Suborbital Spaceplanes

[Northstar1989]

OK, so with the new aerodynamics model coming out, the merits of orbital vs. suborbital spaceplanes in real life seems like a worthwhile discussion...

Neither has ever been built before, of course- but let's just say one was...

Lately I have been on a stint with Suborbital Spaceplanes in KSP (I play with RSS 6.4x, RealFuels, and FAR- so true spaceplanes aren't really an option using nothing more advanced than the stock RAPIER engines...) And after using them for quite a while, I have come to ask- why isn't this something we're doing in real life?

(Above: A Suborbital Spaceplane that I built a while ago in RSS 64K. The most recent version has a stock turbojet engine and additional fuel tank strapped on top and a slightly smaller cargo-bay, for slightly less stressful takeoffs and ascents, and more rocket-like performance...)

You see, the benefits of air-breathing engines for the initial climb and burst of speed are well-known, as are the benefits of wings allowing you to stay airborne with less thrust (with a L/D ratio of 10, for instance, you can stay aloft with a TWR of just 0.1). However, it is difficult to design an aircraft that can close the 10-11 km/s Delta-V gap to orbit without staging: especially once you consider jet engines don't really work well past about 2 km/s atmospheric speed (and that's with pre-cooled intakes)

But, Lift/Drag ratio declines the faster in the hypersonic regime you end up flying, jet engines are deadweight past about Mach 4 or 5 (or in the case of something like SABRE or KSP's RAPIER, just a heavier rocket engine for the thrust they provide- although lighter than a separate dedicated rocket...), and wings are of course completely useless once you finally climb past the Karman Line (the altitude at which no meaningful lift can any longer be generated) and start the final burn to orbit...

So, why not deploy payloads from spaceplanes on a SUBORBITAL trajectory, and have them complete their burns to orbit using dedicated rockets?

The benefits of this vs. a simple rocket that takes off from the surface are numerous:

(1) You gain some altitude and horizontal speed with a stage (the spaceplane itself) that is essentially 100% resuable and can benefit from airplane-like economics.

(2) The first couple km/s of Delta-V to orbit are *BY FAR* the most expensive from a fuel, Thrust, and thus overall cost perspective. Due to the Rocket Equation, it takes much less fuel and thrust to achieve the 3rd and 4th km/s of Delta-V than it did the 1st and 2nd km/s for a given rocket design (put the other way around, it takes exponentially more fuel and thrust on the launchpad for each additional km/s of Delta-V you design into a rocket...)

(3) Because the rocket is deployed and operates above or at the very edge of the atmosphere, its engines can be optimized ENTIRELY for vacuum operation, rather than operation at sea-level... In practical terms, this means the rocket can use a relatively MUCH larger engine nozzle (which results in a higher Exhaust Velocity, and thus Vacuum ISP) without having to worry about extra drag or ISP-loss from over-expanding the exhaust stream relative to atmospheric pressure...

You can also utilize MUCH lower chamber-pressures, because chamber pressure has hardly any effect at all on Vacuum ISP, and really only affects atmospheric ISP (but is one of the most stressful factors on a rocket, and thus results in needing much heavier, more expensive, and less reusable engines...) Even a simple/cheap pressure-fed rocket engine can still achieve respectable ISP outside the atmosphere...

(4) The spaceplane can take off from the runway with a TWR significantly less than 1. TWR values of as little as 0.1 or 0.2 are easily viable in real life with a long enough runway... (especially if the engines are optimized for higher altitudes/speeds, and achieve better TWR there...)

(5) IF something goes wrong with a manned flight during the rocket-driven portion of the mission, you have a lot more altitude to separate the capsule and prepare for parachute-deployment and touchdown than if you launch with rockets from straight off the launchpad... (due to the low G-forces experienced during the spaceplane-portion of the flight, it's also possible to load the crew into the rocket section AFTER taking off from the runway...)

Most of these advantages are already reflected in KSP (except for the part about engine-design: but even KSP, and mods especially, offers a variety of rocket engines optimized for atmospheric or vacuum use...) I can understand players not wanting to go through the extra hassle vs. a pure spaceplane in KSP (especially considering you need to install a mod like Flight Manager for Reusable Stages to be able to swap back to the spaceplane and fly it back to the runway after rocket-deployment....) but the advantages of such an approach in real life are hard to ignore- especially when you consider that suborbital spaceplanes are probably the *ONLY* type of Horizontal Takeoff Horizontal Landing spaceplane we'll see in the reasonable future unless SABRE/SKYLON or Escape Dynamic's Microwave Beamed Power Spaceplanes pan out... (and either technology could still be adapted to using suborbital rather than orbital plane-stages for better total mass-fractions and higher payload-capacity for the same sized plane...)

