Radian SSTO Spaceplane

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So, if I'm reading it correctly, the preferred implementation is a kerolox rocket burning Jet A (not even RP-1). And the Orbital Maneuvering System is Compressed Natural Gas and LOX, which I think has the benefit of being original -- has anyone actually done that before? (LNG yes; CNG, I don't know)

The rocket sled is straight out of Thunderbirds!
 
'Opening up space for the rest of us...' Well, this isn't the only game in town.

www.spacedaily.com

Using High Temperature Composites For Sustainable Space Travel

Sydney, Australia (SPX) Jan 14, 2022 - On the ground, sound waves travel at around 340 metres per second. An aircraft is Supersonic when it exceeds the speed of sound. Hypersonic speed is more than five times the speed of sound - or 'Mac
www.spacedaily.com
 
TomS said:
So, if I'm reading it correctly, the preferred implementation is a kerolox rocket burning Jet A (not even RP-1). And the Orbital Maneuvering System is Compressed Natural Gas and LOX, which I think has the benefit of being original -- has anyone actually done that before? (LNG yes; CNG, I don't know)

The rocket sled is straight out of Thunderbirds!
Click to expand...

Or wartime Germany. The launch system for the Saenger orbital bomber was a monoral 1.4 kilometers long and inclined at 5 degrees. The 100 ton near-spacecraft would be pushed along by two V-2 rocket engines in pods with winglets, one behind the other. It would then burn 90 tons of fuel and skip around the planet on top of the atmosphere.
 
They will need a 0.95 propellant mass fraction, in other words: 95% of propellants and 5% of vehicle and payload. Not sure if the sled is a helper or a nuisance there.
Kerolox all time record isp is 362 for the russian RD-0124 engine.
At least their payload goal is small.
Basic calculation for a 200 tons ship with 95% PMF so merely 10 tons empty, payload 4 mt 9.81*362*ln((200+4)/(10+4))
= 9450 m/s
 
Archibald said:
They will need a 0.95 propellant mass fraction, in other words: 95% of propellants and 5% of vehicle and payload. Not sure if the sled is a helper or a nuisance there.
Kerolox all time record isp is 362 for the russian RD-0124 engine.
At least their payload goal is small.
Basic calculation for a 200 tons ship with 95% PMF so merely 10 tons empty, payload 4 mt 9.81*362*ln((200+4)/(10+4))
= 9450 m/s
Click to expand...

I wonder how much they save by using the sled getting them to flying speed (Mach 0.8?) before they start depleting the vehicle fuel tanks? Not much, I suspect. But even a percent or two would help...
 
TomS said:
Archibald said:
They will need a 0.95 propellant mass fraction, in other words: 95% of propellants and 5% of vehicle and payload. Not sure if the sled is a helper or a nuisance there.
Kerolox all time record isp is 362 for the russian RD-0124 engine.
At least their payload goal is small.
Basic calculation for a 200 tons ship with 95% PMF so merely 10 tons empty, payload 4 mt 9.81*362*ln((200+4)/(10+4))
= 9450 m/s
Click to expand...

I wonder how much they save by using the sled getting them to flying speed (Mach 0.8?) before they start depleting the vehicle fuel tanks? Not much, I suspect. But even a percent or two would help...
Click to expand...
A sled removes perhaps 300 m/s... out of 9000 m/s.
Except the equation is exponential in nature so the sled saves next to zero.
Weight wise undercarriage is roughly 4% of a spaceplane weight so some savings there.
 
TomS said:
Super secret video of early tests.

View: https://www.youtube.com/watch?v=23QR01CwDbU
Click to expand...
That is actually more volumetrically sound...let the nose capsule alone go to orbit. You know, I have said all along that the Great Galactic Ghoul is actually Roko's Basilisk...who cast a spell to where if poor Gary Hudson's name were associated with a project...it was certainly the kiss of death. Poor thing has my level of bad luck.
 
Now, if this were to be launched atop SuperHeavy or something—it would be an easier design, no?
 
publiusr said:
Now, if this were to be launched atop SuperHeavy or something—it would be an easier design, no?
Click to expand...
Easier as compared to what - an SSTO HTHL RLV? What would be the orbital mission, payload mass, on orbit duration, separation velocity, etc.? Or are you simply envisaging a Shuttle II concept with a VTVL reusable booster? Just trying to understand the mental concept and rationale here. But then again, pretty much *anything* is by default easier than an SSTO - I just really don't think the Radian spaceplane concept is the best design point of departure for *any* RLV, or even a reusable next gen orbiter.
 
