SpaceX advances drive for Mars rocket via Raptor power
Post by: mlindner on 03/20/2015 02:30 am
(there's no maxwell-tesla aviable yet afaik)

Maxwell-based Titan X (not Tesla) was announced 3 days ago.
Title: Re: SpaceX advances drive for Mars rocket via Raptor power
Post by: SVBarnard on 03/27/2015 02:08 pm
so as far as i understand it, the BFR will be too big to manufacture at the hawthorne factory so they will need to build a whole new factory for it? And this factory will be built most likely at boca chica spaceport? anyone?
Title: Re: SpaceX advances drive for Mars rocket via Raptor power
Post by: JBF on 03/27/2015 02:10 pm
so as far as i understand it, the BFR will be too big to manufacture at the hawthorne factory so they will need to build a whole new factory for it? And this factory will be built most likely at boca chica spaceport? anyone?

Not too big to build, to big to transport.  At this point it's anyone's guess as to where it will be.
Title: Re: SpaceX advances drive for Mars rocket via Raptor power
Post by: BobHk on 03/27/2015 02:25 pm
so as far as i understand it, the BFR will be too big to manufacture at the hawthorne factory so they will need to build a whole new factory for it? And this factory will be built most likely at boca chica spaceport? anyone?

Not too big to build, to big to transport.  At this point it's anyone's guess as to where it will be.

If SpaceX assembles the rocket on pad (as Shotwell has said they think they will have to) the parts could be small enough to transport on the highway.  Meaning it could be made in Hawthorne.

Nine current rocketbodies of the size of the F9 with a single raptor on the bottom of each could be moved to boca from anywhere, assembled there and clad in an outer shell on site.

Title: Re: SpaceX advances drive for Mars rocket via Raptor power
Post by: TomH on 03/27/2015 02:44 pm
so as far as i understand it, the BFR will be too big to manufacture at the hawthorne factory so they will need to build a whole new factory for it? And this factory will be built most likely at boca chica spaceport? anyone?

Not too big to build, to big to transport.  At this point it's anyone's guess as to where it will be.

If SpaceX assembles the rocket on pad (as Shotwell has said they think they will have to) the parts could be small enough to transport on the highway.  Meaning it could be made in Hawthorne.

Nine current rocketbodies of the size of the F9 with a single raptor on the bottom of each could be moved to boca from anywhere, assembled there and clad in an outer shell on site.

Oh gracious, you can't be serious! Saturn I was called Cluster's Last Stand, and it really needs to live up to that name.

Do you realize how much wasted volume there would be between all those cylinders and how much unnecessary extra mass would exist in the eighteen prop tanks as opposed to two? They you're going to wrap another cylinder around all that? The notion is preposterous.
Title: Re: SpaceX advances drive for Mars rocket via Raptor power
Post by: SVBarnard on 03/27/2015 03:57 pm
do you think its possible that they could use the Michoud Assembly Facility? Sorry if this has been asked before but i dont have the patience to read through every page.

i mean it is theoretically possible that they could rent out space there and move tools and equipment there and build the engines and stages there and then deliver by sea to boca chica?

Are the waters around boca chica deep enough to act as a harbor?

I cant wait til the end of the year when they make they're announcement on the BFR as Elon said beginning of this year.
Title: Re: SpaceX advances drive for Mars rocket via Raptor power
Post by: BobHk on 03/27/2015 04:23 pm
If all BFR has to do is get MCT to its orbit and land on Earth after, it doesn't have to be pretty and can even eschew efficiency ... depends on a lot of things that I have no control over.  We can stick fins and pics of cats on it too, but I am in no way suggesting fins.
Title: Re: SpaceX advances drive for Mars rocket via Raptor power
Post by: guckyfan on 03/27/2015 04:25 pm
The russian Angara comes in 1, 3, or 5 core versions. But they have the restriction of rail transport. They have no choice.

