Possible resurrection of the X-33?

[BillKerman1234]

Here’s a crazy concept: 

The X-33 (not the Venturestar) has about 4Km/s of delta V if it has 20t of payload. So, what if we took a X-33 and put it on top of a hypersonic aircraft with 3Km/s of delta V? We could make an orbital launch system to rival a Falcon 9. For the carrier aircraft we could use a plane powered by SABRE engines, which can fly as fast as Mach 5 and can operate as rockets as well. 

Even crazier concept: what if we took the Venturestar and equipped it with SABRE engines. Would that increase its payload capacity?

As far as I can tell, after the X-33 program was scrapped the X-33 prototype that was 95% built was disassembled. Does anyone know exactly what happened to it and if any of its components components could be salvaged? 

And does anyone actually have any plans for building something like the X-33 in the future?

[magnemoe]

Plausible, if you go hypersonic you can do an separation is vacuum, you will need an plane who is stable with or without the x-33. 
Is it any reason you could not launch an lifting body / winged craft on top of an standard reusable first stage without an fairing. That is if the thermal insulation can handle the environment.

[SRB]

I think that Reaction Engines will just want to use the SABRE Engine to power its own https://en.wikipedia.org/wiki/Skylon_(spacecraft).

Plus, I don’t know if the blueprints/jigs to build the X-33 still exist.

[DDE]

So basically a Spiral but with the booster attached to the spaceplane?

Done to death. Nobody’s willing to take the plunge of developing hypersonic flight, and the M-21/D-21 crash raises concerns over how difficult it would be to tear two aircraft apart at such velocities.

[SRB]

Just now, magnemoe said:

Plausible, if you go hypersonic you can do an separation is vacuum, you will need an plane who is stable with or without the x-33. 
Is it any reason you could not launch an lifting body / winged craft on top of an standard reusable first stage without an fairing. That is if the thermal insulation can handle the environment.

Maybe as a physics question

Just now, ErinBensen said:

I think that Reaction Engines will just want to use the SABRE Engine to power its own https://en.wikipedia.org/wiki/Skylon_(spacecraft).

Plus, I don’t know if the blueprints/jigs to build the X-33 still exist.

No, as a business question

[BillKerman123]

Heres what I had in mind: (yes I drew that myself)

 

X-33 dry mass: 28,600 kg

X-33 payload mass: 20,000 kg

X-33 propellant mass: 95,300 kg

Carrier aircraft dry mass: 80,000 kg

Carrier aircraft propellent mass: 260,000 kg

X-33 Isp (Near-Vac): 400 sec

Carrier aircraft Isp (High-atmospheric): 380 sec

X-33 ∆V: 4,255 m/s

Carrier aircraft ∆V: 3,024 sec

11 hours ago, magnemoe said:

Plausible, if you go hypersonic you can do an separation is vacuum, you will need an plane who is stable with or without the x-33. 
Is it any reason you could not launch an lifting body / winged craft on top of an standard reusable first stage without an fairing. That is if the thermal insulation can handle the environment.

We wouldn't launch on a conventional booster because the entire point is to have it be cheap, and developing a custom reusable first stage that can do retropropulsion and vertical landings is not cheap. Nor is it very efficient, if we go the aircraft approach we can use jets for takeoff, reducing the ∆V needed. 

 

11 hours ago, ErinBensen said:

I think that Reaction Engines will just want to use the SABRE Engine to power its own https://en.wikipedia.org/wiki/Skylon_(spacecraft).

Plus, I don’t know if the blueprints/jigs to build the X-33 still exist.

I have a friend who works with Reaction Engines, and I can confirm first hand that Reaction Engines have no plans on developing Skylon (which is a shame considering how great of a launch vehicle it would be), and are instead focusing solely on SABRE, with the hopes a third party will build the LV. 

I presume the blueprints still exist, the X-33 wast that long ago, most of them will probably have been computerized. Even if they haven't, why would the blueprints have been destroyed? The biggest problem is probably whether or not the 95% assembled prototype still exists. 

 

 

 

 

11 hours ago, DDE said:

So basically a Spiral but with the booster attached to the spaceplane?

Done to death. Nobody’s willing to take the plunge of developing hypersonic flight, and the M-21/D-21 crash raises concerns over how difficult it would be to tear two aircraft apart at such velocities.

Reaction Engines is willing to, there are making SABRE after all. And we can do the separation in a near vacuum environment, say, 50 to 80 Km. 

 

11 hours ago, ErinBensen said:

Maybe as a physics question

No, as a business question

I agree, the problem is business / political. But with SpaceX continuing to develop reusable architecture, other companies may have to build reusable spacecraft of there own to keep up. 

[wumpus]

14 hours ago, DDE said:

So basically a Spiral but with the booster attached to the spaceplane?

Done to death. Nobody’s willing to take the plunge of developing hypersonic flight, and the M-21/D-21 crash raises concerns over how difficult it would be to tear two aircraft apart at such velocities.

