Musk to Mars

[LordFerret]

Folded wings eh? Why then have the things land vertically??? Why not let them come back and land on runways (drones)? That sounds (to me) like a far better idea than a powered vertical landing on a barge.

[PB666]

More vapor-ware. Its interesting that this group has a propensity to present every failed and never used idea as somehow the answer to everyones dreams.

[wumpus]

I  have to strongly question the idea that a Spacex craft could benefit from [conventional] three stage flight.  Consider falcon9 and falcon heavy.  Falcon 9 acts as two stages, and recovers the first with 90% of the engines and disposes of the remaining 10% (which provides something like 2/3 of Falcon 9's delta-v).

Falcon Heavy should act like 2 1/2 stages: the center stage sparing itself as much as it can to give the final stage as much delta-v as possible (since roughly the same stage might get twice as much mass to lift, it is going to have to be going faster when separating).  Expect a few more holes in ICISLY while they learn to land all over again.

The main reason why I question a third stage is that merlin engines are particularly *light*.  Fuel tanks are light.  Fuel is heavy.  If you were using hyrdrogen I would understand a third stage, but with either RP1 or methane that doesn't make as much sense.  The second reason is that as far as staging is concerned, there are two classes of stages: recoverable and non-recoverable.  Adding engines to recoverable engines does not seem to be an issue (note that for all the pining for a falcon5 on these forums, spacex isn't the slightest bit interested in it).  And looking at falcon9's peculiar delta-v budget (1/3 for the lower stage, 2/3 for the upper) I would assume that a third stage would split the upper stages into two unrecoverable stages.  I'm guessing the engine that delivered the final 1/3 of the delta-v (or so) would not be the same as in the other two stages.  At that point there is either the issue of coming up with the cost for a third engine (merlin, raptor,???) or using the merlin (upper) engine in this last stage.  Unfortunately, using a RP1 engine in an upper stage nearly negates all your benefit from the higher ISP of the raptor engine.  I just don't see it happening (I wouldn't rule it out, especially if they move to a 4-5 engine group).

Note that if I designed the falcon heavy (KSP-style, anyway), I would like to stick a pair of COTS (commercial off the shelf) SRBs to the upper stage (yes, shlepping SRBs up with liquid rockets because I can reuse the liquid rockets).  This lets me keep the velocities of the big, expensive rockets low and lets me push the final stage out with rockets I don't have to land.  I'm pretty sure somebody ran the numbers, but I really doubt anyone took the idea very seriously.  No idea how much basic "we don't do that" had to do with why they didn't or if the numbers just didn't work.

 

[PB666]

5 minutes ago, wumpus said:

I  have to strongly question the idea that a Spacex craft could benefit from [conventional] three stage flight.  Consider falcon9 and falcon heavy.  Falcon 9 acts as two stages, and recovers the first with 90% of the engines and disposes of the remaining 10% (which provides something like 2/3 of Falcon 9's delta-v).

Falcon Heavy should act like 2 1/2 stages: the center stage sparing itself as much as it can to give the final stage as much delta-v as possible (since roughly the same stage might get twice as much mass to lift, it is going to have to be going faster when separating).  Expect a few more holes in ICISLY while they learn to land all over again.

The main reason why I question a third stage is that merlin engines are particularly *light*.  Fuel tanks are light.  Fuel is heavy.  If you were using hyrdrogen I would understand a third stage, but with either RP1 or methane that doesn't make as much sense.  The second reason is that as far as staging is concerned, there are two classes of stages: recoverable and non-recoverable.  Adding engines to recoverable engines does not seem to be an issue (note that for all the pining for a falcon5 on these forums, spacex isn't the slightest bit interested in it).  And looking at falcon9's peculiar delta-v budget (1/3 for the lower stage, 2/3 for the upper) I would assume that a third stage would split the upper stages into two unrecoverable stages.  I'm guessing the engine that delivered the final 1/3 of the delta-v (or so) would not be the same as in the other two stages.  At that point there is either the issue of coming up with the cost for a third engine (merlin, raptor,???) or using the merlin (upper) engine in this last stage.  Unfortunately, using a RP1 engine in an upper stage nearly negates all your benefit from the higher ISP of the raptor engine.  I just don't see it happening (I wouldn't rule it out, especially if they move to a 4-5 engine group).

Note that if I designed the falcon heavy (KSP-style, anyway), I would like to stick a pair of COTS (commercial off the shelf) SRBs to the upper stage (yes, shlepping SRBs up with liquid rockets because I can reuse the liquid rockets).  This lets me keep the velocities of the big, expensive rockets low and lets me push the final stage out with rockets I don't have to land.  I'm pretty sure somebody ran the numbers, but I really doubt anyone took the idea very seriously.  No idea how much basic "we don't do that" had to do with why they didn't or if the numbers just didn't work.

Falcon has 2 stages, its payload can be considered a third stage, as they generally carry their own thrusters. In the most recent launch Falcons two stages delivered the payload to GTO and the payload then circularized the orbit. On a recently delivered ISS package, the dragon returned itself to a successful re-entry.

We sure have an abundance of whack facts today.

[wumpus]

Just now, PB666 said:

Falcon has 2 stages, its payload can be considered a third stage, as they generally carry their own thrusters. In the most recent launch Falcons two stages delivered the payload to GTO and the payload then circularized the orbit. On a recently delivered ISS package, the dragon returned itself to a successful re-entry.

We sure have an abundance of whack facts today.

How did you come to the idea of anything other than three stages for falcon9?  Falcon heavy has more (or at least jettisons parts of a "first stage" at different times).  I was trying to answer a hypothetical question of spacex using more than two stages (presumably for raptor/MCT) and finding it unlikely (although if they have significantly less engines than falcon9 it might force a hard decision about upper stages).

PS.  Be a little more specific about a "falcon" having a specific number of stages as there are so two rockets launched with that name and a third scheduled.  There is the falcon [1] with two (one merlin, and something else), falcon 9 (9 merlin, one merlin), and falcon heavy (3x9 merlin,[9 merlin (which fired in the first stage)], one merlin).

