Will StratoLaunch Fly?

[mikegarrison]

18 hours ago, YNM said:

Well, FRP isn't called "plastic" apparently in what I'm learning 

Actually ... it often is, at least in the aviation industry.

[Northstar1989]

On 8/29/2017 at 10:55 AM, wumpus said:

At this point, I doubt that anyone would take the plane for free.  The cost of developing a rocket for it is just too high (and there is no point for multiple pegasus launches, that couldn't be taken seriously).

I do hope somebody joins on with them to design a rocket for this thing.  The physics advantages of airlaunch really are quite impressive.  It might only save the fuel equivalent of 1000-1500 m/s on a ground-launched rocket in reduced drag and increased ISP over the course of the flight, but that's actually an enormous mass of fuel thanks to the rocket equation (the first 1.5 km/s can sometimes be half the mass of the rocket).  Lower fuel mass means you can launch the same payload with fewer/smaller engines- which are of course the most expensive part of the rocket.  And not needing a launchpad is nothing to sneeze at either...

Ideally, somebody like SpaceX or Blue Origin would develop a rocket with a reusable first stage for this thing.  First stage reuse actually becomes much cheaper if your first stage ignites several hundred km WEST of the landing site, heading east, already above the thickest part of the atmosphere... (reduced Delta-V requirements for the first stage mean you can dedicate more mass to extra structural reinforcement and wider engineering margins, so it's possible to re-use the stage more times before you need to retire it...)

Alternatively, a plane like this could be useful for transporting rocket stages across continents, from manufacturing facilities or landing sites to launchpads...

Of course, I doubt Elon Musk or Jeff Besos will bite on either of these ideas.  Musk seems much too caught up with going to Mars here and now to consider major changes to his launch architecture like this- even if those changes have the potential to save a lot of money (a first stage you can safely re-use 50 times is a lot more cost-effective than one you can re-use 5...  And air-launch allows for much more mass to be dedicated to the engineering margins, making this more possible...)  And Bezos doesn't seem to be the type to think far outside the box...

 

Regards,

Northstar

 

P.S.  I *know* some of you are going to tell me to ignore the physics advantages of air-launch and look to the practical engineering challenges.  But it was Elon Musk who said that if you're approaching a difficult or new problem you should start off thinking from first principles- which always come down to underlying physics (Musk got this perspective from his Physics background/education, according to interviews).  And the PHYSICS of air-launch say it has significant advantages over ground-launch in terms of reduced fuel requirements for the rocket, even if engineering says it's difficult to learn how to do cost-effectively...

Edited September 14, 2017 by Northstar1989
Spelling

[Nibb31]

52 minutes ago, Northstar1989 said:

I do hope somebody joins on with them to design a rocket for thos thing.  The physics advantages of airlaunch really are quite impressive.  It might only save the fuel equivalent of 1000-1500 m/s on a ground-launched rocket in reduced drag and increased ISP over the course of the flight, but that's actually an enormous mass of fuel thanks to the rocket equation (the first 1.5 km/s can sometimes be half the mass of the rocket).  Lower fuel mass means you can launch the same payload with fewer/smaller engines- which are of course the most expensive part of the rocket.

Why not just just make your first stage 10% bigger instead? It's no big deal if you can reuse it, but even for an expendable, the extra cost is minimal compared to developing and operating a one-off specialized aircraft and dealing with the complexity of launching a rocket horizontally.

52 minutes ago, Northstar1989 said:

And not needing a launchpad is nothing to sneeze at either...

Ideally, somebody like SpaceX or Blue Origin would develop a rocket with a reusable first stage for this thing.

Musk has criticized air launch several times (and rightly so). He's not suddenly going to embrace it.

52 minutes ago, Northstar1989 said:

 

First stage reuse actually becomes much cheaper if your first stage ignites several hundred km WEST of the landing site, heading east, already above the thickest part of the atmosphere... (reduced Delta-V requirements for the first stage mean you can dedicate more mass to extra structural reinforcement and wider engineering margins, so it's possible to re-use the stage more times before you need to retire it...)

Alternatively, a plane like this could be useful for transporting rocket stages across continents, from manufacturing facilities or landing sites to launchpads...

It's easier to just build your factory near the launch site. Transport by barge or truck is fine.

