Right Side Up: A History of the Space Transportation System

With option of 40 metric tons payload under a 6.6-meter-fairing to Orbit
i know what USAF will say "Shut up and take our money"
Even if it is a NASA design, eh? Well, good, that ought to improve the economics for Boeing by a whole lot. And maybe some of that passes on to NASA, in the form of their later Lifter acquisitions being offered for a lower unit price.
On first generation orbiter, who gonna build it ?

Grumman and Lockheed proposed a Lifting body as orbiter during Shuttle design phase
Martin Marietta build for NASA the X-24
Northrop build the M3-F3 and HL-10


The last two were heavy lobbing to get there Lifting bodies space born.

There might be some confusion here. The post showed us a second generation Orbiter. There are references to its predecessor, but none affirming the predecessor had the successor's lifting body design.

We might think that we have something like analogies of HL-42 and HL-20, only backwards, in that order--first they make the big Orbiter, then they rightsize it by shrinking it down later. (We know it is shrunken because of the S-IVB derivative upper stage used--1/5 the engines and roughly 1/5 the mass of the maximum sized S-II). Perhaps I am mistaken and the original Orbiter was also small, a real Flax Orbiter, and no manned flight has ever used the full power of an unballasted all out boost by the Lifter.

But anyway the nature of the first generation Orbiter seems somewhat up in the air--it could be a wide range of things.

The narrative makes me feel that in a just world, it would be Grumman that got the contract, but not necessarily to be laid out as they proposed; Maxime Faget could demand they make his boxcar with straight wings design. The Air Force could horn in at this point and demand it have delta wings and a heavy load of OMS fuel--maybe get slapped back on the latter point and told if they want it to do military aerobatics in the upper atmosphere they can buy one of their own and fill as much of the payload bay as they like with reserve propellant tanks. Or it could be Grumman's or anyone else's lifting body shape of course!

If I can trust Silverbird Calculator for the maximum possible payload to orbit, somewhere between 100 and 140 tons, this is the mass the first generation Orbiter should have. That is, in the same ballpark as OTL, maybe 20 tons lighter, maybe 20 tons heavier. If it masses exactly the same it should still have somewhat improved payload mass capability, due to omitting the SSMEs from the design.

And yet the authors have stated that more grandiose cargo bay capacity--such as championed by the Air Force OTL and installed on all Orbiters--would not be sought initially, with a slightly narrower and much shorter cargo bay. Presumably this means the Orbiter is designed to haul significantly less than 20 tons.

Clearly then either Silverbird is badly overestimating what a Saturn V S-II perched on a Lifter can put into orbit, or for some other reason the Orbiter is chosen to be less than maximum possible capability. Personally I'd like to think someone is capable of sitting down and thinking it through, realizing space planes are for carrying people and that alone, and designs a very small Orbiter that just accommodates a fair sized crew--7, 8 or so--for some weeks in orbit, but any and all cargo, lab space, etc goes in expendable modules stacked between the Orbiter and the upper stage. This unfortunately means a Space Lab type mission either has to have a new expendable lab module built for it every time, or that the lab module sacrifice much of its structure to enabling it to survive reentry separately somehow. And if we desire down mass, that a specialized hollow-shell true space truck Orbiter be built just for that purpose.

Well now--it could be that this is precisely what is happening in the second generation! We have before us a relatively smaller Orbiter, conceivably something bigger than HL-20 but much smaller than the original Orbiter that is indeed nothing but a ferry/habitat for crew, being tested now with a minimal launcher (S-IVB stage) but in future going to go up on many different sizes of upper stage, to enable additional cargo or modules.
 
Even it's NASA design, the option to get 40 metric tons in orbit is to good temptation to USAF to resist.

The post showed us a second generation Orbiter.
could be based on this design (source Unwanted blog)
HL-10-ILRV-2.gif
 
...Before 1971, though, their involvement in the actual design process is basically as IOTL.

Hmm, I am confused, perhaps I should brush up on this aspect of Shuttle Decision politics OTL.

It is my impression that the Air Force was aloof from the whole thing until they saw NASA was on the ropes and liable to have all Shuttle development nixed.

OMB did offer a booby prize of sorts, a minimal program of investigation of very small space planes to be launched from existing heavy evolved boosters--in effect, given the lack of love for reviving or following up on Saturn 1B I suppose that means Titan derivatives. I've wondered if the total collapse of Shuttle and such a low-budged program might be a POD for a Phoenix from the Ashes sort of thing, with a cash-strapped NASA developing a Hermes-like thing that evolves into a more sensible space launch/spaceplane program in the 1980s, and NASA recovering the ability to put small numbers of astronauts into orbit earlier than 1981 due to a little spaceplane being quicker to develop--perhaps even with USAF backing since the little spaceplane would be the sort of aerobatic thing they like.

But that's neither here nor there in this TL since NASA adopted a plan OMB could accept that is more ambitious.

So when I read "as OTL," that means the Air Force is essentially a bystander, correct? Perhaps more attracted than I guessed to the Lifter, but leaving the work of developing and proving it to the civil agency (as is right and proper; NASA, as heir to old N.A.C.A., but expanded, is after all supposed to develop cutting edge X-planes to prove new frontiers, for private industry and the military to then adopt as they see fit). But watching with some anticipation and hope that it will work out and thinking seriously about appropriating Blue Lifters for their own launches. To do that they need new and improved facilities; I don't think any of the USAF pads at Canaveral are adequate to this Saturn V sized thing and they'd need to use the VAB, and to launch from Vandenberg they'd need to build both assembly building and launching pad there from scratch. They probably don't have to match the VAB entirely in California, they certainly did not in the abortive preparations for STS launches there OTL, but it will be a big investment to consider along with the costs involved acquiring some Lifters, not to mention opportunity costs involved in clouding their relations with Martin by the implication that Titan will be abandoned at some point.

But as far as NASA is concerned, the Air Force is just sitting on the sidelines observing, neither helping nor interfering with Lifter development.

Is that it?
 
Even it's NASA design, the option to get 40 metric tons in orbit is to good temptation to USAF to resist.


could be based on this design (source Unwanted blog)

I think I've seen this before but remind me, what contractor drew this up?
The cockpit does not look like it can hold more than two astronauts. What sort of emergency escape options exist for them? Ejector seat and parachute a la Gemini?

