Sun Synchronous Medium Launcher

[edkyle99]

Atlas E/F, Titan 23G used to put military and civilian weather satellites into sun synchronous orbit from Vandenberg AFB.  Those DMSP and NOAA satellites weighed up to 1.1 tonnes on Atlas and 1.5 tonnes on Titan (not including the orbit inserting kick motor).  Modern versions have gotten heavier, up to 2.5 tonnes or so, but are still small payloads on an Atlas 5 or Delta 4 or Falcon 9 v1.1, which are overkill since they can lift 7-8 tonnes to sun synchronous orbit.  The only solid rocket concepts able to do the job would be Minotaur 6+, which would use six stages or Athena 2cS-4 or -6, which would need four core stages and four or six strap-on boosters.  Neither has flown.

I wondered what could be done with liquid stages and other bits and pieces.  If a first stage was powered by two Merlin 1D engines, 2 tonnes or more could be launched with a 320 sec ISP second stage.  A first stage with three Merlin 1D engines could probably get 3 tonnes to sun synchronous orbit using a similar second stage.  The 2 x Merlin could gross 125 tonnes while the 3 x Merlin could weigh 185 tonnes or so.  Adding a small third stage would fulfill most Delta 2 class mission requirements.

I wonder why this type of smaller/cheaper-than EELV/Falcon 9 size rockets haven't been developed. 

 - Ed Kyle

[Galactic Penguin SST]

Start with a Falcon 5 and cut down the # of engines with uprated engines?

Then again, a RTLS F9 is "only" Soyuz class and the X-company isn't afraid to put small payloads on much larger rockets.....

[bubbagret]

Antares 110 should be right in that range if launched from Vandenberg to an 800km SSO.

[deltaV]

Antares 110 should be right in that range if launched from Vandenberg to an 800km SSO.

Antares 110 has been retired but the replacement Antares 220 should work. See http://en.wikipedia.org/wiki/Antares_%28rocket%29#Configurations_and_numbering .

SpaceX was originally planning a Falcon 5 so they're obviously familiar with the idea of making a rocket like Falcon 9 but with fewer engines. The fact that they haven't done so suggests that there isn't enough of a market to justify the cost of developing and maintaining another rocket. They'll presumably launch this size of payload on a F9 with RTLS first stage.

[rayleighscatter]

There is performance data for the 1 series Antares from Kodiak. Presumably the 2 series should improve on these numbers somewhat.

[llanitedave]

How is such a rocket going to be reusable?  That's the requirement that needs to take precedence over everything else now.  This "smaller, cheaper" Falcon needs to be cheaper than a reusable F-9.

[edkyle99]

Antares comes closest to the idea among current rockets, but it has a relatively heavy first stage compared to the Merlin/Falcons.  It really wants to lift more than it does.  A 3xMerlin with a Falcon 9 like mass ratio topped by a Castor 30 type second stage and a small bipropellant third stage could get 3 tonnes to sun synchronous (800 km) while weighing 90-100ish tonnes less than Antares and producing 140-ish tonnes less thrust at liftoff. 

 - Ed Kyle

[arachnitect]

The steady cadence of launches in this payload category disappeared. Now the payloads are coming back a bit, and wonder where their cheap rides went. Even if the same number of payloads were available, a commercial replacement might still not be possible: 23g and Atlas E/F used surplus ICBM stages.

Titan 23G mostly launched NOAA and DMSP missions.

GPS and Comsats outgrew not only Atlas E/F but Delta II as well.

The DMSP successor (if it ever happens) might end up in a different payload class than NOAA's JPSS (which is much heavier than the Tiros-N and Adv. Tiros-N predecessors).

What will the future hold?
-If OrbATK puts a third stage on Antares it can launch these payloads, even from WFF (if the authorities approve the flight path) but Antares is expensive and will be ineligible to launch DoD payloads.
-Lockheed seems to be very very slowly reintroducing Athena.
-Minotaur rockets might start seeing more activity. I think USAF is looking at expanding the ORS office and giving them some real responsibilities.
-If Spacex can keep their prices down, they'll own this (small) market.
-Customers who don't need to buy an American LV have a lot of choices abroad (Vega, or one of the seventy billion retired Russian ICBMS, etc.)

[GreenShrike]

I wonder why this type of smaller/cheaper-than EELV/Falcon 9 size rockets haven't been developed. 

