Economics of space flight/2nd Stage reusable orbiter

[dmc6960]

I've been caught up lately on the debacle over the economics of reusability of spacecraft. Failures like the X-33, orbital space plane, and all the criticism over the shuttle have gotten me thinking.<br /><br />From what I understand in short, the X-33 failed due to soaring development costs and engineering problems.<br /><br />The Orbital Space Plane never had the true support from NASA.<br /><br />The Shuttle is said to be too complex to economicly refurbish for each flight.<br /><br />One thing I have not been able to find out is what exactly is easily reusable on a spacecraft, what is a maintenence nightmare, and what is downright worthless after each flight. What was the anticipated turnaround time for the X-33 or VentureStar? What had to be serviced? Obviously rocket engines take a beating after each time they are used, but the SSME's have done their task well. As for the cost and time of refurbing each engine after flight, I have no clue. I would be curious to know however. They are also very powerful engines, would I be correct in guessing that a smaller engine on the scale of 50,000-75,000lbs thrust, if built robustly, could be refurbished quickly, easily, and cheaply after each flight? I cant imagine the electronic components deal with much wear. The airframe needs to deal with a lot of stresses, but so do airplanes and they last for thousands of hours in the air. Do RCC heatshields only last once? Are there any revolutionary new materials that could make a better heatsheild than RCC or ceramic tiles? Thats only a fraction of the logistics of spaceflight, but I'm only generalizing here.<br /><br />What I am getting at is something I think has been overlooked as a serious way to get people into orbit for cheap. Whenever I look at a modern expendable rocket, I see a massive first stage with powerful engines, and a small 2nd stage with a much more efficient engine. Also now with SpaceX planning to reuse their first stage, and the reusability of the Shuttle SRM (

 

[holmec]

>why not just stick with a big powerfull 1st stage which 'could' be reusable, and then stick a lifting-body craft with a built-in reusable 2nd stage motor to reach full orbit on top of that<<br /><br />You bring up good points. Points that I have debated myself. Sure we could answer those points in any numberous ways by building a system any number of ways. But looking at the CEV and its launch vehicle. The first stage is a solid rocket booster. I can only imagine that this is resusable.(sure its a shell, but it gets refilled with solid rocket fuel with proven manufacturing processes). So actually that seems to be in a nice package. The CEV itself is reusable. For about 10 flights. This is good because its small enough to be replaced, big enough to reuse (clean, change sewage, restock food, repair systems that broke, maintain all other systems, check everything). Ok NASA for the longest time have been "playing" with lifting bodies. Lifting bodies are fine flying in the horizontal, and ok for landing, though they had some stability problems. Now, here is the thing. When you are reentring Earth's atmosphere from LEO, you have this tremendous potential energy (because your going 18,000 mph), so you really don't need propulsion coming in. Now in such a situation, if you think about it the best configuration for a body is a dart. Not a plane, a dart. Why a dart? A dart naturally has a controlled trajectory and control at high speed. Hence missles look kinda like darts. So what NASA did with the capsule is to make it a shape that would be the head of the dart, but give it a natural breaking capability. I thought they could flare out the sides more to give more of a breaking power and less heat from viscosity. Now instead of fins for the dart, NASA used thruster to control the capsule and in the air two sets of parachutes. Rutan did a dart configuration on SpaceShipOne. When the "fether" is up on SpaceShipOne then the ship is a dart with high drag <div class="Discussion_UserSignature"> <p> </p><p><font color="#0000ff"><em>"SCE to AUX" - John Aaron, curiosity pays off</em></font></p> </div>

 

[spacefire]

I guarantee a reusable lifting body orbiter will be cheaper to maintain and operate than building a capsule of the same size for every flight.<br />A rocket engine might be cheaper to discard, but not a complex craft with life support systems and avionics. <div class="Discussion_UserSignature"> <p>http://asteroid-invasion.blogspot.com</p><p>http://www.solvengineer.com/asteroid-invasion.html </p><p> </p> </div>

 

[holmec]

>I guarantee a reusable lifting body orbiter will be cheaper to maintain and operate than building a capsule of the same size for every flight. <<br /><br />Are you sure about this? One word: Heat-shield. How do you create a heat sheild for a lifting body that is cheaper and easier to maintain thatn a capsule's heat sheild?<br /><br />The biggest prblem here is landing gear. A capsule can have a continuous unbroken, no holes heat-sheild. A landing gear requires a sheat sheild that has joints. Hence the Shuttle Orbiter's tiles.<br /><br />The only other way to prevent burnup on reentry is to slow the craft down enough. Either you have a lot of fuel to burn to slow down, or you use the atmsophere and viscosity. And eventhough SpaceShipOne used this technique, this is not proven from orbit, just suborbit. I hope it would work from orbit. I also wished it worked from a lunar trip. If it did, a SpaceShipTwo and a lifting body could be viable.<br /><br />Also how can a lifting body, a complex shape that requires flaps and contols, be cheaper than a capsule, a more simpler design. Complexity ususally results in higher cost. <br /><br />Also the CEV will last for 10 flights. if your comparing an Apollo capsule to a lifting body thats reusable, you might have a point. Yet the CEV is supposed to be reusable.<br /><br />Also I am sure that after the 10th flight of a CEV, the avionics and equipment will be pulled out and serviced and put back into a new capsule frame. So your not loosing much there.<br /><br />Remember that the CEV will not be an Apollo capsule. It will look like one, but it will be much different in the way its maintained and in the way its constucted. I think we may find out that NASA is going to make a home run with the CEV.<br /><br />Don't get me wrong. I love the lifting body. I love its shape and its compact size. There are inherit stability problems with it but a larger tail can accomodate that. The other thing is that its shape is not suited <div class="Discussion_UserSignature"> <p> </p><p><font color="#0000ff"><em>"SCE to AUX" - John Aaron, curiosity pays off</em></font></p> </div>

