Space Shuttle V2 Thought Experiment

[Nothalogh]

9 minutes ago, sevenperforce said:

H2O2 and hydrazine

The energy density would be atrociously low.

Also, why fear the distilled essence of satan's ballsweat, if it gets you to orbit and back, in style?

Edited February 14, 2016 by Nothalogh

[RocketSquid]

5 minutes ago, sevenperforce said:

...

This is basically what I had as my first rendered concept earlier in this thread.

I was thinking more along the lines of strap-on boosters, actually.

[RocketSquid]

Does anyone know the ratio between the dry and wet mass of a LOX tank?

[sevenperforce]

4 hours ago, Nothalogh said:

The energy density would be atrociously low.

Also, why fear the distilled essence of satan's ballsweat, if it gets you to orbit and back, in style?

Hydrogen peroxide and hydrazine in an open staged-combustion rocket would have a peak vaccuum specific impulse of 404s and a T/W ratio that makes a Merlin 1D look like a turbofan. And that's not even with any sort of optimization analysis; just straight stochiometric.

4 hours ago, RocketSquid said:

I was thinking more along the lines of strap-on boosters, actually.

Ah, to get back from higher/faster than the Falcon 9 first stages can manage.

[fredinno]

11 hours ago, sevenperforce said:

Oh yeah.

Of course, it's not really a lifting body at all. There's a bit of induced hypersonic lift but nothing subsonic because it's vertically landed.

Yeah, for crew return, it's hard to imagine anything simpler, safer, or more reliable than a propulsively-landed capsule a la Dragon V2.

Only tangentially related...but had anyone ever proposed pairing two chemically reactive monopropellants for an SSTO design?

I'm pretty sure chutes, or SRBs are safer, with less failure nodes...

8 hours ago, RocketSquid said:

I had an idea: Fully re-usable liquid-fueled booster. Uses linear aerospike engines at the base of the booster, and is a blended wing/lifting body, with various fuel tanks and some control systems inside. After detachment, it glides down with computer control, and either glides to a landing or deploys parachutes. If intended for SSTO, they could be equipped with a passively cooled TPS for re-entry.

Isn't that really just Delta Clipper?

[DerekL1963]

1 hour ago, fredinno said:

9 hours ago, RocketSquid said:

I had an idea: Fully re-usable liquid-fueled booster. Uses linear aerospike engines at the base of the booster, and is a blended wing/lifting body, with various fuel tanks and some control systems inside. After detachment, it glides down with computer control, and either glides to a landing or deploys parachutes. If intended for SSTO, they could be equipped with a passively cooled TPS for re-entry.

Isn't that really just Delta Clipper

More just a collection of random buzzwords.   Less of a LEGO spacecraft and more of Scrabble spacecraft.

[sevenperforce]

14 hours ago, RocketSquid said:

I was thinking more along the lines of strap-on boosters, actually.

The weight cost of making something like the Falcon 9 stage 1 into a lifting body would probably be prohibitive. 

I'm surprised no one reacted to the projection of 404s peak impulse for a hydrazine-peroxide dual-staged-combustion rocket.

[shynung]

50 minutes ago, sevenperforce said:

The weight cost of making something like the Falcon 9 stage 1 into a lifting body would probably be prohibitive. 

I'm surprised no one reacted to the projection of 404s peak impulse for a hydrazine-peroxide dual-staged-combustion rocket.

Was 404 seconds the vacuum specific impulse or sea level?

[sevenperforce]

30 minutes ago, shynung said:

Was 404 seconds the vacuum specific impulse or sea level?

404 seconds is the vacuum specific impulse of open-staged hydrazine/peroxide at a 1:1 molar ratio. I'll have to run a numerical analysis to see how far that can be improved by varying the ratio. Sea level specific impulse would be dramatically greater, and T/W is also higher than conventional rockets.

Performance that outstrips hydrolox while using dense, liquid-at-room-temp fuels is...promising. 

[shynung]

4 minutes ago, sevenperforce said:

404 seconds is the vacuum specific impulse of open-staged hydrazine/peroxide at a 1:1 molar ratio. I'll have to run a numerical analysis to see how far that can be improved by varying the ratio. Sea level specific impulse would be dramatically greater, and T/W is also higher than conventional rockets.

Are you pretty sure about 404 seconds being SL specific impulse?