[Pipcard]

9 hours ago, fredinno said:

You have to have folded wings on a 4-core Angara-Baikal, of course a 4 booster arrangement would be a pain in the butt. Not on a 4-core F9.

There have been a few cases in which boosters failed to separate, or went boom, but keep in mind that some of the most reliable and "best" LVs use 3 stage, or >2 booster configs, like Atlas and Soyuz.

IN general, the 1-2T GTO payload capacity is more than worth the extra cost of a 3rd stage, especially since they can use the same tank diameter. Just because it means you need another production line doesn't make it something F9 shouldn't ever have. If that was the case, OTRAG would have been an even better rocket.

Plus, Boosters are actually MORE reliable than a 2nd or 3rd stage, since the boosters can be static tested.

That has nothing to do with a 4-core F9. And it's all just speculation, anyways. It could very well be 4-stage, since BFR will be testing the upper limits of CH4 on the rocket equation....

The bolded part of the quote had to do with the difficulty of managing the simultaneous return of four separate boosters. These "difficulties" are the same whether it's folded wings or propulsive boost-back.

There is nothing really wrong about Atlas and Soyuz, but simpler configurations are what SpaceX prefers.

It has everything to do with it, whether it's F9 or future plans for Mars rockets, because Musk decided to go with a "single monster boost stage [+ one upper stage]" for BFR instead of a reusable three-stage, or three-core or five-core configuration, implying that it's because of the philosophy of operational simplicity. Three-core/two-booster reusable FH probably stretches that philosophy to its limit. I might accept a five-core/four-booster FH with smaller baseline cores, if it was only going to be expendable.

http://forum.nasaspaceflight.com/index.php?topic=33494.msg1153752#msg1153752

Quote

Going monolithic instead of tri core gets rid of a lot of complexity of the tri core design since you get rid of cross feed and only have one first stage to land instead of three. Also a monolithic MCT LV will need less servicing between launches than a tri core one since you only have one core to service instead of three. These are important considerations since Musk wants the entire MCT architecture to be fully reusable. - DJPledger

https://forum.nasaspaceflight.com/index.php?topic=35424.msg1282608#msg1282608

Quote

...a three core configuration just adds a bunch of complexity. I think we'll only see a BFR in a single core configuration - and it will be powerful enough to lift whatever pieces necessary to LEO. The fewer pieces you have to work with, the better. Just fly the same configuration more often instead. - Lars-J

And BFR/MCT doesn't need to be more than two reusable stages when the upper stage that would carry people and cargo to Mars can be refueled in orbit with multiple tankers (which would be a variant of that upper stage).

Edited June 10, 2016 by Pipcard

[fredinno]

 

On 6/4/2016 at 9:33 AM, kunok said:

If Trump win, this probably would happen, Musk companies lives from the government money, and Trump and Musk doesn't get together well at all. But in the other hand Trump probably would make collaboration with Russia happen again. The other candidates I don't know much, only that sanders thinks that nasa is not a priority.

Dude, really? You do realize politics are banned here?

In any case, I'll just leave this Trump quote:

"You know, space is actually being taken over privately, which is great. It's being taken over, a lot of private companies going up into space. I like that maybe even better."

http://www.planetary.org/get-involved/be-a-space-advocate/election2016/trump.html?referrer=https://www.google.ca/

7 hours ago, kerbiloid said:

Energy-2 (from buran.ru)

And that never happened anyways.

9 hours ago, 5thHorseman said:

I still say no competition. If SpaceX does it for cheaper then NASA will happily pay them to do it. The only possible reason they would not do that would be because Congress directed them to build it themselves, and I'm not allowed to discuss politics on this forum (I've been warned) so I won't discuss why Congress might do THAT.

You just explained why NASA would never buy a BFR (that, and it's too big for most near-term (non-mars) uses).

[fredinno]

6 hours ago, LordFerret said:

Folded wings eh? Why then have the things land vertically??? Why not let them come back and land on runways (drones)? That sounds (to me) like a far better idea than a powered vertical landing on a barge.

They are landing horizontally....

3 hours ago, wumpus said:

I  have to strongly question the idea that a Spacex craft could benefit from [conventional] three stage flight.  Consider falcon9 and falcon heavy.  Falcon 9 acts as two stages, and recovers the first with 90% of the engines and disposes of the remaining 10% (which provides something like 2/3 of Falcon 9's delta-v).

Falcon Heavy should act like 2 1/2 stages: the center stage sparing itself as much as it can to give the final stage as much delta-v as possible (since roughly the same stage might get twice as much mass to lift, it is going to have to be going faster when separating).  Expect a few more holes in ICISLY while they learn to land all over again.

The main reason why I question a third stage is that merlin engines are particularly *light*.  Fuel tanks are light.  Fuel is heavy.  If you were using hyrdrogen I would understand a third stage, but with either RP1 or methane that doesn't make as much sense.  The second reason is that as far as staging is concerned, there are two classes of stages: recoverable and non-recoverable.  Adding engines to recoverable engines does not seem to be an issue (note that for all the pining for a falcon5 on these forums, spacex isn't the slightest bit interested in it).  And looking at falcon9's peculiar delta-v budget (1/3 for the lower stage, 2/3 for the upper) I would assume that a third stage would split the upper stages into two unrecoverable stages.  I'm guessing the engine that delivered the final 1/3 of the delta-v (or so) would not be the same as in the other two stages.  At that point there is either the issue of coming up with the cost for a third engine (merlin, raptor,???) or using the merlin (upper) engine in this last stage.  Unfortunately, using a RP1 engine in an upper stage nearly negates all your benefit from the higher ISP of the raptor engine.  I just don't see it happening (I wouldn't rule it out, especially if they move to a 4-5 engine group).

Note that if I designed the falcon heavy (KSP-style, anyway), I would like to stick a pair of COTS (commercial off the shelf) SRBs to the upper stage (yes, shlepping SRBs up with liquid rockets because I can reuse the liquid rockets).  This lets me keep the velocities of the big, expensive rockets low and lets me push the final stage out with rockets I don't have to land.  I'm pretty sure somebody ran the numbers, but I really doubt anyone took the idea very seriously.  No idea how much basic "we don't do that" had to do with why they didn't or if the numbers just didn't work.