 

[wumpus]

9 hours ago, Northstar1989 said:

P.S.  I *know* some of you are going to tell me to ignore the physics advantages of air-launch and look to the practical engineering challenges.  But it was Elon Musk who said that if you're approaching a difficult or new problem you should start off thinking from first principles- which always come down to underlying physics (Musk got this perspective from his Physics background/education, according to interviews).  And the PHYSICS of air-launch say it has significant advantages over ground-launch in terms of reduced fuel requirements for the rocket, even if engineering says it's difficult to learn how to do cost-effectively...

Once you go back to first principles, you still have the issue in that it will cost $1Billion to build the rocket.  That's an important first principle in itself.  The other is the square/cube law.  Once you build rockets more than twice what a stratolaunch can carry, the square/cube law can make your rocket more efficient than an "all things being equal" airlaunched rocket.

Isp is another critical "first principle".  If you are sacrificing Isp (especially in your final stage), you can wipe out all benefits from the first bit of delta-v.  PegasusII was originally supposed to have a hydrolox final stage, but that replaced with an "all solid" rocket.  All operating Pegasus rockets use solid stages (a non-cyrogenic hydrazine fourth stage is an option).  Using cryogenic fuels gives the problem of either sufficiently insulating the oxidizer/fuel tanks or continually topping off the rocket.  My understanding was that the x-15 mothership had to carry twice the amount of oxygen as the x-15 to allow it to drop fully fueled (my memory/source might be off on that one, I thought it was due to hydrogen).  If you want a hydrox upper stage, you will certainly need to have some means of supplying hydrogen from the mothership and likely oxygen as well (I think somebody else on this forum went into detail about trying mid-air refueling of hydrogen.  I think it had to do with a "scoop up atmospheric oxygen" idea.

Spacex was originally contracted/expected to design the rocket.  It was called a Falcon Air, and have only 4 Merlin engine.  It is telling that this idea was scrapped *before* spacex abandoned the idea of parachute recovery, as a powered landing with a lighter booster and the same merlin engine is likely difficult.  Spacex would far rather fill falcons with fuel than have more crash.  According to the infallible wiki, Falcon air would deliver 6 tons to LEO while Falcon 9 (1.0) delivered 10 tons to LEO and a similar ratio to GTO (although presumably falcon 9 still needs the inclination change after delivery).  Best guess is that scaling issues are taking away any benefits from the physics of air launch.

One thing that has been ignored so far are launch costs.  Spacex will launch a used rocket for $60M (although part of that cost is probably a mad scramble to make *some* profit, spacex appears to still be in "startup mode" and losing money, although being private they need not file the SEC papers that would make that clear).  Back in 1990, Orbital would launch a Pegasus for a "base price" of $6M (I suspect that the "base price" was unobtainable/useless, but it does give a negotiation point).  If orbital is using launch procedures based on airlines/fedex procedures (who have to cut "launch prices" or airplanes to the bone) vs. using launch procedures designed by NASA which were likely developed for Apollo and only changed to increase safety during the Shuttle era, but never once had to deal with cost issues as the cost of the rocket was so high and the launch cadence wouldn't justify the training/experience needed for cheaper launches.  I think I've kept in the back of my mind is that Blue Origin seems to have grabbed up most of the DC-X guys, and they made a point of reducing these costs (with rockets).

If Orbital wanted to redesign Pegasus (for either stratolaunch or their L1011), they might be able to make significant gains with replacing steel SRB casings with carbon (or even composite).  This was certainly one of the plans for PegasusII, and I doubt that the $6M price tag in 1990 allowed for much use of carbon (although using it in the third stage would go a long way for the lowest price).  Considering how Orbital already uses a Pegasus-derived upper set of stages on other rockets, I suspect that they would be much more likely to upgrade the "standard Pegasus" ( or PegasusXL which ever design is on top of minotaurs and similar) to fit a higher payload in the same mass of rocket and thus improve a much broader product array.

So my questions are:
Can stratolaunch top up cryogenic fuels?
Is Rocket Lab (the electron rocket people) interested in air launch?  Thanks to the square/cube law, small rockets benefit vastly more for air launches.  For those that advertize a "mass to GTO" (rocket lab doesn't), they could likely simply increase this without a redesign with an air launch.  Note that I think a L1011/B52 could launch most in this class instead of a Stratolaunch.
 

[mikegarrison]

2 hours ago, wumpus said:

Once you go back to first principles, you still have the issue in that it will cost $1Billion to build the rocket.  That's an important first principle in itself.  The other is the square/cube law.  Once you build rockets more than twice what a stratolaunch can carry, the square/cube law can make your rocket more efficient than an "all things being equal" airlaunched rocket.