I would presume because there are insufficient payloads available to justify the development expense, especially when the government seems perfectly happy buying Atlas 5s. And if the new medium isn't substantially cheaper than Atlas, then ULA just plays the ultra-reliable card to remain competitive.

Now that the F9 is on the scene, there's the additional complication of needing to not only beat Atlas 5 on price, but also F9. I rather get the impression that even though Antares was supposed to only be a Delta II replacement, it costs more to fly than the heavier Falcon 9, so I presume that succeeding at such a challenge will take a SpaceX-like attention to cost.

If a new medium is priced at, what, $20m or $30m or $40m to fly (half current F9 pricing, and playing in the ballpark of whatever SpaceX charges for a "proven" F9 core) what's the profit margin going to be? 10%? 30%?

Well, 30% of $30m is $9m, but how much money is it going to take to develop the rocket? F9 was supposedly dirt cheap to develop and it was still in the hundreds of millions. At $100m development costs, that's 11+ flights just to start recouping a profit. Are there that many payloads needing to fly? If there are, could the new rocket win the business consistently, versus the expensive-but-reliable Atlas 5; or the cheap-and-getting-to-be-reliable F9; or even international launchers like PSLV and Vega?

And, in the future, should a large SSO market emerge, there will be the spectre of SpaceX perhaps deciding that there's a large enough market in small sats to justify the engineering time to develop a reusable second stage -- or maybe just a lighter and cheaper expendable second stage. If not, S1 reuse will still make it harder to compete for a new medium expendable, though to be honest I expect that the market would have to grow quite large and quite competitive before SpaceX dedicated any market-specific development time.*

I guess what it comes down to is that larger launchers are capable of carrying the payloads, fly at an acceptable price, and apparently the market going forward isn't large enough to warrant the development a new, competitive launcher.


* Indeed, just like Rocketlabs and Firefly are running the risk of SpaceX deciding a Falcon 1 V2.0 has become viable. Actually, how much would the three-core Firefly Beta lift to SSO? Enough to compete in the SSO market?

[edkyle99]

I wonder why this type of smaller/cheaper-than EELV/Falcon 9 size rockets haven't been developed. 

I would presume because there are insufficient payloads available to justify the development expense, especially when the government seems perfectly happy buying Atlas 5s. And if the new medium isn't substantially cheaper than Atlas, then ULA just plays the ultra-reliable card to remain competitive.  ...

It is interesting to compare Angara with EELV and Falcon 9/Falcon Heavy.  The Russians decided to size their universal module so that it was small enough to be about right for the lighter, high inclination LEO missions, but also so that it could be clustered to create more powerful launchers up to the Heavy class.  I can only wonder if the Angara approach is more or less cost effective than the EELV/Falcon 9 common-core approach.  What is apparent is that EELV/Falcon 9 is largely wasted when used on these relatively light payloads.

 - Ed Kyle 

[Lars-J]

I wonder why this type of smaller/cheaper-than EELV/Falcon 9 size rockets haven't been developed. 

I would presume because there are insufficient payloads available to justify the development expense, especially when the government seems perfectly happy buying Atlas 5s. And if the new medium isn't substantially cheaper than Atlas, then ULA just plays the ultra-reliable card to remain competitive.  ...

It is interesting to compare Angara with EELV and Falcon 9/Falcon Heavy.  The Russians decided to size their universal module so that it was small enough to be about right for the lighter, high inclination LEO missions, but also so that it could be clustered to create more powerful launchers up to the Heavy class.  I can only wonder if the Angara approach is more or less cost effective than the EELV/Falcon 9 common-core approach.  What is apparent is that EELV/Falcon 9 is largely wasted when used on these relatively light payloads.

Only if one works under your assumption that the best launcher for a job is one that is *exactly* sized for that job - no more, no less. In reality almost all cargo shipped on water or roads is done in a standard vehicle that is much larger that technically needed. And it is still cheaper to do it that way than to special produce a vehicle that is a perfect fit. (Reusable or not)

[guckyfan]

Angara is designed the way it is with 1,3 or 5 cores because of transport restrictions. The launch site can only be reached by rail.

[edkyle99]

Angara is designed the way it is with 1,3 or 5 cores because of transport restrictions. The launch site can only be reached by rail.

