Artemis Spaceplane

[Skye]

I’m building a massive spaceplane in Juno: New Origins (IMHO better than KSP for customisation & physics), and I’d love to have some design feedback on it, as i’m not quite sure on where to go. I’ll add specs and stuff below.

Basically, I made a massive rocket that can do 1100t to LEO (RSS) fully reusable (16m diameter, ~380m tall), and modelled it off Starship - big booster (but it has an expanded skirt like New Glenn), RTLS both stages, but upper stage is Hydrolox and follows Stoke’s Nova’s design with the Heatshield & engines. The idea was to have a crew version where, like starship, the fairing is “swapped” for a crew hab. This would have given me a 16m wide, ~80m long crew hab space. Prob ~50-100 people, but yesterday I had an idea: make the upper stage a spaceplane. The whole upper stage. After some design work, I came up with a ~190m long (cockpit to engines), 66m wide (wingtip-to-wingtip), 28m tall (as in wheels to top of tail fin) spaceplane. It now has (cargo version) a 123m long cargo bay that opens like a massive clamshell. Feel free to ask for any more specs and stuff.

Versions are:

Cargo

Unmanned, 123 m long x 16m wide x 11m tall fairing. 1100t to 200x200km LEO. Downmass capability of 400t.

Crew

Manned, 100+ passengers, 70m long x 16m wide x 10m tall Hab, with 35m long x 16m wide x 11m tall unpressurised cargo bay, can hold 500t. The pressurised MFM (Multi-Functional-Module), connected to the restroom segment at the back of the main spacecraft, can hold 350t of pressurised cargo, spacesuits, food, water and science. Pressurized downmass capability of 200t (unpressurised: 350t).

By the way, it’s transpirationally cooled with Methane & LOX.

Image here, not everything is correct anymore

[Skye]

Whoop, accidentally attached the image twice    

Edit: fixed!

[lamontagne]

You've reinvented the Von Braun Rocketship!  Made for Collier magazine in 1952.

[lamontagne]

Nice (almost) first post!

BTW you can edit your post and remove the second image.

Now the comments:
- Why the wings if you have a Stokes heat shield?  It's a tail lander so the wings would just be a hinderance.
- Fuel in the wings is unlikely to be a good idea.  A pain to fill, a pain to empty, and a massive pain to manage the center of gravity over time.
-What airport will be able to land this big guy?  If it's a specialized runway, then that's a lot of civil costs for very little gain, unless you really need the cross range wings might give you.  but then, you're not landing at launch site anymore...
- Transpiration cooling with both oxygen and methane seems like an accident waiting to happen?
- If the upper stage is HydroLox, why does it have methane in the wings?   The label should be hydrogen, and the tanks much much much larger...  plus your methane transpiration cooling would now be liquid hydrogen transpiration cooling.
- If you really want the wings, you probably need to go for a lifting body configuration, such as the X-33.  A X-33 twin stage to orbit might be easier to achieve than as a SSTO.
-If you are going for large volumes, bear in mind that hydrogen is far more expensive than methane.  So your large ship might be outperformed economically by smaller methane based rockets.
I now see you crossed out the H2 tanks, and switched to CH4.  Good move.  but it's now Methalox, I believe.

[Skye]

I suppose I have built the von Braun Ferry, though “slightly” modernised & enlarged. I’ve always loved the idea of the Ferry ever since I first saw it from that on photo on the collier magazine (the one where it’s staging)

- Why the wings if you have a Stokes heat shield?  It's a tail lander so the wings would just be a hinderance.

(First test using quotes, sorry if it bugs)

Hydrolox Stoke-shield VTVL design is the old one, the new one is a Methalox VTHL spaceplane w/ transpirational cooling.

- Fuel in the wings is unlikely to be a good idea.  A pain to fill, a pain to empty, and a massive pain to manage the center of gravity over time.
-What airport will be able to land this big guy?  If it's a specialized runway, then that's a lot of civil costs for very little gain, unless you really need the cross range wings might give you.  but then, you're not landing at launch site anymore...