Please discuss.

I know I have a penchant for the grandiose and discussing types of semi-futuristic launch infrastructure and mission-plans that we aren't likely to see for several more decades (if nothing else due to the lack of built-up momentum for implementing these ideas), but this is one of the few ideas I've brought up recently that is actually quite realistically achievable within 18-25 years without any enormous effort: planes such as the X-37 have ALREADY flown on suborbital trajectories simply by steering up- it wouldn't be that hard to simply build a much larger suborbital plane that deploys a small rocket as payload... (especially with newer technology and recent advancements like the SABRE engine being validated...)

This would initially be utilized for a cheaper way to put things like comm/spy satellites in orbit- but I could imagine it being adapted to launching small (potentially manned) capsules for things like space station-resupply and crewing larger interplanetary vessels assembled (as in, hard-docked between payload and transfer-stages, NOT manufactured) in-orbit relatively soon after proof-of-concept with satellites as well...

Regards,

Northstar

Edited February 7, 2015 by Northstar1989

[Skyler4856]

I built a system like this in an earlier version of KSP, it worked quite well...

[Bill Phil]

X-15. Sub-orbital space plane. Or are we not counting it?

[Northstar1989]

X-15. Sub-orbital space plane. Or are we not counting it?

The X-15 is entirely valid, and actually helps to prove my point (that suborbital spaceplanes are entirely feasible in real life), but was not what I meant. I meant a spaceplane that deploys a PAYLOAD that reaches orbit. Preferably a much larger spaceplane than the X-15, so that it can deploy a sizeable payload...

Regards,

Northstar

[Bill Phil]

So...

Like that double space plane concept from Russia, except without the second stage being a space plane?

[Wanderfound]

IIRC, there were also a few missiles launched in this manner; there was an anti-satellite missile launched from a zoom-climbing modified fighter jet.

(wiki wiki)

ASM-135 ASAT from an F-15.

[Kryten]

The X-15 is entirely valid, and actually helps to prove my point (that suborbital spaceplanes are entirely feasible in real life), but was not what I meant. I meant a spaceplane that deploys a PAYLOAD that reaches orbit. Preferably a much larger spaceplane than the X-15, so that it can deploy a sizeable payload...

Hits the same kind of issues as air-launch at larger scales, except much worse. All of the infrastructure to fly a unique aircraft, produce spare parts, keep the pilots trained, maintainence of the aircraft and infrastructure et.c. et.c. add up to a lot of money; this is one of main reasons OSC's Pegasus is so expensive for it's size. Turn the plane into a spaceplane, which much harsher and more esoteric maintenance requirements, and you probably aren't going to be competitive with an expandable rocket stage.

[Armchair Rocket Scientist]

IIRC, Skylon is supposed to be able to do this for larger payloads, approximately doubling its capacity from 15 tons to LEO to 33 tons. However, since the upper stage is expended, the cost per ton would likely be higher than flying as an SSTO.

[Northstar1989]

Hits the same kind of issues as air-launch at larger scales, except much worse.

Air-launch is already turning out to be a cheaper alternative than conventional expendables (if much more limited in payload-capacity), so I don't know why you'd say this...

All of the infrastructure to fly a unique aircraft, produce spare parts,

ANY resuable launch vehicle has these issues. Still, the cost-benefits of reusability have the potential to GREATLY outweigh the costs... And before you point to the Shuttle, let me dismiss that entirely- the problem with the Shuttle is that the engineering-margins were so slim that they had to rebuild the SSME's after EVERY SINGLE LAUNCH. If they had just dropped some of the insane US Air Foce-imposed performance and cross-range requirements, and built the Shuttle to wider engineering standards (so that the engines could have been rebuilt, say, every 40 or 100 launches- real rocket engines already exist with durability this high...) they would have ended up with a bit lower payload-fraction but an overall MUCH cheaper system (and they could have just built it a little bigger still for the same payload-capacity, thus beginning to move *slightly* in the direction of Big Dumb Boosters...)

keep the pilots trained,

Pilots? *snicker* Why would ANYBODY in their right mind fly a spaceplane manned? (especially a suborbital one, where the pilots don't even get to see orbit) An unmanned vehicle is *MUCH* cheaper and lighter. It's been done before- even as far back as the Buran Shuttle developed by the Russians, which flew its one operational mission completely-unmanned, despite having capacity for a sizable crew...

maintainence of the aircraft and infrastructure et.c. et.c. add up to a lot of money;