I never considered that to be sanely adequate. Perhaps a heavier redesign with the crew compartment being a Soyuz type headlight capsule built in might do, with an escape tower for launch emergencies, and the option of flying the whole thing suborbital for later boost mishaps, the capsule/compartment being also an escape option should main TPS fail on reentry. That would cover contingencies as well as Apollo did.

Or more like HL-20--some sort of heavy solid boosters or some other exotic high-thrust scheme to boost the whole spaceplane free of a launch explosion, and relying exclusively on main TPS to survive reentry--as with the Orbiter OTL. At least I'm guessing such a design would have more robust TPS than Orbiter's tiles (which probably are needed for the ATL Orbiter too, they were carried forward to HL-20 as well though in far fewer numbers) and the spaceplane, like all Orbiters in this ATL program, are forward of the cryogenic tanks that posed the ice hazard OTL. Also I can hope this delta-lifting body thing can perhaps be designed to make a ditching into water survivable, which was not the case with Orbiter OTL.

Any system that involves betting on saving the whole spaceplane could use the cargo bay to lift more astronauts as an option, and provide good habitability for several on extended free flying orbital missions.

The notion of relying only on spaceplanes with cargo bays to lift cargo continues to strike me as bloody ludicrous. Most cargo is up-cargo and does not require the sort of coddling OTL STS proposed to give it.
 
By the way, I've been trying to estimate the magnitude of propellant ballasting and the pattern of payload variation. What I do is get an estimate of the delta-V involved with a fully used stage structure, which is in "mission delta-V" terms about 4000 m/sec for the Lifter and 6000 m/sec for an OTL Saturn V S-II as used for Skylab, pushing a 100 ton payload to 185 km orbit. Then I look at how much delta-V would be accomplished on a 300 ton Lifter with a ballast reserve of 100 tons, which amounts to about 850 m/sec, implying that the remaining 2400 tons could push the whole stack to 4850 "mission delta-V" accomplished. Since this speed is some 20 percent faster the mass ratio, which gives the ratio of propellant mass to non-propellant, is higher for the given ISP of the F rockets, whereas the propellant mass is some 4 percent lower; these combined substantially lower the burn out mass and when we subtract the Lifter with its reserve of propellant to brake it the result is drastically lower--while the maximum stack, upper stage plus payload is a bit over 600 tons the ballasted launch can only be fitted with in the ballpark of a quarter that upper stack. However, the much smaller upper stage has substantially less delta-V to accomplish so overall if the full stack can put 100 tons up, 100 tons propellant ballasting reduces payload, deducting estimated stage mass, to 40 tons! Another 100 tons ballasting is too much, it gives a negative upper stack mass and this means that with less than that, we can achieve maximum speed with the bare Lifter alone. At 150 tons ballasting the upper stack falls to 60 tons but with some 1500 m/sec extra delta-V nearly a quarter of this, some 13 tons, can still be payload. The upper stack mass will thus fall off rapidly to zero in the range of say 160 tons ballasting, but the extra velocity the upper stage gets raises the payload these small stacks can deliver, meaning a more linear fall off.

I'd guess NASA would not want to go much lower than 13 tons payload, because the cost of using the Lifter is fixed. Getting many launches out of one amortizes its unit acquisition cost and perhaps aspects of its design cut routine processing costs, so at a wild guess say each launch costs to 20 percent. It would still be cheaper to launch an old-fashioned Saturn 1B and expend it than use a Lifter if in fact the 1B first stage cost less than 1/5 that of a Saturn V first stage. I'm guessing this is about the cutoff; above that level some savings are being realized at least versus EELV. What kind of savings dow we get versus a bog-standard Saturn V launch for 100 tons? Well, the first stage is about 80 percent of the mass, and figuring costs are roughly proportional to mass overall, by saving 80 percent of 80 percent the cost overall is 36 percent for the same result. Thus for a budget allowing 200 tons to be launched in one year on two expendable Saturn V, over 500 could be launched with maximal use of the Lifter, actually 555. Or, one Apollo mission to the Moon a year costs a fifth the budged NASA was spending to send two a year and matching that rate during the Apollo program costs 40 percent as much.

OTOH I think if we think in terms of 40 ton payloads versus routine use of an EELV right-sized for that, it costs 60 percent as much--but of course we've also saved the cost of developing something with 40 percent the capability of Saturn V so we are better off than that, and the same booster we use for that one day we can next time use to launch an entire 100 tons.

Using this sort of estimate, however the 13 ton payload mission will cost some 60 or 70 percent more than having a right-sized EELV handy.

All of this depends on a lot of guesses, but it is suggestive I think. At some point there would be a break-even point for small payloads below which it is expensive to go per ton, but for very large loads the savings are tremendous. How much so depends on how many reuses one can get out of a given Lifter before it must be scrapped, or vice versa before incremental repairs and maintenance have matched the original cost, and if the operational costs of integrating in the Lifter can be reduced by orders of magnitude below those of using a much smaller expendable booster.
 
Even it's NASA design, the option to get 40 metric tons in orbit is to good temptation to USAF to resist.


could be based on this design (source Unwanted blog)
HL-10-ILRV-2.gif
Now a followed timeline, thanks folks :)

On the Air Force and the "Shuttle" it depends on which "Air Force" we're talking about because there were in effect two semi-separate "groups" when discussing AF input. The first group was the regular Air Force who were nominally 'in-charge' of DoD and military launch capability which was lukewarm at best on the whole Shuttle and less than cooperative with NASA in general. They were in fact the ones who gave the 'specifications' attributed to the Air Force for the Shuttle design but they were in fact confident that they would neither be required to use the Shuttle nor have to contribute to it and would retain their planned Titan LV development. Then there was the actual segment of the Air Force who along with the CIA and NRO in general were actually tasked with and developing the "spy" satellites the other group was launching and which were well aware from multiple sources that they WOULD in fact be forced to use the Shuttle if NASA got it rolling and tried to inject some sense and actual requirements into the specifications being given to NASA. (They actually suggested a smaller Shuttle and cargo bay)

Since the latter was part of the super-secret NRO and were not significantly 'high' in the visible AF space launch system food-chain, NASA went with the former groups requirements whom suddenly found out that they were going to be forced to use what they'd asked for. Karma :)

In general the major question is not capability or payload per-se but general operability for what the Air Force "needs" (both groups) versus what the Lifter provides. As per OTL the AF needs/wants to be able to launch out of Vandenberg so there would be a dedicated launch facility as per OTL-Shuttle launch complex built and similar payload losses due to the Polar orbit dogleg. On the other hand I'm pretty sure that as per OTL there will be more than a little resentment and resistance to piling all the DoD payloads into the Lifter basket.

