Reusable Single Stage to Orbit Concept

[Sumontro Sinha]

Hi, I'm new to this site. I have skimmed the pages a bit to keep abreast of new ideas and new viewpoints. From all the threads and articles that I have read, I feel there are a lot of qualified people that post here, and can help with proofing concepts.

From all the literature in NASA, AIAA, Acta Astronautica, and on this forum, I know that a reusable rocket based SSTO is not possible due to the insanely small mass fraction needed. Also, both after experiencing it myself, and hearing it from all the engineers that designed the Shuttle, X-33, and NASP, I know that closing a design by using lots of new technology usually dooms it to not meeting its goals. 

So here's my idea for a reusable SSTO vehicle. The vehicle would have two sets of engines, mixed flow turbofans (Like a F100), and rocket engines (like a RS-68). It would take off and land horizontally. To ascent to orbit, it would use air breathing engines and aerodynamic lift to give the vehicle some velocity and altitude, before boosting into orbit using its rocket engines. It would use a similar lifting entry as the shuttle. Before landing it would reignite its engines, to allow runway misses in case of problems. For atmospheric controls, it would use electromechanical controls powered by on board fuel cells. For OMS and RCS, it would use heritage shuttle hardware, since it has been proven in flight. To keep fuel weight down, it would use LOX/LH2 for the rocket engines. To keep engine weight down, the wings would use the same type of airfoils used on the F-16 to allow high L/D operation at subsonic, transonic, and supersonic speeds.

The only advances in technology, that I think, would be needed, are in the heat shield. The heat shield would have to be more durable, and have a higher temperature resistance than the Shuttle tiles.

I realize the design might seem totally outlandish, but I would appreciate any and all feedback. 

[Rabidpanda]

From all the literature in NASA, AIAA, Acta Astronautica, and on this forum, I know that a reusable rocket based SSTO is not possible due to the insanely small mass fraction needed.

I am of the opinion that a rocket based SSTO RLV is possible if denser fuels are used in the place of hydrolox.  Methylacetylene and lox is an example of a promising combination.

[Sumontro Sinha]

From all the literature in NASA, AIAA, Acta Astronautica, and on this forum, I know that a reusable rocket based SSTO is not possible due to the insanely small mass fraction needed.

I am of the opinion that a rocket based SSTO RLV is possible if denser fuels are used in the place of hydrolox.  Methylacetylene and lox is an example of a promising combination.

Are there existing engines that can run on this combination?

[Rabidpanda]

From all the literature in NASA, AIAA, Acta Astronautica, and on this forum, I know that a reusable rocket based SSTO is not possible due to the insanely small mass fraction needed.

I am of the opinion that a rocket based SSTO RLV is possible if denser fuels are used in the place of hydrolox.  Methylacetylene and lox is an example of a promising combination.

Are there existing engines that can run on this combination?

No.  If you want to use existing engines kerolox would be the best choice.

[gospacex]

So here's my idea for a reusable SSTO vehicle.

Why exactly do you need your vehicle to be RLV and SSTO?

[IsaacKuo]

So here's my idea for a reusable SSTO vehicle. The vehicle would have two sets of engines, mixed flow turbofans (Like a F100), and rocket engines (like a RS-68). It would take off and land horizontally.

This is similar to Rocketplane XP, which would have been strictly suborbital.  The combination of jet engines and rocket engines results in too much dry mass to get to orbit.

[strangequark]

Hi, I'm new to this site. I have skimmed the pages a bit to keep abreast of new ideas and new viewpoints. From all the threads and articles that I have read, I feel there are a lot of qualified people that post here, and can help with proofing concepts.

From all the literature in NASA, AIAA, Acta Astronautica, and on this forum, I know that a reusable rocket based SSTO is not possible due to the insanely small mass fraction needed. Also, both after experiencing it myself, and hearing it from all the engineers that designed the Shuttle, X-33, and NASP, I know that closing a design by using lots of new technology usually dooms it to not meeting its goals. 