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Archibald said:
They will need a 0.95 propellant mass fraction, in other words: 95% of propellants and 5% of vehicle and payload. Not sure if the sled is a helper or a nuisance there.
Kerolox all time record isp is 362 for the russian RD-0124 engine.
At least their payload goal is small.
Basic calculation for a 200 tons ship with 95% PMF so merely 10 tons empty, payload 4 mt 9.81*362*ln((200+4)/(10+4))
= 9450 m/s
Click to expand...
I figured it was something ridiculous like that. Previous designs and other current designs at least attempt to use air-breathing engines up to a given altitude to save having to carry as much oxidiser. This just seems impossible in the extreme.

TomS said:
More from the company.

www.radianaerospace.com

Radian Aerospace – World’s First Single-Stage-to-Orbit Spaceplane

Radian Aerospace is building a next-generation spaceplane planned to be the world's first single-stage-to-orbit, truly reusable space vehicle operating in Low Earth Orbit.
www.radianaerospace.com www.radianaerospace.com


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I'm now even more confused, the sled stays on the ground?

TomS said:
I wonder how much they save by using the sled getting them to flying speed (Mach 0.8?) before they start depleting the vehicle fuel tanks? Not much, I suspect. But even a percent or two would help...
Click to expand...
Well how much of a KE difference is there between 0 and 273m/s vs between 273m/s and 8,000m/s? Answer - about 0.1%, i.e. it's pretty much worthless.

PS: It's even less than 0.1% if you factor in climbing acceleration vs level, i.e. PE difference.
 
Forest Green said:
Well how much of a KE difference is there between 0 and 273m/s vs between 273m/s and 8,000m/s? Answer - about 0.1%, i.e. it's pretty much worthless.
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The value of a sled lies less in the speed it adds and more in the landing gear it deletes. The landing gear requirements for a fully fueled HTOL SSTO spaceplane are massive; for an empty one... not so much. So if you can offload the landing gear for takeoff, you can size the gear for landing only, and save a *lot* of weight. Not only does the gear get smaller and lighter, but it doesn't need to have the actuators to retract the gear and shut the doors.
 
martinbayer said:
publiusr said:
Now, if this were to be launched atop SuperHeavy or something—it would be an easier design, no?
Click to expand...
Easier as compared to what - an SSTO HTHL RLV? are you simply envisaging a Shuttle II concept with a VTVL reusable booster?
Click to expand...
Something like that —-SuperHeavy would give a far better boost than a sled. Booster VTOVL, spaceplane lands horizontally.
 
And all of this is before you get to the wings.

Elon's definitely on the right track with propulsive vertical landing. The only really tricky bit was getting it to work reliably, which they've done. Difficult to see what a winged platform adds at this point.
 
Some elementary engineering considerations: If you launch a TSTO vertically with either a reasonably powerful expendable or reusable booster (because providing the majority of the oomph for initial ascent is what boosters are there for, be they serial, parallel, throwaway, VTHL, or VTVL), there's no need for aerodynamic optimization in the form of a wineglass curve shaped aft body orbiter that pretty much keeps changing fuselage cross sections throughout the whole length with associated fancy shmancy structural engineering and resulting lifecycle costs during ascent. For descent, the STS Orbiters, Buran, and X-37B have consistently demonstrated that prismatic fuselages with an aerodynamically shaped nose section, double delta wings, and swept dorsal fins will get that job done. The only reason for an SSTO RLV to even try to adopt any shape like that is the need to provide all the takeoff thrust in a single airframe that has to accommodate all the necessary engine nozzles at the back end (typically some sort of combined cycle airbreathers, since rocket engines are robustly compact in terms of thrust per engine exhaust area).
 
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M. Sarigul Klijn
M. B. Clapp
S. Pietrobon
K. Sorensen and Bonometti
 
jeffb said:
And all of this is before you get to the wings.

Elon's definitely on the right track with propulsive vertical landing. The only really tricky bit was getting it to work reliably, which they've done. Difficult to see what a winged platform adds at this point.
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Radian tossing SuperHeavy aside means you only need wings for the important bits. It could glide…Starship cannot. If SuperHeavy doesn’t nail its landing—no one dies. Let it do the vertical landing.

Radian would no longer have the SSTO burden…but it would be more than Buran. More fuel, smaller payload—-and much more doable than SSTO with SH “doing the heavy lifting” as it were.

It would need more than OMS pod engines, but maybe not much more.
 
publiusr said:
jeffb said:
And all of this is before you get to the wings.

Elon's definitely on the right track with propulsive vertical landing. The only really tricky bit was getting it to work reliably, which they've done. Difficult to see what a winged platform adds at this point.
Click to expand...
Radian tossing SuperHeavy aside means you only need wings for the important bits. It could glide…Starship cannot. If SuperHeavy doesn’t nail its landing—no one dies. Let it do the vertical landing.

Radian would no longer have the SSTO burden…but it would be more than Buran. More fuel, smaller payload—-and much more doable than SSTO with SH “doing the heavy lifting” as it were.