Isp is another critical "first principle".  If you are sacrificing Isp (especially in your final stage), you can wipe out all benefits from the first bit of delta-v.  PegasusII was originally supposed to have a hydrolox final stage, but that replaced with an "all solid" rocket.  All operating Pegasus rockets use solid stages (a non-cyrogenic hydrazine fourth stage is an option).  Using cryogenic fuels gives the problem of either sufficiently insulating the oxidizer/fuel tanks or continually topping off the rocket.  My understanding was that the x-15 mothership had to carry twice the amount of oxygen as the x-15 to allow it to drop fully fueled (my memory/source might be off on that one, I thought it was due to hydrogen).  If you want a hydrox upper stage, you will certainly need to have some means of supplying hydrogen from the mothership and likely oxygen as well (I think somebody else on this forum went into detail about trying mid-air refueling of hydrogen.  I think it had to do with a "scoop up atmospheric oxygen" idea.

Spacex was originally contracted/expected to design the rocket.  It was called a Falcon Air, and have only 4 Merlin engine.  It is telling that this idea was scrapped *before* spacex abandoned the idea of parachute recovery, as a powered landing with a lighter booster and the same merlin engine is likely difficult.  Spacex would far rather fill falcons with fuel than have more crash.  According to the infallible wiki, Falcon air would deliver 6 tons to LEO while Falcon 9 (1.0) delivered 10 tons to LEO and a similar ratio to GTO (although presumably falcon 9 still needs the inclination change after delivery).  Best guess is that scaling issues are taking away any benefits from the physics of air launch.

One thing that has been ignored so far are launch costs.  Spacex will launch a used rocket for $60M (although part of that cost is probably a mad scramble to make *some* profit, spacex appears to still be in "startup mode" and losing money, although being private they need not file the SEC papers that would make that clear).  Back in 1990, Orbital would launch a Pegasus for a "base price" of $6M (I suspect that the "base price" was unobtainable/useless, but it does give a negotiation point).  If orbital is using launch procedures based on airlines/fedex procedures (who have to cut "launch prices" or airplanes to the bone) vs. using launch procedures designed by NASA which were likely developed for Apollo and only changed to increase safety during the Shuttle era, but never once had to deal with cost issues as the cost of the rocket was so high and the launch cadence wouldn't justify the training/experience needed for cheaper launches.  I think I've kept in the back of my mind is that Blue Origin seems to have grabbed up most of the DC-X guys, and they made a point of reducing these costs (with rockets).

If Orbital wanted to redesign Pegasus (for either stratolaunch or their L1011), they might be able to make significant gains with replacing steel SRB casings with carbon (or even composite).  This was certainly one of the plans for PegasusII, and I doubt that the $6M price tag in 1990 allowed for much use of carbon (although using it in the third stage would go a long way for the lowest price).  Considering how Orbital already uses a Pegasus-derived upper set of stages on other rockets, I suspect that they would be much more likely to upgrade the "standard Pegasus" ( or PegasusXL which ever design is on top of minotaurs and similar) to fit a higher payload in the same mass of rocket and thus improve a much broader product array.

So my questions are:
Can stratolaunch top up cryogenic fuels?
Is Rocket Lab (the electron rocket people) interested in air launch?  Thanks to the square/cube law, small rockets benefit vastly more for air launches.  For those that advertize a "mass to GTO" (rocket lab doesn't), they could likely simply increase this without a redesign with an air launch.  Note that I think a L1011/B52 could launch most in this class instead of a Stratolaunch.
 

There are other benefits. The main one is that you can launch from any inclination you want. But practically that wasn't enough to keep SeaLaunch competitive either.

[YNM]

On 9/3/2017 at 7:56 AM, mikegarrison said:

Actually ... it often is, at least in the aviation industry.

Well, I'm learning something more pertinent to the ground 

 

To whether the concept is viable : Truth be told, it's only going to work for small things. I could only imagine that having some weird stuff where it can be launched from a pad AND from a plane would be pretty rare, but within technical feasibility nonetheless. It's always the trouble with Jack of All : they're king of none.

