Space X to build reusable launch vehicle

[kunkmiester]

But this study does not give any economic reason for going back to the Moon, just how to do it the cheapest way.

For NASA with their focus on robots, it's not much. However, at least 20 million per person is good. There's a company selling seats for a flyby at 200 million a pop, and below fifty I believe is less than people have been paying for rides on Russian rockets.

First few crews to sign up get on TV while training and deciding which goes first. Later anyone who wants to can buy a seat, I'd imagine universities and most industrial countries would be interested.

Build your NERVA rocket on the moon, launch it from there.

[polyill]

Making big plans for the future, Elon gives up not on a weekly achievement

[GIThruster]

DC-X and Roton really did not have near so good a chance to succeed. Both suffer the problem that the pilot cannot steer because he cannot see where he's going. During reentry, plasma stops mission control from piloting, so this turns out to be an extremely difficult issue that there was never found an answer to.

Remote control? Worked for the DC-X, worked for the Buran.
Cameras?
There were never any windows planned in the Venture Star, btw and it was meant to be unpiloted (but with a crew module).
The rest about management at NASA being insane is certainly true.
What is also certainly true is that NASA chose the most ambitious design. The design by Boeing e.g. was basically a larger X37b and that one is working pretty well as we all know (also is remote controlled).
I still think that the DC- X was the best approach though. Wings suck in space
Either way, the Lockheed design was the dumbest of them all.

IIRC, the decision was not really handled by NASA. It was Al Gore's baby. He was riding shotgun over the whole thing for Clinton.

Wings do suck in space, but X-33 didn't have wings. It had an enormous returning fuel tank that had a little glide ability. The main advantage over a capsule is that you can see where you're going-- a spaceplane shape allows cameras to point in the direction of travel. You don't get that with a capsule. There would have been ways around but landing powered requires you carry fuel round trip and that's not especially efficient. The Venturestar would have operated much more cheaply--cheaply enough to be run by private industry and have them turn a buck. If NASA hadn't violated this boundary by building the LiAl tank, it might well be that the project would not have been considered out of control and been defunded by congress. IF Burt Rutan had been consulted from the start, there is an excellent chance Venturestar would be flying today, though whether it would be cheaper than Falcon and Zenit is an open question.

[Skipjack]

No, the venture star was also meant to NOT be controlled by the people on board, but by remote control and automatic approach, just like the X37 is doing quite successfully now and as the DC-X did many, many times without issues.
You do not need cameras for an automated or remotely controled approach, sensors are good enough. You can extend those (and cameras too, if you really want them) on the side, once the vehicle has slowed down enough.
The X33 was originally meant to be a pure lifting body, but it sucked. They originally only has small stabilizing wings on it and over time they got bigger and bigger and the whole thing got heavier and heavier.
The requirement for the thing to have such a huge payload was also totally stupid. Typical NASA thinking. It needs to be a launcher that does everything and everything badly, just like the shuttle was.
Finally, the amount of fuel that you need to cary for the landing is not that extreme.
Either way, the Venture Star was the worst choice that NASA could have made, because it was the most ambitious of all designs. The others tried to achieve less and would have had a much higher chance of success with that.

[charliem]

I've been giving a little more thought to the question of Falcon-9 VTVL. For now I've concentrated on the problem of the 1st stage.

A FEW RELEVANT NUMBERS WE KNOW:

From Falcon 9 first 2 launches:

• 1) The separation of stages 1 and 2 happened at 100-120 km of altitude.
  2) At that moment their inertial speed was ~3.2 km/s.
  3) Total thrust at lift-off was 4.94 MN (vacuum, about 10% less at sea level, or ~4.45 MN).
  4) Merlin 1C engines have an Isp at sea level of ~275 s.
  5) Falcon-9 total mass at launch was 333.4 t (metric), and just before separation about 59 t (my estimation).
  6) The 1st flight 1st stage crashed at 32 deg 07' N, 69 deg 15' W, 1150 km from Cape Canaveral, 400 km short of Bermuda.

WHAT THEY AIM FOR:

From their video looks that SpaceX is aiming to a flight profile a bit like this one for the Rossiyanka rocket, but with the first separation at higher altitude and speed:

http://forum.nasaspaceflight.com/index. ... 5157;image

WHAT THEY NEED:

• 1st: They need delta-v enough for decelerating the 1st stage after separation, and for power-landing. How much depends on the details.
  
  2nd: Maneuvering capability. That should not be a very tough problem given the low mass of the 1st stage after separation, although it will make it heavier (thrusters) and more expensive (thrusters + avionics).
  
  3rd: Keeping the 1st stage in one piece during reentry. It's not clear if the two first flights 1st stages broke or not before crashing, but some sources say that they did.
  
  4th: Heat resistance. Heat load is also dependent of the flight profile. I wonder how much that can be, and if the engines section is tough enough to endure it without modifications. Have no info/ideas by now.
  