So here's my idea for a reusable SSTO vehicle. The vehicle would have two sets of engines, mixed flow turbofans (Like a F100), and rocket engines (like a RS-68). It would take off and land horizontally. To ascent to orbit, it would use air breathing engines and aerodynamic lift to give the vehicle some velocity and altitude, before boosting into orbit using its rocket engines. It would use a similar lifting entry as the shuttle. Before landing it would reignite its engines, to allow runway misses in case of problems. For atmospheric controls, it would use electromechanical controls powered by on board fuel cells. For OMS and RCS, it would use heritage shuttle hardware, since it has been proven in flight. To keep fuel weight down, it would use LOX/LH2 for the rocket engines. To keep engine weight down, the wings would use the same type of airfoils used on the F-16 to allow high L/D operation at subsonic, transonic, and supersonic speeds.

The only advances in technology, that I think, would be needed, are in the heat shield. The heat shield would have to be more durable, and have a higher temperature resistance than the Shuttle tiles.

I realize the design might seem totally outlandish, but I would appreciate any and all feedback. 

The first obvious critique is that your jet engines don't buy you all that much. To achieve LEO, including gravity and drag losses, you have to achieve a delta-V of about 9500 m/s. Your jet engines may buy you 600-700 m/s. With a rocket engine of 450s of Isp, this means you can have an inert fraction of 13.5% instead of 11.5%. To give a basis of comparison, a Delta IV is about 300,000 kg. 2% of the gross liftoff weight is 6000 kg. Two F100 engines already weigh almost 4000kg, and would be grossly insufficient for something the size of a Delta IV. Even if they weren't, you'd eat up any additional savings with the wings. The problem only gets worse with smaller vehicles, because the weight savings are less.

[Hauerg]

IF you really want to go with RLV (an that's a big IF, you need the market, flight rate, and what if you crash one of your few or even the only vehicle??) you should first consider going TWO stages. In an SSTO approach almost every minimal design/development issue will lead to negative payload.

[Cinder]

... Skylon?
http://forum.nasaspaceflight.com/index.php?topic=21530.0

[Sumontro Sinha]

Yes, if you take the Delta IV as the reference for mass fraction, the dry weight would be too much. But the mass fraction of 13.5% is right about that of the Space Shuttle stack, and this concept would get rid of all the staging problems. Because of using aerodynamic lift and lack of extra boost hardware, the fuel needed to overcome the drag and gravity losses at lower altitudes with rocket engines cuts out half the fuel needed by the shuttle. You are correct in saying the jet engines only give you a delta v of 600-700 m/s, and the wings add additional weight. However, unlike on a rocket, they help you both on ascent and entry. Also, the wings and jet engines give the vehicle the ability to test incrementally, so problems can be spotted in a more controlled manner.

In terms of payload to orbit, the design seems to work if the turbojet weight is reduced by increasing the craft L/D to around 15. Then the design seems to be able to take a moderate payload into orbit.

Also, I thought Rocketplane's suborbital concept was the size of a business jet, so it couldn't carry the amount of fuel needed to get to orbit.

[JohnFornaro]

So here's my idea for a reusable SSTO vehicle.

Why exactly do you need your vehicle to be RLV and SSTO?

Pay him no mind.  It's a great idea.  I think that the biggest problem is to build it and launch it for less money than current expendable vehicles, and do that on the first or second launch.  Not that I know how to do this, mind you, but if you don't do this, your vehicle will [ahem] never get off of the ground.

[Sumontro Sinha]

Skylon does not use current engines, and they seem to STILL be having enormous problems with their engines even after nearly 20 years of the development. So while great, it seems it might take a while longer for it to come to fruition.

[Sumontro Sinha]

So here's my idea for a reusable SSTO vehicle.

Why exactly do you need your vehicle to be RLV and SSTO?