It's not cheap, but neither is operating an International Airport. And the planes aren't cheap either (imagine how expensive flight would be if we just build disposable airplanes that we threw away after every launch!) Yet commuter air-travel is a cheap and commonplace occurrence nowadays... As an added bonus, politicians get to generate a lot more jobs *RIGHT HERE AT HOME* with all the extra infrastructure and maintenance, compared to what they get with expendable launch-vehicles (where a lot of the costs are in extremely high-profit precision-manufacturing factories and workshops, which employ a comparatively much smaller number of people for much more irregular/ less dependable work...) which, by the way, and not to take a US-centric view, America buys most of the engines for from the Russians...

this is one of main reasons OSC's Pegasus is so expensive for it's size. Turn the plane into a spaceplane, which much harsher and more esoteric maintenance requirements, and you probably aren't going to be competitive with an expandable rocket stage.

Unfortunately, not. The reason Pegasus is so expensive is because it has VERY LOW market-share (so little, in fact, that I had to look it up after you mentioned it, because I had never even heard of it...) and a high failure-rate (which is the most likely reason for problem #1- only 35/40 missions have succeeded). If as many customers launches on their system as the Titan or Delta IV, I can almost *guarantee* it would be a cheaper launch-solution...

A suborbital spaceplane, by contrast, should be MUCH more reliable, because you don't need to deal with the tricky stability issues of air-launch (which are so hard, in fact, that while I've built not one but TWO successful suborbital spaceplanes in KSP with FAR installed, I've never been able to design an air-launch system that didn't spin wildly out of control, even in stock aero...)

Regards,

Northstar

Edited February 7, 2015 by Northstar1989

[Kibble]

(2) The first couple km/s of Delta-V to orbit are *BY FAR* the most expensive from a fuel, Thrust, and thus overall cost perspective. Due to the Rocket Equation, it takes much less fuel and thrust to achieve the 3rd and 4th km/s of Delta-V than it did the 1st and 2nd km/s for a given rocket design (put the other way around, it takes exponentially more fuel and thrust on the launchpad for each additional km/s of Delta-V you design into a rocket...)

Actually I'm fairly certain its the opposite. Generally upper stages are much more mass sensitive, while lower stages are more robust - adding a kg of mass to the first stage subtracts less payload then adding a kg to the second. Increasing delta vee at all exponentially increases the mass fraction you need, regardless if its performed by an upper or lower stage.

[Kryten]

Air-launch is already turning out to be a cheaper alternative than conventional expendables (if much more limited in payload-capacity), so I don't know why you'd say this...

The only air-launched vehicle on the planet is Pegasus, and you said later in the post you'd never heard of it. How can you say they're a cheaper alternative to anything when you don't even know they exist?

ANY resuable launch vehicle has these issues.

A conventional rocket has it to a lesser extent, there's much less extra systems to have to do maintenance on.

Still, the cost-benefits of reusability have the potential to GREATLY outweigh the costs...

With spaceplanes, that potential only exists with at unfeasibly high launch rates.

And before you point to the Shuttle, let me dismiss that entirely- the problem with the Shuttle is that the engineering-margins were so slim that they had to rebuild the SSME's after EVERY SINGLE LAUNCH. If they had just dropped some of the insane US Air Foce-imposed performance and cross-range requirements, and built the Shuttle to wider engineering standards (so that the engines could have been rebuilt, say, every 40 or 100 launches- real rocket engines already exist with durability this high...) they would have ended up with a bit lower payload-fraction but an overall MUCH cheaper system (and they could have just built it a little bigger still for the same payload-capacity, thus beginning to move *slightly* in the direction of Big Dumb Boosters...)

STS was a lot more than an engine. A major part of the maintenance cost was the tiles; something a propulsively-returning rocket wouldn't need.

Pilots? *snicker* Why would ANYBODY in their right mind fly a spaceplane manned? (especially a suborbital one, where the pilots don't even get to see orbit) An unmanned vehicle is *MUCH* cheaper and lighter. It's been done before- even as far back as the Buran Shuttle developed by the Russians, which flew its one operational mission completely-unmanned, despite having capacity for a sizable crew...

Ask XCOR and the Spaceship Company, the only people currently working on suborbital spaceplanes. Certifying uncrewed aircraft for commercial flight is a nightmare, both financially and in terms of paperwork.

It's not cheap, but neither is operating an International Airport. And the planes aren't cheap either (imagine how expensive flight would be if we just build disposable airplanes that we threw away after every launch!) Yet commuter air-travel is a cheap and commonplace occurrence nowadays...