I think you’re right on fuel in the wings, unless we can do a complex tank that blends the fuselage & wings together (which we might, we’re using 3d printing, but if not, then I’ll just add a small CH4 tank in there to enable transpirational cooling without having plumbing between the fuselage & wings. Def gonna have a little bit of monoprop in the front tho, that shouldn’t be too hard, right? Btw we’re gonna try to have JP-4 in the tail fin for the jet engines. Also shouldn’t be too hard as it’s not cryogenic.

As for the second point, I hadn’t thought about landing, being honest, I always assumed a custom runway at the launch complex. I’ve designed a much smaller one, too (30m long x ~14m wide) and so I didn’t have to think too much as it (the small one) would be able to land on most runways, but this guy is another beast. I’ll see what I can do with research on this & I’ll try to move the landing gear in as far as possible.

- Transpiration cooling with both oxygen and methane seems like an accident waiting to happen?
- If the upper stage is HydroLox, why does it have methane in the wings?   The label should be hydrogen, and the tanks much much much larger...  plus your methane transpiration cooling would now be liquid hydrogen transpiration cooling.
-If you are going for large volumes, bear in mind that hydrogen is far more expensive than methane.  So your large ship might be outperformed economically by smaller methane based rockets.
I now see you crossed out the H2 tanks, and switched to CH4.  Good move.  but it's now Methalox, I believe.

Transpiration cooling will be just Methane, if it was LOX, there would be a higher risk of fire even outside atmosphere (see SS IFT-7, ik it didn’t use transpiration cooling, but it worked for my point), and obviously both would be a nightmare, I’ve read Ignition, and it’s a miracle that the guys working with methalox as a monoprop didn’t all die.

Spaceplane uses Methalox, I just wrote LH2 without thinking, as that was the propellant of the original US design, then decided to go with methalox, so the tanks can be smaller, and use the same prop as the first stage, which simplifies ground ops (plus the US uses the same engines as the booster, so it makes for easier manufacturing). The point about being outperformed by small methane rockets is less of a concern if we also use methane, and for the crew version, we’re looking at ~£5k per seat, as we can have so many passengers that the seats would cover around 20% of the launch cost, and therefore the main launch cost makes most of the profit. (That probably made no sense lol), but basically we can charge really little for seats a still make a profit from the launch itself. Hopefully, we should be fine in terms of cost.

- If you really want the wings, you probably need to go for a lifting body configuration, such as the X-33.  A X-33 twin stage to orbit might be easier to achieve than as a SSTO.

I think the miscommunication was my fault, I probably clarified poorly, but it is a lifting body, and is not an SSTO. It’s the upper stage to a large booster ~160m tall & 16m wide, with a New-Glenn-esque engine skirt that extends to 20m wide. I’ll attach a pic when I can. The booster, funnily, can be a reusable SSTO, but can only do like 20t to LEO, a for its size, that ain’t good enough to pursue. Haven’t done flight tests of the US, but considering the jet engines (used for aborts at low altitude) can be used for takeoff, then the Hades Engines (big rocket engines shared with the first stage booster) can also be used at sea level (slightly curved inwards nozzle ending like the RS-25), it may be able to be an SSTO, but I doubt it, and even if it were, it likely wouldn’t be worth it. May as well stack it on top of a booster, get 2 orders of magnitude more performance.

Hopefully this clarified the bits I previously failed to, clearly I’m not great at doing that first try lol.

I apologise for any bad typos, I have a terrible keyboard that doesn’t register half of my inputs, and autocorrect doesn’t help much.

Btw the specs for Hades are: ~420s ISP & 6400 kN ASL, ~460 ISP & 6900 kN Vac. 1600 kg/s mass flow. 800 BAR chamber pressure (made with 2050-60 material, purely theoretical, but possible. Raptor III’s pump reach roughly that, and there are materials that can withstand ~2000 BAR for the pumps on Hades. It’s fun to dream, at least)

[lamontagne]

You don't need jet fuel if you have methane.  The engines can run on methane with some modifications and you will be needing special engines anyway, I expect.