 

3 stage rockets are very useful. https://www.google.ca/search?sourceid=chrome-psyapi2&ion=1&espv=2&ie=UTF-8&q=falcon 9 payload&oq=falcon 9 payload&aqs=chrome..69i57j0l5.5420j0j7

http://www.spacelaunchreport.com/zenit.html

2-stage Falcon 9 to GTO: 4.8T

3-stage Zenit to GTO: 6T to 3T (depending on inclination, Sea vs Baikinur- keep in mind that the GTO payload includes inclination changes..)

(both rockets have same payload to LEO)

Quote

Falcon Heavy should act like 2 1/2 stages: the center stage sparing itself as much as it can to give the final stage as much delta-v as possible (since roughly the same stage might get twice as much mass to lift, it is going to have to be going faster when separating).  Expect a few more holes in ICISLY while they learn to land all over again.

Unnessessary. People have already looked into it and found that simply using conventional sea landings for the core is more than enough to get 8T to GTO (full RTLS F9H is 6T to GTO) due to the enormous size of the rocket.

 

 

 

3 hours ago, PB666 said:

We sure have an abundance of whack facts today.

????

3 hours ago, wumpus said:

How did you come to the idea of anything other than three stages for falcon9?  Falcon heavy has more (or at least jettisons parts of a "first stage" at different times).  I was trying to answer a hypothetical question of spacex using more than two stages (presumably for raptor/MCT) and finding it unlikely (although if they have significantly less engines than falcon9 it might force a hard decision about upper stages).

PS.  Be a little more specific about a "falcon" having a specific number of stages as there are so two rockets launched with that name and a third scheduled.  There is the falcon [1] with two (one merlin, and something else), falcon 9 (9 merlin, one merlin), and falcon heavy (3x9 merlin,[9 merlin (which fired in the first stage)], one merlin).

F9 uses 2 stages, not 3!

And MCT may use more than 2 stages- it can be used as the Mars Transfer stage, which wouldn't ever be reused anyways.

If the Mars Transfer Stage is electric (it would mean a heavier payload due to needing more shielding water to pass so much through the Van Allen), a 3rd stage would decrease the separation speed for the stages below it.

https://en.wikipedia.org/wiki/Multistage_rocket

2 hours ago, Pipcard said:

The bolded part of the quote had to do with the difficulty of managing the simultaneous return of four separate boosters. These "difficulties" are the same whether it's folded wings or propulsive boost-back.

There is nothing really wrong about Atlas and Soyuz, but simpler configurations are what SpaceX prefers.

It has everything to do with it, whether it's F9 or future plans for Mars rockets, because Musk decided to go with a "single monster boost stage [+ one upper stage]" for BFR instead of a reusable three-stage, or three-core or five-core configuration, implying that it's because of the philosophy of operational simplicity. Three-core/two-booster reusable FH probably stretches that philosophy to its limit. I might accept a five-core/four-booster FH with smaller baseline cores, if it was only going to be expendable.

http://forum.nasaspaceflight.com/index.php?topic=33494.msg1153752#msg1153752

https://forum.nasaspaceflight.com/index.php?topic=35424.msg1282608#msg1282608

And BFR/MCT doesn't need to be more than two reusable stages when the upper stage that would carry people and cargo to Mars can be refueled in orbit with multiple tankers (which would be a variant of that upper stage).

Quote

The bolded part of the quote had to do with the difficulty of managing the simultaneous return of four separate boosters. These "difficulties" are the same whether it's folded wings or propulsive boost-back.

There is nothing really wrong about Atlas and Soyuz, but simpler configurations are what SpaceX prefers.

I read the entire article too, and it implied it was about the folded wings.

Quote

It has everything to do with it, whether it's F9 or future plans for Mars rockets, because Musk decided to go with a "single monster boost stage [+ one upper stage]" for BFR instead of a reusable three-stage, or three-core or five-core configuration, implying that it's because of the philosophy of operational simplicity. Three-core/two-booster reusable FH probably stretches that philosophy to its limit. I might accept a five-core/four-booster FH with smaller baseline cores, if it was only going to be expendable.

Where did he ever state it was 2-stage? All we learned was that is wasn't 3-core....

And by the philosophy of "operational simplicity", SpaceX wouldn't even be using staged combustion methane, which is low-pressure, and highly complex.  Besides, once to start going into Sea Dragon size, rockets increase in size exponentially, resulting in increased thrust and tanks (and higher costs). Couple that to the fact 3-stages/4-stages are best for high-energy destinations, and you have a pretty good case 3-stages may just be cheaper than a bigger 2-stage one. It's basically why SSTOs are used for suborbital, but NEVER Orbital.

Also, your argument so far has been COMPLEXITY. An expendable and reusable rocket using 4 boosters have the same amount of complexity GAINED from using more cores...

If 2nd stage reuse is still on the table, but delayed for later, the F9 solution of using only up to 2-boosters would make more sense- it would reduce payload ~8-9T to LEO, making it in the Delta II payload capacity (with fast sea landings), and then cores may be added (1 booster, 2-booster, 3-booster, 4-booster) if needed. In that case, it would just mean that the current solution is just an interm...

 

2 hours ago, Pipcard said:

http://forum.nasaspaceflight.com/index.php?topic=33494.msg1153752#msg1153752

Quote

Going monolithic instead of tri core gets rid of a lot of complexity of the tri core design since you get rid of cross feed and only have one first stage to land instead of three. Also a monolithic MCT LV will need less servicing between launches than a tri core one since you only have one core to service instead of three. These are important considerations since Musk wants the entire MCT architecture to be fully reusable. - DJPledger

https://forum.nasaspaceflight.com/index.php?topic=35424.msg1282608#msg1282608

Quote

...a three core configuration just adds a bunch of complexity. I think we'll only see a BFR in a single core configuration - and it will be powerful enough to lift whatever pieces necessary to LEO. The fewer pieces you have to work with, the better. Just fly the same configuration more often instead. - Lars-J

Those arguments are against a 3-core MCT, not a 5-core F9H.

