Project LR1 Skyhammer: A New Shuttle [p1]

[kocmolyf]

LR1 SKYHAMMER - PROTOTYPE p1
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Welcome to the first prototype release of the LR1 Skyhammer!

This an ascent prototype only. It has enough functionality to get you off the pad and into orbit, but no further. It has:

- No RCS thrusters.
- No restartable engines.
- No orbital maneuvering engines.
- No aerodynamic control surfaces.
- No landing gear.
- No payload bay doors.

See the included readme for an overview of the vehicle and instructions for flight. Have fun!

p1: [[ame=http://www.orbithangar.com/searchid.php?ID=6646]Download[/ame]]





ORIGINAL POST
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Hey all!

I've been working on a new launch vehicle for a couple weeks. I started it because I wanted a vehicle that was:

1. In a roughly similar payload class as the space shuttle (mass + volume).
2. Modeled in more detail than the XR fleet.
3. Not beholden to an existing specification (like SSU). I didn't want to feel compelled to implement details that weren't fun for completeness' sake.

The Skyhammer (Launch vehicle, Reusable, 1) is meant for putting heavy things into orbit. The basic configuration is obviously taken from the LS-200. There were actual wind tunnel tests done on this shape, so I have some data to work with. It's a stage-and-a-half configuration with external drop tanks and all 7 engines carried on the orbiter. Staging occurs at roughly 5000 m/s; the drop tanks hinge on their rear attachment points and swing up and over the top of the orbiter. The orbiter continues to orbit on the center 3 engines. Before entry and landing, a visor is retracted over the canopy. This allows entry angles of attack ranging from about 30 to over 45. Flaps on both the top and bottom control pitch and roll; the vertical fins contain both rudders and speedbrakes.

I changed the propellants to CH4/O2 to reduce vehicle volume. Orbital maneuvering and reaction control are done with gaseous methane and oxygen rather than hypergolic fuel. Electrical power is provided by fuel cells. Crew count is in flux, but it will probably be around 7. Docking will be performed with a special module in the payload bay. The robotic arm will also be removable. Relative to the real space shuttle, the payload envelope is increased to a 5 x 18 meter cylinder. Payload mass to low-inclination 300 km jumped from 25 tonnes to 50 tonnes.

There's still a lot of work to do on the configuration, let alone modeling, texturing, and programming. But I thought I'd share what I have and get feedback before I get so far along that I can't change anything.

Launch configuration shot. Note the propellant and pressurization connections to the drop tank.

Orthographic 3-view.

Conceptual internal packaging and plumbing.

Orbital configuration with payload bay open.

Payload bay closeup, robotic arm envelope visible.

Orbital manuvering engine plumes.

Primary reaction control thrusters.

Vernier reaction control thusters.

+Z vernier thrusters. These are used for "low Z" proximity operations to avoid plume impingement on the rendezvous target.

Entry configuration with the visor up.

 

[Pipcard]

This is a really cool lifting body project!

 

[PhantomCruiser]

Nice looking!

 

[Interceptor]

Very cool!

 

[Andy44]

Looks almost exactly like a Lockheed Starclipper.

[ame="http://www.orbithangar.com/searchid.php?ID=1221"]Lockheed Starclipper 1.11[/ame]

Only scaled up a bit.

Kind of cool.

 

[Pipcard]

Except the drop tank isn't quite the same.

 

[PhantomCruiser]

I was thinking of a kludged Titov, a la Worlds of 2001. Either way, I WANT ONE!

 

[kocmolyf]

The resemblance to the STAR Clipper is not a coincidence :thumbup:. As mentioned in the OP, the configuration is based off of the Lockheed LS-200, which itself was derived from the STAR Clipper. I changed a few things, but it's definitely still recognizable. Probably the biggest external difference is the smaller drop tanks due to the denser propellants.

 

[Pipcard]

There actually was a version of the Star Clipper proposal with two separate drop tanks.

 

[Andy44]

The OP's version has a more STS-style nose and cockpit, though, which looks more practical than the Lockheed concept's pointy nose. Likely that if Lockheed had gone forward with the design the nose would've evolved into something shaped very much like STS and Buran and the OP's Skyhammer design, as pointy noses don't handle heat well with hypersonic shock waves.

 

[n0mad23]

I love the lines of this - it's all function and form. I'm really hoping that those external fuel tanks actually can make it into orbit, as I can see them as orbital assets in terms of mass and materials all ready in LEO.

This represents my favorite kind of addon - speculative, outside the box, and possible with "off the shelf" parts. I'm looking forward to seeing further development. :tiphat:

 

[kocmolyf]

I love the lines of this - it's all function and form.

Thanks!

I'm really hoping that those external fuel tanks actually can make it into orbit, as I can see them as orbital assets in terms of mass and materials all ready in LEO.

I was ready to write something along the lines of, "Sadly, that would be single stage to orbit, so no", but then I decided to run the numbers and check. It turns out, if you take almost everything out of the payload bay, you can indeed put the drop tanks in orbit! It's probably not as useful as whatever you were going to carry in the bay, though.

I'm looking forward to seeing further development. :tiphat:

I replaced the engine envelopes I used for rough placement with actual nozzles. Like many reusable designs, the thrust chamber and pumps/plumbing are behind the base heat shield inside the vehicle. I also added the reaction control pods (blocky things near the fins) as well as mounting points for the orbital maneuvering engines (the small ones canted out in a weird way). These thrusters were the hardest to place while avoiding intersecting the body, hence their weird shape.

Still a lot of work to do on the aerosurfaces, the payload bay, reaction control thrusters, and the drop tanks (which are totally bare at the moment), to name a few.

 

[n0mad23]

I really dig how you've gone with the reusable design.