Title: Re: SpaceX advances drive for Mars rocket via Raptor power
Post by: SVBarnard on 03/27/2015 04:28 pm

If all BFR has to do is get MCT to its orbit and land on Earth after, it doesn't have to be pretty and can even eschew efficiency ... depends on a lot of things that I have no control over.  We can stick fins and pics of cats on it too, but I am in no way suggesting fins.

surely there will be grind fins?
Title: Re: SpaceX advances drive for Mars rocket via Raptor power
Post by: Sohl on 03/27/2015 08:02 pm
Nine current rocketbodies of the size of the F9 with a single raptor on the bottom of each could be moved to boca from anywhere, assembled there and clad in an outer shell on site.

This kind of modularity helps assembly and transportation, but you lose a lot of mass efficiency.  This would have been a very limiting technical issue for the larger planned OTRAG rockets of the 70s and 80s.  They never got far enough for that to fully hit them though.
Title: Re: SpaceX advances drive for Mars rocket via Raptor power
Post by: PreferToLurk on 03/27/2015 08:17 pm
First off, source for the assertion that Shotwell has indicated SpaceX might have to assemble BFR on the pad?  I have never heard such a thing, and I follow SpaceX about as closely as anyone.  There is a big difference between "building" something near the pad and merely "assembling" something near the pad.

Wasted space was only one of TomH's issues with your idea -- the other being all the wasted weight of the extra tank walls.  Even if you sealed it all up and only put oxidizer in the round tanks and fuel in the concave "tanks" (spaces) you still have a LOT of wasted weight.  Extremely high propellant mass fractions are needed for RTLS activities, and BFR is DEFINITELY going to be RTLS.  I seriously doubt that such a bundled stage could manage to loft an MCT and RTLS without being comprised of either a ridiculously large number of tanks or employing cross feed plus asparagus staging requiring an extremely complicated plumbing scheme and all the risks (plus more weight!) that such a system would require. Besides, how are you going to asparagus stage if you don't leave the tank gaps empty?  once again, even MORE wasted space and weight, requiring even MORE stages to be bundled together. 

TL;DR:

Unworkable.
Title: Re: SpaceX advances drive for Mars rocket via Raptor power
Post by: meekGee on 03/27/2015 08:27 pm
"Assembled on the pad" is not such a bad thing for a reusable rocket. 

If subsequent lifetime is high, you will have a "first time pad" which is also an assembly facility, and after the first launch, the rocket can land and relaunch from the main operations complex which includes landing and launch pads.

Thinking about it further, the first launch from the assembly pad might occur with no payload, and might be only a first stage flight, since at that point the first launch will actually be considered a higher-risk - a "checkout flight" if you will.
Title: Re: SpaceX advances drive for Mars rocket via Raptor power
Post by: BobHk on 03/27/2015 08:37 pm

At roughly 3:50...

https://www.youtube.com/watch?v=EoCDLUHb0y4

Building it on the launch pad isn't fantasy...Shotwell is envisioning even larger tanks than I am.  I'm being more practical in answering an earlier question about whether such a rocket could be road transportable to which my direct assertion is yes, it could.
Title: Re: SpaceX advances drive for Mars rocket via Raptor power
Post by: dror on 03/27/2015 08:58 pm
She actually contradictaed your point in that same sentence, at around 3:50 she said:
"We're gonna have to build that vehicle at the launch site 'cause it is going to be too big to go over road, too big for rails..."
Title: Re: SpaceX advances drive for Mars rocket via Raptor power
Post by: Robotbeat on 03/27/2015 09:15 pm
She said building it at the launch site, not literally on the pad. That jives with what Musk has said about a factory near the launch site.

Oh, and mass inefficiency is not an option because they need to reuse it a lot (and reuse it by propulsive boost back and landing). This is why Falcon 9 v1.1/1.2 has a best in class mass ratio.
Title: Re: SpaceX advances drive for Mars rocket via Raptor power
Post by: spacenut on 03/27/2015 09:29 pm
Russia is also land locked and has very little water transportation.  BFR has thousands of miles of navigable waterways in America in which to manufacture something as bid as BFR on.  We have the Mississippi-Ohio-Missouri-Tennessee Rivers all connected.  We have the intercoastal waterway From Brownsville all around Florida and the East coast.  Large objects can be moved via this waterway.  Atlas and Delta are made in Decatur, Alabama and shipped to the Kennedy.  Michloud cores are shipped to Cape Kennedy.  I think SpaceX will probably use Brownsville. 