As for the "Space Shuttle" builders let's not leave out McDonnell-Douglas who were still pushing their FDL-5 based TAV/Shuttles into the 80s:
http://pmview.com/spaceodysseytwo/spacelvs/sld057.htm, and the various Rockwell designs such as the 45T: http://www.astronautix.com/v/vtohl45t.html. Most of the "Phase-A/B" companies will still be in the running and that's not counting various NASA center designs or outliers like Salkelds "tripropellant" concepts.

Something to keep in mind is that main 'problem' with the Lifting Body designs was the same all the way through the development and right up the X-33; They couldn't get the propellant to 'fit' as they suggested within the mass and structural limits. Making acceptable cylindrical tanks for the LH2 was tough enough, they found making 'lobed' designs almost impossible in practice until the late 80s and even then they were in efficient and massed more than cylindrical tanks for the propellant load. That's why none of the actual LB designs made the Phase-B cut.

The Air Force AND NASA were aware of this since the mid-late-60s when the idea was first proposed, (see:http://www.aerospaceprojectsreview.com/catalog/spacedoc52.jpg) when it was proposed to "modify" a Centaur stage for an orbital M2F2 concept and found not to work. The closest a contactor came to admitting the issue was General Dynamics which at least suggested simply fitting an 'aeroshell' over cylindrical tanks, (http://www.pmview.com/spaceodysseytwo/spacelvs/sld020.htm) but in the end that's what 'everyone' ended up going with because doing otherwise was just not going to work with LH2.

At the time NASA was enamored with LH2, meanwhile the Air Force liked it in 'theory' but not in operation and tolerated it in the Centaur for performance only. (Which is funny given their pushing the "SLS" Solid/LH2 concepts in the early '60s, but I suppose having lost that particular race they really didn't look back much despite constant "studies" for various space launch systems requiring LH2) The Air Force was actually more willing to 'deal' with alternatives to LH2 if they had to and frankly were operationally more interested in anything BUT LH2 for most uses unless there was no other choice.

Boing did a lot of lobbying and political pressure to get the Delta-IV and basically, in the end the Air Force was 'ordered' by Washington to use the Delta-IV even though they preferred the Atlas-V. (And despite using Russian engines and lack of US 'support' the Atlas-V was the only one of the two EELVs that was still 'commercially' viable without said 'support')

And while Lifting Bodies are 'cool' and all, really unless they ARE mostly "empty tanks" they have significant issues with landing speed and operations compared to a wing-body or combined wing/body design.

Randy
 
I think I've seen this before but remind me, what contractor drew this up?
The cockpit does not look like it can hold more than two astronauts. What sort of emergency escape options exist for them? Ejector seat and parachute a la Gemini?

Looks to be the McDonnell Douglass Phase-A (http://www.pmview.com/spaceodysseytwo/spacelvs/sld023.htm) concept. And no there was no 'escape' system in the designs, this was supposed to be as safe as any 'normal' airliner, (and considering how far we've come even there, and how far things had come since the 30s TO that point they weren't "wrong" in thinking that was a good thing) so no escape system was needed. And the 'rest' of the crew and passengers would be in a module in the bay for transport. Recall this wasn't our "Shuttle" which had to act as a mini-space station but a "shuttle" servicing one or more Space Stations. Note the use of 'capitals' there ;)

I never considered that to be sanely adequate. Perhaps a heavier redesign with the crew compartment being a Soyuz type headlight capsule built in might do, with an escape tower for launch emergencies, and the option of flying the whole thing suborbital for later boost mishaps, the capsule/compartment being also an escape option should main TPS fail on reentry. That would cover contingencies as well as Apollo did.
Or more like HL-20--some sort of heavy solid boosters or some other exotic high-thrust scheme to boost the whole spaceplane free of a launch explosion, and relying exclusively on main TPS to survive reentry--as with the Orbiter OTL. At least I'm guessing such a design would have more robust TPS than Orbiter's tiles (which probably are needed for the ATL Orbiter too, they were carried forward to HL-20 as well though in far fewer numbers) and the spaceplane, like all Orbiters in this ATL program, are forward of the cryogenic tanks that posed the ice hazard OTL. Also I can hope this delta-lifting body thing can perhaps be designed to make a ditching into water survivable, which was not the case with Orbiter OTL.

Any system that involves betting on saving the whole spaceplane could use the cargo bay to lift more astronauts as an option, and provide good habitability for several on extended free flying orbital missions.

The notion of relying only on spaceplanes with cargo bays to lift cargo continues to strike me as bloody ludicrous. Most cargo is up-cargo and does not require the sort of coddling OTL STS proposed to give it.

Airliners crashed, while not as 'regularly' as they did previously but they still tended to have accidents on a regular basis so if "space" is as safe as flying... All the same arguments for NOT having that capability that applied "at-the-time" still apply in this case, more so with a more restricted and constrained "orbiter" which is where this is going. I suspect part of the 'right side up' turn here is that having a large 'bay' is less of an issue as you can still use various 'upper-stages' with the Lifter. That however means that passengers and "some" cargo are still going up in the Orbiter at some point and IF you are doing that they live-and-die with that vehicle.

This isn't as cut and dried as it would seem as this is the same attitude that you end up with for any 'space transport' that is going to be in "regular" operation. From "shuttle" to SSTO concepts the main idea was to make them 'as-safe' as airplanes which in fact do not have 'escape systems' or life-boats per-se. The idea is to engineer the 'safety' into the vehicle not into a separate system IN the vehicle.