I've been reading excerpts from the book The Rocket Company online the last few days, and wonder why you chose to go with O2 instead of H202 with this? Granted, liquid oxygen remains considerably cheaper and provides a better performance, but H202 would offer a lot to this platform that O2 can't. For example, it can easily provide its own pressurization for its tank, and can be used to drive a small turbine for powering hydraulic actuators for thrust-vector control of first stage main engines.

I couldn't help think of this when seeing how "alt-space" you've gone all ready with this design all ready. Not to be read as any kind of criticism, but more as the continuing rocket-education of this amateur orbital mechanics hacker. I'm an instant fan of thie LR1 Skyhammer.

 

[kocmolyf]

Good question!

The main reason one might choose H2O2 is that it is liquid at room temperature. Combined with RP1 (kerosene), that means you don't have to deal with any cryogenic propellants at all. The price you pay is performance. On a first stage that's not so bad, but on your second stage that rapidly leads to large propellant mass fractions (especially on the first stage, which has to carry a larger/heavier second stage). As a comparison, RP1 / H2O2 is in the same Isp class as many solid rocket motors. Since the Skyhammer uses a drop tank, it is advantageous to use the same engines and the same propellants in both the internal and external tanks. CH4 / O2 is a pretty good compromise between density and performance. Since methane is cryogenic anyway, it doesn't buy you a whole lot to use a non-cyrogenic oxidizer.

The Skyhammer actually does use so-called "autogenous" pressurization - CH4 and O2 are fed into their respective tanks after being gassified in the engines (those lines are visible in the internal view in the OP). The space shuttle external tank was autogenously pressurized as well - that isn't a property unique to H2O2.

As for hydraulics, Skyhammer doesn't use a shuttle-like APU. It has many individual closed-loop hydraulic systems called electrohydrostatic actuators (commonly 'EHA'). These are electrically-driven hydraulic pumps that are distributed around the vehicle and only take power when in motion. Each one has a little hydraulic circuit that is only connected to a single actuated element (control surface, thrust vector control strut, etc.). They draw from the main electrical system, which in this case will probably be backed by an H2/O2 fuel cell array (since we need the water byproduct for the crew).

Finally, the gradual boiloff from the tanks is useful as both reaction control propellant and pressurant for the tanks themselves. So the main negative of cryogenic fuel can actually be turned into a positive.

So ultimately for this design there's not a lot to recommend H2O2. But if you're building a reusable first stage it's definitely worth considering!

 

[dacamp66]

have you considered moving the drop tanks and/or vertical stabilizers?
in their present locations, there may be a danger of collision on staging.
if you look at the starclipper, the tank(s) are well clear of the vertical stabilizers.

 

[orbitingpluto]

I really like what I see with this Skyhammer, and I hope it's development goes well. I have a few questions for you about it.

1: Does it launch vertically or horizontal?
2: How long of a runway does it need to land?
3: Any chance of supporting different skins/liveries?
4: How will the payload stuff be handled? In Orbiter, I mean. Will there be lines in the scenario file to edit, a .ini file like multistage, or a thing like Payload Manager that does the editing within the sim?

 

[kocmolyf]

have you considered moving the drop tanks and/or vertical stabilizers?

The drop tanks are hinged in such a way that they rotate up and over the top of the orbiter. Here is the current clearance:

Admittedly, that has gotten a bit tight. I had to cant the drop tanks outwards a little bit while messing with the orbiter's mold line, so I ate into the staging clearance. I'm completely redoing the fins at the moment anyway, so I will make sure to give the drop tanks a bit more room.

1: Does it launch vertically or horizontal?
2: How long of a runway does it need to land?

1. Vertically. Vertical launch has big structural advantages - namely, while at full weight, the structure only has to take the loads in one direction. Then your landing gear and supporting structure only have to take the empty weight of the vehicle.
2. I'm not sure about minimum runway length at the moment but given that the LR1 is aerodynamically quite similar to the shuttle, I would expect similar runway requirements.

3: Any chance of supporting different skins/liveries?
4: How will the payload stuff be handled?

These come with the caveat that this is my first Orbiter add-on, so I'm not yet acquainted with the Orbiter SDK. Programming is a part of my job so I don't expect there will be any problems, I just have to figure it out. That said, I intend to support multiple skins (I am not a great 2D artist by any means) and have an in-game payload editor in the vein of the XR fleet (huge kudos to dbeachy for that).

 

[Pipcard]

Just a few questions:
How would you calculate the dry mass of this vehicle?
How is the flight model determined? Do you happen to have access to any CFD software?

 

[fsci123]

During reentry, will the craft simulate heating and damage?
Will the craft be able to dock?
What fuel are you thinking about using and what current engine will you use if any?

 

[kocmolyf]

Just a few questions:
How would you calculate the dry mass of this vehicle?

Very empirical at the moment. I'm using some mass estimating relations for the tanks, but for the actual structure I took it as a factor of the payload mass and the thrust. Using these assumptions I set the target dV, takeoff thrust-to-weight, engine Isp, and propellant densities. I then wrote a program to iterate the size until it found a solution. Currently it's heavier than the shuttle but somewhat lighter in relation to its payload mass.

How is the flight model determined? Do you happen to have access to any CFD software?

You can find some aerodynamic data from the LS-200 online. I'm taking that as a baseline and may try and do some of my own calculations in the future as well. The math for hypersonic flight in particular isn't that daunting.

During reentry, will the craft simulate heating and damage?

Absolutely!

Will the craft be able to dock?
What fuel are you thinking about using

These are both in the OP (yes + CH4/O2).

what current engine will you use if any?

No current engine (there haven't been any methane-oxygen engines used for serious spaceflight anyway). To throw out some numbers, each of the 7 main engines will put out roughly 3 MN of thrust at around 380 s Isp using a full-flow staged combustion cycle.