Pay him no mind.  It's a great idea.  I think that the biggest problem is to build it and launch it for less money than current expendable vehicles, and do that on the first or second launch.  Not that I know how to do this, mind you, but if you don't do this, your vehicle will [ahem] never get off of the ground.

I agree with you. I reviewed a lot of the material on the Shuttle, and listened to the folks that designed it; they all said that if they hit the design flight rate, the cost savings per launch would have been realized. Unfortunately, for them, they did not know the problems/additional costs that the TPS, engines, and increased overhead would bring.

Now for this vehicle, assuming an advance in TPS technology, I feel could launch for less cost than expendables if it brings in a launch rate like that intended for the shuttle (~60 per year). Now are there customers for that amount of launches? That is yet to be seen. I was only looking at the technical feasibility of the approach.

But in terms of development cost, that is a tough nut to crack. I was hoping on some input on which areas would shoot up the development cost and why.

[Cinder]

Pardon me, but what enormous problems?  The engines are due for testing "in ~3 years" which isn't the order of magnitude you'd think of for something facing enormous problems.  IIRC the cooling system is expected to be the most difficult development part, and they reportedly have that one under control.   

Delays, I sure don't see why not.  But enormous problems? 

[Sumontro Sinha]

well, how far has the airframe of the Skylon come? Also, how about the TPS? Are these the same structures and materials used on current aircraft and spacecraft? or are they different? How far is the Skylon vehicle from actually launching into orbit?

[sandrot]

... and they reportedly have that one under control.   

And they have reportedly flown nothing.

[sandrot]

well, how far has the airframe of the Skylon come? Also, how about the TPS? Are these the same structures and materials used on current aircraft and spacecraft? or are they different? How far is the Skylon vehicle from actually launching into orbit?

For information on paper rockets you've got to follow the paper trail.

http://www.reactionengines.co.uk/downloads/SKYLON_User_%20Manual_rev1%5B3%5D.pdf

[Cinder]

Is there a thread I could be directed to that clearly explains for dummies what the difference is, not in hindsight but at the time of development, between a paper rocket that'll turn into flying hardware and one that'll turn into nothing beyond paper figures and line art?

[aero]

Is there a thread I could be directed to that clearly explains for dummies what the difference is, not in hindsight but at the time of development, between a paper rocket that'll turn into flying hardware and one that'll turn into nothing beyond paper figures and line art?

I think most will agree that you don't need a thread. The difference is political will and money. Look at Constellation and Jupiter Direct as examples. Both include paper rockets, and both could have been converted to flight hardware given the money. Of course the money comes as a result of the political will in government programs but a very similar "political" will is in effect for commercial efforts.

As for the subject of this thread, I suggest you read and study everything you can about the Skylon and its Sabre engines. Someone will correct me if I'm wrong but I think the Sabre powered Skylon vehicle comes about as close as we have ever gotten to a viable subject vehicle for this thread.

Note that Mark Hempsell posts here. If we are lucky he will post a list of available public documents that would provide a Skylon/Sabre familiarization and training course. As for me, I suggest starting with the Wikipedia article then following the links included there-in. Google Skylon/Sabre.

[Cinder]

If the Skylon formula works out, I haven't yet seen any arguments for it not being a very viable space access solution for smaller payloads.  One that'd garner enough interest to very possibly break that initial investment friction. 

I have read everything I've come upon, and to the limits of my technical understanding there aren't any show stoppers in sight.   If there are, to the point that the OP formula is clearly a better alternative, even if just considered in a political/economical vacuum (or that Skylon per se's a clear no-go), I'm curious to hear them.

Of course if the topic's "proven technology" tag is an absolutely strict criteria for discussion here, then I have no argument there -- but we're back to the same catch 22 that I can't get my head around as a reasonable premise for speculation on "Reusable single stage to orbit concepts".

And yes, M. Hempsell posted here, IIRC mostly in that thread I linked to.  S. Sinha might be interested in those posts.