The URM is only 2.9 meters diameter.  Proton's core is 4.1 meters diameter and is shipped by rail, so I think that URM sizing was not rail-restricted.

 - Ed Kyle

[edkyle99]

Only if one works under your assumption that the best launcher for a job is one that is *exactly* sized for that job - no more, no less. In reality almost all cargo shipped on water or roads is done in a standard vehicle that is much larger that technically needed. And it is still cheaper to do it that way than to special produce a vehicle that is a perfect fit. (Reusable or not)

The difference is that a single ground transport move doesn't cost 10s of millions of dollars.

 - Ed Kyle

[baldusi]

Angara is designed the way it is with 1,3 or 5 cores because of transport restrictions. The launch site can only be reached by rail.

The URM is only 2.9 meters diameter.  Proton's core is 4.1 meters diameter and is shipped by rail, so I think that URM sizing was not rail-restricted.

 - Ed Kyle

Actually, 4.1m on train requires to prevent opposite trains using the same track on certain parts, and was only available to Baikonour. The specs for Voistochny was 3.8m. I believe that length was also an issue since the Eastern track had some tighter turning radius. In any case the Rus-M modules might have been the biggest possible to the East, which was still plenty bigger than the Angara URM. Basically, they could have done twice as big modules with no transport issues. And used the already developed RD-180 to boot, but I'm not going into that discussion. Your point that they sized for the SSO case and then tried to scale to the most demanding missions is perfectly true.

[Lars-J]

Only if one works under your assumption that the best launcher for a job is one that is *exactly* sized for that job - no more, no less. In reality almost all cargo shipped on water or roads is done in a standard vehicle that is much larger that technically needed. And it is still cheaper to do it that way than to special produce a vehicle that is a perfect fit. (Reusable or not)

The difference is that a single ground transport move doesn't cost 10s of millions of dollars.

This is irrelevant when a new launch vehicle development will cost in the neighborhood of $1 billion (or more) - You then have to judge that cost against A) just producing more of the slightly more powerful LV (reducing its marginal cost) and B) the possibility of dual manifesting. Or doing both.

Then the decision to build a brand new less capable LV starts to look questionable. The tool that you have may be overbuilt, but it is one that you have, and using it makes sense.

[Comga]

Let's suppose that Ms. Shotwell is off by 100% and a reuseable Falcon 9 really costs $12M to $14M instead of her $6M to $7M. 
It has an nexisting launch pad with SSO access at Vandenberg. 
What could be developed to compete with that?

[QuantumG]

Let's suppose that Ms. Shotwell is off by 100% and a reuseable Falcon 9 really costs $12M to $14M instead of her $6M to $7M. 
It has an nexisting launch pad with SSO access at Vandenberg. 
What could be developed to compete with that?

Anything that can launch while their backlog is still full?

I don't understand why people seem to think SpaceX can service all the launch demand in the entire world.. even today's demand is beyond them, let alone the massive launch demand they expect to create after they lower these prices so much. There will always be people willing to pay more to fly sooner.

[guckyfan]

Anything that can launch while their backlog is still full?

That won't be long now.

I don't understand why people seem to think SpaceX can service all the launch demand in the entire world.. even today's demand is beyond them, let alone the massive launch demand they expect to create after they lower these prices so much. There will always be people willing to pay more to fly sooner.

That's the market SpaceX is aiming for. Barry Matsumori has announced very recently that this is why they need 3 east coast launch facilities and ramp up production. Once Boca Chica is ready they will be able to launch at short notice like no other launch provider can. Maybe the smallsat companies will be able to match it but not the traditional launch providers.

[QuantumG]

That won't be long now.

That's the nature of a backlog.. either you have one or you're out of business.

That's the market SpaceX is aiming for. Barry Matsumori has announced very recently that this is why they need 3 east coast launch facilities and ramp up production. Once Boca Chica is ready they will be able to launch at short notice like no other launch provider can. Maybe the smallsat companies will be able to match it but not the traditional launch providers.

I don't think you understand.. there will always be a waiting period for the lowest priced launcher. Either that, or SpaceX will not be able to pay the bills. That's the nature of making price your market differentiator. To repeat myself there will always be people willing to pay more to fly sooner.

[guckyfan]

I don't think you understand..

Well, one of us does not understand, it seems. It is what Matsumori stated.

