Realistic solutions to the difficulties of SSTO?

mboeller · 2005-09-15 05:35:23

Well;

I have found an interessting answer to the SSTO debate just yesterday.

Look here: http://www.astronautix.com/lvs/saturnvb.htm.

This is an 1.5 stage Saturn5. Only the booster engines with structure are recovered. But remember this is technology from the 1960s and uses only kerosin as fuel. So the system is imho rather impressive with an payload fraction of nearly 1%.

I wonder now if the original Atlas with 4 booster engines would have been able to reach LEO as an 1.5 stage system without upper stage too.

Oh, if you need more payload use an upper stage together with the 1.5 stage Saturn5 : http://www.astronautix.com/lvs/saturnvc.htm

publiusr · 2005-09-16 13:19:13

Scott Lowther supplied that info--his website is www.up-ship.com

mboeller · 2005-09-17 05:47:31

Scott Lowther supplied that info--his website is www.up-ship.com

Yes, but you cannot find this info on his website and even the book is not yet available as far as I know. see here: http://www.up-ship.com/apr/aprorder.htm

Personally I hope he will finish this books as soon as possible cause his APR magazine is/was imho outstanding ( I received the last issue last week ).

Ad Astra · 2005-09-18 10:28:05

Jeff Bell had a fun time knocking the DC-X, X-30, and X-33 as technically-unrealistic excuses to make the Soviets spend more money. What he ignores is that some really smart people got behind these ideas at some point, which is why they got as far as they did.

In the famous case of DC-X, the idea had the support of Max Hunter (designer of the Thor missile and Lockheed Starclipper,) Jerry Pournelle (sci-fi author & pundit,) and the other members of the national space council. In turn, the council convinced then-VP Dan Quayle that the idea of SSTO was worth pursuing. Max Hunter and others believed that materials advances in the 1990's would allow SSTO to happen (even if it could orbit less payload than a TSTO of the same liftoff weight.)

DC-X was far too heavy to achieve SSTO, but it was never designed to demonstrate SSTO fuel fractions. Its purpose was to lift off, hover, land, and do it again in short order. A follow-on like DC-XC or DC-Y would demonstrate useful fuel fractions (at least according to the plan, before DC-XA tipped over and burned to the ground.)

X-30 also had the backing of serious engineers, because programs like Copper Canyon demonstrated the idea's basic feasibility. Problems occurred only after the engineers took an in-depth look at the propulsion system and determined that it could only achieve Mach 12 in the atmosphere (even after employing active airframe cooling.) The X-30's successor, X-43, was a remarkably successful and efficient way of testing the basic technologies that will hopefully bring scramjets closer to fruition.

As for Jeff Bell's contention that Aurora was merely an invention of Aviation Week to scare the Soviets, he's flying in the face of highly-respected aerospace analysts who believe that some kind of hypersonic prototype was built and flown.

For the X-33, the decisions of the engineers and managers are much harder to defend. NASA really wanted an SSTO to replace the shuttle, so the proposals they received came across as disappointing. Although McDonnell Douglas and Rockwell offered more potential, Lockheed was willing to kick in its own money to partially fund the X-33 and entirely fund the VentureStar. Never mind the fact that there wasn't traceability between the Mach 15 X-33 and the orbital VentureStar. NASA decided to bite Lockheed's financial carrot instead of cancelling the program like it should have.

GCNRevenger · 2005-09-18 19:32:33

I agree pretty much, but I think the DC-I or whatever the "production" model would have been borderline as far as mass fractions, and I think that reliability is a valid concern to make the system economical. It might have been possible, but it would have been a stretch. An expensive stretch.

The X-30 probobly could be pushed to like Mach-15 with current technology and superior takeoff engines, but it would need to hit about Mach-20 with Scramjet mode for practical SSTO flight. We aren't quite there yet without some "cheating" technology like microwaving the air ahead of the vehicle or spiking the slushed Hydrogen with nanoscale aluminum.

The X-33/Venturestar was a debacle from the start.

Ad Astra · 2005-09-18 21:06:02

Because scramjet-powered craft fly depressed trajectories and have a finite top speed (I think Mach 12 is the thermodynamic limit, regardless of which materials are used,) I don't think they are useful for spacecraft. A scramjet-powered first stage could be used as part of a TSTO, but this introduces the challenge of supersonic separation between the booster and orbiter while in the atmosphere.