Because of the flight volume. You need very high launch rates to afford spaceplanes, just as much as you need very high flight rates to justify modern jet aircraft. Most airlines are one short recession away from bankruptcy, it's another very low margin business.

As an added bonus, politicians get to generate a lot more jobs *RIGHT HERE AT HOME* with all the extra infrastructure and maintenance, compared to what they get with expendable launch-vehicles (where a lot of the costs are in extremely high-profit precision-manufacturing factories and workshops, which employ a comparatively much smaller number of people for much more irregular/ less dependable work...) which, by the way, and not to take a US-centric view, America buys most of the engines for from the Russians...

Launch vehicles are not 'high-profit' anything, it's an inherently low-margin business.

Unfortunately, not. The reason Pegasus is so expensive is because it has VERY LOW market-share (so little, in fact, that I had to look it up after you mentioned it, because I had never even heard of it...) If as many customers launches on their system as the Titan or Delta IV, I can almost *guarantee* it would be a cheaper launch-solution...

Yes you can, but if wishes were fishes we'd all cast nets. Pesasus-sized payloads are a small part of the market, and most of that market is served by extremely cheap russian converted ICBMs. So the only niche for Pegasus is a small part of the small part, US government payloads in this mass class; and the system can't be expanded to more lucrative sizes without having to look at a custom airframe, massively jacking up the cost.

[Bill Phil]

Actually I'm fairly certain its the opposite. Generally upper stages are much more mass sensitive, while lower stages are more robust - adding a kg of mass to the first stage subtracts less payload then adding a kg to the second. Increasing delta vee at all exponentially increases the mass fraction you need, regardless if its performed by an upper or lower stage.

Yeah...

That's because the first stage is generally much more massive, adding a kilogram to the first stage =/= adding a kilogram to the second in terms of the mass fraction in most cases.

The first few minutes of launch are very expensive Dv wise because you just want to GET UP while fighting gravity.

Also:

It takes "less" fuel to get that last few km/s because you have already "invested" a large amount of kinetic energy, and you get a pseudo-oberth effect. Not to mention that the stage is much lighter anyways

[Northstar1989]

Actually I'm fairly certain its the opposite.

I can assure you it's not.

Generally upper stages are much more mass sensitive, while lower stages are more robust - adding a kg of mass to the first stage subtracts less payload then adding a kg to the second.

That's because a kg on the first stage doesn't have to be carried as far Delta-V wise as a kg on the upper stage.

Launch stage are ALWAYS much larger and more powerful than the upper stages are, which serves to validate my point...

Increasing delta vee at all exponentially increases the mass fraction you need, regardless if its performed by an upper or lower stage.

Which is, THIS (what you just said). If you can cut the Delta-V to orbit from 10 km/s to 8 km/s, you cut a lot more off the size and cost than if you cut it again from 8 km/s to 6 km/s, for instance...

Regards,

Northstar

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Yeah...

That's because the first stage is generally much more massive, adding a kilogram to the first stage =/= adding a kilogram to the second in terms of the mass fraction in most cases.

The first few minutes of launch are very expensive Dv wise because you just want to GET UP while fighting gravity.

Also:

It takes "less" fuel to get that last few km/s because you have already "invested" a large amount of kinetic energy, and you get a pseudo-oberth effect. Not to mention that the stage is much lighter anyways

Ninja'd me, and said it better than I said it myself.

[Northstar1989]

The only air-launched vehicle on the planet is Pegasus, and you said later in the post you'd never heard of it. How can you say they're a cheaper alternative to anything when you don't even know they exist?

I was referring to the numerous air-launch systems currently in development (I had no idea that one had already made it). If you've never heard of THEM then how can you say they're not cheap?

A conventional rocket has it to a lesser extent, there's much less extra systems to have to do maintenance on.

There's never BEEN a reusable conventional rocket. So, you're in no better of a position to comment on the costs than I am. OF COURSE an expendable LV has less of these costs- that's BECAUSE IT'S EXPENDABLE! Obviously it doesn't have any costs associated with its re-use!

With spaceplanes, that potential only exists with at unfeasibly high launch rates.

Not at all. The majority of costs for any rocket or spaceplane are in R&D. But, the manufacturing costs are also quite significant- and if you can develop a system that eliminates or reduces these...

STS was a lot more than an engine. A major part of the maintenance cost was the tiles; something a propulsively-returning rocket wouldn't need.

*OR*, a suborbital spaceplane (although the Shuttle tiles were also the result of design-choices that could have been avoided). Returning from suborbital velocities involves a LOT less re-entry heat than returning from orbit, which is another reason this mission-architecture is preferable...

