Delta Clipper and DC-X /DC-XA.

[vulture4]

<p>>>But there is some thing I'm not understanding .Why is plane&nbsp;engines getting more powerful and fuel efficient but not rocket engines?</p><p>The simple answer is that more is being invested in jets, since they are a bigger business, and there is more room to improve them. Both jets and rockets are heat engines, limited by the Carnot cycle. For jets, the compression ratio, the degree it compresses atmospheric air before heating it,&nbsp; is the best indicator of efficiency; for large jets this is now an incredible 40:1, and as stronger and more heat-resistant turbine and compressor blades are developed, triple spools, etc. the compression ratio, and thus the efficiency could go up further. </p><p>For rockets the working fluid starts as a liquid or solid, so it is fully compressed, and the expanded exhaust has most of the energy it can get from the fuel.&nbsp; </p><p>&nbsp;</p>

 

[nec208]

<p><BR/>Replying to:<BR/><DIV CLASS='Discussion_PostQuote'>Plane engines are getting more & more powerful & fuell efficient because most of their reactans mass is air, you suck air, compress it, burn it and you have trust. You can suck more air for more thrust or you can suck the same air in less space to save fuel. Also now there are plans to switch the jet fuel to hydrogen (used in the first jet engine), which is lighter, cleaner & has higher Isp, but storing&nbsp; the liquid hydrogen is complex and not effective for jets Rocket engines carry everything onboard, so you don't have an unlimited reactans mass, so only way to increase performance is to compress the fuel to high pressure (like the N1 engines) and use effective nozzles or aerospike. Rocket engines using hydrogen are more efficient, however the tanks & pipes for liquid hydrogen are expensive so the whole rocket is more expensive than a RP1 rocket.If in the near future storing of liquid hydrogen is improved it would be really cool, we will have greener, faster jets, and cheaper rockets. <br />Posted by marko_doda</DIV></p><p><font size="2">So if there was air in space we would not have this problem? And going in space would be safe and cheap? And you could take a&nbsp;big 747 space plane in space or even bigger.</font></p><p><font size="2">I would like you or someone here to elaborate (((If in the near future storing of liquid hydrogen is improved it would be really cool, we will have greener, faster jets, and cheaper rockets)))</font></p><p><font size="2">Also I would like to say it takes a very big rocket to put space capsule in space.You want to go in space you have 2 option use a space capsule on top of a rocket&nbsp;or a shuttle on a big rocket&nbsp;with 2 or 3 boosters.</font><font size="2">It is clear that to put some thing small in space like small space capsule&nbsp;you need a big rocket.</font></p><p><font size="2">This is not the case with cars and planes has the engine is smaller than the mass that is to be moved.And with rocket&nbsp;the engine is very big than the mass to be move.</font><br /><br />&nbsp;</p> <div class="Discussion_UserSignature"> </div>

 

[marko_doda]

<p>Its not about the engine, it is the fuel/oxidizer and how much energy it takes to do the job, the car just sits on the road and the engine only needs to provide pover so that the wheels can turn under the wieght of the vehicle, even one man can push a car & move it. airplanes use jet engines which blow hot air to speed it up to 900 km per hour, but still, the wings provide lift, not the engines.</p><p>Rockets you must speed it to orbtal, wich requires a lot of energy, so even the most powerfull jet engines cant lift the rocket in the atmosphere, and you need to use rocket engines, wich carry the oxidizer with them, so it gets really heavy and then the only way to go to orbit is to go vertical cause the wings would be to big to be cost effective </p>

 

[vulture4]

<p>Advances are being made. In the 60's liquid hydrogen was a new fuel, engines using it had good Isp but not a lot of thrust, and using LH2 to power the first stage of a large rocket like the Saturn V would have been considered a poor choice. The SSME was a large step forward, but still not enough thrust for launch without the SRBs. The RS-68 has ten percent of the parts of the SSME and twice the thrust, sacrificing slightly in Isp to achieve this. It allows the Delta IV heavy to take off with only liquid hydrogen propulsion, the first rocket ever to do so. Boeing proposed notional variants all the way up to 100MT to LEO, all with liquid propulsion only except for small monolithic SRBs on some variants.&nbsp; </p><p>Cost is the bottom line, and there are orders of magnitude of room for improvement there. If aircraft were expendable, air travel would be an impractical stunt.&nbsp; The fuel that puts the Shuttle in orbit only costs $100K or so; essentially 100% of the cost is the labor to assemble and maintain the vehicle. When we have a fully reusable launch vehicle, human spaceflight will become practical. The DC-X was just an unmanned suborbital test vehicle, but it was a step toward this technology. </p>