The best application of scramjets is for high-speed aircraft, like airliners or bombers. The production scramjets will really be Rocket-based combined cycles or turbine-based combined cycles. Because these vehicles stay in the atmosphere, there is no need for a difficult stage separation, or building up enough speed to fly out of the atmosphere into space.

RobertDyck · 2005-09-18 23:04:49

The X-30 probobly could be pushed to like Mach-15 with current technology and superior takeoff engines, but it would need to hit about Mach-20 with Scramjet mode for practical SSTO flight. We aren't quite there yet without some "cheating" technology like microwaving the air ahead of the vehicle or spiking the slushed Hydrogen with nanoscale aluminum.

Ok. Now what speed could you achieve if the SCRAM jet and LOX/LH2 engine were replaced by an RBCC that smoothly transitioned between airbreathing and LOX by using air augmented rocket mode? What if you do microwave the air ahead of the vehicle? As for spiking slushed hydrogen with nanoscale aluminum, would that increase specific impulse? Aluminum burns hotter but is heavier. If it would help, then let's use it.

Nothing says the solution has to be "purely" one thing. Saturn V used kerosene/LOX for the first stage and LH2/LOX for the second and third stages. Apollo used N2O4/UDMH. It was a mixture of technologies and it worked.

John Creighton · 2005-09-18 23:43:02

Because scramjet-powered craft fly depressed trajectories and have a finite top speed (I think Mach 12 is the thermodynamic limit, regardless of which materials are used,) I don't think they are useful for spacecraft. A scramjet-powered first stage could be used as part of a TSTO, but this introduces the challenge of supersonic separation between the booster and orbiter while in the atmosphere.
The best application of scramjets is for high-speed aircraft, like airliners or bombers. The production scramjets will really be Rocket-based combined cycles or turbine-based combined cycles. Because these vehicles stay in the atmosphere, there is no need for a difficult stage separation, or building up enough speed to fly out of the atmosphere into space.

I don’t get why the separation would have to occur in the atmosphere. Couldn’t you build up speed in the atmosphere with the scram jet, change the trajectory slightly and let the momentum carry you outside of the atmosphere for the separation. I am more concerned about the cooling. Perhaps at Mach 12 this isn’t much of an issue but if you go higher then mach 12 you would want to pass the slush hydrogen over the skin to both cool the skin of the craft and preheat the hydrogen for greater efficiency. This would protect the scramjet but what would protect the vehicle that separates from the scram jet? My only suggestion is that the separated vehicle could be placed far enough to the rear of the scram jet that it is behind the Mach cone.

RobertDyck · 2005-09-19 03:19:21

I read during the X-30/NASP program that the airforce calculated top speed to be mach 14 or 17; two articles. Nothing says mach 12 is the top. The only reason X-43A was limited to mach 10 was its titanium skin. A heat shield using the same materials as the Space Shuttle would have permitted higher speed. The air augmented rocket mode would achieve at least mach 17 if not higher. Use a turbine engine to achieve mach 6 with kerosene, then slushed hydrogen with an air breathing engine to at least mach 17. Orbit requires mach 25 or equivalent in vacuum. That enables SSTO.

TSTO is much easier. The carrier aircraft could use a supersonic turbojet with kerosene jet fuel to mach 6 then separate the orbiter as a rocket. The Russian Sprial was designed to separate from it's aircraft at mach 6. Since the project started in 1965 they required hydrogen fuelled jet engines. It would have used a 2 stage expendable rocket booster plus reusable orbiter. But the point is they designed a vehicle capable of separation at mach 6 at 28-30km altitude. If they can do it, can't America with today's technology? The same Russian company also designed the MAKS, a TSTO with expendable drop tank using a subsonic cargo plane as the carrier. TSTO is easy.

Lastly, John is right. Separation could occur at 100km. SpaceShipOne flew suborbital to 100km without any sort of heat shield. On October 4, 2004, it flew to 112.0km, top speed mach 3.09. A TSTO carrier aircraft could do the same.

evilcitizen · 2005-09-19 03:41:31

Just a question for all of you technical types. I know little about rocket dynamics, having only recently regained an interest in space exploration.