F9H is already 3-core anyways.

2 hours ago, Pipcard said:

Quote

 

And BFR/MCT doesn't need to be more than two reusable stages when the upper stage that would carry people and cargo to Mars can be refueled in orbit with multiple tankers (which would be a variant of that upper stage).

...and increase complexity.  (and refueling is far less understood too!)

See, now I'm using your very own argument against you.

Edited June 10, 2016 by fredinno

[N_Molson]

I like the idea. Put Musk in a capsule and ship the whole to Mars. That will be relief for our ears.

[Pipcard]

1 hour ago, fredinno said:

And by the philosophy of "operational simplicity", SpaceX wouldn't even be using staged combustion methane, which is low-pressure, and highly complex.  Besides, once to start going into Sea Dragon size, rockets increase in size exponentially, resulting in increased thrust and tanks (and higher costs). Couple that to the fact 3-stages/4-stages are best for high-energy destinations, and you have a pretty good case 3-stages may just be cheaper than a bigger 2-stage one. It's basically why SSTOs are used for suborbital, but NEVER Orbital.

Also, your argument so far has been COMPLEXITY. An expendable and reusable rocket using 4 boosters have the same amount of complexity GAINED from using more cores...

If 2nd stage reuse is still on the table, but delayed for later, the F9 solution of using only up to 2-boosters would make more sense- it would reduce payload ~8-9T to LEO, making it in the Delta II payload capacity (with fast sea landings), and then cores may be added (1 booster, 2-booster, 3-booster, 4-booster) if needed. In that case, it would just mean that the current solution is just an interm...

Those arguments are against a 3-core MCT, not a 5-core F9H.

F9H is already 3-core anyways.

...and increase complexity.  (and refueling is far less understood too!)

See, now I'm using your very own argument against you.

"3-stages/4-stages are best for high-energy destinations," but there will probably be just a single upper stage because:

Quote

At the moment, with our limited technology and resources, we have to optimize for cost - and this is what the MCT will do IMO.

You design only ONE spacecraft. You live in it during transit, you land in it, and you live on the surface in it - until bases are constructed. It will be a "jack of all trades but master of none" type of engineering effort in order to optimize for cost [i.e. development/manufacturing/operations cost]. It won't be the most efficient in-space craft, and it won't be the most efficient lander. But hopefully it can be built with whatever resources SpaceX can muster. - Lars-J

The MCT system would have to involve refueling on Mars (I'm guessing with pre-established ISRU capability at the landing site) anyway, and orbital refueling is also their way of not pushing the rocket equation to its limits. With refueling, you don't need to design, manufacture, and operate any more than two types of reusable stages (BFR's "monster boost stage," and the "Big [Freaking] Spaceship" itself). A two-stage system with refueling actually reduces complexity and cost compared to a three-stage or four-stage system without refueling.

_____

Regarding staged combustion methane:

Quote

I am really starting to like the idea of a staged combustion methane engine. The thing is, hydrogen staged engines are complex because hydrogen is very hard to pump, and has vastly different pumping requirements from oxygen. This is what drives the SSME to having two preburners, and two main turbopumps (the separate LPFTP and LPOTP are there to suppress cavitation; which was driven by different choices).
Kerosene staged engines are complex because the power balance and coking dictate an oxygen rich preburner, and all of its assorted design challenges.

Centrifugal pumps are basically constant volumetric flow rate devices. A methox engine’s optimum O/F (~3) is pretty close to the equal volume ratio between O2 and CH4 (2.75). This means the pumps will have nearly identical requirements, and running them off a single spindle should be easy. In addition your turbine pressure drop will be low, so you have a simple 1-stage turbine. Then, your preburner is fuel-rich, running at the sweet spot temp for nickel superalloys (which might as well be brass in this industry), with a “non-coking” fuel. It could be a beautifully simple engine, with excellent sea-level and vacuum characteristics, a very respectable density Isp, and killer T/W. - strangequark

_____

A reusable rocket gains more complexity with multi-core configurations than an expendable one because those separate cores also have to be recovered and serviced.

Those arguments can also apply to 5-core FH, not just 3-core BFR, because both the BFR and FH are intended to have reusable first stages. Notice how they said you would have to land and service three separate vehicles instead of one? That is made much worse with a five core reusable launcher. Yes, FH is 3-core already, but 5-core would only make reuse operations worse.

Edited June 10, 2016 by Pipcard

[PB666]

29 minutes ago, Pipcard said:

"3-stages/4-stages are best for high-energy destinations," but MCT will probably be just a single upper stage because:

The MCT would have to refuel on Mars (I'm guessing with pre-established ISRU capability at the landing site) anyway, and orbital refueling is also their way of dealing with the rocket equation. With refueling, you don't need to design, manufacture, and operate any more than two types of reusable stages (BFR's "monster boost stage," and the MCT itself). Refueling actually reduces complexity compared to a three-stage or four-stage system.

In regards to staged combustion methane:

A reusable rocket gains more complexity with multi-core configurations than an expendable one because those separate cores also have to be recovered and serviced.

Those arguments can also apply to 5-core FH because both the BFR and FH are intended to have reusable first stages. Notice how they said you would have to land and service three separate vehicles instead of one? That is made much worse with a five core reusable launcher. Yes, FH is 3-core already, but 5-core would only make reuse operations worse.

5 core FH has the advantage that the central core can does not have to be active at launch, and you can use the merlin space engines on the core stage, wasting it but with one hell of alot of second stage power to burn. Its equivilent to adding a full stage. For heavier loads you can simply burn up the central core for 10 seconds or so, shut it down and reignite when the 4 side engines are kicked off. 

