SCRAM jet + linear aerospike LV

[starfhury]

How complicated would it be to create an LV using combined SCRAM jet and linear aerospike technology? Looking at the overall design of X-43 and X-33, both vehicles have a fairly similar business end for the propulsion pod? Perhaps a SCRAM jet augmented version of the X-33 would have a better chance of succeeding than either version by themselves. For a version going to space, the air intakes might be mounted on the sides or even atop the vehicle so that the underside can be heat shielded. <div class="Discussion_UserSignature"> </div>

 

[scottb50]

I think it would work perfectly well, the problem is getting to a velocity a SCRAM jet can operate at and carrying enough fuel to provide for both systems as well as the LOX needed for the rocket portion of the flight. <div class="Discussion_UserSignature"> </div>

 

[starfhury]

Well, that's just it. The aerospike engine can accelerate the LV to a speed where the SCRAM jet can operate then throttle back allowing the SCRAM jet to do most of the work. Once the LV has gained enough speed and move beyond the effective range of the SCRAM jet, the aerospike engine can throttle up to full power for the final climb to orbit. The real advantages would come if the two systems share the maximal commonality of parts. Another advantage would be less onboard oxygen carried for the aerospike engine and the possiblity of having some reserve prop left for manuveur on return from orbit. Even if the cargo capacity is not very high, it could find good use as a human, small payload reusable. <div class="Discussion_UserSignature"> </div>

 

[shuttle_rtf]

This is interesting. I don't know how far they got - or where the X-33 (to that point) is currently being stored, but they had it at least to the plumbing of the frame stage, with the liquid oxygen tank installed. <br /><br />Rare picture from the SkunkWorks, Lockheed Martin:<br /><br />

 

[shuttle_rtf]

Re: SCRAM jet + linear aerospike LV [re: Shuttle_RTF] <br />Edit Reply <br /><br />Of course, they had changed the design of the X-33/VentureStar, bringing the cargo bay on top of the craft, making it look a bit like a hunchback. They also planned to do a manned version. Also, would the topic starter's suggestion help with the problem that shelved the VentureStar - being the Liquid Hydrogen tank (one of the tanks at least) failing to overcome design problems.<br /><br />The VentureStar was a brilliant idea - I hope they've still got the fully built launch centre and pad (well, a hanger, a 90 degree trolley and pit) at Edwards..<br /><br />This was one of the last images I saw on how it would look.....<br /><br />RIP Columbia. God Speed Discovery.

 

[shuttle_rtf]

Another image while we're on it.

 

[shuttle_rtf]

And some numbers for you all here. Note the Mach 13 speed for the demonstrator.

 

[scottb50]

<<Well, that's just it. The aerospike engine can accelerate the LV to a speed where the SCRAM jet can operate then throttle back allowing the SCRAM jet to do most of the work.>><br /><br />You would only get about a minutes use out of scram-jets. By the time you reached a speed it could operate at it would be high enough that it would run out of available air in a short time, unless you used it to accelerate in a descent then used the rocket engines to raise the altitude.<br /><br />It still seems like a lot of complication in a process that normally takes about eight minutes. What makes better sense is a single engine type that uses air at lower altitudes and switches over to LOX as it climbs. Getting enough power out of it to get off the ground would be another factor. Having to have a compressor and turbines to drive the compressor would again increase the complication and weight.<br /><br />I still think the best means of getting to orbit is the brute force alternative. <div class="Discussion_UserSignature"> </div>

 

[najab]

The key to making this kind of combined engine work is developing a (sc)ramjet - a ramjet which can work when the airflow through the engine is subsonic and also when it is super sonic. It's not too hard to design a ground assist system to get an aircraft up to the 200mph or so that you need for a ramjet to work: an aircraft carrier's steam catapult can get an F-14 up to >100mph in a hundred feet or so, an electromagnetic catapult a couple of kilometres long might do the trick.<p>If your vehicle can leave the ground on ramjet power, switching to scramjet mode around Mach 6 or so, it could conceivably leave the thick-layer-of-gas-surrounding-the-Earth doing Mach 16 or 17, and then switch to rocket mode to get up to orbital velocity.</p>

 

[mrmorris]

