Radian Crewed SSO Spaceplane

[Asteroza]

Radian was presenting on the FISO telecon

https://fiso.spiritastro.net/telecon/Holder_7-10-24/


Seems like a lot of work on thermal related stuff which might be of interest to others.


Apparently there is a crossfeed from the sled to the spaceplane, and looks like a wet LOX wing tank setup as well.

Nothing obvious about how the altitude compensation for the engines is achieved...

[john smith 19]

Radian was presenting on the FISO telecon

https://fiso.spiritastro.net/telecon/Holder_7-10-24/


Seems like a lot of work on thermal related stuff which might be of interest to others.


Apparently there is a crossfeed from the sled to the spaceplane, and looks like a wet LOX wing tank setup as well.

Nothing obvious about how the altitude compensation for the engines is achieved...

Thanks for this.

Not found any discussion of dry mass fraction so far. All the hardware (inc the payload) can't be more than roughly 12%. Otherwise it don't work. 
[EDIT Around 44min he starts talking about Cg issues. No mention that CH4 is lighter than LOX so why isn't the LOX tank ahead  of the CH4?. I know they are both densified but it's possible the CH4 densifies harder, so it's density is actually greater than the LOX. AFAIK they are both basically linear, but I could be wrong. ]

[Tywin]

The question is... how much can cost this Radian One to development?

[john smith 19]

The question is... how much can cost this Radian One to development?

??

[TrevorMonty]

Not lot to be gained from Payload interview, better of reading Wiki or Eric Berger article.
Eric said 200klbs engine and they will be partnering with another company on development. Usra has 200klb methalox engine in development so maybe them.

True. Said their TPS is called "Durotherm," but not sure that get's us anywhere.

As others have said SSTO is big ask especially when starting from scratch. Something like Dawn's 2stage spaceplane would be better place to start from. The knowledge gained from operating such 2 stage vehicle would be invaluable if making leap to SSTO.

Only if you're first stage has the stretch to go to full orbital. I've heard this line floated before but I've never seen a TSTO evolve to an SSTO, and neither has anyone else. 

Easier to develop TSTO (suborbital spaceplace and expendable US) and they would have operational RLV that could make money while SSTO is being developed. The biggest difference between suborbital(TSTO) and orbital (SSTO) spaceplanes is thermal protection. Construction of vehicle, flight control SW, RCS, changing COG handling issues and engines would all be same. 

Don't forget most difficult item with longest timeline, paperwork. Clearance to operate a large very fast autonomous drone from public airport. This is something thing Dawn has just been give permission after chipping away at it with authorities over years. Deploying something into orbit and reentry (satellite, US or SSTO RLV) is yet more paperwork.

[john smith 19]

Easier to develop TSTO (suborbital spaceplace and expendable US) and they would have operational RLV that could make money while SSTO is being developed. The biggest difference between suborbital(TSTO) and orbital (SSTO) spaceplanes is thermal protection. Construction of vehicle, flight control SW, RCS, changing COG handling issues and engines would all be same. 

We will have to agree to differ on this one. It's one of those nice little stories people tell engineers "Of course we will develop it into an SSTO, when we've proved it."

IMHO this line of reasoning is simply delusional. If you have an engine designed to go from 0 to M23 and back (and a vehicle designed to deliver the equal payload fraction of a TSTO, the actual Achilles heel of all VTOL SSTO vehicles) anything less than doing SSTO is a complete waste of time. 

Of course if you've only got rockets then that approach makes perfect sense.

Don't forget most difficult item with longest timeline, paperwork. Clearance to operate a large very fast autonomous drone from public airport. This is something thing Dawn has just been give permission after chipping away at it with authorities over years. Deploying something into orbit and reentry (satellite, US or SSTO RLV) is yet more paperwork.

As Reaction have been working with the CAA.

[Lampyridae]

Nothing obvious about how the altitude compensation for the engines is achieved...

Some kind of slotted or otherwise permeable rocket nozzle would be my bet. This idea has been around a while.

https://www.researchgate.net/publication/380829841_Numerical_study_on_altitude-compensating_mechanism_of_a_permeable_nozzle

Edit: 9:30 or so they talk about a nozzle extension that kicks in.

[Steven Pietrobon]

I know they are both densified but it's possible the CH4 densifies harder, so it's density is actually greater than the LOX. AFAIK they are both basically linear, but I could be wrong.

The density of LOX varies from 2.7 (boiling points) to 2.88 (10 K above  freezing point) times that of CH4. This could be due to the smaller range between the boiling and melting points of CH4 (21 K) and LOX (36 K).

Density of LOX at 10 K above melting point of 54 K is 1.262 kg/L.
Density of CH4 at 10 K above melting point of 91 K is 0.438 kg/L.

Density of LOX at boiling point of 90 K is 1.14 kg/L.
Density of CH4 at boiling point of 112 K is 0.423 kg/L.

[john smith 19]

The density of LOX varies from 2.7 (boiling points) to 2.88 (10 K above  freezing point) times that of CH4. This could be due to the smaller range between the boiling and melting points of CH4 (21 K) and LOX (36 K).

Density of LOX at 10 K above melting point of 54 K is 1.262 kg/L.
Density of CH4 at 10 K above melting point of 91 K is 0.438 kg/L.