As you may be aware I'm a firm believer in "spacecraft-are-not-aircraft" school so I don't subscribe to that line of thinking but in fact ALMOST ALL designers and engineers of the time did so and designs were done accordingly. I am also not wedded to the "wings-and-wheels" and "spacecraft that 'fly' back are the only reusable spacecraft" school either but again the majority WHERE and planned accordingly. (For that matter most VTLV designers were also quite willing to let the passengers 'live-or-die' with the vehicle. Philp Bono of ROMBUS fame included an escape capsule for the 'flight-crew' and windows so the two hundred passengers could watch THEM whoosh away from the disaster THEY were headed for so... :) ) I also happen to be a minority that thinks that @10,000lbs of 'cargo' and less than 50 passengers, launched more often makes more sense than trying to put hundreds of passengers and 100 tons of cargo into orbit once every couple of months makes WAY more sense but, again, I'm in the minority :)

As far as I can see the Lifter is 'huge' and will have a correspondingly large "Orbiter" when it gets to that point if for no other reason than it CAN put up such an orbiter. It won't be prefect but it will have to perform as its own 'stage' so unless they go with external tanks, (still a real possibility) it will actually be better in some respects than OTL Orbiter but under the circumstances I highly doubt they are going to slap some SRBs on the outside 'just-in-case'

Randy
 
Clearly then either Silverbird is badly overestimating what a Saturn V S-II perched on a Lifter can put into orbit, or for some other reason the Orbiter is chosen to be less than maximum possible capability.

Or, Maybe, You're not going to see S-IIs as the second stage, but just improved S-IVBs.
 
Or, Maybe, You're not going to see S-IIs as the second stage, but just improved S-IVBs.

Of course the actual specs have yet to be published.

I base my guesses on the fact that this is a Saturn V derived vehicle, and also that the economics per ton will always be most favorable with maximum upper stack mass.

We know we are using F-1A derived engines--derived in that they will presumably undergo some redesign to make them many-times reusable. As I understand it the F-1A off the shelf already had remarkable endurance in test firing, so these modifications would not be tremendous. I see no reason to downsize the thrust since the easiest way to do that is to use fewer engines, and the sort of modification I'd expect would be a combination of making parts stronger thus somewhat heavier, and attention to easier access to parts in aid of inspection and refurbishment.

So with identical thrust we have something over 800 tons per engine thrust at sea level--an 18 percent increase over the original F-1 at both sea level and in vacuum and I assume in all regimes between. The total stack mass can thus be 18 percent more than a Saturn V as used historically--indeed it could be more, but then we'd get a more sluggish liftoff and lower burnout speed. The latter is good insofar as it means less stress on the Lifter stage aerobraking down to cruise speed for flyback, and so I think it is conservative to estimate they will want to match the Saturn V's performance in boost, and thus using the extra 18 percent is reasonable for a design maximum. And they could go even bigger but it means the upper stage must accomplish more delta-V and other consequences, which despite lower airspeed might not all be acceptable.

As it happened, as I posted well above, with my wild guess of a 300 ton post-boost/braking mass of the Lifter, the same S-II as used for Skylab fits very closely. Why not use it? It is already developed.

My guess is as the program shakes down in the Mark 1 phase, that several stages will be designed. The Skylab version of S-II will be standard maximum, though as I say they could go even bigger. We already know something like S-IVB will be used for smaller loads. Three intermediate sizes using 2,3, and J-2s engines with maximum tank volume in proportion can be made, but I think the program will just develop the 3-engine version. This gives three types, and each one fully loaded with propellant will give a payload to orbit. My attempts at estimating just what these would be are very tentative, requiring me to know all kinds of things I don't really but the ballparks and pattern will hold I think.

The nature of the propellant ballasting strategy is to cause a rather sharp fall off of upper stack mass, that is orbital boost stage plus payload (plus fairings, launch escape system etc that have a lower and nonlinear impact if they come off before the Lifter burn is finished, but I'm making no attempt to factor them in). But this is because the ballast propellant, acting on the modest mass of the post-braking Lifter (dry mass plus fuel needed to fly back) accomplishes rather dramatic braking, up to around 1500 m/sec when we near upper stack mass being zero, and that speed also represents an increment over standard burn-out speed that lowers the burden of the upper stage. Thus upper stack propellant fractions fall significantly offsetting the sharp fall in total upper stack mass, and payload masses come down from the maximum rather sluggishly at first, in terms of mass of ballast propellant reserved. When we get down to S-IVB appropriate masses the payload has fallen a lot, to around 20 tons and under, and we are getting into a regime where even gung-ho Lifter fans will concede it makes more sense to use a smaller disposable booster. (They might suggest making a very small reusable mini-lifter for this range). Also the economics of using the Lifter are tremendously beneficial if we can assume a really dramatically lower cost for each Lifter burn compared to the cost of a one-shot S-1B, but compared to a theoretical expendable booster right-sized for each payload the Lifter-lowered cost per ton rises until it equals the expendable launch, and then costs more below that. The S-IVB scale is about where I think this turning point would be. And if we go much smaller, the total stack mass plummets rapidly to zero.

Thus what happens next depends on how the "market"--taxpayer funded NASA, DoD, and possible private purchasers--reacts to any savings the system offers. Maximum economy will always be with maximum total payload and that suggests a strategy of a number of launches a year where both NASA and DoD drum up customers with deals to max out the load, with large numbers of spacecraft being launched shotgun style in big batches.

In that case, the big S-II will be the most in demand.

If we assume that orchestrating such big batch launches turns out to be difficult and that realistic payloads fall more in the 20-50 ton range, then I guess the 3-engine middle stage would be most in demand. And if the majority of launches are penny-packet deals where each customer requires their own launch and that falls below 20 tons, then the small single engine stage dominates demand.

But part of the rationale of making such a gigantic booster in the first place is, that sometimes someone will indeed want to launch something--a Skylab type space station for instance, or several modules to make a really ambitious one, or a second iteration of Apollo moon missions, or what have you--that pushes the capacity to the limits all by itself.

For that they will need a capability to install at least an S-II if not something even more grandiose!
 
Thank you for bringing this to my attention. :p

Ranulf was talking about upper stages here. One severe problem with simply wrapping a standard upper stage in an airframe with TPS is that venting and leakage from the tanks is trapped in the airframe and can easily create hazards. This is most especially so when fuel is hydrogen.