<font color="yellow">"...a ramjet which can work when the airflow through the engine is subsonic and also when it is super sonic. It's not too hard to design a ground assist system to get an aircraft up to the 200mph or so that you need for a ramjet to work: ..."</font><br /><br />I think you're incorrect. Ramjet <b>combustion</b> occurs at low subsonic velocities (i.e. inside the engine), but the ramjet itself works best at high-supersonic velocities. I don't think 200 MPH is enough for ramjets to function. From this site:<br /><br /><i>"Air enters the inlet where it is compressed and then enters the combustion zone where it is mixed with the fuel and burned. The hot gases are then expelled through the nozzle developing thrust. <b>The operation of the ramjet depends upon the inlet to decelerate the incoming air to raise the pressure in the combustion zone. The pressure rise makes it possible for the ramjet to operate. The higher the velocity of the incoming air, the more the pressure rise. It is for this reason that the ramjet operates best at high supersonic velocities. At subsonic velocities, the ramjet is inefficient and, in order to start the ramjet, air at a relatively high velocity must enter the inlet.</b><br /><br />The combustion process in an ordinary ramjet takes place at low subsonic velocities. At high supersonic flight velocities, a very large pressure rise is developed that is more than sufficient to support operation of the ramjet. Also, if the inlet has to decelerate a high supersonic velocity air stream to a subsonic velocity, large pressure losses can result. The deceleration process also produces a temperature rise and, at some limiting flight speed, the temperature will approach the limit set by the wall materials and cooling methods. Thus when the temperature increase due to deceleration reaches the limit, it may not be possible to burn fuel in the air stre</i>

 

[najab]

Yeah, I know that ramjets are inefficient at low velocities, I picked 200mph since that's pretty close to the low end of ramjet operation. The greater the velocity imparted by the ground assist, the better off we would be. At 200mph a ramjet works, but you're basically dumping fuel into the combustion chamber like it's on sale!

 

[scottb50]

The V-1 used a ramjet didn't it? I think it had a rocket to get it up to speed. The only difference I see in a Ram-jet and a Scram-jet is the inlet configuration, internally they are basically the same. <br /><br />The point being you have to get from 0-Mach25 or so, a turbo-jet will get you to mach 3-4, a ramjet to mach 6-8 and a scram-jet to mach10+. The problem being they all have to be in the atmosphere to do it and it takes a lot of time and propellant to get to those speeds, let alone orbital velocities.<br /><br />It just doesn't seem like a good option. Maybe a Turbo-jet/ ram-jet first stage and a rocket second stage, but all in a single stage to orbit is well beyond our capabilities. <div class="Discussion_UserSignature"> </div>

 

[starfhury]

Scottb50:<br /><br />'You would only get about a minutes use out of scram-jets. By the time you reached a speed it could operate at it would be high enough that it would run out of available air in a short time, unless you used it to accelerate in a descent then used the rocket engines to raise the altitude."<br /><br />We are not trying to get out of the atmosphere in only eight minutes like a normal rocket. There'd be no point to the SCRAM jet if that were the case. The idea is to use the linear aerospike engine to get the LV to a speed where the SCRAM jet can do it's work. If the LV takes off on a parabolic path instead of vertically, then it would accelerate using the SCRAM jet to gain speed and altitude to the point where the SCRAM jet is no longer effective and the aerospike engine can ramp up again for the final push to orbit.<br />I was thinking that both the aerospike engine and the SCRAMjet would use the aerospike ramp as a common part of the engine. Perhaps even replace some of the mini combustion chambers of the aerospike engine with those of the SCRAM jet combustion instead. They would essentially share the bulk of components with the separation being where the oxygen comes in. From internal to the aerospike combustion chambers and from the air intakes to the SCRAMjet. One turbo pump might provide propellant flow to both engines. <br /><br />A flight profile might appears as: <br />Launch under full aerospike power.<br />As soon as SCRAMjet light off occurs throttle back the aerospike to 10-20 percent to conserve onboard oxygen.<br />Ramp up the SCRAM jet to full power.<br />Switch over to aerospike mode again. <div class="Discussion_UserSignature"> </div>

 

[grooble]

Bottom line: Would it reduce launch costs? And by how much?

 

[rogers_buck]

The two successfull X-43A flights were done with different engine inlet designs for MACH 7 and 10 respectively. I would thing they were testing their modeling with hard data points. It would be interesting to see how a scram jet would have to morph to work at a wider range of velocities. It might not be feasible or desireable to go to the subsonic. Why not a conventional jet stage for the initial acceleration? I believe I read here on SDC that the followin X-43C was to involve replacing the pegasus with a jet stage of some sort.