I was wondering though, what's the drag coefficient like for these different rockets and the current space shuttle they're using? Is it a big difference? Anything they could do to improve their designs in this area?

I'm a wind-tunnel/aerodynamics kind of guy myself and was wondering how much that's used in designing NASA's stuff.

Grypd · 2005-09-19 06:50:53

Does it really require a separation of Mach 6+ as separation at about mach 5 should be possible especially if at a high height with a much reduced air pressure and as such less risk to a TSTO.

This means the lower carrier craft could be using souped up jet engines with a booster either of oxygen or water in the flow through the engines. And using understood engines then maintenance and turn around should be accomplished a lot faster.

The upper stage would have to be a rocket powered vessel and in this case it would need a reusable engine.

SpaceNut · 2005-09-19 12:51:29

Rocket Equations
Equations for model rocketeers - how to accurately predict speed and altitude for your rocket from weight, diameter, motor thrust and impulse seems like a good starting point.

RobertDyck · 2005-09-19 12:58:23

I found this web page from the Glenn Research Center regarding air temperature, pressure, and density at altitude. Plugging in the numbers for 30km altitude (98425 feet) I get -43.6°F at 24.86 lbs/sq ft which works out to 0.17264 PSI. Pressure at sea level is 14.69595 PSI so air at 30km is extremely thin. I could see why mach 6 separation would work there.

John Creighton · 2005-09-19 15:41:31

There seems to be a lot of optimism in this thread about SSTO and TSTO. Robert Dyck went as fart to say that TSTO is easy. And maybe the problems aren’t so great if all you want to do is get to orbit but to be useful the vehicle has to be able reenter the atmosphere land on a runway and be ready to go again in a week. There are very fee vehicles that meat this latter requirement.

On vehicle that does meat the requirement of reentry landing on a runway and a quick turnaround time is the x-37. However, the X-37 only has a 4% payload fraction and we do not have enough information from the program to know if it caries enough fuel for a useful second stage or why the payload fraction is so bad. In all likelihood the X-37 falls far short of a useful reusable second stage vehicle. However, I believe the basic design is good and with a larger vehicle, lighter materials, and less stuff inside it that would be useful to the military but might not be needed by NASA the X-37 could form a good starting point for a second stage vehicle.

The next step can be done for just about any vehicle. The job is to figure out what kind of mass fraction is needed to reach orbit for various velocities at separation. Then you figure out how big the second stage has to be to obtain this mass ratio and then you figure out how big a first stage is needed to carry this vehicle. Hopefully there will be some reasonable range of separation velocities where this is practical.

Commodore · 2005-09-19 15:56:13

I really don't think this will be a huge issue. Once there is a crew requirement greater than that of the CEV, which itself can be probably be extended into a bit longer "Gemini style" capsule, the Air Force is bound to have a hypersonic suborbital bomber, if they don't already. At that point minor modifcations will swap the trancontiental range for orbital velocities.

John Creighton · 2005-09-19 15:59:42

I really don't think this will be a huge issue. Once there is a crew requirement greater than that of the CEV, which itself can be probably be extended into a bit longer "Gemini style" capsule, the Air Force is bound to have a hypersonic suborbital bomber, if they don't already. At that point minor modifcations will swap the trancontiental range for orbital velocities.

I agree that the air force developing hypersonic orbital bomber will make it easier for NASA to develop a good SSTO or TSTO reusable vehicle. However, I don’t think it is easy and at the current time will probably result in a vehicle that is fairly large and will be a significant capital investment.

VTTFSH_V · 2005-09-19 19:21:55

There is no need to invent a good SSTO ship in the first place, at least any time soon. TSTO is fine and simple. It just should be 100% reusable, very durable and have good payload ability (at least 100,000 lbs.).

GCNRevenger · 2005-09-19 20:38:03

I am pretty sure that we can exceed the Mach-12 limit today if we "cheat" (regenerative cooling, shock-front ionization, high temperature fuel additives), but to make a practical SSTO vehicle it really does need to hit about Mach-20, and I don't think that we could hit that... yet. As such, Scramjet engines will probobly be limited to military applications for the time being.