  5th: The powered landing maneuver.

I think that the bigger problem is delta-v, followed by structural integrity, and maybe also the final powered landing.

ABOUT STRUCTURAL INTEGRITY:

Once you have thrusters to maneuver you can use them to help with orienting the stage during reentry to minimize dynamic loads. Low enough and fins and rogue parachutes become another option.

Maybe the problem came from the remaining fuel sloshing, but the two first Falcon 9 didn't have much of that left.

In any case the fact that the drag center of a cylindrical body is near its geometric center, while the mass center is displaced toward the engines, should help with stability.

If the problem was that the empty tanks collapsed from the external pressure, it does not sound that difficult to monitor it and enhance the already present pressurization system to compensate.

THE DELTA-V PROBLEM:

They could minimize the delta-v necessity by modifying the flight profile.

For example if they launched from south Texas instead of Florida (same latitude), they would not have to put the gears in reverse, because at ~1200 km E-NE they have Mississippi, Alabama and Florida. Or they could launch from Florida and land in Bermudas (of course if there's no breaking maneuver then heating at reentry would be a bigger problem, and there's also the issue of transport back to the launch complex).

To get more delta-v for the 1st stage, their options are:

• 1) Separate stages sooner, before all the fuel is spent (and leave the problem of getting to orbit to the 2nd).
  2) Switch to an engine with more Isp.
  3) Enhance the mass fraction by adding fuel so the rocket is heavier at launch, but the same (or, even better, lighter) at separation.

WHAT THEY HAVE:

Mainly what they have is a more powerful engine. Merlin 1D seems to have 12% more thrust than its older brother Merlin 1C, more or less the same Isp (just 1-2% more), and less weight.

That higher thrust will allow to make the 1st stage heavier, adding fuel, and engines being lighter will compensate for some of the weight of the new thrusters and avionics.

Because the Isp is more or less the same, from the rocket equation we can deduce that, if they want to retain the speed of 3.2 km at separation, then the mass fraction will be also the same, but starting from a bigger initial mass that means more final mass too.

If they renounce to a heavier second stage then all that extra mass is fuel.

But the second stage also has an enhanced engine. In this case it would be better if they tune Merlin 1D Vacuum to have the highest Isp possible. In that way, and starting from a second stage of the same weight than before, they'd obtain more delta-v.

That extra delta-v could be used to advance the separation of stages 1 and 2. In that way there would remain even more fuel in the 1st, and it would also travel at a lesser altitude and speed, making reentry easier.

Of course if they solve all these problems still have the issue of controlling the final landing maneuver, and that's where the Grasshopper RLV fits.

[GIThruster]

No, the venture star was also meant to NOT be controlled by the people on board, but by remote control and automatic approach, just like the X37 is doing quite successfully now and as the DC-X did many, many times without issues. . .
Either way, the Venture Star was the worst choice that NASA could have made, because it was the most ambitious of all designs. The others tried to achieve less and would have had a much higher chance of success with that.

The thing that made X-33 more ambitious than its competition was the aerospike, which it did not need. SSME's would have worked fine. It was the bonehead approach of trying all manner of new tech in a single project that killed the project. SSME's are efficient enough that with a properly designed composite tank the thing would have flown fine.

Not sure what you think makes it similar to Shuttle. It's Shuttle's placement of crew and cargo together, with the huge robotic arm; that made it so inefficient. Venturestar was never planned to carry crew--just a large payload. Unlike Shuttle's tile TPS, Venturestar was slated to be metallic and so would have needed very little down time and maintenance by comparison.

And yes, though X-33 and Venterurestar were never meant to be manned, they do need active sensors and cameras to fly. That is a severe problem for capsules like Roton and DC-X that they never solved. The later flew just 8 times and then crashed on landing because it was so frightly difficult to control with no down-looking sensors. That, according to Gary Hudson; is what killed both designs. Capsules require a heat shield where you need your sensors.

[93143]

It's Shuttle's placement of crew and cargo together, with the huge robotic arm; that made it so inefficient.

Not really; the problem was that the orbiter was a do-everything reusable spacecraft that the stack couldn't be flown without. (Not really a problem, if it hadn't been so darn expensive...) The fact that it was manned was one factor among many, though I grant that it seems to have been one of the more major ones, along with the payload mass/volume and cross-range requirements...

But I won't stand for you slagging the Canadarm. The whole thing weighed 450 kg installed - less than half a ton, or well under two percent of STS' payload capability - and it was an invaluable resource. It also folded up neatly to the side of the payload bay, so it didn't crowd the payload. I can't fathom why anyone would complain about it.

[Skipjack]

The thing that made X-33 more ambitious than its competition was the aerospike, which it did not need.