I'd assume that any such separation has to be done outside the atmosphere.  Whether this means using air breathing engines that need oxidizer added past a certain altitude (SABRE), auxiliary rocket engines (traditional KSP spaceplanes), or use the second stage to drag them both out of the atmosphere (requires far too large a vacuum engine, and almost certainly asparagus plumbing).  None of these are very good, and the choice between these and atmospheric separation help keep spaceplane designs on paper.

I also have to question the very concept of using an aerospike as a second stage engine.  A classic de Naval nozzle will be more efficient in vacuum, and almost certainly more efficient in such low atmospheric pressures such as a spaceplane's ceiling (an ideal "vacuum de Naval" nozzle requires an infinitely long nozzle, so any real nozzle will be designed for at least some atmospheric pressure).  The X-33 only made sense as a first stage, and would require considerable rework as a second stage.

[BillKerman1234]

24 minutes ago, wumpus said:

I'd assume that any such separation has to be done outside the atmosphere.  Whether this means using air breathing engines that need oxidizer added past a certain altitude (SABRE), auxiliary rocket engines (traditional KSP spaceplanes), or use the second stage to drag them both out of the atmosphere (requires far too large a vacuum engine, and almost certainly asparagus plumbing).  None of these are very good, and the choice between these and atmospheric separation help keep spaceplane designs on paper.

I also have to question the very concept of using an aerospike as a second stage engine.  A classic de Naval nozzle will be more efficient in vacuum, and almost certainly more efficient in such low atmospheric pressures such as a spaceplane's ceiling (an ideal "vacuum de Naval" nozzle requires an infinitely long nozzle, so any real nozzle will be designed for at least some atmospheric pressure).  The X-33 only made sense as a first stage, and would require considerable rework as a second stage.

We separate rocket stages in the atmosphere all the time, I don’t see how this is any different. Hell, we could just end up strapping solid sep motors to them if we need to. 

And the reason we use the aerospike on the second stage is to avoid retooling the design, and to allow for possible future development into a SSTO. 

[Bill Phil]

1 hour ago, BillKerman1234 said:

We separate rocket stages in the atmosphere all the time, I don’t see how this is any different. Hell, we could just end up strapping solid sep motors to them if we need to. 

And the reason we use the aerospike on the second stage is to avoid retooling the design, and to allow for possible future development into a SSTO. 

Separating rockets is a different beast.

As an aspiring aerospace engineer I can tell you that the sheer forces, dynamic pressure, and other consequences of such high speed flight are nothing to sneeze at. Even the rockets separating is usually something that is thoroughly developed and tested - it's no easy task for rockets either.

That said it is possible, but would entail lots of development.

The aerospike on the X-33/Venturestar is not that good of an engine - even the SSME outperforms it in most respects - indeed the SSME is simpler as well I would wager...

[BillKerman1234]

59 minutes ago, Bill Phil said:

Separating rockets is a different beast.

As an aspiring aerospace engineer I can tell you that the sheer forces, dynamic pressure, and other consequences of such high speed flight are nothing to sneeze at. Even the rockets separating is usually something that is thoroughly developed and tested - it's no easy task for rockets either.

That said it is possible, but would entail lots of development.

The aerospike on the X-33/Venturestar is not that good of an engine - even the SSME outperforms it in most respects - indeed the SSME is simpler as well I would wager...

If both vehicles are stable on their own, then separating them won’t create too many unwanted sheer and torsion forces. As long as you have a greater upwards force on the X-33 than the carrier aircraft you’re fine. As I said, use solids if you have to. 

I am also an aspiring aerospace engineer. I have no way of confirming this, but I would bet the RS-25 is more complex than the RS-2200, since the RS-25 was notoriously difficult to maintain. A RS-68 might do the trick, but you would need to develop a nozzle extension, and why bother when the RS-2200 has already been developed and successfully test fired. Plus, using the XRS-2200 would futureproof the design if you ever want to develop it into a SSTO. 

And for testing the craft we can strap two together (like in Project M.U.S.T.A.R.D.) and launch them on a suborbital trajectory, and if for whatever reason the carrier aircraft doesn’t work out we can have this double X-33 stack carry an upper stage to work as a light launch vehicle. 

[DDE]

15 hours ago, BillKerman1234 said:

I have no way of confirming this, but I would bet the RS-25 is more complex than the RS-2200, since the RS-25 was notoriously difficult to maintain

20 TCs in what seemed to be a staged combustion cycle?

Not bloody likely.

[StrandedonEarth]

On 5/30/2019 at 10:41 AM, BillKerman1234 said:

If both vehicles are stable on their own, then separating them won’t create too many unwanted sheer and torsion forces. As long as you have a greater upwards force on the X-33 than the carrier aircraft you’re fine.

The main factor is the airflow between the vehicles as they separate at supersonic or hypersonic speeds, especially how turbulence and/or shockwaves interact and affect both vehicles, which may vary greatly depending on the AoA's. Lots of simulation and testing required, and the aero forces involved are huge. IIRC that is/was one of the major considerations in developing FH and DIVH, ensuring separations would go smoothly.