In this thread the whole problem of attempting ambitious recovery of upper stages is postponed, perhaps indefinitely. The booster stage in the Saturn V was 80 percent of the total mass, saving money on that stage with reuse dwarfs the savings that might be achieved, by more elaborate and expensive means, to recover the upper stage or useful parts of it.

So although continuing to use expendable upper stages is a bit of a deviation from the ideal of a reusable launch system, this is after all an interim system. Upper stage engines are J-2S which aren't nearly as costly to make as SSMEs would be--nor has the TL sunk any money or effort into developing SSMEs, so that's resources available for something else.

The Triamese concept Ranulf's link goes to is interesting enough but as RC says, it doesn't work well.

I found the separation speed amazingly low.
 
Ranulf was talking about upper stages here. One severe problem with simply wrapping a standard upper stage in an airframe with TPS is that venting and leakage from the tanks is trapped in the airframe and can easily create hazards. This is most especially so when fuel is hydrogen.
Well, I was more talking about the interesting concept of an Atlas flyback booster combined with a Centaur derived shuttle. Yes, it has its problems, but it is an interesting concept from the 60s. And Scott just got 4 bucks from me for the document... :p
 
The Air Force AND NASA were aware of this since the mid-late-60s when the idea was first proposed, (see:http://www.aerospaceprojectsreview.com/catalog/spacedoc52.jpg) when it was proposed to "modify" a Centaur stage for an orbital M2F2 concept and found not to work. The closest a contactor came to admitting the issue was General Dynamics which at least suggested simply fitting an 'aeroshell' over cylindrical tanks, (http://www.pmview.com/spaceodysseytwo/spacelvs/sld020.htm) but in the end that's what 'everyone' ended up going with because doing otherwise was just not going to work with LH2.

Now there's an interesting concept, though I have to wonder about how easy it would really have been to reconfigure a balloon tank for the loads of winged flight. The S-IC, like a lot of Saturn hardware, was built like a locomotive by comparison--I wouldn't want to be in the pilot's seat if the Atlas core suddenly depressurizes!
 
I see I haven't commented yet, which is mostly because, as always, most of this material is a tad too technical for me to make any valuable comments. However, in more narrative terms (a domain I'm more confident to comment on), I really like the way these updates are set up in different launch phases, the launch of the phase two space shuttle giving us an insight into where the TL is going. I wonder though what the scope of the story is going to be, as so far it's been mostly concerned with the contract wrangling so common to large aerospace projects. But then we are still in the early phases of course.

Not sure if the Soviet Union will get a spot in the limelight here, but I'm nonetheless curious what their response to a flyback booster would be. Shameless copying does not seem in order here, unless they think that their already-broken N1 project would work better with wings on the first stage. It would be a true spacecraft horrorshow!

Thumbs up for this TL and the flyback Saturn, and I'm eager to see just how ambitious the US space program will get once launch costs start going down.
 
Actually, though I think the N1 is too far gone at this stage (both technically and politically), something Shevak has commented on before might well be technically possible, and perhaps inspired by what is being designed here with the Saturn flyback. The very 'Fuel ballasting' method, to brake the first stage for re-entry at lower speeds, could well happen for the N1, perhaps with some crude effort to use the engines or parachutes to recover it. Frankly I think in practise it would likely be a disaster. Probably well covered up, but in time it might work. After a lot of failures. Again, I think that though the N1 has possibilities, it's already too far gone in this TL to be used. Russia has already moved on from that nightmare and has a new disaster. At least one that OTL became much more reliable... eventually :) That one however, by it's shape, might well be far more tricky to work for stable re-entry without rather complex control systems to stabilize it. Reusable Protons (are they called that yet? I forget when the name was applied) again might be possible, but the teething troubles and the shape might well make them ignore attempting to make a re-entry system for it.

True. I really don't see them attempting to redesign one of their own existing first stages to be a fly back booster. However OTL that wasn't what happened with Buran anyway. They really did attempt to copy it pretty well. Here, if the inclination comes, it's far more likely they'd do the same. Attempt to use some of their existing, proven engines on a frame that mimics the Saturn flyback. But with the infighting in the Politburo and their space agency(ies), even after things have stabilized a little, this could well fizzle and leave them struggling to find their own grand effort to make it seem as if they are doing something the Americans are not.
 
...Not sure if the Soviet Union will get a spot in the limelight here, but I'm nonetheless curious what their response to a flyback booster would be. Shameless copying does not seem in order here, unless they think that their already-broken N1 project would work better with wings on the first stage. It would be a true spacecraft horrorshow!...

Ah, but there is one feature of the Lifter that might be targeted for improvement in a later iteration--and that is, it is bloody huge. It is going to be most economical, on a per ton to orbit basis, at maximum lift, in the 100+ ton range. Excellent for putting up a really big space station fast, in big modules, or a return to Luna mission cheaper than Apollo. Or launching a big Orbiter, which I do believe has its place. But if the Monday-morning quarterbacking wiseacres are correct, we would rarely need 100+ ton capacity and can get by with any attainable ambition, even say a Mars mission, on 30 tons or so. Maybe less and if OTL experience is a guide, payloads smaller than that will dominate the market. Getting really good economy out of the Saturn V based Lifter will require getting "customers" to agree to bundle their payloads in big batches, and to maintain a launch rate even as high as STS averaged OTL, 8 times a year, would require that the total "market" for tons to orbit average something like 5 times OTL. The payloads themselves are a big cost item, so it means that the ATL Western nations increase their overall spending, from all sectors (US military, foreign allied military, NASA, foreign civil science programs, and commercial both US and abroad) and that also assumes Lifter sucks all the oxygen out of rival launchers--those patronized by the USAF, European and Japanese ventures, everything gets sucked into Lifter from Cape Canaveral or Vandenberg. Or the USA expands its Saturn V capable launch sites. At one time a plan for STS was to develop a Texan coastal launch site near Houston for instance. Could the USA wind up cooperating with Europe to the extent that we lease facilities at Kourou--bearing in mind that Kourou was invested in by the French and others because they could see that STS was not economical and a market niche for Ariane existed? Kourou is a nice site, very near the equator and if I believe the site's web page blessed with a lower incidence of tropical storm related bad weather than Canaveral. But clearly a European space alliance is not going to feel great about relying on an American made booster exclusively, even if they do have more say about Kourou or distant Woomera than they do about US soil sites.