It would need more than OMS pod engines, but maybe not much more.
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I'll bite - since any SSTO like Radian would need an OMS capability anyway, why would there be a need to add dedicated engine pods for that in a TSTO orbiter version?
 
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Here we go ! First, a PNG where I put all the salient information from the documents - bringing them together.

And then the documents, all of them (somewhat remarquably) from the 2000's.

Plus that webpage as old as the WWW.
 

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From all this, there are a host of interesting points about air-launch to orbit.

-Optimal altitude: 50 000 ft, no need to go higher.
-Optimal AoA: 30 degrees
-Optimal speed for the mothership
a) Mach 0.85 removes 1100 m/s out of Earth ascent 9400 m/s
b) Mach 2 removes 1600 m/s out of Earth ascent 9400 m/s
c) Mach 3 removes 2000 m/s out of Earth ascent 9400 m/s
d) but if you want to remove 3000 m/s, then it is Mach 5.5: in the depth of the heat barrier and hypersonic

- Something else: 9400 m/s is for hydrolox. Anything denser can go lower: as low as 9038 m/s for RP-1 / H2O2

- Equator vs KSC vs Baikonur: 58 m/s penalty for KSC, 142 m/s for Baikonur

- the ISS orbits Earth at 7800 m/s but ascending to it takes +1500 m/s of steering / gravity / drag losses

- yet a 747 right over the equator dropping a keroxide booster or rocketplane at 50 000 ft, Mach 0.85 and (if that's even possible) 30 degree AoA can
- exactly cancel all the ascent losses
- and get ascent to orbit matching orbital velocity, both at 7800 m/s

And from Mach 2 onwards, the part of ascent to orbit done on rocket engines (the voracious ones that need tons of bottled, liquid oxidizer) goes below orbital velocity values: 7300 m/s for a Mach 2 mothership; 6900 m/s for a Mach 3 one.

As for Skylon, by starting the rocket at Mach 5.5, it saves the said rocket 3000 m/s out of 9400 m/s: it has to perform "only" 6400 m/s and this led to massive amounts of LOX dead weight being saved.

Even then, Skylon fuel fraction is 0.84 - still better than hydrolox SSTO (0.88) or non-hydrolox SSTO (0.93 for a SSTO with Raptor & 380 seconds; 0.94 to 0.96 for anything with a lower isp: from 360 to 310).

Hence, if Radian SSTO don't want to use hydrolox for a SSTO rocketplane, it is "fuel fraction 0.95 or bust" - and this, with minuscule payload. Screw the fuel fraction to 0.93 and boom, Radian delta-v goes below 9000 m/s - and you end suborbital very, very quickly.

The rocket equation is a... female dog.

Now let's shift to different planetary bodies.
Mars surface to orbit: 4200 m/s
Moon surface to orbit: 2400 m/s
Moon surface to escape: 2700 m/s
For the sake of comparison
Earth surface to Earth escape velocity: 11200 m/s.

"We are living on the wrong planet for SSTO. Mars ? no problem !" Elon Musk, 2018.

He was spot on.

I once calculated fuel fractions for chemical SSTOs. With the all time chemical rocket isp record of 542 seconds (lithium, oops, fluorine, gasp, LH2, the horror) fuel fraction would not go below 0.83. Even nuclear would go no lower than 0.75. Hydrolox needs 0.88 as a bare minimum.

For the sake of comparison
- B-52H fuel fraction: 0.64
- Rutan's Voyager, 1986: 0.74
- Rutan's Global Flyer, 2007: 0.82
- Titan II first stage booster all time rocket record: 0.962 - could go SSTO but with zero payload and not reusable. Even with Russian staged combustion engines, specific impulse 330 - 360, fuel fraction would still need to stick to 0.94.
- A coke can is 0.95 mass fraction: 95% coca cola in weight, 5% of tin can around the coke.

- the B-58 Hustler still has the all time record for the lightest undercarriage, reported to its MTOW: 2.5%. Most of the time it is 4% of MTOW.

At the end of the day, a good case could be make that Earth size, mass, and density and thick atmopshere by requesting 7800 m/s to 9400 m/s just brings chemical rocket SSTOs on their knees: dragging them to next to impossible fuel fractions.
Chemical rocket SSTO with 0.80 fuel fraction result in a delta-v of 5000 - 7000 m/s (depends if LH2 or not).
So to hit Earth orbit, fuel fraction has to hit impossible numbers: 0.88 or 0.95.

Now Mars is proof that on a smaller body, you can get into orbit for merely 4200 m/s.
Often wondering how much it would take to go into orbit around Venus rocky body (forget the hellish atmosphere).
Being 10% smaller and 25% less dense than Earth, I bet you orbital velocity there must be 7000 m/s: just a bit less than Earth - and just enough to make chemical rocket SSTO barely feasible there.