 

[mcs_seattle]

Why not use a lot more RCC and a lot less tiles on the shuttle?<br />

 

[holmec]

I think the answer is cost. The tiles were cheaper than the RCC and needed to withstand less heat for much of the body surface of the Shuttle Orbiter. <div class="Discussion_UserSignature"> <p> </p><p><font color="#0000ff"><em>"SCE to AUX" - John Aaron, curiosity pays off</em></font></p> </div>

 

[holmec]

>The NASA requirement is "upto 10 flights" Zero is included in that requirement.<<br /><br />Let's hope for the best. <div class="Discussion_UserSignature"> <p> </p><p><font color="#0000ff"><em>"SCE to AUX" - John Aaron, curiosity pays off</em></font></p> </div>

 

[holmec]

>". And eventhough SpaceShipOne used this technique, this is not proven from orbit, just suborbit. I hope it would work from orbit."<br /><br />It will not work from orbit. <<br /><br />I think you might be right just because of the G forces. What is your reason? <div class="Discussion_UserSignature"> <p> </p><p><font color="#0000ff"><em>"SCE to AUX" - John Aaron, curiosity pays off</em></font></p> </div>

 

[holmec]

>There is too much enery to get rid of with that method.<<br /><br />For what the frame, the people? Please specify. <br /><br />Sure there is lots of energy and shedding energy is the key. But say what will fail first is where the rubber meats the road. <div class="Discussion_UserSignature"> <p> </p><p><font color="#0000ff"><em>"SCE to AUX" - John Aaron, curiosity pays off</em></font></p> </div>

 

[tap_sa]

Btw what 'method' are we talking about here? You make it sounds as if SS1 use some other means to slow down than capsules/shuttle. This is not the case, both SS1 during it's suborbital hops and all existing real spacecrafts use atmospheric drag to slow down. Tweaking wingtips in some clever manner doesn't change that.

 

[holmec]

Rutan used hi drag on a suborbital mish. Shuttle is coming in with much more energy. The feather provides hi drag and control without complicated avionics. So the SS1's body is perpendicular to its direction. the Shuttle does not maintain perperdicular angle to the direction of travel. Yes they are different.<br /><br />The real difference is that suborbital capsules had a heat shield and the SS1 did not. It found a work around. <div class="Discussion_UserSignature"> <p> </p><p><font color="#0000ff"><em>"SCE to AUX" - John Aaron, curiosity pays off</em></font></p> </div>

 

[spacefire]

<font color="yellow">The biggest prblem here is landing gear. A capsule can have a continuous unbroken, no holes heat-sheild. A landing gear requires a sheat sheild that has joints. Hence the Shuttle Orbiter's tiles. </font><br /><br />Assuming: 1)the heat shield will need to be reapplied after every flight ine ach case<br />2) once you lower the gear there's no reason to bring it back up<br /><br />You can make an uninterrupted heatshield and instead of doors have blow-panels for the gear.<br /> <div class="Discussion_UserSignature"> <p>http://asteroid-invasion.blogspot.com</p><p>http://www.solvengineer.com/asteroid-invasion.html </p><p> </p> </div>

 

[tap_sa]

I wasn't referring to details of orientation and guidance, only to the fact of using atmospheric drag to slow down. Your earlier post gave impression that you think this is different from shuttle coming down belly red hot, which it's not. Only reason why SS1 doesn't need heatshield is the slow re-entry speed. It's slow because of the mission profile, not the craft design feather thingies.

 

[tap_sa]

<font color="yellow">"The real difference is that suborbital capsules had a heat shield and the SS1 did not. "</font><br /><br />What suborbital capsules? If you are thinking early Mercury flights here they were suborbital only because NASA proceeded cautiously towards LEO. They tested orbital vehicle with underpowered booster to check up the systems before the real thing. And even the slowest manned suborbital Mercury mission went at least twice as fast as SS1.