[Racescort666]

RE: FRP being called "plastic"

In the auto industry, you have essentially 2 entities describing composites: marketing, and engineering. Engineering will definitely joke about stuff being made out of plastic when it's a composite (carbon/graphite or not). There is definitely a distinction made between carbon fiber and fiberglass though. Also, manufacturing technique like SMC will sometimes be used to describe them. Regardless, marketing will try to make it sound way fancier than it actually is, hence, the tongue-in-cheek description of "plastic". 

Since the catch all term "composite" is a bit too broad and includes things like concrete, FRP is the preferred term for the pedantic. But since FRP stands for fiber reinforced plastic, I'd say that shortening it to "plastic" is acceptable when said in a sarcastic tone.

Back to your regularly scheduled programming...

[YNM]

Hang a sec.

1 hour ago, Racescort666 said:

... Since the catch all term "composite" is a bit too broad and includes things like concrete, FRP is the preferred term for the pedantic.

Wait, concrete IS concrete. I read from one document of AASHTO (or FHWA, or so I remembered) that even blacktop/"asphalt" IS concrete : Asphalt Concrete. Composite would be something made of various things (like, wood + steel intertwined would count as composite, concrete and steel should count as composite but I presume it's bugger-all on that side). Composite constituents can stand on it's own ; concrete constituent can't, or so I imagine so far !

--------

1 hour ago, Racescort666 said:

Back to your regularly scheduled programming...

Last post On Topic with Edits :

2 hours ago, YNM said:

To whether the concept is viable : Truth be told, it's only going to work for small things.

I could only imagine that having some weird stuff where it can be launched from a pad AND from a plane would be pretty rare, but within technical feasibility nonetheless. Those are the ones that Stratolaunch is supposed to attract.

But always, the trouble with Jack of All : they're king of none.

 

Edited September 5, 2017 by YNM

[mikegarrison]

Concrete is a composite material, made up of sand and rocky aggregate held together by a binder (cement). Reinforced concrete is also a composite, because it includes steel in order to take the tension loads.

Asphalt concrete is likewise rocky aggregate held together by a binder (bitumen aka. asphalt).

Fiberglass (aka. GFRP) is a composite material made up of glass fibers held together by a binder (polymer aka. plastic).

CFRP is a composite material made of up carbon fibers held together by a binder (polymer aka. plastic).

 

These are all composite materials, as opposed to something like iron (an elemental metal) or steel (an alloyed metal).

Wood is a natural composite material, made up of fibers for strength held together by a binder (lignin). There are also manufactured wood composites, made of chipped or planed wood held together by a glue binder.

Edited September 5, 2017 by mikegarrison

[Northstar1989]

On 9/4/2017 at 3:18 AM, Nibb31 said:

Why not just just make your first stage 10% bigger instead? It's no big deal if you can reuse it, but even for an expendable, the extra cost is minimal compared to developing and operating a one-off specialized aircraft and dealing with the complexity of launching a rocket horizontally.

Musk has criticized air launch several times (and rightly so). He's not suddenly going to embrace it.

It's easier to just build your factory near the launch site. Transport by barge or truck is fine.

 

Did you not read what I wrote?  By mass, the first couple km/s can often add up to HALF THE MASS OF THE ROCKET.  That's not just a matter of making your first stage 10% larger- that's a matter of more than doubling its size.

The Falcon 9 first stage only provides around 3.7 km/s of Delta-V before burn-out.  1.5 km/s represents more than 40% of the Delta-V of the first stage, more than half the burn-time (the Merlin 1D has a sea-level ISP of 282 seconds, so by the time the Falcon 9 has lost half its first stage mass- or 38% of the mass of the rocket, it has accelerated 1.321 km/s according to the Rocket Equation, neglecting increases in ISP due to gaining altitude) and thus more than half of the rocket's fuel-mass (50% of the mass of the 421,300 kg first stage is 210,650 kg- about 38% of the launchpad mass of 549,054 kg F9 Full Thrust).

1.5 km/s in Delta-V savings represents the difference between needing to equip the first stage with 9 Merlin 1D+ engines, and the need to only equip it with 6 engines (as when you reduce the first stage mass by 50%, you reduce the rocket's total mass by 38%).

Since the engines and, especially, the associated turbopumps are the most expensive component of a rocket, this easily represents a 10-20% reduction in cost-to-orbit, maybe more- *AT LEAST* 6-12 million dollars a flight (a Falcon 9 launch costs $62 million).

Is that worth the development of a specialized carrier-plane and adapting a rocket for air-launch?  You tell me.  The makers of the Pegasus couldn't do it affordably- but SpaceX has already shown many times the ability to develop technology for a fraction of the cost in a feaction of the time of their competitors...