If BFR is to have 15 million lbs of thrust (twice Saturn V), does anyone know what power Raptor has yet?  Nine would have 1.66 million.  18 would have 833 thousand.  Just wondering. 
Title: Re: SpaceX advances drive for Mars rocket via Raptor power
Post by: matthewkantar on 03/27/2015 11:00 pm


Only impractical until someone develops an engine that is efficient and powerful enough to overcome the issues you indicated.  Just too many negative waves, man.

 








I know whenever I come up with a massive improvement in propulsion efficiency, I like to eat up my hard earned margin with unnecessary tankage, plumbing and complexity.

Matthew
Title: Re: SpaceX advances drive for Mars rocket via Raptor power
Post by: RotoSequence on 03/27/2015 11:09 pm
The tank structures are probably the least complex part of the booster. I wouldn't be surprised if SpaceX fabricated the engines, the helium tanks, landing legs, and other complex parts at Hawthorn, and trucked them to a final assembly building at Brownsville. I imagine they could fabricate the rest of the rocket's parts and do the assembly in Texas, with a minimum amount of workforce duplication, minimal redundancies, and low logistical overhead.
Title: Re: SpaceX advances drive for Mars rocket via Raptor power
Post by: Chris Bergin on 03/28/2015 12:56 am
It's one thing when a member is uncivil, but it's another thing when people insist on multi-quoting it.

Some of you have been here long enough to know better. Edit, then trimmed.

We will not allow the quality of this site's forum to be reduced by anyone, and we will moderate to avoid it - usually resulting in someone leaving and going off to another site to say how mean and "power mad" we are because we don't allow profanity or poo jokes to rank up post counts (seriously)....... ;D
Title: Re: SpaceX advances drive for Mars rocket via Raptor power
Post by: Burninate on 03/28/2015 04:26 am
so as far as i understand it, the BFR will be too big to manufacture at the hawthorne factory so they will need to build a whole new factory for it? And this factory will be built most likely at boca chica spaceport? anyone?

Not too big to build, to big to transport.  At this point it's anyone's guess as to where it will be.

If SpaceX assembles the rocket on pad (as Shotwell has said they think they will have to) the parts could be small enough to transport on the highway.  Meaning it could be made in Hawthorne.

Nine current rocketbodies of the size of the F9 with a single raptor on the bottom of each could be moved to boca from anywhere, assembled there and clad in an outer shell on site.

Oh gracious, you can't be serious! Saturn I was called Cluster's Last Stand, and it really needs to live up to that name.

Do you realize how much wasted volume there would be between all those cylinders and how much unnecessary extra mass would exist in the eighteen prop tanks as opposed to two? They you're going to wrap another cylinder around all that? The notion is preposterous.

I thought this was worthy of a thread. (http://forum.nasaspaceflight.com/index.php?topic=37161.0)

If you'd like to elaborate, it would be appreciated.
Title: Re: SpaceX advances drive for Mars rocket via Raptor power
Post by: AncientU on 03/28/2015 11:50 am
"Assembled on the pad" is not such a bad thing for a reusable rocket. 

If subsequent lifetime is high, you will have a "first time pad" which is also an assembly facility, and after the first launch, the rocket can land and relaunch from the main operations complex which includes landing and launch pads.

Thinking about it further, the first launch from the assembly pad might occur with no payload, and might be only a first stage flight, since at that point the first launch will actually be considered a higher-risk - a "checkout flight" if you will.

It's such a bad idea... Fabrication involves tooling and access that would have to be hauled out each time a new vehicle was needed -- rendering the launch facility inoperable for many months.  Think of the traveling paint house, or the swarm of workers touching various parts of the vehicle along its length, or rolling the vehicle on its long axis to access all parts from the floor... 

