Discussion A REAL Delta Glider (well, almost)

[T.Neo]

Yes! NERVA in the variant for reaching LEO was planed as an upper stage for the saturnV, with no option of reusability, so no cooling needed. If it blows up it produces alot space rubbish/debris, but it was the spirit of the 60s and 70s, or just the missing of knowledge about that.

Do you have a source for that? I know the drop-in NTR stages were not reusable, I'm asking whether they were intended to blow up or not.

I'm pretty sure that by then, they knew that an exploding stage would at least create a lot of debris...

A space tug doesn't need strong NTR thrusters like a LEO-shuttle, because it is allready in LEO and has enough time for its job, it uses a small NTR and so heat is not a big problem.

Yes! That's a very good point, although it does not remove the heat problem. It just reduces it.

But i would really suggest you to use LANTR, when this enables mutch smaller reactors, the extra thrust comes from the oxygen injection.
But for the same ISp and thrust you have to use LOX and LH2, which an pure CH4-NTR only can do by big reactors. But maybe you can use the air in the first flight phase as an afterburner and later a small LOX-tank when air is to thinn, then later in space the shuttle has lost some fuel mass, so that small reactors are strong enough for doing the rest thrust to orbit, MAYBE.

No, I will not use LANTR. I've already explained, that LANTR even with LOX/LH2, has less specific impulse than I do with methane! The extra thrust with the LOX injection only comes with a corresponding reduction in exhaust velocity.

I am already using pure airbreathing propulsion in the lower atmosphere, this is advantageous as it negates, for example, the need to ignite the reactors on the ground.

The extra complexity isn't warranted by the lower capability that LANTR provides...

Thrust is not problematic for me, specific impulse is. Even though I need more thrust than an LEO tug, for example, I already have around more than twice the needed thrust. The main engines are used relatively late in the ascent, and I am also not trying to do vertical climbs or aerobatics. I don't need superpowerful engines.

maybe the fact we don't have a NTR-LEO-shuttle are next to the NIMBY NIMBY exact all these technical problems.

It's less to do with OMG-nuclear-its-bad-do-not-want-NIMBY-NIMBY-NIMBY! and more to do with economics and politics in general. Heck, that's the reason why we don't have a chemical shuttle (ok, well, we do, sortof, but you get my point).

The more and more I look at this, the more hurdles it has, but that is also just engineering, not to mention the fact that I highly doubt that after all the work that has been done on NTR, any such "achilles heel", so to speak, would have been so easily missed...

 

[Axel]

Damn i edited my post as you did answer on the first :lol:

I'm pretty sure that by then, they knew that an exploding stage would at least create a lot of debris...

NERVA in the variant for flying from earth's surface to space was planed as an upper stage for the saturnV, to fly payload to moon or mars with no option of reusability, so no strong cooling needed and it had blowed up. This would be no problem, because the NERVA stage would be at an interplanetary flight path with the payload after its MECO at that moment with no return, so no rubbish/debris in LEO.

No, I will not use LANTR. I've already explained, that LANTR even with LOX/LH2, has less specific impulse than I do with methane! The extra thrust with the LOX injection only comes with a corresponding reduction in exhaust velocity.

Hm then i did not read your post, but at "AtomicRockets" webside both LOX/LH2-LANTR and CH4-NTR have nearly the same Isp.

But i have another idea for increasing the ISp - "post accelearation" of the particles by electromagnetic fields, its not my idea but i found it in the net. You reach 500-1000ms more, but they will use it for reducing the heat inside the reactor core for a longer life time!!! That could solve your problem. But the article is about interplanetary NTR transfer vessels with small thrust, i dont know if its possible to produce a strong field for a shuttle.

 

[T.Neo]

NERVA in the variant for flying from earth's surface to space was planed as an upper stage for the saturnV, to fly payload to moon or mars with no option of reusability, so no strong cooling needed and it had blowed up. This would be no problem, because the NERVA stage would be at an interplanetary flight path with the payload after its MECO at that moment with no return, so no rubbish/debris in LEO.