Astronautix :

Quote

Oxidizer: H2O2. Oxidizer: H2O2. Fuel: Hydrazine. Fuel: Hydrazine. Propellant Formulation: H2O2-98%/Hydrazine. Propellant Formulation: H2O2-95%/Hydrazine. Optimum Oxidizer to Fuel Ratio: 2.01. Optimum Oxidizer to Fuel Ratio: 2.17. Temperature of Combustion: 2,910 deg K. Temperature of Combustion: 2,850 deg K. Ratio of Specific Heats: 1.22. Density: 1.26 g/cc. Density: 1.26 g/cc. Characteristic velocity c: 1,750 m/s (5,740 ft/sec). Isp Shifting:285 sec. Isp Frozen: 280 sec. Mol: 19.00 M (62.00 ft). Oxidizer Density: 1.440 g/cc. Oxidizer Density: 1.440 g/cc. Oxidizer Freezing Point: -1 deg C. Oxidizer Freezing Point: -1 deg C. Oxidizer Boiling Point: 150 deg C. Oxidizer Boiling Point: 150 deg C. Fuel Density: 1.008 g/cc. Fuel Density: 1.008 g/cc. Fuel Freezing Point: 2.00 deg C. Fuel Freezing Point: 2.00 deg C. Fuel Boiling Point: 113 deg C. Fuel Boiling Point: 113 deg C.

Assuming Astronautix's 285 sec was SL, the vacuum couldn't have gone very far above 300.

[RocketSquid]

8 hours ago, DerekL1963 said:

More just a collection of random buzzwords.   Less of a LEGO spacecraft and more of Scrabble spacecraft.

Fine. You think I'm just rattling off words that sound cool. However, I can explain it in simpler terms.

Simpler Terms:

Spoiler

It is re-usable, therefore, it can be used again. A linear aerospike is a real engine concept that has been extensively developed. Blended wing bodies and Lifting bodies are both real things that actually work. It holds fuel, and lands with parachutes. If you do not know what those are, you should not be on the KSP forums talking about rockets. Passively cooled TPS means that its thermal protection system does not ablate or have coolant pumps.

Simplest terms (using the XKCD simplewriter)

Spoiler

This space engine has fire shooters that have three sides, and can be used again. It has stuff inside for burning. After it falls off of the space car, it flies with wings or can land with a big sheet that slows it down. It is controlled by a computer, and has an outside that cools itself down as it falls. It has a special shape that gives it lift, and its wings are part of its body.

Also, I have some back-of-the-envelope stats:

Dry mass: ~2.394 t

Wet mass: ~61.8 t

Delta v: ~9398 m/s without cargo

Propellants: LOX/RP-1

Thrust: ~909 kN

TWR: 1.5, fully fueled, but without cargo.

Two of these would be almost capable of satisfying this challenge.

[DerekL1963]

51 minutes ago, RocketSquid said:

Fine. You think I'm just rattling off words that sound cool.

That would because you *are*, and the same with your "back of the envelope" stats.   It's just number salad because you've pulled terms and numbers out of thin air.  (Or, if they aren't from thin air, show your work - how did you derive dry mass?)

[RocketSquid]

1 hour ago, DerekL1963 said:

That would because you *are*, and the same with your "back of the envelope" stats.   It's just number salad because you've pulled terms and numbers out of thin air.  (Or, if they aren't from thin air, show your work - how did you derive dry mass?)

No, I am not just rattling off words, I understand them, and clearly you did not read any of my post. I did not pull terms out of thin air, which I EXPLAINED in my post. I play KSP, I read aerospace engineering articles in my free time, and I am not just coming through and shouting "I think we need a big streamlined aerocapped superthruster"

I derived all masses from TWR, engine thrust, and the fuel mass to tank mass ratio. TWR was taken from the space shuttle stats, and thrust is from the published stats for the XRS-2200.

Engine thrust= 909 kN. 2 thirds of 909 is 606. 606/9.8=61,836 kg, or 61.836 t. An RP-1 tank weighs 1% of the weight of the fuel it contains. If we assume 1.836 t is left for avionics and engine mass, the fully fueled tank weighs 60 t. 60/11=0.594 t dry mass for the tank alone. Add that to 1.836, and you get a dry mass of 2.394 t. Also, I never claimed that these values were exact, that's why they're back-of-the-envelope values.

[sevenperforce]

3 hours ago, shynung said:

Are you pretty sure about 404 seconds being SL specific impulse?

Astronautix 

Assuming Astronautix's 285 sec was SL, the vacuum couldn't have gone very far above 300.

Peroxide and hydrazine pumped into a single combustion chamber have a crappy ISP, true. But staged/induced supersonic shockwave combustion carries a lot more promise; I did a little iterative optimization by hand and got a vacuum ISP of 414s at a 2:3 molar ratio (N2H4/H2O2).

Even if the supersonic combustion mode can't manage efficiencies quite as high as, say, the SSMEs, the exhaust velocity is still going to be on the order of 3700-4000 m/s, with T/W comparable to the SRBs and extraordinarily compact, lightweight tankage. Plus, monoprop fuels make pre-preburning turbopumps super simple.