The problem with 4 core landings is that if you make the gravity turns, its hard as heck to get back to a ground landing, which means you either have to attempt 4 landings on one barge or have 4 barges to land on. If you ran asparagas you could land two on the ground and two on two barges (or two very precise landings on opposite sides of one barge), but that requires igniting the core engines once the 2 were released. Its still going to be huge benefit though because once the other 2 are released the 2 that remain are going to power up a rocket that once complete

[Pipcard]

5 minutes ago, PB666 said:

which means you either have to attempt 4 landings on one barge

Yep, more reusable cores = more landing attempts = more chances for failure.

[Frozen_Heart]

https://www.reddit.com/r/space/comments/4nha8y/spacex_will_launch_the_maiden_voyage_of_its_mars/

 

Woah...

Edited June 10, 2016 by Frozen_Heart

[wumpus]

1 hour ago, Pipcard said:

Yep, more reusable cores = more landing attempts = more chances for failure.

Since they've already replaced one barge (it wasn't all that expensive), I suspect that four landings mean four barges.  And "more chances for failure" also means "more chances for success" or really "more statistically significant results".  Although it *does* mean that they will have to train up three more teams to safely land the rockets, likely with some extremely expensive failures.

3 hours ago, N_Molson said:

I like the idea. Put Musk in a capsule and ship the whole to Mars. That will be relief for our ears.

The problem is not with Musk himself, but those (guilty!) who try to speculate on any information he may be keeping to himself.  Don't even ask about those who insist about recovery reducing costs by >60%.

[Spaceception]

Running on Mars:

 

[fredinno]

5 hours ago, Pipcard said:

"3-stages/4-stages are best for high-energy destinations," but there will probably be just a single upper stage because:

The MCT system would have to involve refueling on Mars (I'm guessing with pre-established ISRU capability at the landing site) anyway, and orbital refueling is also their way of not pushing the rocket equation to its limits. With refueling, you don't need to design, manufacture, and operate any more than two types of reusable stages (BFR's "monster boost stage," and the "Big [Freaking] Spaceship" itself). A two-stage system with refueling actually reduces complexity and cost compared to a three-stage or four-stage system without refueling.

_____

Regarding staged combustion methane:

_____

A reusable rocket gains more complexity with multi-core configurations than an expendable one because those separate cores also have to be recovered and serviced.

Those arguments can also apply to 5-core FH, not just 3-core BFR, because both the BFR and FH are intended to have reusable first stages. Notice how they said you would have to land and service three separate vehicles instead of one? That is made much worse with a five core reusable launcher. Yes, FH is 3-core already, but 5-core would only make reuse operations worse.

Quote

"3-stages/4-stages are best for high-energy destinations," but there will probably be just a single upper stage because:

The MCT system would have to involve refueling on Mars (I'm guessing with pre-established ISRU capability at the landing site) anyway, and orbital refueling is also their way of not pushing the rocket equation to its limits. With refueling, you don't need to design, manufacture, and operate any more than two types of reusable stages (BFR's "monster boost stage," and the "Big [Freaking] Spaceship" itself). A two-stage system with refueling actually reduces complexity and cost compared to a three-stage or four-stage system without refueling.

You still need huge rockets, after all, LEO capacity is around 4.5x Mars capacity, assuming expendable. (for F9). Granted, MCT has higher ISP, but it's still nowhere near the H2 rockets. Anyways, I digress. If it was really just using smaller rockets, it would not be suitable for Mars Colonization, because the number needed to launch 1000 people to Mars every year with required cargo would be near the total rocket launches of the world ever year.

 

"A two-stage system with refueling actually reduces complexity and cost compared to a three-stage or four-stage system without refueling."

Source? And not a forum post, an ACTUAL REPORT. 

So far, rocket companies have been more willing to add stages than make use of "simpler" refueling....

But seriously, this is about a 4-core F9, let's go back to topic...

Quote

Regarding staged combustion methane:

Oh... ok, so MAYBE methane isn't completely overhyped crap. I still don't think it's worth a new rocket diameter (isp-density is closer to H2 than RP-1) and new engines. (Not to mention methane has marginally higher ISP than RP-1).

That's the first time I've seen a convincing argument for methane. Thank you. We could have gotten over that M-III problem a lot sooner if you stated that 2 months ago.

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A reusable rocket gains more complexity with multi-core configurations than an expendable one because those separate cores also have to be recovered and serviced.

Those arguments can also apply to 5-core FH, not just 3-core BFR, because both the BFR and FH are intended to have reusable first stages. Notice how they said you would have to land and service three separate vehicles instead of one? That is made much worse with a five core reusable launcher. Yes, FH is 3-core already, but 5-core would only make reuse operations worse.

Yeah, and those core boosters use practically the same infrastructure and tooling to build and maintain/service them

And 5-core would make reuse operations WORSE? If it's so bad, land 2 RTLS, and 2 barge landings, thus the boosters have very little chance of meeting.

If it's STILL a problem, seperate 2 boosters 5 seconds after the first 2 boosters. That's what Delta II did.

And they are controlled by computers anyways, meaning there is minimal overlap with human resources. The worst that might happen is a booster blows up on a barge.

4 hours ago, PB666 said:

5 core FH has the advantage that the central core can does not have to be active at launch, and you can use the merlin space engines on the core stage, wasting it but with one hell of alot of second stage power to burn. Its equivilent to adding a full stage. For heavier loads you can simply burn up the central core for 10 seconds or so, shut it down and reignite when the 4 side engines are kicked off. 

The problem with 4 core landings is that if you make the gravity turns, its hard as heck to get back to a ground landing, which means you either have to attempt 4 landings on one barge or have 4 barges to land on. If you ran asparagas you could land two on the ground and two on two barges (or two very precise landings on opposite sides of one barge), but that requires igniting the core engines once the 2 were released. Its still going to be huge benefit though because once the other 2 are released the 2 that remain are going to power up a rocket that once complete

Or you can just expend the core stage, and use the 2nd stage as a 3rd stage.

In practice, you would probably have 4 barges, all for landing. Those barges aren't that expensive, compared to the rocket.  And the landing pad at the cape has 5 landing pads anyways.

Most SpaceX landings are designated barge landings.

4 hours ago, Pipcard said:

Yep, more reusable cores = more landing attempts = more chances for failure.