 

[holmec]

>And even the slowest manned suborbital Mercury mission went at least twice as fast as SS1<<br /><br />And you made my case. <div class="Discussion_UserSignature"> <p> </p><p><font color="#0000ff"><em>"SCE to AUX" - John Aaron, curiosity pays off</em></font></p> </div>

 

[holmec]

>I wasn't referring to details of orientation and guidance, only to the fact of using atmospheric drag to slow down. Your earlier post gave impression that you think this is different from shuttle coming down belly red hot, which it's not. Only reason why SS1 doesn't need heatshield is the slow re-entry speed. It's slow because of the mission profile, not the craft design feather thingies.<<br /><br />And a slow re-entry is the point. Rutan made this point on the Discovery Channel's Dark Sky DVD. All other manned craft uptil SS1 needed a heat sheild and this is the difference I was refering to. Rutan's technique is new. Its composed of auto orientation via the feathering, max drag, and slow speed, and light weight. While the Shuttle comes in much faster and thus burns. I was talking in the difference of techniques not of neccearily technology. Thus I used the word method, refering to in a procedural point of view. <br /><br />Granted they both plunge into the atmoshpere. <div class="Discussion_UserSignature"> <p> </p><p><font color="#0000ff"><em>"SCE to AUX" - John Aaron, curiosity pays off</em></font></p> </div>

 

[tap_sa]

<font color="yellow">"And you made my case."</font><br /><br />I don't think so. SS1 doesn't go half the speed of Mercury-Redstones because Rutan just found out something marvelous that NASA missed in the early 60s. It does so because SS1's goal is just to reach 100km altitude while NASA's goal was to test orbital craft at near orbital altitudes and velocities.

 

[tap_sa]

<font color="yellow">"All other manned craft uptil SS1 needed a heat sheild and this is the difference I was refering to. "</font><br /><br />All other manned crafts (save for the two suborbital Mercury flights) return from stable orbit in at least 100nm altitude. SS1 returns from 100km jump straight up straight down. It's apples and oranges.

 

[holmec]

>All other manned crafts (save for the two suborbital Mercury flights) return from stable orbit in at least 100nm altitude. SS1 returns from 100km jump straight up straight down. It's apples and oranges.<<br /><br />Granted.<br /><br />The only closely comparable to SS1 is X-15. And X-15 needed a heat sheild to leave atmosphere. <br /><br />But still SS1 technique of reentry is unique. <div class="Discussion_UserSignature"> <p> </p><p><font color="#0000ff"><em>"SCE to AUX" - John Aaron, curiosity pays off</em></font></p> </div>

 

[tap_sa]

<font color="yellow">" X-15 needed a heat sheild to leave atmosphere. "</font><br /><br />...because it's purpose was to study the effects of <i>hypersonic</i> flights <img src="/images/icons/wink.gif" />

 

[holmec]

Feedom7 116mile altitude<br />http://www-pao.ksc.nasa.gov/kscpao/history/mercury/mr-3/mr-3.htm<br /><br />SS1 went 69.6 miles. <br /><br />Sure they had different purposes. SS1 made two trips in less than 2 weeks on a $20million shoe string budget. Freedom7 only 1 with all the backing of the US and to figure out how to operate in space. <div class="Discussion_UserSignature"> <p> </p><p><font color="#0000ff"><em>"SCE to AUX" - John Aaron, curiosity pays off</em></font></p> </div>

 

[holmec]

>You make it sounds as if SS1 use some other means to slow down than capsules/shuttle.<<br /><br />Not in slowing down. IN CONTROLLING THE SLOWDOWN! so heat shielding was not necessary.<br /><br />This gave advantage in the X Prize because no heavy heat shield needed. <div class="Discussion_UserSignature"> <p> </p><p><font color="#0000ff"><em>"SCE to AUX" - John Aaron, curiosity pays off</em></font></p> </div>

 

[tap_sa]

None of the X-Prize entries had any heatshield to speak of simply because the speed during mission never goes much past mach 3 and even that for a very short period of time. Orbital speed is mach ~25. <br /><br />SS1's horisontal velocity at apogee is practically zero while Mercurys were doing thousands of miles per hour.<br /><br />There's only two ways to come down from orbit without burning up: a) have a heatshield or b) powered deceleration and descent. Latter is only theoretical curiosity and remains so for a <i>very</i> long time. <br /><br />and c) space elevator may come some day, hopefully

 

[holmec]

There is another way. High drag. But you may sacrifice the crew for it. But maybe it may be possible with Aerobraking technique before making the plunge.<br /><br />This is a realm I believe we have to yet take advantage of. That is the hi drag/mass. Helios has a large amount of lift/weight and thus has been able to sustain flight only useing solar electric power. Well what happens when a hi drag body comes into the atmosphere?<br /><br />If we could use techniques base on hi drag for reentry we may be able to reduce the risk involved to people and equipment. That may mean less cost and less liablility. <div class="Discussion_UserSignature"> <p> </p><p><font color="#0000ff"><em>"SCE to AUX" - John Aaron, curiosity pays off</em></font></p> </div>

 

[holmec]

>None of the X-Prize entries had any heatshield to speak of simply because the speed during mission never goes much past mach 3 and even that for a very short period of time. Orbital speed is mach ~25.<br /><br />SS1's horisontal velocity at apogee is practically zero while Mercurys were doing thousands of miles per hour. <<br /><br />your not telling me anything new. I don't understand your argument. <div class="Discussion_UserSignature"> <p> </p><p><font color="#0000ff"><em>"SCE to AUX" - John Aaron, curiosity pays off</em></font></p> </div>