Assemble an aircraft at the airport gate?
Title: Re: SpaceX advances drive for Mars rocket via Raptor power
Post by: meekGee on 03/28/2015 04:17 pm
"Assembled on the pad" is not such a bad thing for a reusable rocket. 

If subsequent lifetime is high, you will have a "first time pad" which is also an assembly facility, and after the first launch, the rocket can land and relaunch from the main operations complex which includes landing and launch pads.

Thinking about it further, the first launch from the assembly pad might occur with no payload, and might be only a first stage flight, since at that point the first launch will actually be considered a higher-risk - a "checkout flight" if you will.

It's such a bad idea... Fabrication involves tooling and access that would have to be hauled out each time a new vehicle was needed -- rendering the launch facility inoperable for many months.  Think of the traveling paint house, or the swarm of workers touching various parts of the vehicle along its length, or rolling the vehicle on its long axis to access all parts from the floor... 

Assemble an aircraft at the airport gate?

But that's why I explicitly differentiated between the "first time pad" which is also the assembly facility, and the operational facility which is used for landing and re-launches.

The first time pad is more like "an assembly plant with limited launch capability" then "a pad which is also an assembly plant".

Think about building a ship. The launching facility, whether it's a rail or a dry dock, is a very limited sea-port.   You don't build the ship in the middle of a commercial port, but the ship does leave the construction site via its normal mode of locomotion - floating on water, possibly under power (or tugged, but that's irrelevant here)

I'm even suggesting that the assembly plant pad does not have any payload processing capability, or even maybe not second stage integration - the first stage is built, launched on a suborbital RTLS checkout flight, and never sees the assembly plant again.
Title: Re: SpaceX advances drive for Mars rocket via Raptor power
Post by: Robotbeat on 03/28/2015 04:23 pm
Why the crap would you launch from your factory, singing all the equipment or requiring it's its* removal? Empty liquid rockets like BFR are very lightweight (SpaceX is capable of mass ratios of about 30:1), the ship analogy is a horrible one.

No, this is all from a misunderstanding: Shotwell never said the BFR would be built on the pad. Go check!!!! She said "at" the launch site.

*fracking iPhone auto-incorrect
Title: Re: SpaceX advances drive for Mars rocket via Raptor power
Post by: meekGee on 03/28/2015 05:04 pm
Why the crap would you launch from your factory, singing all the equipment or requiring it's its* removal? Empty liquid rockets like BFR are very lightweight (SpaceX is capable of mass ratios of about 30:1), the ship analogy is a horrible one.

No, this is all from a misunderstanding: Shotwell never said the BFR would be built on the pad. Go check!!!! She said "at" the launch site.

*fracking iPhone auto-incorrect

No, you would not do it that stupidly.   Might as well ask what about the poor assembly workers that will be fried in the process.  (Or the ship builders that will drown when you fill the dry dock).

Instead, you'd assemble BFR near your main launch complex.  In the same general area.  As it happens, the main jig that BFR sits on during assembly can also support a launch.  You'd pull back the assembly equipment, and launch it from there.

This way you're not risking your main operations facility during the first launch, which is the riskiest.