[QuantumG]

Well, one of us does not understand, it seems. It is what Matsumori stated.

Huh? You think that just because SpaceX aims to ramp up production that they're going to be able to meet all forseeable demand instantly? Suddenly SpaceX is beyond basic economics?

[guckyfan]

Well, one of us does not understand, it seems. It is what Matsumori stated.

Huh? You think that just because SpaceX aims to ramp up production that they're going to be able to meet all forseeable demand instantly? Suddenly SpaceX is beyond basic economics?

Who talked about all foreseeable demand? I certainly did not. They will file significant capacity though. Capacity will ramp up from there as will demand.

The 4000 satellites with 5 year turnover will require 800 satellites every year. So if in 5 as indicated by Elon Musk or maybe 7 years they can fly the first 800 they will have very significant capacity in orbit. Ramping that up by another 800 every year should keep up with rising demand.

[su27k]

There will always be people willing to pay more to fly sooner.

Not a lot of people I would presume... To fly sooner you have to have a payload, and I suspect it takes a lot longer to build the payload than readying a reusable Falcon 9.

[simonbp]

The "pay more to fly sooner" market may mainly be USAF wanting on-demand launches to a particular inclination and phasing (in response to a military situation). IMHO that's the market Stratolaunch is going after.

But Stratolaunch could also fill the SSO role that Ed was asking about, and from CCAFS to get cheaper payload processing.

[edkyle99]

This is irrelevant when a new launch vehicle development will cost in the neighborhood of $1 billion (or more) - You then have to judge that cost against A) just producing more of the slightly more powerful LV (reducing its marginal cost) and B) the possibility of dual manifesting. Or doing both.

Then the decision to build a brand new less capable LV starts to look questionable. The tool that you have may be overbuilt, but it is one that you have, and using it makes sense.

If it really does cost $1 billion to develop, but the smaller launch vehicle costs half as much to fly as the oversized vehicle (let's say it costs $40 million less per flight) the payback occurs after 25 flights, or 33 for $30 million, or 20 for $50 million, and so on.

 - Ed Kyle

[guckyfan]

(let's say it costs $40 million less per flight)

Hard to do when the bigger vehicle costs 40 million $ per flight. Or even when it costs 60 million $ per flight.

[edkyle99]

(let's say it costs $40 million less per flight)

Hard to do when the bigger vehicle costs 40 million $ per flight. Or even when it costs 60 million $ per flight.

Whatever Falcon 9 really costs, a rocket that uses 1/3rd as many engines should cost perhaps 1/2 as much, or less.

 - Ed Kyle

[notsorandom]

This thread was started more as a thought experiment than a business proposal. If SpaceX can get your payload to orbit reliably for the best price then of course you go with them and don't care how over capacity the rocket is. However its no fun to speculate about that.

[edkyle99]

This thread was started more as a thought experiment than a business proposal. If SpaceX can get your payload to orbit reliably for the best price then of course you go with them and don't care how over capacity the rocket is. However its no fun to speculate about that.

What I wonder is, since SpaceX, ULA, and Orbital all seem focused on those heavier payloads, whether there is market opportunity for someone else.  In my view it should be possible to undercut the costs of their larger rockets and the infrastructure that goes with them if a system is designed specifically to handle these smaller payloads.

 - Ed Kyle

[Space Ghost 1962]

This thread was started more as a thought experiment than a business proposal. If SpaceX can get your payload to orbit reliably for the best price then of course you go with them and don't care how over capacity the rocket is. However its no fun to speculate about that.

... whether there is market opportunity for someone else.

Antares addresses a smaller market than either SX or ULA (many others too). How has that made them more successful? Answer - not really.

...  In my view it should be possible to undercut the costs of their larger rockets and the infrastructure that goes with them if a system is designed specifically to handle these smaller payloads.

In assembling Antares launch system with infrastructure, OA chose extremely cost effectively to make a go of it. Few could do better like this. IMHO, they risked too much given how it turned out.

Small market and frugal decisions don't necessarily lead to a viable (or stable) business.

And now you want smaller ... cheaper ... still? You'll get more risk, less viable. Don't you already have your answer?