What about the huge crossrange that it did not need, what about the composite tank that it did not need, why did it have to have a payload and payload bay exactly like the shuttle?
The huge size of the thing combined with the need to erect it for every launch also would have made problems. You cant possibly pack it on the back of a 747 and fly it back to the cape, so what would they have done if it had to land somewhere else? With a VTOL vehicle all you need is a concrete pad and some fuel tanks and you can launch and land almost anywhere. No need for gigantic facilities to erect the thing and do god knows what.

And yes, though X-33 and Venterurestar were never meant to be manned, they do need active sensors and cameras to fly.

The Venture Star would have had a crew payload module, of course. Some even wanted it to be piloted. The X33 was meant to be a subscale remote controled prototype.

That is a severe problem for capsules like Roton and DC-X that they never solved. The later flew just 8 times and then crashed on landing because it was so frightly difficult to control with no down-looking sensors.

But the DC-X was a huge success and demonstrated all the abilities needed. Please read up on that!
The crash was because a leg did not extent.
It had a hard landing once, but that caused only very minor damage and was fixed within a few days. The hard landing was attributed to an overworked crew which was constantly fired and rehired and all that. Not a good environment to work in.
There are a thousand ways to solve the issues with the sensor placement. I dont see at all why that would be a bigger one than on the X33. Either way, it was obviously solved very well for the DC-X.
The Roton had problems and was indeed very hard to fly, but that had several reasons. One was that it was actually meant to be flown by the on board crew which had limited view of the ground. That only was the lesser problem, the bigger one was the whole rotor thing, which turned out to be very difficult to control.
Still the Roton made several successful flights and the piloting issues could have been resolved with remote control. The rotor and trimming issues were the bigger problems overall.

[GIThruster]

But the DC-X was a huge success and demonstrated all the abilities needed. Please read up on that!

I've seen that reading of the facts and can't agree with it. It flew only 8 times and had severe mishaps on more than half of them, including 2 fires, an explosion and the accident blamed on overworked crew. IMHO, it's a stupid design. Trying to balance a pencil on the tip of one's finger is essentially what landing vertical and powered is trying to do, and given the slightest mishap, crosswind, etc, you have a crash. Add to this that you have to carry large amounts of fuel round trip and you have one silly notion piled up atop the next.

What's not in Musk's envisioned version is I'm sure, the use of parachutes for most of the return trip. That makes some sense, but I honestly doubt he'll ever be able to balance such an ungainly launch stage in a useful manor. We're here talking about losing large mass fraction and risking destruction of the stage in event of any small problem, simply to avoid picking up the stage at sea. I doubt it will ever be tried.

[kunkmiester]

Is there a real difference in the delta V that means a horizontal TOL and vertical TOL vehicle can't be the same weight?

Makes me wonder if the falcon couldn't be turned on it's side, and flown from a runway if it's capable of carrying the delva V to make a powered vertical landing. A bit of reshaping--you want a lifting body, not a winged plane apparently, though I fail to see the issue with wings.

Killing half or more of the payload would probably mean nothing if it's actually capable of beign completely reused, look at Skylon.

[GIThruster]

Is there a real difference in the delta V that means a horizontal TOL and vertical TOL vehicle can't be the same weight?

Makes me wonder if the falcon couldn't be turned on it's side, and flown from a runway if it's capable of carrying the delva V to make a powered vertical landing. A bit of reshaping--you want a lifting body, not a winged plane apparently, though I fail to see the issue with wings.

Killing half or more of the payload would probably mean nothing if it's actually capable of beign completely reused, look at Skylon.

DC-X and X-33 were much more similar than most realize. They were both designed to burn H2 which means a huge tank. In both, the size of the tank was used to spread out the thermal loading during reentry, so the craft could use the very low maintenance metallic TPS and so be commercially viable. The cost of flying back in X-33 is found in the control surfaces and landing gear. Since the gear was intended only to be used when the tank was empty, the gear wasn't expected to weigh much. The cost of powering back in DC-X was in the weight of the fuel making a round trip. Those are the significant design differences. Details like engine type really ought not have come into the decision making process and if someone had funded both projects and the aerospike worked on the Venturestar, you can guess it would have been incorporated into the DC-Y and follow-ons.

DC-X was planned to reenter atmo same as X-33--pointy end first. It was only after it had slowed hugely that it was supposed to rotate and restart its engines. When you read that everything needed to pull off the DC-X flight was accomplished, all I can say is, not by a longshot! It never did more than fly up a few thousand feet and never for more than 3 minutes. Never had to rotate with its skin burning hot, never had a test of the heat shield, never did much of anything and when it did fly, it crashed, burned or exploded more than half the time. Because it was returning with fuel, the danger involved with a mishap, especially on the pad, was enormous. Dropping a very hot rocket on it's side and bursting a composite tank, that still has appreciable amounts of H2 and O2 is a prescription for a nightmare.