 

[nec208]

<p><BR/>Replying to:<BR/><DIV CLASS='Discussion_PostQuote'>Its not about the engine, it is the fuel/oxidizer and how much energy it takes to do the job, the car just sits on the road and the engine only needs to provide pover so that the wheels can turn under the wieght of the vehicle, even one man can push a car & move it. airplanes use jet engines which blow hot air to speed it up to 900 km per hour, but still, the wings provide lift, not the engines.Rockets you must speed it to orbtal, wich requires a lot of energy, so even the most powerfull jet engines cant lift the rocket in the atmosphere, and you need to use rocket engines, wich carry the oxidizer with them, so it gets really heavy and then the only way to go to orbit is to go vertical cause the wings would be to big to be cost effective <br />Posted by marko_doda</DIV></p><p>It is the air that pushes the&nbsp;plane up .The faster the egine the more air.But like the other poster was saying the only reason car engines and plane engines are getting faster every year is because of moving parts .But rockets have no moving parts.</p><p>&nbsp;The rocket engine can safe on fuel by burning less fuel.If there was no air no plane will work.</p><p>&nbsp;</p> <div class="Discussion_UserSignature"> </div>

 

[annodomini2]

<p><BR/>Replying to:<BR/><DIV CLASS='Discussion_PostQuote'>It is the air that pushes the&nbsp;plane up .The faster the egine the more air.But like the other poster was saying the only reason car engines and plane engines are getting faster every year is because of moving parts .But rockets have no moving parts.&nbsp;The rocket engine can safe on fuel by burning less fuel.If there was no air no plane will work.&nbsp; <br /> Posted by nec208</DIV></p><p>Yes as the plane is travelling faster it encounters a greater volume of air.</p><p>&nbsp;But, the friction with air goes up square that of speed</p><p>&nbsp;</p><p>Cars are getting more efficient due to the way they operate and moving parts.</p><p>&nbsp;</p><p>Jet engines are getting more efficient due to changes in the aerodynamics inside the engine.</p><p>&nbsp;</p><p>There is a company called reaction engines who are working on an airbreathing rocket engine also known as LACE (Liquid Air Cycle engine), which could offer the possibility of SSTO with their skylon spaceplane, but this has yet to be proven. </p> <div class="Discussion_UserSignature"> </div>

 

[pmn1]

From the Astronautics site

http://www.astronautix.com/lvs/shuttle.htm

VTOVL orbital launch vehicle. Status: Study 1971. Manufacturer's Designation: SERV.

Chrysler ballistic single stage to orbit alternate shuttle proposal of June 1971. This was the most detailed design study ever performed on a VTOVL SSTO launch vehicle. The 2,040 tonne SERV was designed to deliver a 53 tonne payload to orbit in a capacious 7 m x 18 m payload bay.

The Chrysler SERV single-stage-to-orbit ballistic vehicle was the subject of a six-volume report produced under the $ 1.9 million NASA contract NAS8-26341. The booster could be launched from the existing LC39 built for the Saturn V. SERV would be built at NASA's Michoud facility and transported by a 'Bay'-class vessel modified to carry the wide load through the existing inland waterway system between Michoud and Cape Canaveral. SERV was a squat 27.4 m in diameter and 20.3 m tall. A payload of 52,800 kg, housed in a 7 m x 18.3 m cargo bay, could be transported to a 185 km/28.5 deg orbit. The vehicle was powered by a 12-module aerospike engine, 26.6 m in diameter and 2.5 m tall, producing 2.45 million kilograms of thrust at a specific impulse of 347 seconds at lift-off. The engine could be throttled to 80%, and the turbopumps were interlinked, so that the failure of any one pump could be compensated for by bringing the others up to 120% of their rated capacity. Protective doors covered the engine during the base-first re-entry, which would be accurate enough to bring the booster to within 6500 m of the aim point.. After slowing to subsonic speed,. 28 x 11,400 kgf turbojet engines powered by JP-4 fuel braked the spacecraft to a hover and soft touchdown on landing pads 2.8 km from the Vertical Assembly Building at the Kennedy Space Center. For manned missions, a MURP spaceplane would be used for separate return of the crew to earth. Total development costs was estimated as $3.565 billion, with each SERV costing $350 million in FY1971 dollars, and being rated for 100 flights over a 10 year service life.