Sources on the Falcon 9:

http://www.spaceflightinsider.com/hangar/falcon/

https://en.m.wikipedia.org/wiki/Falcon_9

http://forum.nasaspaceflight.com/index.php?topic=40566.0

Edited September 14, 2017 by Northstar1989

[Northstar1989]

On 9/4/2017 at 0:30 PM, wumpus said:

Once you go back to first principles, you still have the issue in that it will cost $1Billion to build the rocket.  That's an important first principle in itself.  The other is the square/cube law.  Once you build rockets more than twice what a stratolaunch can carry, the square/cube law can make your rocket more efficient than an "all things being equal" airlaunched rocket.

Isp is another critical "first principle".  If you are sacrificing Isp (especially in your final stage), you can wipe out all benefits from the first bit of delta-v.  PegasusII was originally supposed to have a hydrolox final stage, but that replaced with an "all solid" rocket.  All operating Pegasus rockets use solid stages (a non-cyrogenic hydrazine fourth stage is an option).  Using cryogenic fuels gives the problem of either sufficiently insulating the oxidizer/fuel tanks or continually topping off the rocket.  My understanding was that the x-15 mothership had to carry twice the amount of oxygen as the x-15 to allow it to drop fully fueled (my memory/source might be off on that one, I thought it was due to hydrogen).  If you want a hydrox upper stage, you will certainly need to have some means of supplying hydrogen from the mothership and likely oxygen as well (I think somebody else on this forum went into detail about trying mid-air refueling of hydrogen.  I think it had to do with a "scoop up atmospheric oxygen" idea.

$1 Billion to build WHAT rocket?  The Falcon 9 v1.0 only cost $300 million to develop according to NASA and SpaceX:

http://www.parabolicarc.com/2011/05/31/nasa-analysis-falcon-9-cheaper-traditional-approach/

Subsequent improvements and attempt to develop re-usability have been more expensive, with some estimating it has cost as much as $700 million to make subsequent upgrades permitting the Falcon 9 to be reusable, though I doubt the authenticity of those claims as more than 2x the original cost to develop the rocket seems a little extreme...

Regardless, SpaceX uses Kero/LOX all the way through its rockets- not Hydro/LOX.  So the difficulties in keeping a cryogenic rocket fueled up before air-launch really aren't as extreme as with Hydro/LOX, even if they are substantial...

As for scooping up atmospheric O2- yes, you could do that.  But the rocket won't be attached to the carrier-plane *THAT LONG*, so it really makes a lot more sense just to equip the carrier plane with a small LOX tank that feeds into the cryogenic stages via an umbilical, just like SpaceX does to their rockets before launch from the pad...

Not that atmospheric scoops are necessarily a bad technology to develop.  They are useful for Propulsive Fluid Accumulators and spaceplanes, among other things.  But why add difficulty to an already-onorous R&D project (adapting a Kero/LOX rocket for air-launch and developing a flight-rated umbilical system) if you don't have to?

Edited September 14, 2017 by Northstar1989

[Nibb31]

40 minutes ago, Northstar1989 said:

Did you not read what I wrote?  By mass, the first couple km/s can often add up to HALF THE MASS OF THE ROCKET.  That's not just a matter of making your first stage 10% larger- that's a matter of more than doubling its size.

OMG! Are you saying that.... Elon could be wrong ?????

https://en.wikipedia.org/wiki/Air_launch_to_orbit#Disadvantages

[Northstar1989]

On 9/4/2017 at 0:30 PM, wumpus said:

Isp is another critical "first principle".

-SNIPPED-

Spacex was originally contracted/expected to design the rocket.  It was called a Falcon Air, and have only 4 Merlin engine.  It is telling that this idea was scrapped *before* spacex abandoned the idea of parachute recovery, as a powered landing with a lighter booster and the same merlin engine is likely difficult.  Spacex would far rather fill falcons with fuel than have more crash.  According to the infallible wiki, Falcon air would deliver 6 tons to LEO while Falcon 9 (1.0) delivered 10 tons to LEO and a similar ratio to GTO (although presumably falcon 9 still needs the inclination change after delivery).  Best guess is that scaling issues are taking away any benefits from the physics of air launch.