Yeah, and guess what?

SpaceX gets to practice landings a lot more, and thus the overall failure rate is mitigated.

[Pipcard]

2 hours ago, fredinno said:

"A two-stage system with refueling actually reduces complexity and cost compared to a three-stage or four-stage system without refueling."

Source? And not a forum post, an ACTUAL REPORT.

Sorry I can't find actual reports instead of speculation threads, just not until Musk reveals it in September.

Quote

So far, rocket companies have been more willing to add stages than make use of "simpler" refueling....

Yeah, because they aren't planning to reuse those stages. Nor are they planning a reusable interplanetary transportation system. When you have a reusable launch system, the fewer stages you have to deal with, the better (see the bottom of this post for why).

Quote

Oh... ok, so MAYBE methane isn't completely overhyped crap. I still don't think it's worth a new rocket diameter (isp-density is closer to H2 than RP-1) and new engines. (Not to mention methane has marginally higher ISP than RP-1).

That's the first time I've seen a convincing argument for methane. Thank you. We could have gotten over that M-III problem a lot sooner if you stated that 2 months ago.

For all your opposition to methalox, you even said:

On 2/11/2016 at 10:38 AM, fredinno said:

Lower density, Marginally better performance than RP-1 doesn't really make it worth the investment- unless you are reusing engines.

And guess what, most rockets that are planned to use methalox engines are also planned to reuse those engines as well (including my fictional M-III). Even Soyuz-5, "a traditional throw-away rocket designed to test innovative methane engines could serve as a bridge toward next-generation reusable boosters."

Quote

Yeah, and those core boosters use practically the same infrastructure and tooling to build and maintain/service them

They can use the same infrastructure for manufacturing and processing, but when you have more separate cores or more stages, more man-hours are required to process them. That's why fewer reusable stages are less complex (but SSTO comes with its own problems).

Edited June 11, 2016 by Pipcard

[fredinno]

14 hours ago, Pipcard said:

Sorry I can't find actual reports instead of speculation threads, just not until Musk reveals it in September.

Yeah, because they aren't planning to reuse those stages. Nor are they planning a reusable interplanetary transportation system. When you have a reusable launch system, the fewer stages you have to deal with, the better (see the bottom of this post for why).

For all your opposition to methalox, you even said:

And guess what, most rockets that are planned to use methalox engines are also planned to reuse those engines as well (including my fictional M-III). Even Soyuz-5, "a traditional throw-away rocket designed to test innovative methane engines could serve as a bridge toward next-generation reusable boosters."

They can use the same infrastructure for manufacturing and processing, but when you have more separate cores or more stages, more man-hours are required to process them. That's why fewer reusable stages are less complex (but SSTO comes with its own problems).

Quote

Sorry I can't find actual reports instead of speculation threads, just not until Musk reveals it in September.

It can be for rockets in general...

14 hours ago, Pipcard said:

On 2/11/2016 at 10:38 AM, fredinno said:

Lower density, Marginally better performance than RP-1 doesn't really make it worth the investment- unless you are reusing engines.

And guess what, most rockets that are planned to use methalox engines are also planned to reuse those engines as well (including my fictional M-III). Even Soyuz-5, "a traditional throw-away rocket designed to test innovative methane engines could serve as a bridge toward next-generation reusable boosters."

So? That doesn't mean anything, H2 engines and RP-1 engines have just as many plans for reuse. And stop going off topic, seriously..

Hell, even F9 still has 0 plans to use CH4.

And New Shepard uses H2, and is reusable.

CH4 is not the end-all of reusable engines. H2 may actually be better at higher economies of scale.

14 hours ago, Pipcard said:

Quote

Yeah, and those core boosters use practically the same infrastructure and tooling to build and maintain/service them

They can use the same infrastructure for manufacturing and processing, but when you have more separate cores or more stages, more man-hours are required to process them. That's why fewer reusable stages are less complex (but SSTO comes with its own problems).

So, I would assume by that logic, you would rather have a single 29T to LEO SSTO? Imagine if IXV launched on such a thing. Such a waste of payload capacity.

And a what's easier to maintain, a single large booster, or 5 smaller ones? I would state  the latter, since it allows for economies of scale, and use of machines to maintain the boosters.

14 hours ago, Pipcard said:

 

Quote

So far, rocket companies have been more willing to add stages than make use of "simpler" refueling....

Yeah, because they aren't planning to reuse those stages. Nor are they planning a reusable interplanetary transportation system. When you have a reusable launch system, the fewer stages you have to deal with, the better (see the bottom of this post for why).

Oh yeah? Has SpaceX done in-space refueling, or have any plans for that?

How about Blue Origin?

Is there any DOD/NASA large scale in-space refueling project?

The closest thing I could find is ULA's IVF space tugs, but they are still staying as concepts. Probably since reusable space tugs don't offer very much advantage right now, since you still need HLVs to launch the fuel (thus, it just increases complexity, for a marginal increase in reusability.)

[wumpus]

17 hours ago, fredinno said:

"A two-stage system with refueling actually reduces complexity and cost compared to a three-stage or four-stage system without refueling."

I'm assuming this refueling happens in space?  I've tended to assume that any orbit-assembled refueling would contain an entire stage, unless this absolutely would not fit on a single launch vehicle (and even then multiple stages would likely make more sense).  While it sounds good, I suspect that any ability to refuel in space would be equally applicable to cross-stage fueling (for situations with separate fuel tanks in detachable stages and refueling the main tank from one detachable fuel tank).

That and all non-human cargo leaving orbit is likely going to use electrical propulsion.  And ideally some of that refueling (for chemical-powered human flights) after significant levels of delta-v (like in a LTI-sized orbit ready to leave for Mars).

[Pipcard]

21 hours ago, fredinno said:

It can be for rockets in general...

Well, it's regarding a launch vehicle for reusable interplanetary transportation, so we'll have to wait.

Quote

So, I would assume by that logic, you would rather have a single 29T to LEO SSTO? Imagine if IXV launched on such a thing. Such a waste of payload capacity.