The reason why SSTO would be so much better then TSTO is really very easy: simplicity of operation. With only one vehicle to deal with, no re-mating operations, no vehicle matching, none of that, an SSTO offers the only way barring a space elevator for average middle-class people to really go into space.

I also think that an SSTO would be an enabling technology, again barring a space elevator, that would make large-scale colonization away from Earth possible. TSTO could support moving some hundreds of people anually, but SSTO could move thousands.

It is also the only way that, barring an elevator, in the long run we could have large-scale trade between worlds and space stations. There is no other way to move cargoes efficiently enough... Make no mistake (barring an elevator), real "airline like" access to space is the only way that we will truely become a space-faring rather than planet-hopping species...

...In the mean time however, SSTO doesn't make sense. The technology isn't there yet, and there is no need for a very large number of flights. TSTO would be much much easier to pull off technologically, and wouldn't require scramjets or shock front ionization or anything like that.

An large carrier plane, either using advanced (LOX/H2O augmented?) jet engines or jet+rocket would be expensive but not overly difficult to build. It wouldn't need hyper-efficient engines, since it only has to sprint for a short time at high speed/altitude to deliver the orbiter to seperation.

The orbiter itself would not need any especially fancy technologies beyond a little-better-than-now heat shield and advanced second generation reuseable Hydrogen engines, perhaps with slushed LH2.

A TSTO vehicle would serve us up until early Lunar mining, small-scale Mars colonization, and large scale tourism for the rich... perhaps manned missions to Jupiter. The orbiter ought to come in at least two, perhaps four flavors:
-Manned, room for 12 passengers and an airlock
-Unmanned cargo
-Tanker for fuel
-"Truck" style with 4-6 crew and small (pressurized?) cargo bay for repair missions or split cargo/crew rotations.

Ad Astra · 2005-09-19 20:51:44

One vehicle that does meat the requirement of reentry landing on a runway and a quick turnaround time is the x-37. However, the X-37 only has a 4% payload fraction and we do not have enough information from the program to know if it caries enough fuel for a useful second stage or why the payload fraction is so bad. In all likelihood the X-37 falls far short of a useful reusable second stage vehicle. However, I believe the basic design is good and with a larger vehicle, lighter materials, and less stuff inside it that would be useful to the military but might not be needed by NASA the X-37 could form a good starting point for a second stage vehicle.

X-37 is really a payload, like the manned capsules before it. It doesn't have much propellant, other than for maneuvering once on-orbit. X-37's orbital capabilities are moot right now because there isn't any money to fund it after the White Knight drop tests end.

Would the X-37 shape make for a good booster? I wouldn't think so, because the shape has a low fineness ratio and would produce a lot of drag. Many re-entry vehicles are designed to be draggy so they bleed off energy in the atmosphere.

I've often looked at the X-34 as a good shape for a booster. But we have to remember that the X-34's wings were designed for the pitching maneuver that would have followed separation from the mothership. So the X-34's wings were probably oversized for a booster that is only going to be generating lift after its propellants are used up.

A good shape for the flyback booster was the Rockwell X-33 concept. Looking like a bloated X-34, it was a winged rocket that would have glided to a landing after a suborbital ~Mach 15 flight.

PurduesUSAFguy · 2005-09-19 21:29:19

One vehicle that does meat the requirement of reentry landing on a runway and a quick turnaround time is the x-37. However, the X-37 only has a 4% payload fraction and we do not have enough information from the program to know if it caries enough fuel for a useful second stage or why the payload fraction is so bad. In all likelihood the X-37 falls far short of a useful reusable second stage vehicle. However, I believe the basic design is good and with a larger vehicle, lighter materials, and less stuff inside it that would be useful to the military but might not be needed by NASA the X-37 could form a good starting point for a second stage vehicle.
X-37 is really a payload, like the manned capsules before it. It doesn't have much propellant, other than for maneuvering once on-orbit. X-37's orbital capabilities are moot right now because there isn't any money to fund it after the White Knight drop tests end.
Would the X-37 shape make for a good booster? I wouldn't think so, because the shape has a low fineness ratio and would rpduce a lot of drag. Many re-entry vehicles are designed to be draggy so they bleed off energy in the atmosphere.
I've often looked at the X-34 as a good shape for a booster. But we have to remember that the X-34's wings were designed for the pitching maneuver that would have followed separation from the mothership. So the X-34's wings were probably oversized for a booster that is only going to be generating lift after its propellants are used up.
A good shape for the flyback booster was the Rockwell X-33 concept. Looking like a bloated X-34, it was a winged rocket that would have glided to a landing after a suborbital ~Mach 15 flight.