As had Philip Bonob at Douglas before them, the Chrysler team, led by Charles Tharratt, fervently believed that they had the best solution to providing America with routine access to space. But NASA was wedded to the concept of a winged shuttle and never gave SERV any serious consideration.

Manufacturer: Chrysler. LEO Payload: 52,800 kg (116,400 lb). to: 185 km Orbit. at: 28.50 degrees. Liftoff Thrust: 25,795.300 kN (5,799,014 lbf). Total Mass: 2,040,816 kg (4,499,229 lb). Core Diameter: 27.40 m (89.80 ft). Total Length: 20.30 m (66.60 ft). Development Cost $: 3,565.000 million. in: 1971 average dollars. Flyaway Unit Cost $: 350.000 million. in: 1971 unit dollars.

* Stage1: 1 x Shuttle SERV-1. Gross Mass: 2,040,816 kg (4,499,229 lb). Empty Mass: 226,757 kg (499,913 lb). Motor: 1 x Plug-Nozzle SERV. Thrust (vac): 31,980.515 kN (7,189,506 lbf). Isp: 455 sec. Burn time: 249 sec. Length: 20.27 m (66.50 ft). Diameter: 18.29 m (60.00 ft). Propellants: Lox/LH2.



Was this idea workable and why did they design for 52,800kg to LEO, this is way above what NASA and the USAF were looking at?

 

[vattas]

Sorry, but what's the point of VTOVL (and powered landing) - bringing all this fuel needed to land up and then down?

 

[pmn1]

Some more information on SERV

http://forum.nasaspaceflight.com/index.php?topic=5771.0

 

[annodomini2]

Sorry, but what's the point of VTOVL (and powered landing) - bringing all this fuel needed to land up and then down?

True on earth an aerobraking landing system is more practical where a dense atmosphere is present, but on the moon there is very little atmosphere and so this type of system is necessary.

 

[vattas]

True on earth an aerobraking landing system is more practical where a dense atmosphere is present, but on the moon there is very little atmosphere and so this type of system is necessary.

Of course, you have no other choice on space bodies without atmosphere. But why do this on Earth?
OK, one of the reasons to do this can be if you want to bring down something really heavy. I imagine, that designing parachutes for 100t+ spacecraft could be a real challenge. The question is, is there anything so heavy that we NEED to bring down? I think not.
It would be interesting to hear, why Armadilo Aerospace choose VTVL approach for their vehicles. Because they plan to use developed technology for making lunar crafts or what?

 

[annodomini2]

True on earth an aerobraking landing system is more practical where a dense atmosphere is present, but on the moon there is very little atmosphere and so this type of system is necessary.

Of course, you have no other choice on space bodies without atmosphere. But why do this on Earth?
OK, one of the reasons to do this can be if you want to bring down something really heavy. I imagine, that designing parachutes for 100t+ spacecraft could be a real challenge. The question is, is there anything so heavy that we NEED to bring down? I think not.
It would be interesting to hear, why Armadilo Aerospace choose VTVL approach for their vehicles. Because they plan to use developed technology for making lunar crafts or what?

Research and development, these are test vehicles, one of the issues with large liquid fuelled engines is stopping and restarting them without reliability problems.

Programs like this are good for testing reliability improvements in engine design, they are also useful for testing control systems to handle powered landing.

As a conventional liquid fuelled launcher powered landing is not really an option from a payload perspective doesn't make it commercially viable

As a passenger vehicle though powered landing may be useful for the occupants of the vehicle, but for earth use using aerobraking makes more sense.

 

[annodomini2]

True on earth an aerobraking landing system is more practical where a dense atmosphere is present, but on the moon there is very little atmosphere and so this type of system is necessary.

Of course, you have no other choice on space bodies without atmosphere. But why do this on Earth?
OK, one of the reasons to do this can be if you want to bring down something really heavy. I imagine, that designing parachutes for 100t+ spacecraft could be a real challenge. The question is, is there anything so heavy that we NEED to bring down? I think not.
It would be interesting to hear, why Armadilo Aerospace choose VTVL approach for their vehicles. Because they plan to use developed technology for making lunar crafts or what?

Research and development, these are test vehicles, one of the issues with large liquid fuelled engines is stopping and restarting them without reliability problems.

Programs like this are good for testing reliability improvements in engine design, they are also useful for testing control systems to handle powered landing.

As a conventional liquid fuelled launcher powered landing is not really an option from a payload perspective doesn't make it commercially viable

As a passenger vehicle though powered landing may be useful for the occupants of the vehicle, but for earth use using aerobraking makes more sense.