[notsorandom]

There are necessary components to every rocket no matter how big or small the rocket. Some of them can't really be scaled much. Avionics for example will generally be cheaper per kg of payload if the rocket carries more payload. Though the overall rocket is typically cheaper there is a pretty well established trend in price per kg being higher the smaller the rocket's capacity. I suspect that there is a point where this really starts hurting smaller rockets.

[edkyle99]

In assembling Antares launch system with infrastructure, OA chose extremely cost effectively to make a go of it. Few could do better like this. IMHO, they risked too much given how it turned out.

Small market and frugal decisions don't necessarily lead to a viable (or stable) business.

And now you want smaller ... cheaper ... still? You'll get more risk, less viable. Don't you already have your answer?

Antares doesn't fit the market I envision.  It is too big - able to lift more than 4 tonnes to sun synchronous orbit - its design driven by ISS requirements.  (Give me a rocket with only one NK-33 or RD-19x engine.  Give me a small, maybe even mobile launcher rather than the big, complex Wallops Antares infrastructure.)

Last year, 25 of the world's 92 orbital launch attempts were made by rockets only capable of lifting 3 tonnes or less to sun synchronous LEO.  Only one of those 25 was from the U.S. (a Delta 2-7320).    Other countries have even recently developed new rockets of this class (Kuaizhou, Vega, Epsilon), while the U.S. has phased out its capabilities (Atlas E, Titan 23G and soon Delta 2) - which led to the ridiculous examples of Atlas 5 launching 1.2 tonne DMSP and 2.8 tonne Worldview 3 and Falcon 9 v1.1 putting up 600 kg Cassiope and 1 tonne Orbcomm in recent months.  Even one of China's new CZ-5 series rockets is designed for smaller payloads.  What does the rest of the world know that the U.S. seems to ignore?

 - Ed Kyle

[arachnitect]

In assembling Antares launch system with infrastructure, OA chose extremely cost effectively to make a go of it. Few could do better like this. IMHO, they risked too much given how it turned out.

Small market and frugal decisions don't necessarily lead to a viable (or stable) business.

And now you want smaller ... cheaper ... still? You'll get more risk, less viable. Don't you already have your answer?

Antares doesn't fit the market I envision.  It is too big - able to lift more than 4 tonnes to sun synchronous orbit - its design driven by ISS requirements.  (Give me a rocket with only one NK-33 or RD-19x engine.  Give me a small, maybe even mobile launcher rather than the big, complex Wallops Antares infrastructure.)

Last year, 25 of the world's 92 orbital launch attempts were made by rockets only capable of lifting 3 tonnes or less to sun synchronous LEO.  Only one of those 25 was from the U.S. (a Delta 2-7320).    Other countries have even recently developed new rockets of this class (Kuaizhou, Vega, Epsilon), while the U.S. has phased out its capabilities (Atlas E, Titan 23G and soon Delta 2) - which led to the ridiculous examples of Atlas 5 launching 1.2 tonne DMSP and 2.8 tonne Worldview 3 and Falcon 9 v1.1 putting up 600 kg Cassiope and 1 tonne Orbcomm in recent months.  Even one of China's new CZ-5 series rockets is designed for smaller payloads.  What does the rest of the world know that the U.S. seems to ignore?

 - Ed Kyle

The economics of small rockets in the US is weird. Maybe it has something to do with high labor and infrastructure costs? I'm puzzled, for example, at the renewed infatuation with air-launch in the very small "market." I'll bet building and maintaining a launch site in the US costs much more than in other countries. Without a good launch cadence, fixed costs just destroy the business case for a new rocket.

Atlas E/F and Titan 23G weren't so much "retired" as used up. There aren't any more surplus liquid ICBM boosters in the US. Orbital and Lockheed are offering systems made from clusters of ICBM solids, both surplus and derived.

Looking again at the old DMSP/Tiros satellites after seeing this post http://forum.nasaspaceflight.com/index.php?topic=37129.msg1350535#msg1350535 I see that not only were they smaller than JPSS (who knows what the DMSP successor will look like), but they also did the launch vehicles a huge favor by carrying a big chunk of dV onboard in the form of the ISS/Star-37. They don't build them like they used to: we're building bigger, more capable, longer-lived satellites rather than launching frequently. USAF was launching DMSP constantly and they still had coverage gaps.

Spacex is the obvious company to do what you've proposed, they have good propulsion options for 1st and 2nd stages. For now they're trying to build reusable rockets though; we'll see if it works or not.