Ask XCOR and the Spaceship Company, the only people currently working on suborbital spaceplanes. Certifying uncrewed aircraft for commercial flight is a nightmare, both financially and in terms of paperwork.

I don't count bureaucratic costs as part of the real costs of a program. If the only reason something won't work is because the FAA or Congress is being a bunch of whiny brats about it, then the solution is to replace the people responsible or wait until they retire- not to say that there's something wrong with the mission design... As you can tell, I don't have a lot of respect for current politicians and bureaucrats...

Because of the flight volume. You need very high launch rates to afford spaceplanes, just as much as you need very high flight rates to justify modern jet aircraft. Most airlines are one short recession away from bankruptcy, it's another very low margin business.

No, modern jet airliners could easily operate with much lower flight rates if the ticket prices were higher and people were willing to pay them. The problem with commuter air-travel is, partly, that it faces a lot of competition from inherently cheaper transportation technologies like cars/buses and trains. So they can't raise their prices, and the floor is very low. A spaceplane would operate in an environment where the prices (and revenue streams) are currently VERY large. So, they don't have to be cost-effective on NEARLY the level of a commuter aircraft, and I don't expect them to be. $500/kg would be an extremely reasonable cost for LEO payload, but it would be unimaginably expensive for commuter air travel...

Launch vehicles are not 'high-profit' anything, it's an inherently low-margin business.

No, the DESIGN AND OPERATION of launch vehicles is an inherently low-margin business. The manufacturing (which is usually performed by subcontractors) is an EXTREMELY high-margin business (this is also a HUGE part of the reason why Space-X has so much lower costs- they operate their own manufacturing plants, do it all in one place, and don't subcontract it out at insane prices... In economic terms, vertical-integration...)

There are companies out there that make a part for a spacecraft for $10 in raw materials and $190 in design and labor, and then turn around and sell it for $1000. How's THAT for high-margin business?

Yes you can, but if wishes were fishes we'd all cast nets. Pesasus-sized payloads are a small part of the market, and most of that market is served by extremely cheap russian converted ICBMs. So the only niche for Pegasus is a small part of the small part, US government payloads in this mass class; and the system can't be expanded to more lucrative sizes without having to look at a custom airframe, massively jacking up the cost.

You're right that it's the tiny payload-capacity that helps to limit Pegasus' market-share. That's more a result of the current market-environment more than anything else. It's been hard for private companies to raise the funds to design and build larger launch vehicles. Big companies like the United Launch Alliance have a virtual stranglehold on the US Market, and use regulatory instruments as a bludgeon to try and stamp out competition. The ULA is greedy and monopolistic, not unlike the history of MANY other giant corporations/trusts throughout US history that dominated their respective markets in the same way... I wouldn't be surprised if they've also been slashing their launch-prices (perhaps even to break-even levels) whenever a competitor firm starts to scare them enough, simply to try and keep competitors out of the market entirely...

Don't even make me BEGIN on some of the legal-drama between the ULA and Space-X, for instance. The ULA tried *very hard* (although, fortunately, unsuccessfully) to make sure Space-X could never get regulatory approval for some of their Falcon 9 re-usability plans... It's a jungle out there, and ULA is the 800-pound Gorilla with a bad attitude...

Regards,

Northstar

Edited February 7, 2015 by Northstar1989

[Kibble]

The first few minutes of launch are very expensive Dv wise because you just want to GET UP while fighting gravity.

That's why solid boosters are used, when they're used. Making the rocket a horizontally-launched plane is a much more complex solution to this small problem.

[Kryten]

I was referring to the numerous air-launch systems currently in development (I had no idea that one had already made it). If you've never heard of THEM then how can you say they're not cheap?

Those being GO, Stratolaunch, and... that's it, really. Given the existence of EV-1 and -2, you're still unaware of most such systems, and all of them that havea actually flown.

There's never BEEN a reusable conventional rocket. So, you're in no better of a position to comment on the costs than I am. OF COURSE an expendable LV has less of these costs- that's BECAUSE IT'S EXPENDABLE! Obviously it doesn't have any costs associated with its re-use!

Falcon 9 is pretty close... and the maintenance costs for the legs and a few small control fins are going to compare extremely favourably to full plane-like aerodynamic surfaces. There's a reason all the reusable first-stagtes actually in development are either reasonably conventional rockets (BO, F9R) or rely on subsidisation through passenger flight (Lynx Mk. III). If RTLS with conventional rockets is viable, there's no need or reason to add the additional weight and complexity of a spaceplane, full stop.