If it explodes on the pad, you'd have lost only the assembly pad, which was not intended to be used again until the next BFR is manufactured.  Your ongoing operations and main launch pads are just fine.
Title: Re: SpaceX advances drive for Mars rocket via Raptor power
Post by: spacenut on 03/28/2015 07:27 pm
They were going to build a big air force tanker plane at Mobile, but the contract was given to Boeing.  There might still be the large building where the assembly was going to take place.  The rockets could be made there and shipped to any launch site along the coast just like the SLS and Saturn V cores.  No need to add extra weight of multiple cores.  We still don't know for sure, but we do know what can be and what has been done with existing infrastructure.
Title: Re: SpaceX advances drive for Mars rocket via Raptor power
Post by: SVBarnard on 03/28/2015 08:11 pm
is michoud out of the question? and if anything is going to be shipped to boca chica how deep are the waters there?
Title: Re: SpaceX advances drive for Mars rocket via Raptor power
Post by: spacenut on 03/28/2015 08:42 pm
Doesn't have to be deep for a barge to deliver the rocket.  Gulf coast is shallow compared to the Atlantic coast.  A barge can get to Brownsville or leave from there, small ships do already.  There are 100's of shallow water oil rigs off the Gulf coast.  The rocket could be launched from a modified oil rig just off shore.  Cruise ships port at New Orleans and Mobile.  Don't know about Corpus Christi or Galveston what sizes can get in there.  Ships also leave Pensacola, Panama City and Tampa-St. Petersburg area.  So 10-12m size rockets or rocket tanks are no problem along the coast. 
Title: Re: SpaceX advances drive for Mars rocket via Raptor power
Post by: TomH on 03/29/2015 04:28 am
is michoud out of the question? and if anything is going to be shipped to boca chica how deep are the waters there?

Ceiling and overhead cranes are too low. Ten m. diameter Saturn V S-I and S-II stages were built there without overhead cranes. Cranes were installed for STS tank construction. There was debate over removing cranes and/or raising the ceiling, but it was decided not to, thus SLS core dia. is 8.4 m just as STS tank was.
Title: Re: SpaceX advances drive for Mars rocket via Raptor power
Post by: AncientU on 03/29/2015 09:45 pm
is michoud out of the question? and if anything is going to be shipped to boca chica how deep are the waters there?

Ceiling and overhead cranes are too low. Ten m. diameter Saturn V S-I and S-II stages were built there without overhead cranes. Cranes were installed for STS tank construction. There was debate over removing cranes an/or raising the ceiling, but it was decided not to, thud SLS core dis. is 8.4 m just as STS tank was.

I've heard this before... That a fifty-year old building ceiling height contributed to the SLS design decision -- that's incredibly backward.  Still impossible to believe!!!!!!

If SpaceX needs a building to fabricate the BFR, they'll build one -- and it's ceiling will be dictated by the rocket diameter as any rational building decision would be made.  It will be close to a launch site and/or a navigable waterway so the stages can be floated out to other launch sites. 

It's a big box.  Why the discussion?
Title: Re: SpaceX advances drive for Mars rocket via Raptor power
Post by: JBF on 03/29/2015 10:02 pm
It's a big box.  Why the discussion?

Are you sure you are on the right forum? ;)
Title: Re: SpaceX advances drive for Mars rocket via Raptor power
Post by: Lobo on 03/30/2015 03:43 pm
She said building it at the launch site, not literally on the pad. That jives with what Musk has said about a factory near the launch site.


@this.

Also, to assembly something like this on the pad, it'd need a setup like SLC-6, SLC-3, SLC-4 (Old Titan configuration), etc, only much larger.  Like VAB scale in height and about 1/4 of the VAB in width.   While they certainly -could- do that, up until this point SpaceX seems to much prefer horizontal integration.

I'd expect there to be a factory near the pad with the tooling that makes new cores, and new MCT's.  MCT will likely share a lot of structure and componets wtih BFR's US, so that would make sense.  Then the stages are rolled over from the factory to the HIF close to the pad where they will all be stacked horizontally.  Then rolled to the pad on a very large TEL. 
Additionally the factory would be large enough to bring in flown cores for inspection and refurbishment as needed, as well as storage.  Probably look something like MAF back in the day when there were multiple S-1C's on the floor.
Title: Re: SpaceX advances drive for Mars rocket via Raptor power
Post by: spacenut on 03/30/2015 06:53 pm
Is that four first stages in there, or two first and two second stages?  Where was the third stage built, Huntsville and shipped down river like Atlas and Delta?

Title: Re: SpaceX advances drive for Mars rocket via Raptor power
Post by: go4mars on 03/30/2015 07:57 pm
Why is everyone assuming that it won't be built on something that floats?
Title: Re: SpaceX advances drive for Mars rocket via Raptor power
Post by: UberNobody on 03/30/2015 08:32 pm
Why is everyone assuming that it won't be built on something that floats?
Because precision manufacturing is really difficult if not impossible if you have to deal with wave action of any kind.  I think you mean assembled, but if you want to float the pieces over, why not just float the whole thing over?  A coastal integration facility isn't that difficult.