One thing that has been ignored so far are launch costs.  Spacex will launch a used rocket for $60M (although part of that cost is probably a mad scramble to make *some* profit, spacex appears to still be in "startup mode" and losing money, although being private they need not file the SEC papers that would make that clear).  Back in 1990, Orbital would launch a Pegasus for a "base price" of $6M (I suspect that the "base price" was unobtainable/useless, but it does give a negotiation point).  If orbital is using launch procedures based on airlines/fedex procedures (who have to cut "launch prices" or airplanes to the bone) vs. using launch procedures designed by NASA which were likely developed for Apollo and only changed to increase safety during the Shuttle era, but never once had to deal with cost issues as the cost of the rocket was so high and the launch cadence wouldn't justify the training/experience needed for cheaper launches.  I think I've kept in the back of my mind is that Blue Origin seems to have grabbed up most of the DC-X guys, and they made a point of reducing these costs (with rockets).

ISP is *higher* with an air-launch, comparing apples to apples (Kero/LOX to Kero/LOX, or SRB to SRB).  There is nothing about air-launch that inherently requires use of an SRB instead of cryogenic, though I suspect the REAL reason that was done with the Pegasus is due to restrictions on the size of a rocket you can feasibly launch from a modified cargo jet (you can air-launch slightly more payload to orbit on an SRB than a Hydro/LOX stage of the same size, though the Hydro/LOX stage will weigh less and the rocket will have a much higher payload-fraction...)

However the Stratolaunch "Roc" has much more space between the twin fuselages than their earlier carrier plane had space for the Pegasus, whereas I suspect the structural strain on the rocket-mount will be much more of an issue with the Roc, so Kero/LOX rockets are likely preferable as they weigh less...

 

As for the "Falcon Air"- four Merlin engines for about 60% of the payload of a Falcon 9.  Sounds about right- considering my own calculations jyst revealed 6 engines is about right to match the Falcon 9's payload capacity pound-for-pound...  I wonder if they could manage to mount a 6-engine Falcon Air to the Roc instead, or if that would be too heavy...

Ultimately, I suspect SpaceX's motivations were more complex and long-term than anyone is giving them credit for, though.  Elon Musk ultimately dreams of Mars, and he KNOWS that something as enormous as the I.T.S. can *NEVER* be launched from a carrier-plane, so I suspect he decided the Falcon Air would just be a needless distraction.

That doesn't mean the Physics don't favor it though- for the specific niche-case of launching commercial satellites to orbit, air-launch should be superior.  It should also work towards the longer-term goals of HYPERSONIC air-launch and launch from a sub-orbital spaceplane, which should be harder still.  It doesn't measure up to the cost-savings of developing a Mass Driver launch system, a Microwave Beamed Power launch system, or Propulsive Fluid Accumulators though...

Edited September 14, 2017 by Northstar1989

[Northstar1989]

28 minutes ago, Nibb31 said:

OMG! Are you saying that.... Elon could be wrong ?????

https://en.wikipedia.org/wiki/Air_launch_to_orbit#Disadvantages

Musk isn't infallible.  He was caught on the spot by that question- and he responded with a hand-wave kind of answer that isn't really 100% accurate...

The numbers say you should be able to reduce the size of your launch-stage by 50%, not 5%.  And you can get 50% more payload to orbit with an identical rocket (a 4-engine variant of the Falcon 6 shoul d be able to air-launch 2/3rd the payload of a Falcon 9 to orbit, and a 6-engine variant match it so a 9-engine variant...)

The cost-savings are much more substantial than Elon makes it seem.  But he's a businessmen, and businessmen are used to making up numbers on the fly to illustrate a point.

And he *IS* right about there being an upper size limit on how large of a rocket you can air-launch... (the "Roc" is already pushing the boundaries of what serms possible with conventional planes...  I suspect MAYBE you could scale up to about the scale of payloads requiring a Falcon Heavy someday- especially if you developed a rocket-powered carrier-plane that reaches a high-altitude supersonic, or suborbital trajectory.  But you probably will never launch an ITS from a carrier-plane...)

 

EDIT: I almost said you will *CERTAINLY* never launch something the size of the ITS from a carrier-plane, but then I was reminded of a TRULY ENORMOUS spaceplane I once read about, I believe somewhere on Project Rho.  I mean, the thing must have been almost the size of a small city!  So, never say never unless you're really darn sure about it.  People used to call landing a launch-stage impossible, after all.  Kudos to anyone who can find it for me somewhere on their website:

http://www.projectrho.com/public_html/rocket/surfaceorbit.php

Edited September 14, 2017 by Northstar1989

[DerekL1963]

8 hours ago, Northstar1989 said:

Did you not read what I wrote?  By mass, the first couple km/s can often add up to HALF THE MASS OF THE ROCKET.  That's not just a matter of making your first stage 10% larger- that's a matter of more than doubling its size.