 

[nacnud]

...and how do you stop the scram jet melting at high mach numbers...<br /><br />...and how many g is caused when the LV has to pull up near the end of its scram jet run in order to get out of the atmosphere...<br /><br />just curiouse <img src="/images/icons/smile.gif" />

 

[international_space_agency_org]

I have found this thread very interesting, as I have been thinking about these very same issues for more than 10 years now.<br /><br />Please check out the below post in the Space Business & Technology section. The post is under the heading of the International Space Plane Program.<br /><br />http://uplink.space.com/showflat.php?Cat=&Board=businesstech&Number=98292&page=0&view=collapsed&sb=5&o=0&fpart=<br /><br />Venturestar and the X-43 Hyper/Scram Jet are both great programs.<br /><br />The technologies and knowledge from both programs will have a great and positive effect on each other.<br /><br />The International Space Plane Program is an effort to create such a hybrid SSTO aerodynamic space vehicle.<br /><br />The hybrid SSTO space vehicle would be supported by a robust magnetic assisted launch system (ie: Space Ramp) http://www.skyramp.org<br /><br />The three technologies combined, could field a very robust and capable system in 5 to 7 years.<br /><br />In the picture below, you will see a prototype model of the International Space Plane. The ISP SSTO space vehicle used 8 aerospike/afterburning engines (4 on each side) In the center would be a hypersonic scram jet propulsion system which would reconfigure in flight to a pure rocket motor. The vehicle would get the majority of its initial launch velocity and acceleration from the Assisted Launch System (ie: Space Ramp). This model of the ISP prototype was done in 1986.<br /><br />I would love for you folks to contribute your experience and knowledge to the ISP Program post, and effort.<br />

 

[najab]

><i>Why not a conventional jet stage for the initial acceleration?</i><p>I have no problem with that except that jet engines don't work in space. <img src="/images/icons/smile.gif" /> From 700 to 25,000mph they're nothing but dead weight - that's quite a bit of extra mass to haul up to orbit.</p>

 

[international_space_agency_org]

Hey folks, please check out this Space Music Video!<br /><br />It shows the "concept & idea" of an electromagnetic ramp space launch system in use, if not a practical and effective system, or how one would really look in the finer details! <br /><br />It however shows very well the concept and idea in use! ;-)<br /><br />http://www.mikeburn.com/video/Starship_Bobota_By_Mike_Burn.mpg<br />

 

[propforce]

<i>".... The two successfull X-43A flights were done with different engine inlet designs for MACH 7 and 10 respectively. I would thing they were testing their modeling with hard data points. It would be interesting to see how a scram jet would have to morph to work at a wider range of velocities. ..."</i><br /><br />... with a variable geometry inlet ? <img src="/images/icons/wink.gif" /> <div class="Discussion_UserSignature"> </div>

 

[propforce]

<i> .... I have no problem with that except that jet engines don't work in space. From 700 to 25,000mph they're nothing but dead weight - that's quite a bit of extra mass to haul up to orbit. ..."</i><br /><br />You could make a jet engine work upto Mach 3, then close the inlet to the jet engine and divert the flow to the dual mode ramjet/scramjet ?<br /> <div class="Discussion_UserSignature"> </div>

 

[rogers_buck]

I was thinking along the lines of take-off of the stack sans fuel. Aerial fueling of the scram jet stage at conventional speeds. An all-out SR-71ish acceleration to scram-jet ignition. Followed by seperation and a glide return of the jet-winged stage. This would be along the lines of the original dinosaur concept. <br /><br />A Spruce Goose could lift a payload of 300,000lbs for reference. The jet stage would only have to take off with an empty stack. If the stack was a lifting body shape than it would help offset its own weight when airborne and fueled. Do you think it is possible, allowing for modern materials, to recreate something like the Valcurie but with a heavier lift capacity that could still hit Mach 2.5 @ 50,000 ft?<br /><br />If you can survive the heat at Mach 20+, the orbiter would only have to point the nose up to achieve orbit.<br />

 

[rogers_buck]

>> You could make a jet engine work upto Mach 3, then close the inlet to the jet engine and divert the flow to the dual mode ramjet/scramjet ? <br /><br />Or jettoson the jet.

 

[elguapoguano]

I guess I never really understood how a Scramjet would be beneficial getting a vessel into space. I mean for the engine to work it would have to have atmospheric oxygen to be sucked into the engine. flying a craft within the atmosphere at Mach 20 would produce how much heating? Could a vehicle sustain such extream temps long enough to achieve the speeds it would take to be beneficial? <div class="Discussion_UserSignature"> <font color="#ff0000"><u><em>Don't let your sig line incite a gay thread ;>)</em></u></font> </div>

 

[rogers_buck]

You use your aerodynamic surfaces to keep you in the atmosphere as you accelerate to MACH 20+. At speed you nose up and let your inertia carry you into orbit. You'll need conventional rocket burns to circularize, etc., but momentum is the key.