You'd probably want an open aerospike of some kind...

[DerekL1963]

1 hour ago, RocketSquid said:

2 hours ago, DerekL1963 said:

That would because you *are*, and the same with your "back of the envelope" stats.   It's just number salad because you've pulled terms and numbers out of thin air.  (Or, if they aren't from thin air, show your work - how did you derive dry mass?)

No, I am not just rattling off words, I understand them, and clearly you did not read any of my post. I did not pull terms out of thin air, which I EXPLAINED in my post. I play KSP, I read aerospace engineering articles in my free time, and I am not just coming through and shouting "I think we need a big streamlined aerocapped superthruster"

I derived all masses from TWR, engine thrust, and the fuel mass to tank mass ratio

You can't "derive" any mass from TWR and engine thrust - because you can't know TWR unless you know the mass first!  I very clearly did read your post and you very clearly are pulling stuff from thin air.

So, I'll repeat my question - how did you arrive at your figures for dry mass?

[RocketSquid]

9 minutes ago, DerekL1963 said:

You can't "derive" any mass from TWR and engine thrust - because you can't know TWR unless you know the mass first!  I very clearly did read your post and you very clearly are pulling stuff from thin air.

So, I'll repeat my question - how did you arrive at your figures for dry mass?

Once again, you did not read the ENTIRE post. I used a TWR of 1.5 from the beginning so that it could carry a moderate amount of cargo, specifically 30.918 t for the aerospike engines I used. I selected 1.5 initially based on the original space shuttle.

[Nothalogh]

2 hours ago, RocketSquid said:

 "a big streamlined aerocapped superthruster"

Shut up and take my money

[DerekL1963]

2 hours ago, RocketSquid said:

Once again, you did not read the ENTIRE post. I used a TWR of 1.5 from the beginning

Yes, I did read the entire post - that's why I questioned the validity of your mass estimates in the first place, because you very obviously hadn't made any.  You started with TWR - a number you can't possibly know because you don't know the mass.

*That* is why I call your mass numbers something pulled out of thin air.  Because you didn't estimate the mass of your vehicle and work the equations forwards, you worked them backwards starting with numbers that aren't valid unless you know the mass to start with.   You can do that in high school algebra, in abstract problems - but you can't do it engineering, in real world problems.   You haven't estimated the actual weight, you've derived the theoretical maximum weight and then presented it as the actual weight.   And failed to grasp that there is a difference between the two.

It's cargo cult engineering at it's finest, people know that terms are important, but they don't know what they actually mean or how they're actually arrived at.

[RocketSquid]

Just now, DerekL1963 said:

Yes, I did read the entire post - that's why I questioned the validity of your mass estimates in the first place, because you very obviously hadn't made any.  You started with TWR - a number you can't possibly know because you don't know the mass.

*That* is why I call your mass numbers something pulled out of thin air.  Because you didn't estimate the mass of your vehicle and work the equations forwards, you worked them backwards starting with numbers that aren't valid unless you know the mass to start with.   You can do that in high school algebra, in abstract problems - but you can't do it engineering, in real world problems.   You haven't estimated the actual weight, you've derived the theoretical maximum weight and then presented it as the actual weight.   And failed to grasp that there is a difference between the two.

It's cargo cult engineering at it's finest, people know that terms are important, but they don't know what they actually mean or how they're actually arrived at.

I have found the theoretical weight for a given engine and TWR, and designed a booster that weighs that much. I can know the TWR, since that is the starting condition of the booster. Additionally, I can derive the mass through an alternative method: Two of these should carry at least 60 t. Since each engine can lift roughly 95 t, each booster can weigh at most 61.836 t. I estimated the mass of the aeroshell, avionics, and engine to be 1.836 t, leaving 60 t for fuel and fuel tanks. Since this thing will be running on RP-1, the mass of the tank is roughly 1% of the mass of the fuel. Since this is a back-of-the-envelope calculation, it is both approximate and theoretical by intent.

At this point, you are delving into an ad hominem attack rather than offering constructive criticism. Until you can be helpful, I will be ignoring your posts, unless of course you continue with the ad hominem attacks, in which case I will report you.

[sevenperforce]

It's fine to start with a target performance spec and build a vehicle around it. You just have to justify that you can fit the components of your vehicle into those specs. The onus is on the designer to show that.

In this case, I'd be suspicious of structural integrity and re-entry handling. Trying to put those tanks into a blended lifting body requires that the structure handle highly asymmetric stresses where it would typically only take axial stresses. Weight cost of that additional structural support plus heat resistant shielding is really going to crowd those specs. 