I don't think ULA is interested in starting another vehicle family right now. They had plenty of opportunities to restart Delta II but they probably can't even sell the last one.

If Alaska keeps subsidizing KLC, Athena could come back from the dead.

OrbitalATK brackets this payload class with Antares and Minotaur. They could build something on top of 3.7m solids, but really they'd only be competing with themselves. The less said about Stratolunch the better.

Who's left? Blue Origin? SNC decides to get into the LV business? Virgin Galactic?

Okay how about a 1 BE-4 first stage (bolt on roll control) 2nd stage is an "undersized" storable bi-propellant stage (preferably non-toxic to simplify ground handling). Vehicle is built up on the pad with a really austere MST (like Wallops 0B). Maybe I'll run some numbers and see if it pencils out at all...

[GreenShrike]

Other countries have even recently developed new rockets of this class (Kuaizhou, Vega, Epsilon)

How much does it cost to fly on an Epsilon or Vega launcher? Wikipedia says around US$32M and €32M respectively, with development budgets of >$200M and €710M. And how much does it cost to fly on JAXA and ESA medium/heavy launchers?  It would be stupidly wasteful to put a 500kg SSO sat on an H2A or Ariane 5. Even an ESA Soyuz isn't so cheap as to have anyone want to use one to lift such a light payload.

By avoiding the cost of heavy launcher, a half dozen or so national launches will see the lighter rockets pay for themselves. Any commercial sales thereafter are gravy. The sheer savings of having a light launcher available for national use probably galvanized their respective governments to finance the launchers' developments. 

What does the rest of the world know that the U.S. seems to ignore?

Which is why I think it's more "have" than "know". They have the development money.

The US government is busy developing SLS, and they're even penny-pinching commercial crew to get it done. So the government doesn't have any spare cash to throw at a small launcher. But do they really need one? Isn't the Minotaur 4-6 series of rockets available and in the right range for throw weight? How's Minotaur-C doing on the civilian side of the market? I don't think its flown yet.

Large US aerospace companies themselves seem to be loathe to spend their own money developing hardware absent a development contract. ATK said they'd build Liberty even if they didn't get into CCiCap, right? Is Lockheed Martin's Athena III a real rocket, or a set of blueprints waiting on a sale to begin production? And who's going to buy the first launch except at a discount? And if the rocket is discounted, who's paying for the R&D? Who's going to roll the dice on a few hundred million dollar bet with shareholders to answer to?

Small US aerospace companies don't have the money for the development of even a light launcher, unless they have a billionaire financing them. Two out of the three of those have a primary goal of Mars, and if they build small, it'll only be as a stepping stone.

Maybe Blue Origin will build their own Falcon 1, but Jeff Bezos has a lot more money than Elon Musk did, so they can start higher up the food chain and not worry about commercializing their experimental vehicle(s).

SpaceX thinks they can get Falcon 9 flights down to some ridiculously low price. Even if they can just manage a mildly silly one, they'll be around the same price with their reusable medium as an expendable light launcher. Oh, and with a F9's lift capability, maybe the sat builder doesn't have to sweat bullets and dollars trimming the sat design down to a svelte single tonne; maybe they can make it a bulky but cheap 2-3 tonnes, and toss in an extra propellant tank for good measure. At any rate, SpaceX believes they already have a launcher that can compete for light SSO launches, so they're not going to spend the engineering time on a smaller rocket.

As for the third company, I'll admit that I really don't see how Stratolaunch is going to compete, but I'm not Paul Allen, so I also don't have to worry about it and can just sit back and hope to see it fly someday. If it doesn't, I'm not going to be stuck with a Roc-shaped hole in my wallet.

So who's left that can finance a new launcher? In a class restricted to around what's apparently a quarter of available launches? Against a half dozen flying vehicles in the same class? *And* who thinks betting against SpaceX succeeding at their goals is at all safe?

Not, I think, the US government, and not large public companies, but possibly smaller companies funded as a billionaire's hobby project. But I doubt it.

[Space Ghost 1962]

Small market and frugal decisions don't necessarily lead to a viable (or stable) business.

(Give me a rocket with only one NK-33 or RD-19x engine.  Give me a small, maybe even mobile launcher rather than the big, complex Wallops Antares infrastructure.)