Comparing Falcon to both these, first thing is it cannot use its fuel tank body to distribute the heat loading as the others, because it has a denser fuel and a much smaller tank. Falcon burns kero. The tank can't be used as a speed break in the same way. This requires much more powered thrusting above atmo to stop it from burning up on reentry. The simplest way back for Falcon, parachuting into the sea; is in many ways more difficult because of the smaller tank. Adding to the difficulty a cool powered landing doesn't seem to me to make much sense. OTOH, since they already need to restart the engines to deorbit, doing it again close to the ground might make some sense. You'd need to have a very careful look at the numbers and be mighty sure you can balance a rocket like that. Seems a little reckless to me but I suppose if there's no one within a dozen miles and the rocket goes BOOM, it's only money.

[Skipjack]

It flew only 8 times and had severe mishaps on more than half of them, including 2 fires, an explosion and the accident blamed on overworked crew.

The DC-X and the DC-XA combined flew a total of 12 times, not 8.
The DC-X flew 8 times. the DC-XA 4 times.

never did much of anything and when it did fly, it crashed, burned or exploded more than half the time.

Where are you getting this from??
It only exploded once, when it fell over. The rest were minor fires and one (very small) explosion caused by deliberately putting the vehicle into situations that would be cause problems and none of them caused any permanent damage to the vehicle (with the exception of the one where it tipped over).
The explosion when it fell over also only happened when a pressure test of the tank caused it to leak. The actual accident of it tipping over by itself would have not caused the explosion, It was the combination of a leaking tank (from tests done to the tank) and the vehicle falling over that caused the explosion.
Dont forget that this is a test vehicle, a prototype. It is meant to break. It is meant to be put through all sorts of situations that will make it fail. You want to provoque failure, because that is how you learn for future flight operations.
This is why it was called an X- vehicle.

It never did more than fly up a few thousand feet and never for more than 3 minutes. Never had to rotate with its skin burning hot, never had a test of the heat shield, never did much of anything and when it did fly

Remind me again, what did the X33 accomplish? Oh, yes that is right, NOTHING! Because it cost several orders of magnitude more than the DC-X and still ran out of money.
Compared to that the DC-X was waaaay more successful. It demonstrated fast turnarround times (26 hours) for a rocket powered VTOL vehicle, pin point landing for a VTOL vehicle. It demonstrated the entire flight profile intended including high angle of attack for the vehicle (but at a lower altitude of "only" 3100 meters). It also provided first tests of such a VTOL SSTO vehicle, something that had never been attempted before.
All that for a vehicle that cost about 50 million to build, today NASA cant even do a design study on paper for that amount of money.

[GIThruster]

You can argue that because it's an X plane it's supposed to fail, but certainly DC-X failed. X-33 did not even get the chance to fail. DC-X's composite tank was built by Scaled Composites so it worked, even after being smacked and cracked and burned and exploded. NASA hired a bunch of people who had never built a composite so their tank failed before even a first flight was attempted. Neither program "succeeded" in being more than an expensive curiosity.

The real question is whether its a good idea to land a spacecraft (like Falcon) with reverse thrust. IMHO, it is not. It's very dangerous and less economical than a glide reentry. It is however the only way to land in environs without atmosphere.

You're acting as if DC-X was somehow the first to accomplish powered landing, but Eagle did this on the Moon in 1969 and Luna did this unmanned in 1966.

Forgive me if DC-X makes me yawn but move along people. . .nothing to see here.

The only thing DC might have done that would have been new was the powered reentry and rotation phase of a return to atmo flight, and it was not designed to go that high. That would have required DC-Y.

[Skipjack]

You can believe whatever you want, but there are many people that I know that think differently, people like Gary C. Hudson, e.g.
You know, people that actually know what they are talking about and you have not said anything that convinces me otherwise.

Either way, I am sure that the people at SpaceX also know what they are doing. They have been quite successful so far.
I am very sure that they will make it work. The result might not be exactly like in the video, but I doubt that they expect it to be that either.
It is quite clear to me that ever since von Braun left NASA, or NaySay as Burt Rutan calls them, have not built a single working launch vehicle and have done nothing but waste billions over billions on very, very expensive paper rockets and cancelled projects that saw tremendous cost overruns.
This allone is enough to convince me that NASA should not be trusted with building new LVs. Instead this should be left completely to commercial providers.

[DeltaV]

http://www.aviationweek.com/aw/generic/ ... Commercial Crew Initiative Called Underfunded&channel=space

HOUSTON — Funding for NASA’s commercial crew space transportation services initiative appears headed for funding problems that could undermine the agency’s efforts to regain the independent U.S. human launch capability that lapsed with the shuttle program’s retirement earlier this year, members of NASA’s Aerospace Safety Advisory Panel (ASAP) warned Oct. 21.

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