Did you not notice that I had also said "SSTO comes with its own problems" and "however, 1-stage goes too far and you lose a lot of your payload capacity because of the nature of the rocket equation"?

Quote

And a what's easier to maintain, a single large booster, or 5 smaller ones? I would state the latter, since it allows for economies of scale, and use of machines to maintain the boosters.

And you would need either more time or machines or manpower to inspect them.

edit: anyways, I posed a question on the NASAspaceflight forum regarding the pros and cons of multi-core reusable boosters. (the reason why there is no 5-core FH or 3-core MCT)

Quote

Oh yeah? Has SpaceX done in-space refueling, or have any plans for that?

they plan to do refueling - from Musk himself:

Quote

I mean, if you do a densified liquid methalox rocket with on-orbit refueling, so like you load the spacecraft into orbit and then you send a whole bunch of refueling missions to fill up the tanks and you have the Mars colonial fleet - essentially - that gets built up during the time between Earth-Mars synchronizations, which occur every 26 months, then the fleet all departs at the optimal transfer point.

Edited June 12, 2016 by Pipcard

[fredinno]

On 2016-06-11 at 1:49 PM, wumpus said:

I'm assuming this refueling happens in space?  I've tended to assume that any orbit-assembled refueling would contain an entire stage, unless this absolutely would not fit on a single launch vehicle (and even then multiple stages would likely make more sense).  While it sounds good, I suspect that any ability to refuel in space would be equally applicable to cross-stage fueling (for situations with separate fuel tanks in detachable stages and refueling the main tank from one detachable fuel tank).

That and all non-human cargo leaving orbit is likely going to use electrical propulsion.  And ideally some of that refueling (for chemical-powered human flights) after significant levels of delta-v (like in a LTI-sized orbit ready to leave for Mars).

Crossfeed requires a higher level of complexity- namely restartability of the engine after a few seconds to prevent bubbles from forming in the propellant.

23 hours ago, Pipcard said:

Did you not notice that I had also said "SSTO comes with its own problems" and "however, 1-stage goes too far and you lose a lot of your payload capacity because of the nature of the rocket equation"?

So, you'd rather have a single 29T to LEO TSTO vehicle for even the smallest payloads?

23 hours ago, Pipcard said:

And you would need either more time or machines or manpower to inspect them.

edit: anyways, I posed a question on the NASAspaceflight forum regarding the pros and cons of multi-core reusable boosters. (the reason why there is no 5-core FH or 3-core MCT)

Interesting.

23 hours ago, Pipcard said:

Quote

 

they plan to do refueling - from Musk himself:

Quote

I mean, if you do a densified liquid methalox rocket with on-orbit refueling, so like you load the spacecraft into orbit and then you send a whole bunch of refueling missions to fill up the tanks and you have the Mars colonial fleet - essentially - that gets built up during the time between Earth-Mars synchronizations, which occur every 26 months, then the fleet all departs at the optimal transfer point.

Then it's just a SLS-sized system? Then why is he building a new pad? Can't he use LC-39A?

No one really knows, I guess.

We'll have to wait.

[Pipcard]

2 hours ago, fredinno said:

So, you'd rather have a single 29T to LEO TSTO vehicle for even the smallest payloads?

Maybe a ~20T vehicle (in expendable mode) today, when economic reusability is still in its proving stages. With SpaceX planning to sell F9R launches at $40 million, and enough capacity to launch multiple small satellites (the ones that would go on Vega or Falcon 1 for example) or have that small satellite be a secondary payload in order to split launch costs, they only need to produce for one launch vehicle family right now. If and when economic reusability is fully proven, you can scale up a monolithic reusable TSTO even further. I know this is yet another NASAspaceflight forum post and I indeed do that too much here, and you'd rather see actual, professional sources, but this is just explaining the idea:

Quote

if they have a fully reusable large single core LV as the base for their commercial and governmental work, the reusability changes the equation because you are no longer wasting a much larger rocket than needed on a small payload.  No real drawback to using such an oversized LV to launch an 8mt payload to LEO or a 5mt payload to GTO, because all the parts come back and are reused.  It's just a matter of fuel, and they could short fuel the LV as necessary for the payload. - Lobo

Thus, the fully reusable BFR could replace the F9/FH family once it's operational. Multi-purpose, not only for Mars. And using the same monolithic fully reusable launcher for all payloads also ups its flight rate.

Quote

Then it's just a SLS-sized system? Then why is he building a new pad? Can't he use LC-39A?

No one really knows, I guess.

We'll have to wait.

It might be even bigger than SLS, especially if it's supposed to "land 100 tonnes of useful payload on Mars." I'm still not sure how SpaceX is going to scale up in 6-8 years for such an endeavour, developing an interplanetary spaceliner. I've seen some people (like in this NASAspaceflight thread for example) saying that they're going to fund the MCT system with revenue from current launch systems, their massive internet satellite constellation (which they haven't officially announced yet), and investment by other billionaires.

Edited June 13, 2016 by Pipcard

[LordFerret]

On 6/10/2016 at 7:44 PM, Frozen_Heart said:

https://www.reddit.com/r/space/comments/4nha8y/spacex_will_launch_the_maiden_voyage_of_its_mars/

 

Woah...

That's interesting. Perhaps that idea of an IPO not being far off is not all that far fetched. Then again, the Washington Post leaning in the direction it does, I have little faith or trust in a lot of what it reports.

[kerbiloid]

On 10.06.2016 at 11:15 PM, fredinno said:

They are landing horizontally.

Yet not are.

On 11.06.2016 at 1:15 AM, PB666 said:

The problem with 4 core landings is that if you make the gravity turns, its hard as heck to get back to a ground landing, which means you either have to attempt 4 landings on one barge or have 4 barges to land on. If you ran asparagas you could land two on the ground and two on two barges (or two very precise landings on opposite sides of one barge)

The next thing we hear soon: "SpaceX rents an aircraft carrier."

The next next thing: "Floating cities on Mars: is it real? Yes! We just should melt the polar caps with nukes."

On 11.06.2016 at 1:21 AM, Pipcard said:

more landing attempts = more chances for failure

More landing attempts = more chances for success.