Depending on how old you are, you will remember, or you can look up, the problem with the noise from such a large plane in existing airports.  If this design is for a story, you can do away with that objection with a bit of handwaving 
At first glance you have enough fuel to land in a controlled way, but can you take off again?  You don't want to end up stranded at an airport!
I don't know if lifting bodies can actually take off, but I expect not.  All the ones I have ever seen were for landing only.

[lamontagne]

What is the monopropellant for?
AFAIK, most monopropellant represent huge handling pains, so if you can avoid them, that would be best?

[Skye]

Jet engines can run on methane?! Well, I suppose they can run on LH2. What affect would methane have on performance? The reason I went for jet fuel is because it is higher density, but depending on various factors, methane might be better. As for the noise, I’m 14 so I probably wouldn’t know about the problem, but I’ll look it up.

The design isn’t a story, and it’s got a long explanation, but in a nutshell, I want to start a launch service company (Phoenix Aerospace) with fully reusable rockets off the bat. Starting with reusable sounding rockets, (maybe) a small-lift, but I doubt it, a medium-lift which I am actually very proud of and have been working on for months to be extremely realistic (17t fully reusable to LEO in RSS!), a super-heavy lift in the class of Starship, and then this massive beast and its huge booster. Luckily, I’m starting work from a relatively young age so I have lots of time to iron out any flaws that I can possibly find in-game (using Juno: New Origins for best customisation). Sadly, I can’t handwave the noise away and have to find a solution. (Also, this is - obviously - planned for wayyyyyy down the line. Like, 2050-2060)

I think we would have enough fuel to land, but you have a good point. We can’t exactly fit this monster in the boot of a car and just drive it home!

I’ve now considered boats, but they’re too expensive, and flying this on the back of a plane would be a bad idea because:

1: it’s way too big and heavy

& 2: flying a perfectly good, we’ll-functioning plane on another plane is just silly, at that point, you may as well fly the (space)plane!

So for quick and cheap(ish) transport, the best plan would be to just fly the plane back under its own power. The problem is, if we use methane for the jet engines, that’ll be an issue. What aeroport has liquid methane on standby? I’d like to use CH4 for jet fuel, it simplifies ops, but the problem is aeroport landings. Jet fuel in the tail would be better for those situations as it would allow for a quick fuel-&-go after a checkup or two (this would likely be an abort, after all. Most landings would be at the launch complex’s runway)

So I’m unsure. Would it be worth making the jets able to run on methane and jet fuel?

Monoprop is for RCS and Orbital Manoeuvring

[lamontagne]

Yes, they can run on natural gas (methane) just fine.
https://aviationweek.com/air-transport/aircraft-propulsion/can-aviation-use-liquified-natural-gas-reduce-its-carbon

The reason they don't in practice is mainly bulk, and the mass of the large strong pressure tank required that breaks the economics.

I see from your bio that you are British, so I suggest you look up the history of Concorde a little bit, if only for national pride  .  You should find plenty of information on the problem of noise at airports, that kind of killed the bird.

[Skye]

Makes sense, JP-4 is cheaper, easier to store, less dangerous, & denser. It’s a better choice for the application, so they use it.

I’d love to do some research on Concorde, I’ll look around on the web!

I actually went to see Concorde 002 in the spring of last year, was even allowed inside it! Walked right down the length of it, super cool! - though surprisingly cramped! 