Not at all. The majority of costs for any rocket or spaceplane are in R&D. But, the manufacturing costs are also quite significant- and if you can develop a system that eliminates or reduces these...

'Not at all'-because why, exactly? I've seen the quotes for Skylon, I've seen the quotes for Venturestar, for HOTOL, nobody expected/s them to make any money without much higher flight rates than are currently supportable. If you disagree, come up with some figures, don't just say 'I don't think so'.

*OR*, a suborbital spaceplane (although the Shuttle tiles were also the result of design-choices that could have been avoided). Returning from suborbital velocities involves a LOT less re-entry heat than returning from orbit, which is another reason this mission-architecture is preferable...

But at temperatures too low to need proper heat-shielding, there's no advantage to bringing wings along. VTVL would work just fine.

I don't count bureaucratic costs as part of the real costs of a program. If the only reason something won't work is because the FAA or Congress is being a bunch of whiny brats about it, then the solution is to replace the people responsible or wait until they retire- not to say that there's something wrong with the mission design... As you can tell, I don't have a lot of respect for current politicians and bureaucrats...

It's the world we have to live in. If you have to ignore aspects of reality you don't like to make your argument, you don't have an argument.

No, modern jet airliners could easily operate with much lower flight rates if the ticket prices were higher and people were willing to pay them. The problem with commuter air-travel is, partly, that it faces a lot of competition from inherently cheaper transportation technologies like cars/buses and trains. So they can't raise their prices, and the floor is very low. A spaceplane would operate in an environment where the prices (and revenue streams) are currently VERY large. So, they don't have to be cost-effective on NEARLY the level of a commuter aircraft, and I don't expect them to be. $500/kg would be an extremely reasonable cost for LEO payload, but it would be unimaginably expensive for commuter air travel...

Spaceplanes do have a major competitor; rockets, whether they be expendable or VTVL. Expandable beats them at sufficiently low flight rates, and I'm not sure they could hope to top a fully realised VTVL system at all.

No, the DESIGN AND OPERATION of launch vehicles is an inherently low-margin business. The manufacturing (which is usually performed by subcontractors) is an EXTREMELY high-margin business (this is also a HUGE part of the reason why Space-X has so much lower costs- they operate their own manufacturing plants, do it all in one place, and don't subcontract it out at insane prices... In economic terms, vertical-integration...)

Bull. Name one manufacturer that doesn't operate it's own rockets. You can't seperate actions that are being performed by the same company, the overall business is still low-margin; payloads are where the money's at.

There are companies out there that make a part for a spacecraft for $10 in raw materials and $190 in design and labor, and then turn around and sell it for $1000. How's THAT for high-margin business?

There are people out there that don't understand quality control or certification. I'm talking to one of them.

You're right that it's the tiny payload-capacity that helps to limit Pegasus' market-share. That's more a result of the current market-environment more than anything else.

Again, it's what we have to live with, and you can't just ignore it.

I wouldn't be surprised if they've also been slashing their launch-prices (perhaps even to break-even levels) whenever a competitor firm starts to scare them enough, simply to try and keep competitors out of the market entirely...

LM lost most of their market share long before the ULA formation, to Proton and Ariane; Boeing only retained market share by moving in with russian suppliers (they run ILS and previously had a large stake in SeaLaunch). ULA was the result of the bottom falling out of the market, and it's not in much of a position to slash anything. They're already barely at break-even, as I've said, most launcher suppliers are.

[magnemoe]

IIRC, there were also a few missiles launched in this manner; there was an anti-satellite missile launched from a zoom-climbing modified fighter jet.

(wiki wiki)

ASM-135 ASAT from an F-15.

Yes, this has the benefit that F15 can already fly high and fast for planes, its also designed for dropping stuff. However the ASM-135 was also suborbital.

The F15 is not capable of reaching 1 km/s and you need 9, main benefit is that you get so high you don't get much drag with an small missile and more important it makes the system mobile so you can use it from any airbase.

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Actually I'm fairly certain its the opposite. Generally upper stages are much more mass sensitive, while lower stages are more robust - adding a kg of mass to the first stage subtracts less payload then adding a kg to the second. Increasing delta vee at all exponentially increases the mass fraction you need, regardless if its performed by an upper or lower stage.

The first stage is more expensive as it is far larger and need far more trust.

you would however put you money in keeping the weight of upper stage down as 1 kg lighter upper stage give 1 kg more payload, or you can make the first stage around 5 kg heavier.