So if it works to justify the price of building and maintaining a Lifter Mark I based system, all the better for us space nuts, but we are looking at an ATL where the total space budget across the Free World has mushroomed tremendously, and yet tolerates a Yankee monopoly on launches. It seems more likely to me that for Lifter to keep itself that busy, efficiently, the market must balloon to even higher levels making room for nationalism to develop rivals overseas with NASA/USAF handling only a portion of the total tonnage.

Otherwise, the market will top out at levels considerably higher than OTL, but either making markedly less efficient use of the Lifter with a comparable number of launches, or very very few launches indeed maxing it out. Which entails higher per launch costs in terms of the fixed annual infrastructure the sites and production factories must maintain year after year thus further undercutting potential economies. The higher the average cost of a ton to orbit, the more competitive feasible foreign or conceivably private developed US rival schemes would be.

Now then look at N-1 again. Post-mortem, the fundamental problem with it is that its development was, in typical Soviet fashion, scanted of pre-launch tests, and to a hard to estimate extent, its design with 24 engines on the first stage was inherently risky. Furthermore, it was being stretched to an unreasonable degree to hit the minimum mass to orbit necessary to sustain a Soyuz L/LK lunar landing mission, which IMHO they should have resolved by going to a two-launch strategy, scaling back the goals for a single launch to something more reasonable and observing that the load lifted by two launches would allow much more generous margins for their moon mission. It may be that the inherent flaws in Soviet development bit them too hard on such a grand scale to be sustained by any approach. And it may be that 24 engines is too many for anyone, although the large numbers of engines used in other systems that have enjoyed good success, such as Saturn 1 or Falcon 9, suggest this was not as awful a hurdle to clear as it seems--admittedly, 24 is a heck of a lot more engines than 8 or 9!

OK, then, let's say the Soviets bitterly agree that N-1 was just too bloody much for them, and that to match the Yankees going head to head with them would merely compound the folly and waste.

Very well--what of a much smaller "Lifterski" that uses just say 4,5, or 6 of the engines developed for N-1's A block? Offhand we can see it would have a lift to orbit comparable to Proton, which they already have. (However, as late as 1972 the dang thing still had not cleared the hurdle of Soviet certification as standard equipment, such was its failure record up to that point). It might work out to be somewhat better than Proton to be sure, and if the Americans have their heads screwed on right, Soviets too ought to enjoy major economies by recovering and reusing the booster many times. Their maximum capacity would remain limited to Proton levels, but the wiseacres say that is good enough, or would be with 10 or so tons increment.

Suppose instead of 24 engines (in some versions, kicked up to 30!) the Soviets were to develop a flyback booster of their own using just say 7 of those same engines?

As it happens, the Soviet engines were designed for somewhat higher ISP (at sea level and in vacuum, designed for sea level optimization of course) than the F-1A attained. I picked 7 engines because that forms a hexagon with a 7th engine packed neatly in the middle. It might be better to forego that engine since it suffers a worse battering by being surrounded by 6 neighbors, the outer ring of them having only 3 at most in such proximity--reduced to just 2 in case a 6-engine hexagon is chosen, though the more distant ones would contribute to problems too. The seventh engine would raise wear and tear on the outer ring and be much more battered by that ring, by a factor of 2 or more. The only J-2 to fail in Apollo was a center engine after all.

Still, let's look at 7 for a moment anyway. The first stage engines developed for N-1 were designated NK-15, with modified versions for the upper stages but set that aside for the moment. I get somewhat conflicting data from this source, Brügges's site versus Encyclopedia Astronautica which he also cites but criticizes. Combining their inputs conservatively, what we have is an engine that can produce at least 140.6 tons of thrust at sea level, with a vacuum ISP and thrust of 318 sec and 1544 KN respectively. Each masses 1250 kg, so taking 7 of them gets us 984.2 tons of lift on the pad. They are designed to burn for at least 113 seconds, and consume 495 kg/sec each, thus seven of them will consume at least 391 tons, more if they can burn longer. Assume that the Soviets decide to go for a moderately more conservative burn out speed (at max payload; they too will be using propellant ballasting) such that delta-V at that point is 3600 m/sec, say burn is extended to 120 seconds for total propellant mass of 416 tons, about 1/6 the tonnage I guessed for Lifter (2500 tons). This implies a maximum lift-off mass of 610 tons, about (1/5.6) times the American system. Say the post-braking mass of the stage is 60 tons all up, which might be an unfairly high estimate. This leaves merely 134 tons for the upper stack, which must attain orbit from a lower speed than the American version. With the burnout speed being less than 90 percent the American (delta-V is less by that amount, but both systems must lose real velocity to gravity loss and air drag so the 400 m/sec difference will count for more) the aerodynamic drag will be far less on the Soviet version, so 1/5 Lifter braked mass is probably a gross overestimate, we ought to be able to transfer 10 tons or more to the upper stack. But let's roll with 60 for the moment.

Soviet launchers have a tendency to go for higher G loads than American, which cuts gravity loss significantly, such that perhaps the Soviet upper stage has less mission delta V than the American, not more--the 400 m/sec deficit already made up to an extent by lower gravity loss in the booster burn (some 30 seconds less burn time) and heavy upper stage thrusts can close the gap further or surpass it. Let us conservatively guess that the Soviet upper stack has 6 km/sec delta-V to provide, and must use developed Soviet engines and tankage, either derived from N-1 using more ker-lox or from Proton using hypergolic propellant. On this page, look at the N-1 Block G, the fourth stage. Brugges gives the all up stage mass as 59 tons, 56 of which are propellant, with a single NK-19 engine of thrust 451.1 KN and ISP of 345 sec (!). It does seem unlikely this would be adequate for 74 tons of payload (what we need to match up the mass) but the 3rd stage, V block, is clearly much too large. I'd have to iterate around a lot in Silverbird Calculator (which is probably valid to use since I am estimating a maximum payload version here).