Also makes sense that Concorde’s death was somewhat aided by the noise issue. Not sure people would appreciate having a Concorde with very loud jet engines on the runway, then using EXTREMELY loud afterburners, before breaking the sound barrier. (I know I and a lot of other aerospace enthusiasts would love it, but the public wouldn’t, sadly)

Shame it was retired, hopefully this will prove a worthy spiritual successor (I might just name one of them Concorde to honour it!  )

[Skye]

Ok, after some flight testing, it can’t get off the runway with jet engines (12 MN isn’t enough to move 13 Kilotons (shock horror)) so I use all the Hades engines too and it BARELY gets is off the runway (like, the runway’s on a beach and after we get off the runway, we have to pitch up HARD and we skim the water for like 7-8km before we can get 20m height. As in, the engine skirt is literally slightly submerged), but it’s fine, it’s not meant to be an SSTO, so it doesn’t need to. I only do these runway takeoff tests to ensure systems work properly in flight, then once I develop further, I use teleport and set speed to put it in LEO and ensure orbital systems like cargo bays & solar arrays work there, then once everything is working well, I put it on a booster and do some VTHL flight tests. But anyways, I’ve done some HTHL tests & found that it:

1: is very stable at hypersonic velocities, &

2: falls like a brick when subsonic, despite having like 1100 m² wing area. Anything I can do to help the glide ratio while still keeping it stable @ hypersonic speeds?

(Btw I tweaked the Hades Engine & now it has a T:W of ~1.1 in vac (1.03 ASL) so it can do hotstaging!)

[lamontagne]

What is the Hades engine?  A thrust to weight ratio of 1.1:1 is very bad, so perhaps something is off there? Or you are using the expression in a different manner than usual?  Perhaps it's the thrust to weight ratio of the stage at the beginning of the burn?

https://en.wikipedia.org/wiki/Thrust-to-weight_ratio

An advanced engine would have a thrust to weight of 200 or more.

As far as flight goes, are you running it in aircraft mode full or rocket propellant or empty?  It should be mostly empty, as you hardly need the oxygen and methane of the main engines, perhaps that would help.  Empty, the mass will be a fraction of the 13 000 tonnes, if the software allows it.  that's 13 000 tonnes for the second stage alone, right?

Most jet engines cannot move from subsonic to supersonic flight to hypersonic flight.  The Skylon Sabre engine might have been an exception, but it never got built.
It's asking a lot from an engine to operate in such different regimes.  So perhaps keep the airplane subsonic for regular flight regimes?  Perhaps fly subsonic back to the launch tower, wherever it it?  Preferably on a barge far from anything else....

[lamontagne]

BTW I haven't checked the wingspan but it might be excessive for most airports.

This paper on liquid natural gas might interest you.  The point here is that if liquid natural gas is better than jet fuel, it might replace the fuel over the next few decades.  so the airports would have liquid natural gas available.

https://www.mdpi.com/1996-1073/13/22/5925

BTW do you use Google Scholar?  It's a great resource to get information on very specific subjects more in depth than through Wikipedia.

[InterestedEngineer]

Ok, after some flight testing, it can’t get off the runway with jet engines (12 MN isn’t enough to move 13 Kilotons (shock horror)) so I use all the Hades engines too and it BARELY gets is off the runway (like, the runway’s on a beach and after we get off the runway, we have to pitch up HARD and we skim the water for like 7-8km before we can get 20m height. As in, the engine skirt is literally slightly submerged), but it’s fine, it’s not meant to be an SSTO, so it doesn’t need to. I only do these runway takeoff tests to ensure systems work properly in flight, then once I develop further, I use teleport and set speed to put it in LEO and ensure orbital systems like cargo bays & solar arrays work there, then once everything is working well, I put it on a booster and do some VTHL flight tests. But anyways, I’ve done some HTHL tests & found that it:

1: is very stable at hypersonic velocities, &

2: falls like a brick when subsonic, despite having like 1100 m² wing area. Anything I can do to help the glide ratio while still keeping it stable @ hypersonic speeds?

(Btw I tweaked the Hades Engine & now it has a T:W of ~1.1 in vac (1.03 ASL) so it can do hotstaging!)

You'd better calculate the pascal load on your landing gear.  I suspect they far exceed the capabilities of inflated rubber tires.

Also better calculate the mass of said landing gear.  It's dead weight all the way up.

