Envisioning the world of 2100

[gturner]

Hrm... I think you've missed my idea. Even though the structure is laying horizontally, like an aircraft on a runway, no horizontal motion takes place during launch. It just lifts off vertically and then rotates 90 degrees to decrease drag.

The point is that even if the rocket is free, raising it into position is expensive and time consuming. Think of the Saturn V mock-up at Huntsville. Building it was pretty simple (since it's not a real rocket), but standing it on its end for the display was a bitch, and the model didn't even need access for support (a Saturn V launch tower, crawler, and VAB). If you left it laying flat when on the ground, maintenance and support are pretty trivial. All you'd need is a step ladder. You don't have to pump fuel 300 feet vertically, you don't have to design a tower that can withstand rocket exhaust, and you don't have a tower you can crash into on the way up.

[sojourner]

^You're kidding, right? So, your going to add all this complication (re: weight) to every rocket just so you can get into it easier? Instead of building it into a standing structure that gets re-used every time?

When was the last time a launch failed due to collision with the launch tower?

The reason it was a bitch putting that SV on display is that it had sat around for 20+ years and was erected outside. It would have been done a lot easier if newly built and assembled in the VAB. A standing structure designed specifically to assemble Saturn components.

How is this magical rocket going to take off horizontally without sufficiently strong engines at the other end? OH, put some there? Now you have dead weight in the vertical position and the end of the rocket that needs to save the most weight.

I have a feeling you're just "taking the piss" here. You're smarter than that last post you just made, though you seldom show it anymore on TBBS.

[gturner]

But the standing rocket can only get re-used once every couple of weeks, at best, because it's standing, and you have to restack it because an SSTO isn't viable. An airliner can turn around about as fast as you can fuel it.


A re-usable vertical rocket will probably never land on the launch pad next to a tower because of the collision hazard, given that an empty stage responds about 10 times more to wind gusts than a fueled stage. So the vertical stage will most likely land in the middle of big concrete slab the size of a mall parking lot. Then you have to lift it up and secure it a transport vehicle, which will probably take a day, and then roll it back to the VAB, which will take half a day.

When the second stage lands and you have to repeat the process, then lift the second stage to restack the rocket. Then you have to transport the whole thing back to the pad. In the case of a Saturn V, even empty it weighs over a quarter million pounds and is 350+ feet tall. Transporting it is like moving a 35 story skyscraper, and it's subject to wind loads, so the crawler has to weigh 6 million pounds and keep the rocket vertical to within a sixth of a degree.

The fastest the vertical Saturn V was assembled and launched was about two months. The fastest the highly-resuable Space Shuttle was turned around was 54 days. Beating that with a tall vertical rocket is going to be hard, because tall things are inherently hard to work on, hard to move, and hard to assemble. On its side, a Saturn V is trivial, no bigger than a small WW-II destroyer.

The point is that if you want a cheap system, you can't do it vertically because it adds too much cost to every mission. It takes a crew of 30 just to drive the crawler, and then you have all the pad support. You're adding hundreds of personnel to each launch, every time, and limiting the flight rate to once every few weeks, more likely about a dozen launches a year. In that case you've addd about a million or two dollars to the cost of the launch, which is five or ten times more than the fuel cost. It's not important when the system you operate is extremely expensive, but it becomes extremely important if you got reliable and cheap enough to where even fuel was a significant part of the bottom line.

Going up horizontally adds complexity, but we often add complexity to lower operating cots. All jump jets add enormous complexity to rotate the thrust through 90 degrees because it's vastly better than trying to tail-sit, and line maintenance on a tale-sitter would be a nightmare requiring lifts and access ladders.

And you already have engines near the front of the rocket, used to propel the second stage. Currently they're just dead-weight during the launch. Cross-feed them from the main tank and you gain the lift-off advantages of a strap-on or piggy-back configuration with the low drag of a stacked configuration later in the flight.

And of course you can always build a re-usable stage 0 whose only purpose is the first minute of flight, handling the entirety of the horizontal load and the lift-off thrust requirements so that you not only don't suffer a performance loss, you get a performance gain, while completely avoiding the needs for a VAB, cranes, lifts, crawlers, and towers. All you'd need is a pre-fab commercial building or conventional aircraft hanger, a truck driver, and a strip of concrete.

[sojourner]

So, "taking the piss" it is.

[gturner]

No, doing the math.