But using target specs as a starting point is entirely valid as long as you're willing to take those things into the balance. If anything, that's a more useful approach than just trying to design a rocket piece by piece, because it tells you much more readily whether you'll be able to get the performance you need. 

[RocketSquid]

5 minutes ago, sevenperforce said:

It's fine to start with a target performance spec and build a vehicle around it. You just have to justify that you can fit the components of your vehicle into those specs. The onus is on the designer to show that.

In this case, I'd be suspicious of structural integrity and re-entry handling. Trying to put those tanks into a blended lifting body requires that the structure handle highly asymmetric stresses where it would typically only take axial stresses. Weight cost of that additional structural support plus heat resistant shielding is really going to crowd those specs. 

But using target specs as a starting point is entirely valid as long as you're willing to take those things into the balance. If anything, that's a more useful approach than just trying to design a rocket piece by piece, because it tells you much more readily whether you'll be able to get the performance you need. 

Thank you, I'll be sure to address the structural concerns before I finalize it. Hopefully, it will endure less stress during ascent, since it will (probably) have balanced forces on each side, but separation and re-entry could be a serious problem.

[sevenperforce]

Yeah, ascent is the relatively easy part; tanks lend themselves well to handling axial stress. Controlled separation shouldn't be a problem either. Anaxial stress on re-entry is going to be a poodle. 

I confess I'm still not sure what your form factor and details are going to look like. Are you thinking of an SSTO that can function as an asparagus strap-on booster and achieves a higher dV than the Falcon 9 first stage merely because it can survive re-entry? 

[RocketSquid]

6 minutes ago, sevenperforce said:

Yeah, ascent is the relatively easy part; tanks lend themselves well to handling axial stress. Controlled separation shouldn't be a problem either. Anaxial stress on re-entry is going to be a poodle. 

I confess I'm still not sure what your form factor and details are going to look like. Are you thinking of an SSTO that can function as an asparagus strap-on booster and achieves a higher dV than the Falcon 9 first stage merely because it can survive re-entry? 

Not quite. The boosters could SSTO, or nearly SSTO, without cargo. With cargo, not so much. It probably wouldn't be useful for asparagus, since my current plans call for LH2 fuel in the orbiter. I'm not quite sure what the Falcon 9's dV is, but the dV I gave would really just be comparable to a Falcon 9 first stage with no second stage or payload, just a nose cap.

[sevenperforce]

The Falcon 9 first stage can do SSTO with about 400 m/s to spare, if I recall correctly.

Other than the aerospike engine, what advantage does this have over a scaled Falcon 9 stage 1?

[DerekL1963]

3 hours ago, RocketSquid said:

I have found the theoretical weight for a given engine and TWR, and designed a booster that weighs that much.

Then why haven't you shown your design despite being asked for it?  Why has it been like pulling teeth to obtain those numbers?
 

3 hours ago, RocketSquid said:

I can know the TWR, since that is the starting condition of the booster.

o.0  No, you can't know the TWR unless you know the mass.  I cannot repeat and emphasize this enough, it's one of the most basic axioms of rocket design.  (You can assume the TWR, but that's treading on very, very thin engineering ice.)  The mass is the starting condition for the booster and the foundation for all other calculations.
 

3 hours ago, RocketSquid said:

Additionally, I can derive the mass through an alternative method: Two of these should carry at least 60 t. Since each engine can lift roughly 95 t, each booster can weigh at most 61.836 t. I estimated the mass of the aeroshell, avionics, and engine to be 1.836 t, leaving 60 t for fuel and fuel tanks. Since this thing will be running on RP-1, the mass of the tank is roughly 1% of the mass of the fuel. Since this is a back-of-the-envelope calculation, it is both approximate and theoretical by intent.

That's not an alternative method - it's the only method.  That being said, those numbers look way off, two tons of aeroshell (even without TPS) isn't going to buy you much in the way of structure.   (And I wouldn't be surprised if your thrust web ended up eating a significant fraction of that.)  And are the control surfaces included in that?  Where is your recovery system (parachutes and landing gear) in your weight estimates?  For that matter, what is your recovery method?

Your tank estimates seem similarly off - you can't use conventional rocket numbers as these tanks will have to take stresses in directions that a conventional rocket doesn't, meaning your tanks will be heavier as will your structure.
 

3 hours ago, RocketSquid said:

At this point, you are delving into an ad hominem attack rather than offering constructive criticism.

I have tried repeatedly to offer constructive criticism, only to be shot down because you don't seem to grasp what I'm saying.   Serious question, is English your native language?  Because we have a communications gap, and it's either language or you really don't grasp the engineering as well as you think you do and don't (or won't) grasp the existence of the gap.  (And no, this is not ad hominem.  I have yet to make such an "attack", nor do I plan to.   Pointing out the errors in your design process is not an attack.)