[Skye]

It’s around 60t, but not a big deal. It’s meant to be reusable, so I can’t drop it like Star Raker, or I wouldn’t be able to land. How would I calculate the Pascal load? (I’m not good with equations yet ) and how could I theoretically improve the landing gear’s load capability? (I have 4 in the front, 6 just behind centre of mass)

Wingspan is ~60-70m, prob too much lol 

No, I don’t use google scholar, what is it?

Hades is the engine used on the Plane, as well as the booster that powers the plane. When the booster & upper stage are fully loaded, it should have a T:W of ~1.9:1

There has definitely been a mixup, my bad. Yeah I meant the T:W of the stage at the start of the burn. The T:W of 1.1 is when the 21 Hades engines are on the fully loaded plane, and it’s just staged. The ending T:W should be around 3.5:1

Thrust of ~7,000 kN, 413s Isp ASL

~7,800 kN, 446s Isp Vac

Mass flow ~1,900 kg/s

Methalox

800 BAR chamber pressure

Slightly curved in nozzle like RS-25 for better usability across different pressures

Dry mass of 2.68t

T:W of 261:1 (engine alone)

For these flight tests, it’s full of rocket prop to stress it as much as possible. I should probably empty it for at least one or two. I assume a T:W of ~0.8 at takeoff with just jet engines & no methalox. Of course, that doesn’t matter very much as it won’t be taking off horizontally, only landing, but it’s useful for if we need to boost before landing.

Empty, it’s (the crew version, with about 3000t of cabins, private quarters and tons of luxury) about 5 Kt, (with 500t payload) but it has about 400t of monoprop for TONS of orbital manoeuvring. So without anything at all, it’s about 1.1 kt, but that’s with a 200t guidance & control unit. The cargo version is ~1.6kt with monoprop & guidance unit. It can prob do around 1000t to LEO (maybe more, but 1000t is the target)

Software does allow tank draining, and yes, it is 13000t for the second stage alone. About 40000t for the full rocket w/ booster.

For flight profile, in terms of an actual launch, the jets will never have to work hypersonic, as the plane will see from the booster in vacuum, immediately using the main engines. The jet engine would only be used in a low-altitude abort or to boost in the lower atmosphere for another loop around on landing or to reach a further-away-than-expected landing site.

As far as flight goes, are you running it in aircraft mode full or rocket propellant or empty?  It should be mostly empty, as you hardly need the oxygen and methane of the main engines, perhaps that would help.

Btw do you mean that it hardly needs the methalox in general or just on landing? On landing, that’s absolutely correct as the tanks should be basically empty, but in general, it needs around 8000t of methalox. About 99% of which is for ascent, large-scale orbital manoeuvring and deorbit burn, but a little is needed for the transpirational cooling on reentry. 

The jet engines do have afterburner, and can get to ~16 MN each, (they’re BIG. like 32t, 3.5m wide, 8m long). It seems like it’d be able to get to maybe Mach 2 or 3 without any methalox in there, but that’s probably max speed for transport back to “base”. I don’t think we’ll be operating them @ hypersonic speeds.

I hope this cleared up any issues 

[lamontagne]

Google Scholar is a part of Google where you can search for scientific papers by subject, author, date, etc.  It's great to build up a reference base, including thousands of papers by NASA people.  When you click on papers with links to the right, you get the actual papers, not just the abstracts.
https://scholar.google.com/

What is the landing and take off mass of the ship?  There are probably errors in the masses, because they don't add up well.  Perhaps use a spreadsheet, such as Google Sheets if you don't have Excel, to keep your numbers straight!

Ok, let's suppose the landing mass is 10 000 tonnes empty.  Converted into a force, that is 10 000 x 1000 to get kg, and kg x 9.81 to get Newtons. So about 98 100 000 Newtons.
This is the vertical force due to the mass of the ship that the landing gear must support.