Suppose that at present the vertical launch orientation adds 2 to 5% to the launch costs, and the structural penalties and extra engines required for a horizontal launch would reduce the payload by 30 to 50%. If you made the switch now, the dollars per pound would be 2 to 3 times higher, so we don't do that. But as you start building fully resuable stages with low-cost, high reliability engines, your launch costs drop to a tenth of what they currently are. But the costs of that vertical processing are undiminished, if not increased, because once your stack becomes resuable you have to haul the empties vertically, too. If the vertical costs are undiminshed and you drop the launch costs 10 fold, then that 2 to 5% added expense becomes 20 to 50% of your launch cost. If the expenses increase further due to the empties, the vertical processing could be the majority of your cost, and will be the determining factor on your flight rate.

So you have two companies, the Vertical Corporation whose rocket delivers twice the payload of the Horizontal Company. But to do that, they have a fourth the flight rate and four times the personnel and support costs of the Horizontal Company. Per man-hour they can only launch an eighth as much as the Horizontal Company, and their investment in support equipment is about eight times higher. They go out of business and the Horizontal Company spawns spin-offs and copycats, and people used to the horizontal launch of rockets five and six hundred feet long, which are as ordinary as a Harrier or F-35 takeoff, wonder who would be insane enough to think you could stand such a thing on its end and make any money at it.

I point this out because the SLS stack is already limited by the door height of the VAB, Congress is never going to approve an even taller building, and no private company is going to try to build a rocket maintenance shed that 700 feet tall. No private company is going to order a 6 million ton crawler or build a giant launch tower because they can't afford it. Even if they did, the structures would be tied up with vertical integration and month per flight processing times while their horizontal competitors could be launching flying machines on a daily basis with a tenth the personnel.

If we had to stand airliners on their ends to get a plane in the air or land one we'd still be riding trains because an airline flight would be a very rare and expensive show. Is it any wonder that spaceflight is rare and expensive when the launch configuration can't be anything but?

[sojourner]

airplanes =/= rockets. You have lots of bad assumptions there. I've seen your tactic of taking an absurd position on a subject and trying to make it look reasonable in other threads. No one buys it. When you want to talk about the subject earnestly, get back to us.

[gturner]

I can't help it if you can't conceive of doing anything the least bit different from the way they did things in the 1940's, no matter how inefficient it is.

The cost to build the mobile launch platform for the SLS is about $300 million dollars. Even through the project was started for Bush's Ares program, it won't be completed till 2016, and just the modifications from the Ares configuration are budgeted for 1000 man years of design and construction work. That gives you the ability to launch a rocket every few weeks, at maximum, because each rocket has to be assembled in the VAB, loaded onto the mobile platform, rolled out, and then sat on the pad for a few days.

If the SLS flies 45 times, the mobile launch platform alone adds $10 million to the cost of each launch, or about two million dollars per seat. There's no engineering breakthrough that's going to lower the cost of a steel tower by some factor of three, so cheap space flight cannot ever happen as long as you use a big giant tower for the launch. And that's not even figuring in the VAB, which would have a replacement cost somewhere in the $5 to $10 billion dollar range, and which eats up over a hundred million a year.

When space flight advocates talk about a future with $100 a pound to orbit, or even $10 a pound, you can't keep using a launch tower if it alone is adding more cost than that. Even if the rockets were free, the cost of maintaining the support equipment required for the vertical launches keeps the price per launch hardly better than buying an airliner, using it once, and throwing it away.

And if there's an explosion on the pad, which could certainly happen, the entire sytem will be grounded for the several years it will take to build a new tower. As in-depth NASA studies found, the tower will not in any way survive a pad explosion. Not surprisingly, they found the most likely cause of a pad explosion was a collision with the launch tower, which became a major worry with the Ares design. Of course you could build several towers for redundancy, but then you've spent over a billion dollars.

We got to this point because the early small rockets are trivially easy to raise, and when the space race started in earnest we just threw money at the problem. The Russians didn't build and transport their Soyuz vertically because they couldn't afford to, whereas we could afford to do almost anything. SpaceX took a page from the Russians and became the only US launch provider that doesn't build their rockets vertically, just standing them up prior to launch, and not coincidentally is by far the lowest cost provider.

If they were extremely confident in their engine start, they could lift the nose up with just 30 SuperDracos, and they're already going to use eight of those in the Dragon capsule just as abort engines. They don't need to do that because their rocket is small enough to raise vertically right at the launch pad, but as rockets get bigger that operation becomes much more difficult and expensive, and eventually impractical.

So, a question: How many Orion capsule abort motors would it take to raise the entire SLS to vertical while its fully fueled? About six. If you use twelve you could lift the entire rocket, including the SRBs, and flip it vertically in the air. The abort motor is the tiny little thing on top of the stack. Lifting and fipping are infinitely easier than getting such a vehicle to go supersonic, and then getting it all the way to outer space.