[sgt_flyer]

7k dV total ? I don't think that will be enough to achieve LEO . Besides, spaceX is trying to make the BFR, which might be a less risky method for a fully reusable two stages to orbit rocket  (you have much less aero forces to worry about during separation)

[satnet]

You also have a huge change in center of mass while trying to maintain the same center of thrust. Traditional rockets only shift it vertically so the thrust vector still passes through the center of mass. You could fire the engines on both craft, but that means the X-33 has less fuel post separation. All of the problems are probably solvable, but you need to answer the question: in the face of these challenges how is this better than BFR or something like it?

[KerikBalm]

On 5/30/2019 at 12:43 AM, DDE said:

So basically a Spiral but with the booster attached to the spaceplane?

Done to death. Nobody’s willing to take the plunge of developing hypersonic flight, and the M-21/D-21 crash raises concerns over how difficult it would be to tear two aircraft apart at such velocities.

Well, if the carrier vehicle is sabre equipped, then there's a lot that can be gained by giving it some oxidizer, and boosting the payload a little on rocket power after airbreathing is no longer possible. This presumes that the craft combo can get high enough under the rocket thrust before separation. Separating while still in airbreathing mode means that you're separating while there's still very significant aerodynamic forces.

I imagine that more active separation measures can be taken than what the D-21 did. *cough* sepratrons *cough* .. .well not literally sepratrons, but I'd guess you can design them so that the airflow separates them naturally/automatically, and throw in some automated control/stability that was lacking back in 1966 ... the solution seems to already be known anyway:

https://en.wikipedia.org/wiki/Lockheed_D-21#Testing_and_carrier_change

" Unlike the three previous launches this one was performed straight and level, not in an outside loop to assist in the separation of the drone from the aircraft. The D-21 suffered engine problems and struck the M-21's tail after separation "

Have the carrier aircraft start to pitch down just prior to release. Also a closed cycle rocket engine should be more reliable upon release than a ramjet. It should also have a lot higher TWR and the 2nd stage should GTFO much quicker.

Light the 2nd stage's rocket just as its released, while the carrier aircraft is pitching down, and it seems there should be no problem.

On 5/30/2019 at 12:25 PM, BillKerman123 said:

Heres what I had in mind: (yes I drew that myself)

 

...

X-33 Isp (Near-Vac): 400 sec

Carrier aircraft Isp (High-atmospheric): 380 sec

Your Isps are pretty low for liquid hydrogen propulsion. The SABRE does not work without liquid hydrogen (the precooler depends on it)

I also don't seea point in giving the carrier aircraft an Aerospike engine, because:

1) It wouldn't use said engine until its at high altitude, and it would only operate in a narrow atmospheric pressure range, there's no point to an aerospike design in those circumstances

2) The Sabre engines are intended to have a closed cycle mode with excellent vacuum performance... why would you throw on an aerospike engine to do what the SABREs can already do... its just redundant and adds to dry mass.

I suspect the limiting factor for thrust will be when fully fueled on takeoff, and the sabre closed cycle thrust alone should be fine when its time to separate the carrier and the 2nd stage.

[Wjolcz]

I'd rather see DC-X resurrected, tbh.

Oh, wait. It already was. It's just that its name starts with F and actually puts significant payloads into orbit.

1 hour ago, KerikBalm said:

1) It wouldn't use said engine until its at high altitude, and it would only operate in a narrow atmospheric pressure range, there's no point to an aerospike design in those circumstances.

Isn't that the exact opposite of how the aerospike should be used? Perhaps you meant the X-33 not the carrier aircraft?

Edited June 6, 2019 by Wjolcz

[KerikBalm]

7 minutes ago, Wjolcz said:

I'd rather see DC-X resurrected, tbh.

Oh, wait. It already was. It's just that its name starts with F and actually puts significant payloads into orbit.

Isn't that the exact opposite of how the aerospike should be used? Perhaps you meant the X-33 not the carrier aircraft?

Yes, it is the exact opposite of how it should be used, which is why its in my list of "I also don't see a point in giving the carrier aircraft an Aerospike engine".

It has SABRE air breathing engines, why would it use an aerospike?

[BillKerman1234]

On 6/6/2019 at 11:51 AM, KerikBalm said:

Yes, it is the exact opposite of how it should be used, which is why its in my list of "I also don't see a point in giving the carrier aircraft an Aerospike engine".

It has SABRE air breathing engines, why would it use an aerospike?

It has an aerospike because I got carried away when drawing it, and I thought it looked cool. In real life the carrier would just use SABREs to get to 30 to 70 km and then the X-33 separates. And were using an aerospike on the X-33 because this is supposed to be a quick and dirty Falcon 9 competitor, and retooling it for bell nozzles would be expensive. 

Edited June 7, 2019 by BillKerman1234

[DDE]

 

[Nuke]

if you started strapping on sabre engines, and they work as advertised, you probably wouldn't even need the linear aerospike anymore. 

and to be fair its the more plausible route for reaction engines to sell the engines to other aerospace companies to use on their spaceplanes, than to try and build skylon in house. 

Edited June 10, 2019 by Nuke