I don't know much about the Rockwell X-33 concept, but I got the distinct impression that it was essentially the Shuttle fattened up enough to contain the external tanks volume, I could be wrong and it could be more advanced then that bit </shrug> Like I said I don't really know.

As far as a TSTO based around a hypersonic first stage carrier, well just watch the AF, that might be coming sooner then you think.

VTTFSH_V · 2005-09-20 00:25:55

Do you all know that the first shuttle design concept was the orbiter piggy-backed on a modified 747? The idea was scrapped because of cost. That design does not require any re-mating or matching, just a little extra logistics on the ground, which is perfectly manageable.

Take this into consideration:

http://www.bristolspaceplanes.com/proje … ebus.shtml

Ad Astra · 2005-09-20 00:51:14

In response to the last two posts:

Rockwell's X-33 design looked a lot like the shuttle (it even used an SSME,) but it really had no common parts with NASA's albatross. Some of the Rockwell drawings even show two tails instead of one.

The Rockwell design wasn't bad. It relied on tried and true lifting reentry (unlike the radical powered landing from the DC-X and the eventual McDD X-33 design,) and the structural concept was much more conventional than LockMart's. In short, it represented the lowest risk of the three designs.

Could the Rockwell design have scaled up into an SSTO? Heck no. But none of the competing X-33 designs had a shot, either. That was the folly of the X-33 program: there was little traceability between a subscale Mach 15 rocket and an orbital rocket with a 50,000 pound payload. The contractors tried. NASA should be blamed for fostering an unsound idea.

As far as launch from a 747: this was not considered for the space shuttle, but it was the focus for Boeing and Rockwell mini-shuttles in the late 70's and early 80's. The Air Force wanted a small shuttlecraft that could reach orbit on short notice. This has been a recurring theme with the Air Force. Plenty of money has been spent over the years on various studies, and lots of splendid artwork has been released, but no hardware has been publicly demonstrated.

Launching from the back of a 747 is not all it's cracked up to be. For starters, the 747 doesn't give much of a speed boost--only Mach 0.8. Further, the idea of captive carry on top of the mothership gives engineers goosebumps. Most expect the rocketplane to come crashing down on the mothership, as was the case with the D-21 + M-21 combo.

Russia's MAKS was the most advanced of the "launch from a cargo aircraft" concepts, but there are still doubts about its viability. Would it be able to maintain control after release from the An-225? Could the orbiter weight be kept down so the appropriate fuel fraction could be achieved? Mach 0.8 is not a significant head start, seeing as how the rocket has to reach Mach 25+.

The best air-launch proposal I've seen is a moribund concept called "Bladerunner." Aside from a lawsuit from Ridley Scott, I don't see any problems with it. The rocket would be extracted from a cargo plane, but would still be flying at Mach 0.7. Its scissor wings would generate lift, unlike the ill-conceived "AirLaunch" being promoted by Gary Hudson and t/Space. The two-stage approach ensured that room for growth and realistic fuel fractions would be maintained.

GCNRevenger · 2005-09-20 18:11:23

Well, I think NASA ought to be contemplating a true 100% "no really" reuseable shuttle, probobly a TSTO, sometime following the first few Mars landings. That would be the time to put some momentum into development, so that it would be moving forward after the development money following the initial Mars ships and base has been freed up.

Ad Astra · 2005-09-20 18:30:59

To be honest, NASA should have come up with a true RLV to replace the shuttle before embarking on the ISS or lunar return. The shuttle has been the ISS's choke point, because it wasn't reliable enough to meet the ISS assembly schedule. Of course, almost all of the modules were designed to be flown on the shuttle. NASA crossed its fingers and hoped there wouldn't be another shuttle accident; the agency couldn't beat the odds, and ISS suffered.

Likewise, if you're a fan of Rand Simberg, you're currently lamenting the lack of reusability in NASA's moon plan. With a reliable RLV, you could launch the moon ships in 20-ton chunks, then fuel them up and send them on their merry way.