Indeed Silverbird gives just 13 tons here which is not terrible compared to R-7 but does not even match Proton. But it also falls short of the upper stack maximum by some 62 tons! Let us assume a comparable distribution of stage to payload mass for the maximum--82 percent booster--so we need a 110 ton booster which is nearly double the G block estimate--raise the net mass by that amount, doubling the thrust as well.

I took this approach some iterations and also considered substituting a single NK-15V engine, which has the advantage that it is essentially the same as the first stage engines but vacuum optimized, so its construction cost will be more economical than using a more divergent engine or set of them, offsetting somewhat inferior performance. At most we get around 16 tons payload, which is inferior to Proton of course, and about half that magic 30 ton goal. Perhaps going back to the drawing board with 9 engines instead of 7? This is no worse than Falcon 9 after all and about the same as Saturn 1 so why not? That would close the gap with Proton.

Speaking of Proton, what happens if we scale down the Mark 2 second stage, data for which can also be found at Brügges's site? At 2/3 the standard stage mass, we would have 7.8 tons dry, 104 tons of propellant, and an engine set delivering 2352 KN at ISP 327 sec. That only delivers 14.5 tons to orbit.

Well then, let us look at what 10 engines can do!

Raising propellant and dry mass in proportion, and with it the first stage burnout mass, we would of course raise the upper stack mass to 191 tons. Using a 156 ton stage derived from the G stage of N-1, with a 9 ton dry mass and thus 147 tons of propellant and 3 engines...I iterated a few times, and with upper stage mass being 10 tons dry holding 158.5 tons propellant, the payload comes in just over 22 tons, more than matching Proton payloads to LEO.

Considering the very large thrust margin, we can probably put bigger stages on it too. Note that the gross mass of the upper stack is larger than Apollo's lunar stack atop a full S-IVB, so if the Soviets develop hydrogen engines they will be able to multiply their capacity further still.

Meanwhile with propellant ballasting, this booster can also launch smaller payloads. But being much smaller than the American version (post-braking mass 86 tons and holding 594 tons of propellant) it will be cheaper to develop and maintain. Thus even allowing for Soviet inefficiencies and a late start, they might well have it operational in the same time frame the vaster American version is, or perhaps even sooner. It would be called upon to launch lighter loads only rarely compared to the American version, and its economics would more aggressively cut Soviet launch costs until Americans developed a smaller version themselves, if optimism about filling 100 ton payloads for frequent launches turns out not to be warranted. Meanwhile the Soviets can contemplate going even bigger, or multiplying their payloads by developing high altitude hydrogen engines to replace the ker-lox interim second stage with. Simply swapping in the ISP of a J-2 and throwing in a ton of dry mass penalty, I suddenly get over 37 tons to orbit! I suppose I should have put more tons of load into the stage dry mass, but clearly by using hydrogen there there is very much to extend the capability--even bearing in mind the need to scale down the propellant load.

So that is something Ivan can do. And note that if a ten-engine booster is too risky, a 5 engine booster that begins with a mere 8 tons to LEO capability can still replace the R-7 system, and developing hydrogen engines for its upper stage can put it back in the Proton-rivaling game.

Six engines might be about right.
 
All right! Now I'm excited! Here's the program I'd recommend to the Soviets:

Design the basic Lifterski around a nominal 6 engine plan, but leave room and permanently installed plumbing for a seventh engine filling the hexagon, expanding the kerosene tankage by 1/6 and adding a drop tank on the belly for the oxygen. Further expansion can allow for up to three belly strap-on modules bearing up to three more engines for a total of 10, compromising reusability of course as these and the oxygen tank for 7 engines are disposable. But also they can delete engines from the basic six, instead of propellant ballasting. Perhaps avoid propellant ballasting completely!

The basic 6 engine design, a bit overweight to be sure, should be quite capable of launching a Soyuz with a ker-lox upper stage, and competitive with Proton with an advanced hydrogen engine upper stage; these are of course always disposable.

OTL, it was not STS as a launch system, but alleged military missions for the Orbiter (never to my knowledge attempted of course) that Air Force officers trash-talking scared the Kremlin with--with talk of missions to bomb Moscow, or steal Soviet satellites in orbit. But here, you see, the Orbiter development is delayed for one thing, and also more likely to be a purely civil NASA project, with the Air Force horning in on design and performance specs rather late in the process if at all. Any frightening talk by the Air Force will come later and clearly be more speculative, contingent on either the Air Force redesigning it or putting in a bid for their own clean-paper space fighter/bomber/recon craft that will be more of a political hot potato in Washington, as a separate project that is clearly more warlike. No one will be advocating for Orbiter as a payload delivery system, not at any rate unless it is part of a package to recover the upper stage engines TAOS style. But I think by then the wisdom of separating any Orbiter from engine recovery would dawn on American designers. Besides, the J type engines are much simpler and cheaper than SSMEs, and with the Lifter being incompatible with parallel boost off the launch pad, the rationale for those highly ambitious and expensive engines would be eliminated. Air start is what one must do with J engines, and air start is the only option for upper stage engines in this design.

I suppose it might be possible at that to design a TAOS type Shuttle that lights its expensive high-pressure engines on the ground after all, mounting it belly to belly with a Lifter. But I don't think that is a likely direction of evolution.

So, the Russians initially are not challenged to duplicate an alleged American weapons system, hence no drive for something like Buran--at any rate, it would be delayed.

Whereas a Lifterski aimed at lowering Soviet launch costs seems entirely within the capability of Soviet design, at a much more modest development cost than either the US Lifter program (because of its much lower mass and thrust) or Energia OTL. Assuming the Soviets have a fixed resource budget, this leaves them a lot left over for payloads. They can go ahead with little reduction in their OTL R-7/Proton based program while Lifterski is being developed, to improve their proficiency in space operations and maintain a manned presence in LEO while the Yankees have nothing in the 1970s, then move their Soyuz and Proton-sized payloads over to a light Lifter boost system, in the process eliminating use of hypergolic launchers completely while investing more in developing advanced hydrogen upper stages. The engines used in Energia also had to fire at sea level, but they will avoid that challenge here and the scale of thrust needed for hydrogen upper stages will be far lower, so attaining good hydrogen upper stages should be well within their grasp. They would then suffer for not having hundred ton capability, but having over a third of it is pretty good and if a heavy Lifterski launch costs less than 1/3 an Energia launch they are way ahead.