Density of LOX at boiling point of 90 K is 1.14 kg/L.
Density of CH4 at boiling point of 112 K is 0.423 kg/L.

Thanks for this Steven. That was the only thing I could think of that would put the LOX just in front of the engine and behind the fuel tank.

The Cp/Cg mismatch has been known about for decades. It's part of the reason SS has a LOX tank in the nose. It's why Reaction moved their engines into nacelles at the wing tips.

I don't  see how Radian are going to make this work over roughly 23 mach numbers. 

[Spiceman]

The density of LOX varies from 2.7 (boiling points) to 2.88 (10 K above  freezing point) times that of CH4. This could be due to the smaller range between the boiling and melting points of CH4 (21 K) and LOX (36 K).

Density of LOX at 10 K above melting point of 54 K is 1.262 kg/L.
Density of CH4 at 10 K above melting point of 91 K is 0.438 kg/L.

Density of LOX at boiling point of 90 K is 1.14 kg/L.
Density of CH4 at boiling point of 112 K is 0.423 kg/L.

Thanks for this Steven. That was the only thing I could think of that would put the LOX just in front of the engine and behind the fuel tank.

The Cp/Cg mismatch has been known about for decades. It's part of the reason SS has a LOX tank in the nose. It's why Reaction moved their engines into nacelles at the wing tips.

I don't  see how Radian are going to make this work over roughly 23 mach numbers. 

You nailed it.

-It was already a giant PITA for Concorde, 60 years ago. And this was only fuel, and only Mach 2.

-It also plagued HOTOL four decades ago: it had the wing and the engine and the air intake all in the back, and thus severe CoG issues. They were so desperate they put not only canards in the front, but also the fin. Did not worked, they iterated again and again with no solution found: only the payload to orbit shrinking again and again, as if 7 metric tons was enough in the first place.

-As you noted, by 1989-1990 this led to the Skylon design (alas, Skylon traded that issue for another one: the engine noise impact on the rear fuselage - there was a NASA tech paper about it).

-Note that REL's USAF TSTO has a different shape from Skylon, perhaps to try and solve the CoG issue: here we go again, iterating like HOTOL: damn.

-Heck even the Space Shuttle (with no hydrolox prop tanks whatsoever in the orbiter) had a lot of weight in the rear: the delta and the OMS pods and 3*SSMEs...

-Sometimes I wonder whether the X-37 shape is not the best - to balance all that weight in the rear. If only because it has the wings in the middle. Then again it has a V-tail so...

https://www.theengineer.co.uk/media/wv3guqi3/rel-tsto.jpg

[zubenelgenubi: Attach files. Do not embed them.]

[john smith 19]

You nailed it.

-It was already a giant PITA for Concorde, 60 years ago. And this was only fuel, and only Mach 2.

Actually it's a problem for all large vehicles going M1+. The B58 Hustler, B70 Valkyrie both (AFAIK) did a lot of fuel shuffling, and I'm pretty sure the SR71 was not immune from it either.

-It also plagued HOTOL four decades ago: it had the wing and the engine and the air intake all in the back, and thus severe CoG issues. They were so desperate they put not only canards in the front, but also the fin. Did not worked, they iterated again and again with no solution found: only the payload to orbit shrinking again and again, as if 7 metric tons was enough in the first place.

Alan Bond mentioned the massive loads on the canards, and the huge hydraulics needed to move them. 

-As you noted, by 1989-1990 this led to the Skylon design (alas, Skylon traded that issue for another one: the engine noise impact on the rear fuselage - there was a NASA tech paper about it).

-Note that REL's USAF TSTO has a different shape from Skylon, perhaps to try and solve the CoG issue: here we go again, iterating like HOTOL: damn.

I'm aware of a NASA paper on plume impingement and Reaction never denied the fact that the engines would be very loud at full thrust, hence going to orbit was going to need a special runway to take a payload to orbit (not that special. Any runway that could handle a fully loaded B36 of the late 40's would be a candidate aside from the noise )

Both NASA and CNES (who Reaction have partnered with) looked at "Pen nib" rear fuselages, due to plume impingement.

It is much better to identify and solve these issues in design before building, than find them in construction (or test). 

-Heck even the Space Shuttle (with no hydrolox prop tanks whatsoever in the orbiter) had a lot of weight in the rear: the delta and the OMS pods and 3*SSMEs...

Which necessitated a fly-by-wire control system as the vehicle is completely un-flyable without computer assistance and hydraulics. Lose either and you get to a low enough altitude, set up the pole and drop down it. Anything else is literally suicide. 

-Sometimes I wonder whether the X-37 shape is not the best - to balance all that weight in the rear. If only because it has the wings in the middle. Then again it has a V-tail so...

X37b is a payload during ascent. It's wrapped in a payload fairing and it's engines are for orbit changes only.

IIRC there were proposals for V-tail Shuttles, either in the original design competitions or for later replacements. IIRC one of the studies concluded with less shadowing by the fuselage they would have more control authority at high AoA, reducing use of RCS thrusters.

I think they found some SW upgrades that gave the same benefit.

Personally I would have used that as an opportunity to flush the OMS/RCS high in the atmosphere, making a much easier to approach and safer system. I guess NASA chose to save the cost of the fuel at $60/lb