I imagine it is easier to build a big boat than assemble a rocket while floating on water.  This is all assuming water launch, which only makes sense if you can't find a spot on land that fits the bill.
Title: Re: SpaceX advances drive for Mars rocket via Raptor power
Post by: Lobo on 03/30/2015 10:14 pm
Why is everyone assuming that it won't be built on something that floats?

Why would we assume it would?
Title: Re: SpaceX advances drive for Mars rocket via Raptor power
Post by: Lobo on 03/30/2015 10:21 pm
Is that four first stages in there, or two first and two second stages?  Where was the third stage built, Huntsville and shipped down river like Atlas and Delta?

Four S-1C's (1st stages).  S-1C's and S-1B's were the only two stages built at MAF, by Boeing and Chrysler respectively.

The S-II was built by North American in Seal Beach, CA and barged to KSC.
The S-IVB was built by Douglas in Huntington Beach, CA and flown to KSC.

So they wouldn't have been in the MAF with the S-1C's and S-1B's.

Here's a shot of the S-1B's lined up at MAF.
Title: Re: SpaceX advances drive for Mars rocket via Raptor power
Post by: go4mars on 03/31/2015 02:21 am
Why is everyone assuming that it won't be built on something that floats?

Why would we assume it would?
The liftoff thrust will dramatically exceed any prescedent.  At sea from semi-submersible launch pad or spar removes (some) unprecedented pad challenges (while bringing more easily solvable ones), and keeps the NIMBY Neighbours from going deaf.  If it's built upon it's transporter, then there's no need to devise extra methods to transfer and handle the giant rocket.

Wave action doesn't need to be a concern for construction.  Can jack-up a barge, or more likely, float it up a canal toward a mostly land-logistics assembly node.  Although I admit the idea of the inner calm around an assembly/launch spar within a construction seastead appeals to me for the longer-term, grander-scale efficiencies.

Also, in building a colony of millions, every bit of delta-V is important for the cost of tickets and cargo.  So I believe equatorial barge-to-barge launches are a virtual certainty (though I'm sure some of you disagree with that premise).  If that's the concept of operations for re-flights...
Title: Re: SpaceX advances drive for Mars rocket via Raptor power
Post by: rcoppola on 03/31/2015 12:34 pm
Additional info and extremely interesting follow up to the CFD modeling SpaceX is working on to help with Raptor development:

http://www.theplatform.net/2015/03/27/rockets-shake-and-rattle-so-spacex-rolls-homegrown-cfd/
Title: Re: SpaceX advances drive for Mars rocket via Raptor power
Post by: AncientU on 03/31/2015 01:04 pm
Why is everyone assuming that it won't be built on something that floats?

Why would we assume it would?
The liftoff thrust will dramatically exceed any prescedent.  At sea from semi-submersible launch pad or spar removes (some) unprecedented pad challenges (while bringing more easily solvable ones), and keeps the NIMBY Neighbours from going deaf.  If it's built upon it's transporter, then there's no need to devise extra methods to transfer and handle the giant rocket.

Wave action doesn't need to be a concern for construction.  Can jack-up a barge, or more likely, float it up a canal toward a mostly land-logistics assembly node.  Although I admit the idea of the inner calm around an assembly/launch spar within a construction seastead appeals to me for the longer-term, grander-scale efficiencies.

Also, in building a colony of millions, every bit of delta-V is important for the cost of tickets and cargo.  So I believe equatorial barge-to-barge launches are a virtual certainty (though I'm sure some of you disagree with that premise).  If that's the concept of operations for re-flights...