[Crazy Eddie]

gturner wrote:

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Hrm... I think you've missed my idea. Even though the structure is laying horizontally, like an aircraft on a runway, no horizontal motion takes place during launch. It just lifts off vertically and then rotates 90 degrees to decrease drag.

You'd need a hell of a lot of JTO rockets to pull that off, and the risks would not outweigh the benefits.

I think that simply dropping the rocket out of a carrier aircraft makes a lot more sense to accomplish that, especially since the air-dropped launch allows you to always launch your rocket from the equator and potentially at a relatively high altitude which can increase your mass fraction by reducing drag and saving some fuel.

[gturner]

Well, it's definitely different. I prefer the carrier aircraft idea for all reasons except size. The Stratolaunch being built in Mojave can only carry a Falcon 4 or Falcon 5, and it's the biggest yet (about 200K lbs thrust). Something like the B-1 or British Vulcan would scale up quite nicely, and the Vulcan's thick low-aspect ratio wing is structurally an easy thing to scale up tremendously. Thrust isn't a problem because you can use as many engines as it takes, perhaps using GE-90's with about 3 times the thrust that the Stratolauncher's old 747 engines use. You could even design for supersonic flight using something like a vast array of GE F-404's we'll be retiring with the F-18 B's and C's. But the cost would probably be several bilion and you're probably not going to get much beyond the payload capability of a Falcon 9 or Falcon H, which while nothing to sneeze at shouldn't be the end point of space launch. However the Stratojet also shows that you can hang something like a fully fueled Falcon horizontally from some hardpoints and it's good for 1.4 or so G's with a human-rated safety factor, otherwise they wouldn't be able to fly with it. That means there really are no significant structural penalties in a horizontal lift-off. Hypersonic flight vehicles that pull several G's with pressurized tanks tend to be pretty tough.

What I'm trying to get around is the size limits on reusable launchers set by the carrying capacity of crawlers, the tower height, and the processing building, and the scaling laws likely are part of what makes the SLS cost/LEO pound so much higher than the Falcon 9 or Soyuz. Part of that is the engines, structure, and manufacturing, and part of that is the tower, VAB, and vertical processing. Once you severly cut engine, structure, and manufacturing costs, as SpaceX has done, you're left with the vertical operations costs. If you start re-using the entire rocket, as SpaceX intends to do, the vertical costs will start to dominate the bottom line. The Falcon 9, Soyuz, and Zenit avoid that by being fairly short and doing as little as possible upright, with a simple boom that raises the rocket. That gives way pretty quickly to a tower as the rocket size increases, and tower costs would probably follow a cube or fourth power law versus height. At some point most of your employees are tower-painters.

In contrast, a single maneuver right after lift-off is pretty simple. You know the rocket's launch mass and moment of inertia and can exactly calculate the thrust profile and impulse required. A lot of military missiles use a stage 0 booster and post-launch maneuver just to avoid back-blast from the main engine. The Navy even launches ICBM's from underwater. Some of the rocket hobbyists already have difficulties erecting their towers and rockets, and then have to climb precarious extension ladders for launch prep. If they'd add some high-thrust low-impulse solids they could leave it horizontal, blast it ten or twenty feet in the air while rotating, fire one opposite motor to kill the rotation, and then ignite the main motor, using anything from a simple timed sequence to a sophisticated control system (which the BATF really frowns on). It might be fun to play with some Estes motors and a simple controller just to show something weird and new in a hobby launch.

Doing something like that on the Falcon 9 would only take two Orion abort motors (which have 500,000 lbs thrust each and a 5.5 second burn). It's pointless on the Falcon, but they're not blowing a billion dollars on facilities. Air-starting the first stage shouldn't be shocking because we've been air-starting second and third stages, in flight, since the 1940's.

If you go liquid fueled for all the motors, you could have an intact abort and landing capability, and only about half the main engines at the base would need to rotate to lift the back end. If you want to avoid the weight penalty of liquid engines at the forward end, just use expendable solids, although that would probably rule out an intact landing unless you went ahead and seperated the stages and did an upper-stage fuel burn till it was light enough to set down. It's really not a major engineering challenge, and the result would have vastly more control authority in pitch and yaw.

[sojourner]

gturner wrote:

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It's really not a major engineering challenge

Seriously? If you think this is true, go post the idea on nasaspaceflight.com where the engineers actually hang out. I would love to see the reaction you get.