That doesn't make what Nibb said wrong.  That increase in first stage mass is cheap - it's all tankage and fuel.  (And setting aside that the mass savings from a smaller first stage are partially offset by the mass increases in all stages to allow for horizontal carry and to withstand the stresses of the drop.)

 

7 hours ago, Northstar1989 said:

That doesn't mean the Physics don't favor it though- for the specific niche-case of launching commercial satellites to orbit, air-launch should be superior.

But this discussion isn't just about the physics.  It's also about the costs, particularly the elephant in the room - the launching aircraft.  (Estimated at $300 million six years ago for Stratolaunch, almost certainly much higher than that in reality.)  That's long been the basic economic problem for air launch systems, the economics only make sense if you're launching a significant number of payloads.  Otherwise, you end up with Pegasus, one of the more expensive civilian launchers rather than being one of the cheapest.  (Another part of this is because air launch doesn't save any man hours in the launch campaign, in fact it adds to them.)

[wumpus]

7 hours ago, Northstar1989 said:

ISP is *higher* with an air-launch, comparing apples to apples (Kero/LOX to Kero/LOX, or SRB to SRB).  There is nothing about air-launch that inherently requires use of an SRB instead of cryogenic, though I suspect the REAL reason that was done with the Pegasus is due to restrictions on the size of a rocket you can feasibly launch from a modified cargo jet (you can air-launch slightly more payload to orbit on an SRB than a Hydro/LOX stage of the same size, though the Hydro/LOX stage will weigh less and the rocket will have a much higher payload-fraction...)[snip]

As for the "Falcon Air"- four Merlin engines for about 60% of the payload of a Falcon 9.  Sounds about right- considering my own calculations jyst revealed 6 engines is about right to match the Falcon 9's payload capacity pound-for-pound...  I wonder if they could manage to mount a 6-engine Falcon Air to the Roc instead, or if that would be too heavy...[snip]

While there is nothing to make air launch liquid fuels unfeasible (X-15 did it), Orbital ditched that idea and moved to a three-stage all solid rocket on PegasusII until it was canceled.  Hydrolox is particularly bad for air-launch use due to the need to keep topping up your hydrogen from the mothership (you would do the same with oxygen, just that you would need to supply so much more hydrogen).

The four engine "Falcon Air" was presumably sized for  the Stratolaunch, simply scaling up the size isn't likely to fit.  Don't forget that this was based off the Falcon 9 1.0 and essentially impossible to recover (they were planning on parachutes).  With ground launch, Spacex has steadily scaled up the Falcon 9 to include both recovery and doubling the payload while increasing the total mass by 60%.  I would assume that anything launched by stratolaunch would have no ability to scale up the mass/size.

The obvious issue the stratolaunch backs itself into is that it strictly limits the size of the satellite it can launch, while still requiring basically the same number of flights to design the rocket as the big boys.  The Delta-II was able to scale itself by adding various numbers of SRB boosters ("more boosters") and the Delta-Heavy and Falcon-Heavy "simply" combine boosters to build a vastly larger rocket.  These are then more efficient and can lob large numbers of "stratolaunch sized" satellites into orbit even more efficiently than a small stratolaunch rocket even with it's 50% efficiency.

Note that how this thing gets to Mars is only one of Elon Musk's concerns.  Recovery is a particular bugaboo of his, and it isn't clear that spacex could use current recovery methods to recover Falcon Air.  But the real reason Spacex still exists at all is the CRS program.  CRS requires 2-3 tons of cargo and is delivered by a 2 ton dragon capsule.  If Spacex was tied to Falcon air and couldn't cut the dragon down to fit the falcon air payload requirements, spacex would go bankrupt.  Just from memory, CRS is one of the lightest LEO payloads falcon 9 carries (excluding multiple launches),  and I don't see how they could afford to justify falcon air without CRS.

Remember: all this is to simply justify the *rocket*.  Justifying the Roc is pretty hopeless, and pretty much is all about wondering if anyone will bother to pick it up after bankruptcy.  I wouldn't be surprised if Airbus or Boeing picks it up as a "guppy replacement" cargo plane and drive the price out of consideration for a company like Orbital (assuming the Pegasus II could be justified at all).