I don't think the old paradigm of squeezing out every m/s of delta-v and every ounce (gram) of payload mass applies.  This is one-off mission thinking.  BFR will be used for bulk cargo and ranges of passengers... and extreme light weighting and optimizing for performance are too expensive.  I believe that it will be as large as practical to still be affordable and reusable.  If the payload doesn't fit on the current manifest, catch the next ride...

It will most likely be launched on or near the U.S. coast, probably with at least one launch site close to the fab facilities.  RTLS is the most practical return approach because it will be so FB.
Title: Re: SpaceX advances drive for Mars rocket via Raptor power
Post by: spacenut on 03/31/2015 01:54 pm
Do you guys think SpaceX might start out with a 500k thrust engine and evolve it to 1 million?  They did it with Merlin, went from 60 something thousand to 147,000 and now 165,000.  More than double. 
Title: Re: SpaceX advances drive for Mars rocket via Raptor power
Post by: guckyfan on 03/31/2015 02:14 pm
Do you guys think SpaceX might start out with a 500k thrust engine and evolve it to 1 million?  They did it with Merlin, went from 60 something thousand to 147,000 and now 165,000.  More than double.

Quite possible. Let's wait and see the diameter of the first version. If it looks very short and stubby they have probably designed in the option to double the length over time.  :)
Title: Re: SpaceX advances drive for Mars rocket via Raptor power
Post by: meekGee on 03/31/2015 03:30 pm
Additional info and extremely interesting follow up to the CFD modeling SpaceX is working on to help with Raptor development:

http://www.theplatform.net/2015/03/27/rockets-shake-and-rattle-so-spacex-rolls-homegrown-cfd/

Impressive.
Title: Re: SpaceX advances drive for Mars rocket via Raptor power
Post by: baldusi on 03/31/2015 04:37 pm
Do you guys think SpaceX might start out with a 500k thrust engine and evolve it to 1 million?  They did it with Merlin, went from 60 something thousand to 147,000 and now 165,000.  More than double.
Who knows? Elon did stated that 500k was the best T/W compromise, even taking all the extra plumbing into consideration. There's an additional issue in T/W, and that's the interstage mass. The bigger the rocket, the fatter they get (i.e. progressively wider and proportionally less tall). There was talks of MCT being 12.5m and even 15m wide.
But the stubbier they are, the more mass that the interstage uses, proportionally. Thus, increasing the number of nozzles on the second stage would probably significantly reduce its length, and thus its mass. I believe that this point specifically was quite an issue in the mass optimization. Thus, I would only see bigger engines with probably bigger LV.
Title: Re: SpaceX advances drive for Mars rocket via Raptor power
Post by: spacenut on 03/31/2015 06:29 pm
Or a 3 core heavy version.  Lars_J suggested this somewhere and it make sense.  One core for about 75-100 tons, a 3 core version for 225-300 tons to LEO.  That way there won't be about 30 engines on a big core.  Also at 75-100 a single core can get a lot of other launches that are too big for Falcon heavy.
Title: Re: SpaceX advances drive for Mars rocket via Raptor power
Post by: philw1776 on 03/31/2015 06:43 pm
Additional info and extremely interesting follow up to the CFD modeling SpaceX is working on to help with Raptor development:

http://www.theplatform.net/2015/03/27/rockets-shake-and-rattle-so-spacex-rolls-homegrown-cfd/

Interesting comments on the article by a guy working for years on the NASP hypersonic program.  They did the CFD modeling but built no hardware.  Small model differences lead exponentially to vastly different results.  He was concerned about SpaceX doing the same but so far their culture is to build and fly something and iterate on improvements.  Models are an essential tool for rapid development, eliminating many dead end hardware prototype expenses, but they are not reality.
Title: Re: SpaceX advances drive for Mars rocket via Raptor power
Post by: baldusi on 03/31/2015 07:47 pm
Or a 3 core heavy version.  Lars_J suggested this somewhere and it make sense.  One core for about 75-100 tons, a 3 core version for 225-300 tons to LEO.  That way there won't be about 30 engines on a big core.  Also at 75-100 a single core can get a lot of other launches that are too big for Falcon heavy.
AIUI, they are trying to avoid having h