Fear you miss my point. A light Delta II / Soyuz 2.1v as "commercial" economics may be unsupportable.

Last year, 25 of the world's 92 orbital launch attempts were made by rockets only capable of lifting 3 tonnes or less to sun synchronous LEO.  Only one of those 25 was from the U.S. (a Delta 2-7320).

Agreed about market opportunity. Suggest it is "inaccessible" in America.

Other countries have even recently developed new rockets of this class (Kuaizhou, Vega, Epsilon), while the U.S. has phased out its capabilities (Atlas E, Titan 23G and soon Delta 2)

Delta came from Thor IRBM. Atlas/Titan ICBM. Leveraged development/existing pad. Vega leverages Ariane/other base. Epsilon attempts to evade high H2 development costs for consolidation.

... - which led to the ridiculous examples of Atlas 5 launching 1.2 tonne DMSP and 2.8 tonne Worldview 3 and Falcon 9 v1.1 putting up 600 kg Cassiope and 1 tonne Orbcomm in recent months.

Paid for by not developing EELV/F9 "lite" versions.

...  Even one of China's new CZ-5 series rockets is designed for smaller payloads.  What does the rest of the world know that the U.S. seems to ignore?

There are limits to LEGO/"dial a rocket" architectures. China, Russia, India, ... do not have American industrial base.

The economics of small rockets in the US is weird.

What is different is national policy and industrial support for it.

Funding of "soft power" with a HLV is not for free, especially in America. Nor is a nat sec "launch monopoly" to specifically address a narrow need/cadence/100% reliability demand. OA/SX live in the "remainder" economy.

Maybe it has something to do with high labor and infrastructure costs? I'm puzzled, for example, at the renewed infatuation with air-launch in the very small "market." I'll bet building and maintaining a launch site in the US costs much more than in other countries. Without a good launch cadence, fixed costs just destroy the business case for a new rocket.

Stratolaunch/BO are "big ego plays". Firefly is a speculation to "cling on" to niche market need.  Super Strypi attempts to probe the bottom of the cost/technology of launch - cheap pad/LV/ops for responsive launch. VG is funded too poorly and has other conflicting goals to expect much.

... They don't build them like they used to: we're building bigger, more capable, longer-lived satellites rather than launching frequently.

... In other words, excess launch capacity translated into the need for DMSP living longer without the restrictions of payload.

Spacex is the obvious company to do what you've proposed, they have good propulsion options for 1st and 2nd stages. For now they're trying to build reusable rockets though; we'll see if it works or not.

To accomplish SX mission, they have a disincentive to serve this need with another LV.

The incentive to address Ed's OP is with reusable launch frequency where primary cost is propellant and a fraction of a LV.

I don't think ULA is interested in starting another vehicle family right now. They had plenty of opportunities to restart Delta II but they probably can't even sell the last one.

ULA's replacement of Delta II was EELV Lite. Never happened - end of story for ULA.

If Alaska keeps subsidizing KLC, Athena could come back from the dead.

KLC has been on the edge for most of its existence. The total cost of SSO launch is why Athena has not come back - current launch market is "too cheap" ironically for much interest. Too much risk in "volume" not happening.

... By avoiding the cost of heavy launcher, a half dozen or so national launches will see the lighter rockets pay for themselves. Any commercial sales thereafter are gravy. The sheer savings of having a light launcher available for national use probably galvanized their respective governments to finance the launchers' developments. 

Variation on subsidy. "Gap minimizer". And, given Soyuz ST, unpredictable "payoff".

What does the rest of the world know that the U.S. seems to ignore?

Which is why I think it's more "have" than "know". They have the development money.

The US government is busy developing SLS, and they're even penny-pinching commercial crew to get it done. So the government doesn't have any spare cash to throw at a small launcher. But do they really need one? Isn't the Minotaur 4-6 series of rockets available and in the right range for throw weight? How's Minotaur-C doing on the civilian side of the market? I don't think its flown yet.

Because the market isn't able to support it with reliable cost/volume of launch.

Large US aerospace companies themselves seem to be loathe to spend their own money developing hardware absent a development contract. ATK said they'd build Liberty even if they didn't get into CCiCap, right? Is Lockheed Martin's Athena III a real rocket, or a set of blueprints waiting on a sale to begin production? And who's going to buy the first launch except at a discount? And if the rocket is discounted, who's paying for the R&D? Who's going to roll the dice on a few hundred million dollar bet with shareholders to answer to?