[mikegarrison]

29 minutes ago, wumpus said:

Remember: all this is to simply justify the *rocket*.  Justifying the Roc is pretty hopeless, and pretty much is all about wondering if anyone will bother to pick it up after bankruptcy.  I wouldn't be surprised if Airbus or Boeing picks it up as a "guppy replacement" cargo plane and drive the price out of consideration for a company like Orbital (assuming the Pegasus II could be justified at all).

Stratolaunch Systems is owned by Paul Allen, so he could build 100 Roc planes and not really notice it in his bank account.

It would not work as a large cargo freighter.

[_Augustus_]

26 minutes ago, mikegarrison said:

Stratolaunch Systems is owned by Paul Allen, so he could build 100 Roc planes and not really notice it in his bank account.

So why can't he build his own rocket?

[wumpus]

3 hours ago, mikegarrison said:

It would not work as a large cargo freighter.

It can carry ~400,000lbs  loads with little envelope issues.  You will have significant carrying/hardpoint/harness issues, along with a need to build a fairing (which might get used plenty of times if you are boeing/airbus).  I'm guessing that anyone using this would have extreme envelope issues.

NASA considered building something like stratolaunch to carry the shuttle, presumably before a 747 was qualified.

[regex]

Quote

Will StratoLaunch Fly?

Probably.

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Will StratoLaunch Launch?

lolno

[Helmetman]

Will stratolaunch fly/launch?

See user above me...

I find it more a farce that some entrepreneur with a big bank account without any or *some knowledge gets his business *cough* engineering company running without a idea, concept or ambition to do it properly (*some knowledge = not enough) 

So B747's and lockeheed L1011's did this and can do this still? So what's the mind, personal or companies limitation to build this then if it was already done before? Is it just to get a few ton to orbit that can be done cheaper with regular rockets concerning the runway, industry and certifications they'd still have to go for? This sounds like some of those bureaucratic CEO's with science and engineering ambitions without knowing what both words mean and think they can be von braun or korolev 2.0.

Sad to say, but even Kim Jung'un seems on a route for more kg's to orbit then these guys are. And while I'm at it, screw the guy I just mentioned. Thinking about what I just said, I know now what stratolaunch can be good for...

 

[kerbiloid]

If when they get bothered with the idea to launch 6 t of payload with this monster _{(according to wiki)}, they can try their best as maritime overlords.

1. Carrying personal 200 t dieselpunk submarine, landing on water and getting to the underwater _{Spectre base} castle.

2. Building an autonomous drone ship island like SpaceX has.

3. Flying aircraft carrier (like in Sky Captain, but not a zeppelin).

4. Also flying to Antarctic base.

Edited September 19, 2017 by kerbiloid

[mikegarrison]

12 hours ago, Helmetman said:

Will stratolaunch fly/launch?

See user above me...

I find it more a farce that some entrepreneur with a big bank account without any or *some knowledge gets his business *cough* engineering company running without a idea, concept or ambition to do it properly (*some knowledge = not enough) 

So B747's and lockeheed L1011's did this and can do this still? So what's the mind, personal or companies limitation to build this then if it was already done before? Is it just to get a few ton to orbit that can be done cheaper with regular rockets concerning the runway, industry and certifications they'd still have to go for? This sounds like some of those bureaucratic CEO's with science and engineering ambitions without knowing what both words mean and think they can be von braun or korolev 2.0.

Sad to say, but even Kim Jung'un seems on a route for more kg's to orbit then these guys are. And while I'm at it, screw the guy I just mentioned. Thinking about what I just said, I know now what stratolaunch can be good for...

 

Well, I'll just point out that this amateur with a big bank account *did* manage to put together the first privately funded/designed spaceship that carried a live human into space (three times, including twice in a week).

Besides, if we're going to be making fun of amateurs with big bank accounts, that kind of describes Elon Musk and Jeff Bezos, too.

[Helmetman]

@mikegarrison  You are very right, and it wasn't specifically to make fun of them.

But reading about this myself for some time already and the topic replies covering the implications, lack of need, maybe net loss for required infrastructure (runway) and everything else gets me annoyed about the fundamental priorities of this project.

Edited September 19, 2017 by Helmetman

[tater]

 

It's a bit annoying he said "747 engines" instead of Pratt&Whitney PW4000 engines, as 747s have been offered with different engine choices over the years.