Do you have a source that says definitively that it'd blow up?

Hm then i did not read your post, but at "AtomicRockets" webside both LOX/LH2-LANTR and CH4-NTR have nearly the same Isp.

Here's the difference: that is based of the performance of the original NERVA design. Mine is based of the performance of (ironically) the LANTR study. Using CH4 reduces performance less than LOX injection with LH2 does...

But i have another idea for increasing the ISp - "post accelearation" of the particles by electromagnetic fields, its not my idea but i found it in the net. You reach 500-1000ms more, but they will use it for reducing the heat inside the reactor core for a longer life time!!! That could solve your problem. But the article is about interplanetary NTR transfer vessels with small thrust, i dont know if its possible to produce a strong field for a shuttle.

I don't think that'd work here, it probably wouldn't be practical at all.

 

[Axel]

Do you have a source that says definitively that it'd blow up?
No i dont have, but it doesnt matter as the upper stage is at an interplanetary course. But i think it will blow up, because i cant see any radiators at the NERVA design and its relativ powerfull. And radiators are extra mass which reduces the payload capacity. Before the engine shut down its cooled by the propellant.


To the "post acceleration" it works only in space/vacuum. Its similar to the ion engine concept, the propellant particles will be ionisized and accelerated by strong fields, at the end of the nozzle. But its a nice concept of newer NTR studys for interplanetary travel.

 

[Urwumpe]

Why not just increasing the temperature of the radiator a bit? if you increase temperature from about 770K (500°C) to 1000K (727°C), you get 2.8 times more radiative power on the radiators. Next, you can use the wings of a DG-like vehicles as reflectors for the radiators, if the distance to the radiator is not too low. If you for example deploy three radiator arrays in 45° steps from the top of the vehicle, you could get already 56.7 kW radiative power per square meter, the overlapping of the radiation cones would lower the effectivity only a bit.

If you deploy three 10 x 1 m arrays, you get about 1.36 MW thermal power of the radiators. Which would mean 225 kW electrical power. Not enough for powering DG-like thrusters, but: excluding about 15 kW electrical power for avionics and life support (and payloads), you could have 210 kW fed into a VASIMR engine pair, resulting in mind-blowing 8.6N thrust in the highest thrust level...

For get a NTR or other nuclear propulsion concepts for a relatively small spaceplane... it will not fit. alone the mass properties should be a warning - you would need to install something very heavy in the nose of the vehicle for compensation.

 

[T.Neo]

If you deploy three 10 x 1 m arrays, you get about 1.36 MW thermal power of the radiators. Which would mean 225 kW electrical power. Not enough for powering DG-like thrusters, but: excluding about 15 kW electrical power for avionics and life support (and payloads), you could have 210 kW fed into a VASIMR engine pair, resulting in mind-blowing 8.6N thrust in the highest thrust level...

If my calculations are correct, a mind-blowing 8.6 newton thruster would require more than 10 days to accomplish a 100 m/s burn...

It might allow for a dV of more than 2km/s with my current OMS propellant mass, but as to how practically that could be achieved... :shifty:

Would two 2.5x6 radiators 180 degrees apart not be better? I have a feeling there is something to the arrangement you're suggesting that I don't fully understand.

For get a NTR or other nuclear propulsion concepts for a relatively small spaceplane... it will not fit. alone the mass properties should be a warning - you would need to install something very heavy in the nose of the vehicle for compensation.

I don't know if this vehicle could be called "relatively small", it's already comparable in mass and larger dimensionally than the shuttle.

I still have a lot of mass at the back of the vehicle though...

 

[T.Neo]

Ok, more updates, finally. In the conundrum between waste heat and Delta-V, I decided to fit the package together aerodynamically. Hull was complete fairly early on, just did the wings and tail recently.