Bottom line: we need a planet a bit more massive than Mars but a bit less than Venus and Earth. A planet with an orbital velocity of 6500 m/s.
 
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publiusr said:
martinbayer said:
publiusr said:
Now, if this were to be launched atop SuperHeavy or something—it would be an easier design, no?
Click to expand...
Easier as compared to what - an SSTO HTHL RLV? are you simply envisaging a Shuttle II concept with a VTVL reusable booster?
Click to expand...
Something like that —-SuperHeavy would give a far better boost than a sled. Booster VTOVL, spaceplane lands horizontally.
Click to expand...
Here it is (Vertical Takeoffs and Horizontal landings (VTOHL)) . That includes @Orionblamblam remarks on the landing gear weights gains):

1634136184327.gif

I am stuttering a bit, apparently, but the beauty of it is that I see increasingly others like you in this venerable assembly, converging on the concept
 
Orionblamblam said:
The value of a sled lies less in the speed it adds and more in the landing gear it deletes. The landing gear requirements for a fully fueled HTOL SSTO spaceplane are massive; for an empty one... not so much. So if you can offload the landing gear for takeoff, you can size the gear for landing only, and save a *lot* of weight. Not only does the gear get smaller and lighter, but it doesn't need to have the actuators to retract the gear and shut the doors.
Click to expand...
So how does the gear retract then? Manually? or did you just mean the actuators can be smaller too?
 
TomcatViP said:
I am stuttering a bit, apparently, but the beauty of it is that I see increasingly others like you in this venerable assembly, converging on the concept
Click to expand...
I guess it depends how much retractable wings will weigh, plus the heating and aero aspects of such when retracted during take-off. It's certainly not a bad idea, RLVs solved part of the problem, the only remaining part is giving them horizontal landing back where they took off from.
 
Store kinetic energy in a small, advanced battery, or top off an existing unit. If the X-15 could land with skids, so can this.
 
Forest Green said:
Orionblamblam said:
The value of a sled lies less in the speed it adds and more in the landing gear it deletes. The landing gear requirements for a fully fueled HTOL SSTO spaceplane are massive; for an empty one... not so much. So if you can offload the landing gear for takeoff, you can size the gear for landing only, and save a *lot* of weight. Not only does the gear get smaller and lighter, but it doesn't need to have the actuators to retract the gear and shut the doors.
Click to expand...
So how does the gear retract then? Manually? or did you just mean the actuators can be smaller too?
Click to expand...

You don't retract them in flight. The vehicle launches with them stowed, which is probably done with external assistance during the process of mating the vehicle to the sled. Then they deploy using a one-way mechanism before landing. The Shuttle, for example, used a combination of hydraulics, pyros, and gravity to help open the doors and deploy the landing gear. Once down, they stayed down.
 
Forest Green said:
Orionblamblam said:
The value of a sled lies less in the speed it adds and more in the landing gear it deletes. The landing gear requirements for a fully fueled HTOL SSTO spaceplane are massive; for an empty one... not so much. So if you can offload the landing gear for takeoff, you can size the gear for landing only, and save a *lot* of weight. Not only does the gear get smaller and lighter, but it doesn't need to have the actuators to retract the gear and shut the doors.
Click to expand...
So how does the gear retract then? Manually? or did you just mean the actuators can be smaller too?
Click to expand...
Same way it retracted on the Space Shuttle: the ground crew does it. You might be surprised to find out that Hollywood lied to us all when it showed the landing gear retract on the Space Shuttle after it crashed into the LA river in that movie "The Core." The Orbiter had no ability to retract the gear... because why would it need to? It starts a mission with the gear already retracted. An SSTO, either a vertical launcher or a horizontal launcher that uses some sort of sled, would also begin with gear retracted.
 
Archibald said:
From all this, there are a host of interesting points about air-launch to orbit.

-Optimal altitude: 50 000 ft, no need to go higher.
-Optimal AoA: 30 degrees
-Optimal speed for the mothership
a) Mach 0.85 removes 1100 m/s out of Earth ascent 9400 m/s
b) Mach 2 removes 1600 m/s out of Earth ascent 9400 m/s
c) Mach 3 removes 2000 m/s out of Earth ascent 9400 m/s
d) but if you want to remove 3000 m/s, then it is Mach 5.5: in the depth of the heat barrier and hypersonic
Click to expand...
And this is where Super Heavy and a pop-trajectory helps Radian as an upper stage-you said no need to go higher than 50,000 ft...yet SH gets you above the murk and therefore the heating and shaves off m/s both. Now what can Radian get away with, math wise? SH can be the eggshell so Radian doesn't have to be.
 
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