On 11.06.2016 at 2:44 AM, Frozen_Heart said:

https://www.reddit.com/r/space/comments/4nha8y/spacex_will_launch_the_maiden_voyage_of_its_mars/

Quote

SpaceX will launch the maiden voyage of its Mars Colonial Transporter to Mars in 2022

They would name the ship Iron Maiden.

On 11.06.2016 at 10:23 PM, fredinno said:

Has SpaceX done in-space refueling, or have any plans for that?

They should:

Spoiler

The same, but with Falcons.

 

 

[fredinno]

3 hours ago, Pipcard said:

Maybe a ~20T vehicle (in expendable mode) today, when economic reusability is still in its proving stages. With SpaceX planning to sell F9R launches at $40 million, and enough capacity to launch multiple small satellites (the ones that would go on Vega or Falcon 1 for example) or have that small satellite be a secondary payload in order to split launch costs, they only need to produce for one launch vehicle family right now. If and when economic reusability is fully proven, you can scale up a monolithic reusable TSTO even further. I know this is yet another NASAspaceflight forum post and I indeed do that too much here, and you'd rather see actual, professional sources, but this is just explaining the idea:

Quote

if they have a fully reusable large single core LV as the base for their commercial and governmental work, the reusability changes the equation because you are no longer wasting a much larger rocket than needed on a small payload.  No real drawback to using such an oversized LV to launch an 8mt payload to LEO or a 5mt payload to GTO, because all the parts come back and are reused.  It's just a matter of fuel, and they could short fuel the LV as necessary for the payload. - Lobo

Thus, the fully reusable BFR could replace the F9/FH family once it's operational. Multi-purpose, not only for Mars. And using the same monolithic fully reusable launcher for all payloads also ups its flight rate.

Just because you can launch everything on one rocket, doesn't mean you should. Even for a fully reusable rocket, a single 29T rocket (if the rocket is full CH4 or RP-1, a rocket with a H2 2nd stage can settle for a lower LEO payload capacity, like 25T to LEO, due to superior GTO capacity)

Let's use the IXV example again. How in the WORLD would you give it secondary payloads? It would be a 1-2T payload on a rocket designed for 29x its payload capacity. Assuming full reuse, you still have to build a rocket every ~10 flights, and the massive rockets are harder to maintain (w/ F-1 sized engines).

Reuse doesn't remove costs. It only saves optimistically 40% in cost (both stages). The rest of the cost structure, like testing and inspection, get larger- testing a larger engine of a TSTO RLV is more expensive. It also increases the complexity and integration costs you seem to be so worried about, since deploying 10 satellites is more complex than orbiting one, and larger rockets are more complex and difficult to develop.

Not to mention, satellite companies WANT to be able to choose where they go, instead of being dropped in a compromise orbit that needs to be shared with 50 other satellites. That's why smallsat launchers are taking off, even though it is more expensive. Hell, companies will sometimes buy entire Ariane 5s just for one payload just for that reason. (However, for GTO, launching 2 satellites is far more economical, since all the satellites are in roughly the same orbit. LEO sats practically require dedicated rockets.)

Thus, you will go through those rockets much faster than normal- and the reuse will make it difficult to achieve mass-production anyways, producing 3 a year, assuming a 30x a year launch rate. A planetary probe launch that year would leave you producing 4 a year.

Meanwhile, a reusable Angara solution allows you to produce ~15 cores a year with reuse and a 30x per year launch rate, much closer to mass-production, and optimize for any payload with little development cost (depending on what satellites you launch that year).

4 hours ago, Pipcard said:

Thus, the fully reusable BFR could replace the F9/FH family once it's operational. Multi-purpose, not only for Mars. And using the same monolithic fully reusable launcher for all payloads also ups its flight rate.

LOLWUT

Imagine launching an SLS to launch IXV

You make me chuckle. You probably could use the SLS core as a reusable SSTO and launch IXV!

On a serious note, who would do that? I can't see SpaceX spending 500 Million dollars making a rocket, only to then launch 5T satellites. That would cost mare than any F9.

It seems similar to the attitude that the Shuttle would reduce costs to launch, and everything should launch on it, because it was 50% reusable (including the "reusable" SRBs), even though it needed every single launch it could possibly get to break even with commercial launchers.

4 hours ago, Pipcard said:

Quote

Then it's just a SLS-sized system? Then why is he building a new pad? Can't he use LC-39A?

No one really knows, I guess.

We'll have to wait.

It might be even bigger than SLS, especially if it's supposed to "land 100 tonnes of useful payload on Mars." I'm still not sure how SpaceX is going to scale up in 6-8 years for such an endeavour, developing an interplanetary spaceliner. I've seen some people (like in this NASAspaceflight thread for example) saying that they're going to fund the MCT system with revenue from current launch systems, their massive internet satellite constellation (which they haven't officially announced yet), and investment by other billionaires.

And yet you said: "it might use space refueling", so it could just do that to send 100T to Mars.

Granted, even a 210T to LEO vehicle (ie Saturn C-8) was capable of launching at LC-39A.

And we can even go up to 362T to LEO, which supposedly used the same facilities as Saturn. No idea if that exended to pads.

http://www.astronautix.com/lvs/satv4260.htm

I think we can safely say it's probably not using refueling for at least the first 3 decades of its existence if it seriously needs a new pad.

Quote

they're going to fund the MCT system with revenue from current launch systems

Doubtful.

Quote

their massive internet satellite constellation (which they haven't officially announced yet)

Because it was "delayed" and made "low priority". Apparently Elon layed off the idea once he realized it wouldn't sell as well as he hoped.

Quote

and investment by other billionaires.

That sounds like something out of Mars One. Doesn't sound too good. I wouldn't want to waste my money on something that probably won't happen, not until I see them cutting metal on those giant cores.

46 minutes ago, kerbiloid said:

Yet not are.

will.

47 minutes ago, kerbiloid said:

They should:

  Hide contents

The same, but with Falcons.

This is what it would look like.

Not as cool in my opinion.