As per recommendations from RisingFury, I steered away from a shuttle-like wingplan to a more SR-71-ish one, to assist with ascent. My large apparent area to the airstream (mostly due to my large, side-by-side propellant tanks) means that heating is minimal, and I can use a similar TPS to Skylon- saving mass, saving maintainance costs and time, and reducing TPS fragility, which in turn reduces the potential for critical accidents due to TPS failure.

Although windows/hatches/bay doors/etc have not been meshed yet, I have made provision for them... the position of the payload bay and the crew cabin for example are already sorted out (mostly). The OMS propellant tanks stick out of the body, but that's only because their pods have not been meshed yet.

Feedback/comments on where I've gone horribly wrong (or right) are welcome.

Image key:

Blue: Airframe.

Red: Main engines.

Yellow: GOX tank (OMS propellant).

Pink: Syntin tank (OMS propellant).

Orange: OMS engine.

 

[T.Neo]

Yesterday I stumbled across the Astronautix page for Skylon.

It contained a mass breakdown, something I am constantly searching for in regards to spacecraft:

Skylon Vehicle Mass Summary - Configuration C1

◦Main Engines: 9,628 kg
◦Nacelle, Inlet, Bypass: 3,500 kg
◦Wing: 5,115 kg
◦Fuselage: aeroshell, insulation, structure, payload bay: 8,130 kg
◦Main tankage, cryo insulation: 2,816 kg
◦Undercarriage: 4,170 kg
◦Aerodynamic control, hydraulics: 2,660 kg
◦Auxiliary systems, pressurants, coolants etc: 5,016 kg
•Basic Mass: 41,035 kg
◦OMS/RCS propellant: 2,357 kg
◦Ascent Fuel: 66,807 kg
◦Ascent Oxidiser: 150,235 kg
◦Propellant margins and residuals: 1,282 kg
•Total fluids: 220,681 kg
◦Mass margin: 1,284 kg
◦Payload: 12,000 kg
•Gross takeoff mass: 275,000 kg

I noted several similarities, and areas where I need to improve (read: create data for, because it doesn't exist yet).

For example, I can probably dedicate much of the structural mass of the hull to the propellant tanks- the skin around them just being an "aeroshell" to protect against thermal and aerodynamic forces. This could mean that I could shift structural mass into the nose, aft section and wings, where it is needed.

This mass breakdown also finally gave me the mass figures for at least the early version of the SABRE engines, so I can model the thrust/mass of my engines on that. I'm in a bit of a conundrum over the placement of the airbreathing engines; a forward position would provide an uninterrupted airflow, and would also somewhat counterbalance the mass at the rear of the vehicle. However, the whole fuselage will now have to tolerate the hot exhaust gases of the engines, so placing them at the rear of the fuselage seems more sound. However, that contributes to the mass at the rear of the vehicle, which is probably already too high...

 

[Wishbone]

Can OMS be relocated to the nose? In space it won't matter much if you're burning "backwards".

 

[T.Neo]

I did give it a cursory thought, however space in the nose is quite limited (I'm worried about getting the RCS and landing gear to fit into the nosecone forward of the crew cabin). OMS pods sticking out of the nose would probably not be very aerodynamically sound either.

What I can do, however- at least, what I think I can do, is mount the OMS engines at the rear, and mount the propellant tanks themselves far further forward- in front of the current center of gravity. This, only if the propellant can effectively be piped to the engines. The OMS pods will blend nicely into the wing-root, and should be relatively aerodynamic.

 

[T.Neo]

This idea is utter rubbish as well... I guess I'm incapable of coming up with anything plausible... maybe my next addon concept should be a small chip of metal that orbits the Earth... can't go wrong with that.

Though I'm sure I would. :dry:

 

[Wishbone]

Huh? The idea may be rubbish, but you are learning a lot along the way. The fact is you have singlehandedly done preliminary design starting from a mere concept.