[gturner]

I've been discussing it in threads filled with NASA people. Former MSC flight directors blog too, you know, and just last night I was having an interesting discussion with one of the engineers who had the numbers of the Columbia foam strike before most others did. Of course nobody has plans for this type of launch, since we have lots of money to throw at the high-expense, low-risk path, but making a flight vehicle change course by 90 degrees isn't exactly difficult, though some people obviously think it's inconceivable.

[gturner]

I'll add that 9 out of 10 aerospace or control engineers would agree that the horizontal orientation is easier to control than a vertical rocket steerred from the back, because it would be like hovering a Harrier instead of balancing a broomhandle. There's no question that horizontal touch-down is much easier, not even requiring a digital flight computer to control orientation, because you've got full pitch, roll, and yaw authority, no big instability due to gravity wanting to tip you over, and you've got a big fat landing gear spread to set down on.

The problem with rear steer is that if your nose tips left, you drift left, and have to shift the base left to stay balanced, and further left to kill your drift and return to your original position, and then you have to shift to the right to kill the horizontal motion. The control problem is so difficult that NASA didn't even attempt rear steering with the lunar module, instead keeping the engine pointed through the center of mass, using side-mounted thrusters to keep the vehicle's orientation locked to a vertical gyro, also to move it around in X and Y. By comparison, horizontal take-off is a no-brainer. Once you're up, there are no precision requirements for the pitch maneuver because there's nothing you can crash into, much like the way a submarine-launched ICBM can dance around all over the place right after it clears the water. Compared to clearing the tower with a rear-steering tail-sitter (and there are very strict limits on allowable launch-area winds because of that), it's like doing a bellyflop compared to a ballet.

The advantage of the tail-sitter is of course simplicity, at least at first blush, because you just light the motor and only have two axes to contol (ignoring roll). It's based on a missile, not an easily controllable flying machine with oddles of thrust. We do it the way we do because spaceflight developed from missile programs instead of aviation programs. Or as Admiral Gehman, who lead the Columbia investigation, summed up the fatal, underlying flaw in NASA culture, “We do it this way, because this is the way we’ve always done it.” As rockets became bigger and more unwieldy, we just threw money at ground support instead of suspecting that there might be a simpler option. The large tail-sitting rocket is simpler, but the large tail-sitting rocket system is not.

[sojourner]

Oh for fuck's sake. Please don't try and move the goal posts. We're not talking about the inherent control advantages between vertical and horizontal flight. We're talking about the engineering fuck whittery of a rocket that takes off vertically while lying on it's side and THEN transitions 90 degrees before trying to achieve orbit. Like I said, go to nasaspaceflight.com and post this idea. See what kind of reaction you get. There's a difference between "I have talked to NASA people" and "I brought up this idea with them".

[gturner]

Why would NASA be interested in an idea that would throw most of them out of work and render much of their support structure obsolete, or can't you see that obvious consequence? They will build whatever the Senate tells them to build. They're not even trying to build a re-usable rocket anymore, much less innovate.

Apparently you also never saw the DC-X fly. It did loops. NASA didn't go for it. In fact, what they did go for is way crazier than horizontal launch, lighting two giant solids on the bet that they wouldn't have a differential thrust problem in a vehicle with no abort system at all, while using a piggyback configuration with wings where the aerodynamics and structural complexities were mind-boggling. They made whole chains of decisions on the Shuttle that carried greater risks and greater complexity than lifting a rocket into the air with rockets and then aiming it, which is something rocket folks have done ever since guidance systems were developed.

In contrast, horizontal launch wouldn't take but a couple of days to design, and Mythbusters could film it for an episode. You could do it with only two pre-determined fixed burns, one slightly forward of the center of mass that lifts and rotates around the center of percussion relative the thrust location (the majority of the Wiki references for the math on that are me), and one to slow the rotation after 90 degrees. I wouldn't use just one lift and rotate motor for structural reasons, but that's all there is to it.

By the way, the DC-X burned because it was a tail sitter that had a landing leg failure, and a re-usable tail sitter tips all the way over when that happens. A horizontal lander would just drop one end several feet and get dented. It's also a given that tail sitters can't have nice, shock absorbing landing gear like an airplane because then the gear wouldn't be stiff enough to hold it vertically without wobbling and tipping problems, which means they have to set down very, very gently. Almost all of Elon Musks problems with grasshopper are probably going to stem from the combination of balance and stiff narrow landing legs.

I don't know if any SpaceX engineers read where I comment (lots of former NASA and Rockwell people do) but the blogger who runs the site runs into Elon Musk pretty often. Maybe he'll mention it sometime.

[sojourner]

Nevermind. Come back when you're serious.