A tire is a form of inflated balloon.  The pressure in the tire supports the aircraft at landing.  The pressure is measured in Pascals.  There is an interesting relationship between force and pressure, since 1 Pascal = 1 Newton/m2 (meter square)

Supposing the tires are pressurized at 200 psi (old units of pounds per square inch)  This is 6894 1 379 000 Pascal.
So the contact surface of the tires must be 98 100 000 N / 1 379 000 Pa = 71 m2

The contact surface of the tires (the flat part that touches the ground) needs to be about 71 m2! 120m x 120m!!
If you estimate that each tire has about 20 cm x 20 cm touching the ground, you need 1 700 tires!!!
That is not going to weight only 60 tonnes!  So there is something off in the software, if it gives you that value.

Your landing gear is going to look like a huge large Self Propelled Modular transporter.
https://engineeredrigginggroup.com/equipment/self-propelled-modular-transporters-spmts/

Like the ones that move Starship elements around.

[lamontagne]

I think we're still having trouble with masses 

Let's look at your top stage.  It's about 16m wide x 10m high by 120m long. Simplifying greatly, that 10x16x120 = 19 200 m3.  Knowing that oxygen masses 1 tonne per m3, I'm certain that 13 000 tonnes is the fueled mass.  If it has 8000 tonnes of methalox, that means the vehicle masses 13 000 - 8 000 = 5 000 tonnes. 
That is much too heavy.  If I look at the second stage of Starship as reference, It takes about 100 tonnes to hold 1500 tonnes of methalox.  So a mass ratio of 15.  Therefore your top stage should not mass much more than 8000 /15 = 500 tonnes.  With about 500 tonnes of cargo. 

500 tonnes gives a rather more reasonable landing gear 20 times smaller.  Still, that's 1 700 tires / 20 = 85 tires.  Still a big number.  So actually the 60t of the software might be correct, but it really eats into your 150500 tonnes cargo, since 60t of it is now landing gear.


Hum, there is an error somewhere.  I will correct the last two posts as soon as I find it.!
Should be correct now, multiplied the pressure by 200!!

As a reality check, landing gear is about 4% of the take off mass, so for a Boeing 747 taking off at 350 tonnes the landing gear might mass 8 tonnes.
retro engineering the 60 tonnes and 4%, I get a 1500 tonnes mass for your second stage.

[InterestedEngineer]

It’s around 60t, but not a big deal. It’s meant to be reusable, so I can’t drop it like Star Raker, or I wouldn’t be able to land. How would I calculate the Pascal load? (I’m not good with equations yet ) and how could I theoretically improve the landing gear’s load capability? (I have 4 in the front, 6 just behind centre of mass)

fully loaded with fuel, what is the mass rolling down the runway?

Pascals is just N/m².  FIgure out what good tires can handle, what their contact patch is, and do the math.

for example the Antonov An-225 Mriya has a MTOW of 640t, and the landing gear masses about 30t, 28 tires on the main landing gear alone.  Each tire is  needs a 640*9.8 / 28 = 225kN.  Given aircraft tires are about 200 psi or 1.38MPa, the contact patch is 225kN/1.38MPa = .163m² = 16x16 inch contact patch.

If you have a MTOW:dry ratio of 10 then your landing gear consumes half your max dry mass (640/10 = 64).  Versus say a Starship caught on chopsticks has a "landing gear" of about 15t of fuel, 2t of lifting pads & structure,  or 17/350 = 5% of max dry mass

The weakest spot of "massive spaceplanes" is the mass of the landing gear.

[Skye]

~13kt, but with only jet fuel it’s around 1-2 kt.

K, I’ll work it out, and get back to you. Might ask my dad for a little help, he’s really good at this kinda thing. I’ll prob be able to do it myself tho. 

[Skye]

The mass is now outdated, sorry. After a lot of dry mass cuts, it’s now more like 10kt (no cargo) with a ~80m long tank. (Now 11m wall, width is still 16m). Propellant (methalox, jet fuel, monoprop) is around 8-8.5kt (just methalox is ~7-7.5kt) The methalox, btw is subcooled & densified, stored at around 10 BAR. It also has a couple additives,which reduce I_sp a little, but decently increase density. Total density is around 1.65x that of regular, unmodified, uncooled / pressurised methalox.

Also it turns out length is more like 200m and wingspan is ~120m, after some updates.

Hope this helps