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You're right that it's the tiny payload-capacity that helps to limit Pegasus' market-share. That's more a result of the current market-environment more than anything else. It's been hard for private companies to raise the funds to design and build larger launch vehicles. Big companies like the United Launch Alliance have a virtual stranglehold on the US Market, and use regulatory instruments as a bludgeon to try and stamp out competition. The ULA is greedy and monopolistic, not unlike the history of MANY other giant corporations/trusts throughout US history that dominated their respective markets in the same way... I wouldn't be surprised if they've also been slashing their launch-prices (perhaps even to break-even levels) whenever a competitor firm starts to scare them enough, simply to try and keep competitors out of the market entirely...

Don't even make me BEGIN on some of the legal-drama between the ULA and Space-X, for instance. The ULA tried *very hard* (although, fortunately, unsuccessfully) to make sure Space-X could never get regulatory approval for some of their Falcon 9 re-usability plans... It's a jungle out there, and ULA is the 800-pound Gorilla with a bad attitude...

Regards,

Northstar

Probably as most stuff who fit on a Pegasus can get cheap secondary payload slots.

Exception is if you want to put a small satellite in an unusual orbit here the Pegasus has the benefit of being flexible however most stuff who fly in this orbits are too large.

Some of the low orbit communication networks under planning might change this.

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An suborbital spaceplanes has some benefits, first you reuse the first stage, secondary you have an good chance of recover the payload if something goes wrong.

However its some challenges, first you need to go fast for it to make much sense, you also want to launch decent sized payloads. Now dropping something heavy from a plane in hypersonic speed is a challenge in it self.

Solution is to drop it during the ballistic phase after engine cutoff at 50-100 km attitude, this makes the deployment more like space operations and you don't need fairing on payload, you put the cargo hatches on top as you need some heat shielding on bottom.

However this require an large hypersonic plane something who is expensive to build even if you don't develop new engines, you use jets up to mach 2, then switch to rocket and go suborbital.

The cost of developing the plane is that stops this, also its not so much better than an falcon9 reusable solution who is way cheaper to develop and is more flexible.

Its has been lots of ideas around this but cost and risk has result in nothing being made.

Skylon version 1 would make a lot of sense as suborbital only, much less demanding, cheaper to develop and has an larger payload capacity to orbit than an skylon who reach orbit so for satellites who need an extra stage to go higher than LEO you would just go suborbital and add an larger upper stage.

[KerikBalm]

I was referring to the numerous air-launch systems currently in development (I had no idea that one had already made it). If you've never heard of THEM then how can you say they're not cheap?

If they aren't actually in operation, how can you say they are cheap? Its an unsupported assertion.

There's never BEEN a reusable conventional rocket. So, you're in no better of a position to comment on the costs than I am.

Well, Space X has a reusable VTVL design .... suborbital though. It seems as close (or closer) to becoming a reality as these suborbital spaceplane launches.

The majority of costs for any rocket or spaceplane are in R&D. But, the manufacturing costs are also quite significant- and if you can develop a system that eliminates or reduces these...

That depends... the longer you use a desing, the more manufacturing matters, the less R&D does. The USSR/ Russian kept updatin teir same old launcher and capsule... while the US did mercury, then gemini, then apollo, then STS, now SLS/orion. I tink the soviet/Russian R&D costs are pretty small compared to manufacturing costs now.

*OR*, a suborbital spaceplane (although the Shuttle tiles were also the result of design-choices that could have been avoided). Returning from suborbital velocities involves a LOT less re-entry heat than returning from orbit, which is another reason this mission-architecture is preferable...

The same goes or VTVL rockets.

I don't count bureaucratic costs as part of the real costs of a program. If the only reason something won't work is because the FAA or Congress is being a bunch of whiny brats about it, then the solution is to replace the people responsible or wait until they retire- not to say that there's something wrong with the mission design... As you can tell, I don't have a lot of respect for current politicians and bureaucrats...

I'm with you on this one.

The other issues are innate, physical limits. This is just a matter of arbitrary human behavior that can be changed.

If the US congress has an issue with it... a company could go somewhere else.... preferably closer to the equator.

A suborbital spaceplane could make use of infrastructure already in place in most countries. VTVL rockets require a bit more investment to get the infrastructure ready to go in a near equatorial country.

VTVL rockets would also be unmanned, and facing these human-made problems

That's more a result of the current market-environment more than anything else. It's been hard for private companies to raise the funds to design and build larger launch vehicles.

There are physical limits on the size you can make an aircraft before its airframe is too heavy, or too flimsy.

All that having been said...

Air breathers are more efficient from an energy standpoint...