Its not the first launch, it is a reliable manifest with enough frequency. One needs a constant payoff.

And, like with Antares and KLC, launch failures set you back a year or so - need to fund this.

Also, even with billion dollar programs involving multibillion mega firms like LockMart and Boeing, you can be reticent to "play". Atlas V program did everything to minimally address EELV to minimize downside risk - they didn't even want to play, but had to be "encouraged" to do so.

So who's left that can finance a new launcher? In a class restricted to around what's apparently a quarter of available launches? Against a half dozen flying vehicles in the same class? *And* who thinks betting against SpaceX succeeding at their goals is at all safe?

What one is up against is few parts, market fragmentation, lack of repeatability in demand, and the potential for launch costs dropping and launch frequency rising. Not attractive to finance because too many ways to lose.

RD-190/3 et al limited to non defense launches - hmm, there goes an important segment. And the negative propensity for further downside risk from future potential "risks".

AJ/SX engines? Available? If not a F9/Antares "compatible", where would you launch?

Conceivably, the best possibility is a single engine Antares or a three engined F9, each with a "tank shrink". Your costs are smallest, you can qualify for flight easiest, and the same components/systems/GSE would be used in the same way.

Falcon Lite. Antares Lite. "Less filling, tastes great"

[arachnitect]

I've been playing around with rockets built on top of a single BE-4. I'm just using a simple rocket equation spreadsheet, so to say my methods are crude is an understatement.

My original idea of a 1x BE-4 stage with a Delta II upper stage on top was a bit of a disappointment. Something like the Ariane 5 EPS does better, but is probably far too little thrust. Something like Agena lies in between, with the same problem of low thrust.

Centaur or a similar stage powered by BE-3(U) have very good performance, but again I have no idea what the gravity losses are like (bad, I suspect). Also now we're dealing with LH2.

Strapping 4x Falcon 1 second stages together makes a nice 2nd stage for this rocket. Yet again, gravity losses may be in play. I don't expect Blue Origin and Spacex engines to end up on the same rocket, but I use it as a model of a pressure fed hydrocarbon stage.

Looking at RD-0110/RD-0124 it quickly becomes obvious why Orbital was pursuing it. These engines offer good performance, relatively high thrust and without the hassle of LH2. There are some other Russian options, but these would probably be the best choice.

What we have available in the US is very good LH2 stages and lots of solid motors (i.e. missile parts). What we don't have is a relatively cheap and simple pump-fed hydrocarbon or storable fuel engine in the 300 kN range.

[LouScheffer]

Modern versions have gotten heavier, up to 2.5 tonnes or so, but are still small payloads on an Atlas 5 or Delta 4 or Falcon 9 v1.1, which are overkill since they can lift 7-8 tonnes to sun synchronous orbit.  [...]

I wondered what could be done with liquid stages and other bits and pieces.

If SpaceX wanted to get serious about this, they could just put a low-cost second stage on top of their existing Falcon-9 first stage (which will be cheap if re-use works as they hope).   Make it short and fat, so they can build it on their existing equipment, and revive the Kestrel engine, which is pressure-fed and should be cheap.  ISP is not great (~317) but more fuel is a simple workaround when you've got an oversized first stage anyway.

This should be as cheap to develop and cheap to fly as any competitor.  Same tooling, same fuels, same ground infrastructure, already flown engine, an existing (overkill) fairing, especially if they can recover it.  The first stage already exists and has high production volumes and a fast cadence.  Any rocket is going to expend the second stage, and theirs can be super cheap, since it has no need for unobtainium since the first stage has more lift than they need.  No need for fancy alloys, maybe don't even isogrid the tanks.  A crude analysis shows that even with a rotten mass fraction of 10 (25 tonnes of fuel, 2.5 tons empty) and the (cheap) kestrel, they could loft 2.5 tons or so.

I, for one, would not want to try competing with this.

[Space Ghost 1962]

Economics work better to keep US the same as possible, and because you change stage 1, make all your changes there.

So stage 1 is "undersized", stages earlier/lower/slower (reuse?) and stage 2 does the rest of the work.

US economics of design far more difficult to "change manage" and certain economics of function are "baked in".