We currently fear on-orbit construction because our current launchers are too hard to launch in a timely fashion, and not reliable enough. If we can make rockets reliable like airliners, high flight rates will be easy, orbital assembly will be easy, and going to the moon and beyond will be affordable.

Don't expect to see NASA building an RLV. When Rutan & co. see a market for one, they will build it. Until then, they'll keep flying suborbitally to raise awareness (and lower costs) of space tourism.

GCNRevenger · 2005-09-20 19:00:46

As nice as that would be, I don't think a Shuttle-II is the best idea at the moment. Segmenting Lunar payloads into too many pieces if a bad idea, you couldn't use Mars prototype HABs for a Moon base, nor launch a Mars ship in a small enough number of pieces. Even if we did have a Shuttle-II, we would want a heavy lifter for larger diameter payloads most likly anyway. Cutting each mission into too many little pieces adds too much expense too.

A Lunar program using an RLV on the Earth end therefore only makes sense if the Lunar vehicle(s) were reuseable. Reuseability doesn't make much sense either in the shorter term; the TLI stage will be dumb and cheap, the expendable lander won't be horribly expensive per-copy to build, and the capsule will be (somewhat) reuseable. Since we won't be needing more than a few flights a year to the Moon, and the demand for Lunar reasources isn't very large yet, spending buckets of money on reuseable Lunar vehicles with inferior payload is a bad idea. There is no need for hyper-cheap Lunar or Martian access... yet.

Oh, and you would definatly need a space station purpose built for constructing Lunar vehicles, the ISS design couldn't support a "shipyard" even if Shuttle did work as its 1970's/1980's fraudulent advertised form.

The only likly viable RLVs would be either a giant DC-X or a TSTO spaceplane, which although would be really cool, would lack payload volume and won't quite be "airliner like." Only a more mature second-generation DC-X type vehicle (air breathing?) or a true SSTO spaceplane could do that.

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#26 2005-09-15 05:35:23

Re: Realistic solutions to the difficulties of SSTO?

#27 2005-09-16 13:19:13

Re: Realistic solutions to the difficulties of SSTO?

#28 2005-09-17 05:47:31

Re: Realistic solutions to the difficulties of SSTO?

#29 2005-09-18 10:28:05

Re: Realistic solutions to the difficulties of SSTO?

#30 2005-09-18 19:32:33

Re: Realistic solutions to the difficulties of SSTO?

#31 2005-09-18 21:06:02

Re: Realistic solutions to the difficulties of SSTO?

#32 2005-09-18 23:04:49

Re: Realistic solutions to the difficulties of SSTO?

#33 2005-09-18 23:43:02

Re: Realistic solutions to the difficulties of SSTO?

#34 2005-09-19 03:19:21

Re: Realistic solutions to the difficulties of SSTO?

#35 2005-09-19 03:41:31

Re: Realistic solutions to the difficulties of SSTO?

#36 2005-09-19 06:50:53

Re: Realistic solutions to the difficulties of SSTO?

#37 2005-09-19 12:51:29

Re: Realistic solutions to the difficulties of SSTO?

#38 2005-09-19 12:58:23

Re: Realistic solutions to the difficulties of SSTO?

#39 2005-09-19 15:41:31

Re: Realistic solutions to the difficulties of SSTO?

#40 2005-09-19 15:56:13

Re: Realistic solutions to the difficulties of SSTO?

#41 2005-09-19 15:59:42

Re: Realistic solutions to the difficulties of SSTO?

#42 2005-09-19 19:21:55

Re: Realistic solutions to the difficulties of SSTO?

#43 2005-09-19 20:38:03

Re: Realistic solutions to the difficulties of SSTO?

#44 2005-09-19 20:51:44

Re: Realistic solutions to the difficulties of SSTO?

#45 2005-09-19 21:29:19

Re: Realistic solutions to the difficulties of SSTO?

#46 2005-09-20 00:25:55

Re: Realistic solutions to the difficulties of SSTO?

#47 2005-09-20 00:51:14

Re: Realistic solutions to the difficulties of SSTO?

#48 2005-09-20 18:11:23

Re: Realistic solutions to the difficulties of SSTO?

#49 2005-09-20 18:30:59

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#50 2005-09-20 19:00:46

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