Fully reusable air breathing spaceplanes would seem to be the most ecologically friendly way of getting things to space (except for space ladders, space guns, etc).

If we imagine some future effort to put massive amounts of material in orbit (colonization craft, etc) suborbital space plane first stages would seem to be the best way to do it.

A prodigious launch rate would help recoup the costs of their reusability.

I'd like to see them one day, but for now, I'm hoping for the VTVL space X boosters to work.

[Bill Phil]

That's why solid boosters are used, when they're used. Making the rocket a horizontally-launched plane is a much more complex solution to this small problem.

Exactly. Although SRBs are also high thrust, which is always better if you want the most efficient possible burn.

[cpast]

I'm with you on this one.

The other issues are innate, physical limits. This is just a matter of arbitrary human behavior that can be changed.

If the US congress has an issue with it... a company could go somewhere else.... preferably closer to the equator.

A suborbital spaceplane could make use of infrastructure already in place in most countries. VTVL rockets require a bit more investment to get the infrastructure ready to go in a near equatorial country.

VTVL rockets would also be unmanned, and facing these human-made problems

Arbitrary human behavior is actually quite hard to change. Just because it's not fun to talk about the issues that have to be resolved, and you have to deal with something that's not just the laws of physics, doesn't mean it's something you can easily work around or that it's not going to kill your project just as much as if there were a physics issue to solve (and it's actually going to be *harder* to resolve than just about anything that's ultimately an engineering problem). Launch sites are also not cheap to build and maintain; there's a reason SpaceX uses USAF bases for launches. Expensive infrastructure is one of those things that tends to not be outsourced unless absolutely necessary; you don't want to build up lots of infrastructure only to lose it to political developments in the country it's located in.

[magnemoe]

One idea I read was to do in flight refueling of LOX, this has the benefit of not needing the heavy landing gear or trust needed to take off fully loaded.

You load up with fuel and take off, meet the tanker. fuel up, continue on jets up to mach 3, start the rocket engine and go suborbital, release upper stage with payload and returns.

This might also be relevant for skylon.

[Superluminaut]

You could probably slap a payload on white knight, however it would be small. Balloons also can't carry too much. Rockets are just much more powerful than airplanes.

[Superluminaut]

I just looked up some specifications. The XB-70 could carry the weight of a fully fueled and loaded f9 upper stage heading for leo. But only to 20km and Mach 3, well bellow the 80km and Mach 10 at which the stage is designed to ignite. Also the XB-70 project cost $750,000,000 per vehicle in 1965.

[wumpus]

One idea I read was to do in flight refueling of LOX, this has the benefit of not needing the heavy landing gear or trust needed to take off fully loaded. You load up with fuel and take off, meet the tanker. fuel up, continue on jets up to mach 3, start the rocket engine and go suborbital, release upper stage with payload and returns.This might also be relevant for skylon.

The obvious problem is the only comparable aircraft is the SR-71 blackbird. If you've ever had the chance to look down the nose of one of those, you will see that its cross-sectional area is *tiny*. Pretty much as small as Kelly Johnson could get it (for obvious reasons). It isn't all that long and it would be hard to imagine it carrying something much bigger than a pegasus (and even that "only" carries 1 Tonne). For something made in the Apollo era (listed as 1966) it still isn't clear that we could duplicate much of it (what can we produce for a superstructure that is better than titanium? My guess is that a modern "blackbird" might not leak: *huge* in lowering fuel costs, and I suspect it desperately needed artificial stabilization (as did the U2), but little real advances in making it a launch platform.Anyone who really thinks spaceplanes are the answer really ought to price out the jet engines needed for such a beast. Modern commercial airlines barely break even (or worse) on 20 minute turn around. If that jet engine isn't in the air/space >80% of the time, things are going to get seriously expensive. Rockets make a lot of sense when the craft is expendable, and fuel use is irrelevant. Rockets make even more sense when you can use them a few times (and SpaceX isn't claiming more than 10 uses for any rocket, and throwing at least one away every Falcon 9 flight).After reading the title I was assuming that this thread was more likely about Skylon flying suborbital flights to NYC or similar. Sadly, it appears to need nearly as much to accomplish that (deltaV around 7km/s) as to get to orbit. I can't see Skylon being remotely profitable either way (orbital or suborbital).

[Nibb31]

You could probably slap a payload on white knight, however it would be small. Balloons also can't carry too much. Rockets are just much more powerful than airplanes.

That's what Virgin is doing as an attempt to diversify White Knight operations. Again, the OP has probably never heard of it.

Edited February 10, 2015 by Nibb31