Another advantage the Soviets would enjoy--the Lifterski might well have flyback jets and fuel reserves for them, but it might not too. The Russians launch over Soviet land, and first stage separation, which I have suggested would happen earlier than with the Lifter, happens not too many hundred kilometers downrange from Baikonur. With the dry rocket plane all up well under 100 tons, more like 40-50 at most, it would be possible for it to glide to a landing on no fuel. If this is not good enough for reaching Baikonur, it surely would be good enough for landing on Soviet air fields in Kazakhstan or Siberia, and from there, some dedicated cargo plane like the OTL modified Antonov used to squire Buran around (but lighter, an off the shelf design would be suitable for redesign to put it on the back I'd think) could then load it on and haul it the rest of the way home.

That's just not an option for the American Lifter. The dang thing is sure to mass more than 200 tons, perhaps twice that, and no airplane yet developed on Earth can take it up. It pretty much has to be designed to fly on turbojets. Perhaps these are not needed on launch missions if it can glide all the way back, but anyway the only ways to shuttle it from the factory to a launch site, or from one launch site to another (Vandenberg to Canaveral or vice versa) would be for it to ferry itself; jet engines must be installed at least temporarily. The alternative is to load it onto a barge and take waterways--meaning a trip through the Panama Canal to get it from California to Florida!

The authors have pretty much implied it will have jets for flyback from launch, so ferrying it around is just a matter of supplying it with fuel--assuming it is designed for takeoff as well as landing airborne. Landing is harder than takeoff so it should be able to fly itself, if necessary with the help of rocket assisted thrust on takeoff.

Anyway the Russians can develop a much cheaper if less capable system. I am not at all sure they would, or if they do they might delay until the American Lifter has proven its economics. But I have little doubt they can.

And if they have by say 1990, if we assume Soviet collapse more or less as OTL and on schedule, the Russian program would be more economical assuming the small Lifterski saves roubles as well as the big one saves dollars--and being right-sized for most orbital missions, it ought to do so more efficiently than the American system does. Mir, which might well exist on schedule and perhaps more elaborately due to cheaper Soviet launch costs, might be sustainable for longer on the same skimpy Russian budgets, and perhaps no US President will see the need to intervene if the Russian regime decides space successes are important to its prestige and standing in the world--no threat of mass layoffs of Russian rocket people who might sell their expertise to third parties Uncle Sam disapproves of. Thus Russian and Western programs potter on separate from each other.

In that case on the whole Russia will slip farther back despite lowered launch costs--but maybe they can better secure a place in the capitalist global economy selling launch services. The American program by then will either have proven itself a fiasco, or proven that recoverable boosters are indeed a capacity multiplier, and shaken down to develop a rightsize version to maximize economy--whatever that right size may be. Presumably Western tonnage to orbit will have been much increased over OTL by then and annual launch rates measured in tons to orbit yearly would be running higher still, so the Soviet and their post-Communist successors would have a hard time keeping up relatively. But perhaps levels only modestly heavier than OTL will seem reasonable in the ATL, bearing in mind the disparity of wealth between First and Second world.
 
One issue with this is the history of why the N-1 was what it was. In the 60s the Russians were not certain they could get rendezvous and docking easily and that at least partly pushed for heavier payloads, the reason they wanted it in one launch rather than two. Limit the risks involved. Also there is the prestige. Bigger is better! The Soviet people proudly launch massive payloads into orbit! Honestly I think looks are going to be a huge factor in this. How will it look to have the US lifting large shuttle/payloads (comparatively speaking) and the Russian Lifterski system lofting much lower payloads, even if they can do it cheaply? True they eventually will likely develop something akin to the OTL heavier lifter systems, as you say (and likely non-reusable due to development costs), but to see the US doing supposedly reusable efforts with larger systems and them seen as doing 'piddly little reusables' will not help the Soviet image. Image is everything!

Seven engines is helpful, but frankly I'd think a double scale from that would work fine... probably. It'd never look anything like the N-1 though, no matter what engines go into the design. Consider who is running the Soviet space machine right now :)

EDIT: As for the Lifterski's frame not having the drag of the Saturn flyback... well, the shape actually would likely have more for it's size. It'd be just like an Apollo command module coming back after the engines cut out :) I think you mentioned this before Shevak. I think from that the drag would be more proportionately, though probably not quite up to the larger Saturn flyback.
 
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Shevek,

We'll have specs posted in the next few weeks, as the American program hits the milestones in the program history that correspond. I can say S-II has no place in the program--while it does boost payload about as much as it raises costs in our models, that's only true on payloads over 75 tons, which are few and far between, and only if it flies more than one or two times a year. Fletcher having a keener sense of reality than Paine, NASA doean't see that as likely. Thus, when payloads in that size are necesaty, NASA thinks they can simply assemble more frequent medium-heavy Lifters than have to support a third production line for a component the size of the Lifter itself hat may only fly every few years. We may post our 1971 cost estimates with the topline performance levels after the next post.

As for the Soviets...well, you'll have to wait and see for a bit. You're in some of the right ballpark, but starting from some wrong aspects. Patupi has it right that there's no chance Glushko won't aim to at least match American capabilities, though there's operational benefits to being smaller. He built Energia/Buran IOTL as a downscope of his original superheavy moon rocket concepts (which explains a lot about its ability to launch without Buran). He's going to be starting from a similar base goal here, and the question will be what he can get permission to build.
 
I can't say it is unrealistic for the Soviets to hold the Idiot Ball alas.

Too bad about the S-II, it means NASA knows they won't max out the Lifter ever and thus should make it smaller. But then I don't know that they haven't either. It was only my guess they'd start with a full Saturn V upgraded with 5 F-1A engines; they could easily use just 3 of the engines, or even two. That would bring maximum loads down into near hailing distance to the 20-40 ton range more likely based on OTL to be the norm.

Possible guessed at spoiler struck out! Will run that by the authors before blabbing it. At this point I am only guessing.
 
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