Sci-Fi World Building: Design a martian spaceplane

[Artlav]

Compressed CO2 fed through a NTR

Uranium mines on Mars... A classic of golden era sci-fi.

 

[Pipcard]

A while back, I was playing around with a "switchblade" configuration for the DG, for Mars suborbital flights and unpowered landings.

On the left is the standard DG wingspan.

Very loosely based on the Northrop Switchblade - Wikipedia, the free encyclopedia

Just throwing it out as an alternative to the folded wing.

XR-1.02 Wyvern

 

[Donamy]

A blimp with inflatable rigid wings.

 

[Hlynkacg]

There's several problems here... only the first of which is engineering the optimal solution. The tough thing is devising a low-maintenance solution that the "isolated stations" can actually support and doesn't become a useless hunk of metal when a critical part breaks down.

The other thing is fuel/propellant: That has to be available too.

The thin atmosphere of Mars provides several advantages and disadvantages.

First, you need a lot of lift for landing and takeoff. VTOL or a tailsitter might be a better solution than a craft with wings large enough to generate the needed lift for takeoff and landing without needing a stupendiously long landing strip that will also be difficult to maintain.

An advantage is that you reach supersonic speeds pretty soon and with a lot less structural burden to the plane, meaning it would need less maintenance than a plane cruising at comparable speeds on earth. So the wings, once you're up to velocity, don't need to be that large... the plane will more follow a suborbital logic than a cruising one.

Something like a tailsitter that can get out of the densest atmosphere fast, then can gain velocity for a more or less balistic trajectory to the target, and something along the lines of wings, majorly used for braking, does seem like a rather good solution in the eyes of this complete non-engineer... Anything with too complex machinery (like a scram or somesuch) or variable geometry wings sounds a bit too sophisticated to be succesfully maintained by a near future Mars colony.

Can't say anything about the engines and the propellant, though. Don't know what kind of propellant would be feasible to produce on Mars.

This is a lot of the stuff I've been thinking about. ^

I'm pretty much committed to a horizontal arrangement both for the aesthetics and ease of loading and unloading.

During my test flights in the Xr2 and Delta Glider I used hover thrusters to supplement my aerodynamic lift. As such my take-off and landing runs were about what they'd be on Earth. I really like the idea of combining a Delta wing or lifting-body spacecraft with "jump-jet" style vectored thrust.

http://youtu.be/20sV9sZ03y8?t=1m11s

Note how the main engine rotates downward to provide additional lifting force.

The basic flight profile I'm envisioning is a rolling take-off using vectored thrust, follwed by climb-out using a combination of aerodynamic lift and the main engines. Once hypersonic the spacecraft can either pitch up to exit the atmosphere or follow a "skip-glide" trajectory to another landing site on the martian surface. To land the spacecraft would use aerodynamic lift and drag to steer itself to it's destination and bleed off most of it's velocity, transitioning to vectored thrust as it goes sub-sonic. At this point the spacecraft would be light enough (due to fuel consumption) to make a vertical landing at it's destination.

Compressed CO2 fed through a NTR or a thermal storage bed. ISP's terrible, but all you need is electricity to compress the CO2, and you've got fuel ANYWHERE.

Uranium mines on Mars... A classic of golden era sci-fi.

My orbital spacecraft plan to use Methane or Ammonia fed through thorium-fueled molten salt NTRs. Thorium being readily available both on the moon and in the asteroid belt. That said, the landers need something a bit safer for human consumption. Don't want to be irradiating the landing zone now do we?

I'm leaning towards Methane + LOX fueled chemical rockets for the landers at the moment unless I can find an easily produced hypergolic.

 

[MaverickSawyer]

LOX/Methane is about as good as you can get on Mars. It's actually a pretty storeable propellant mix there, and there are ways to reliably restart the engine a LOT of times that are under development. All I'll say is, it's based on acoustics. Can't say any more.

 

[Hlynkacg]

LOX/Methane is about as good as you can get on Mars. It's actually a pretty storeable propellant mix there, and there are ways to reliably restart the engine a LOT of times that are under development.

That's exactly what I was thinking.

 

[BruceJohnJennerLawso]

You mentioned suborbital, right? Although it would restrict flexibility a fair bit, why not try some sort of mass driver to punch it up to speed at takeoff instead of all rocket propulsion? If you can get a decent velocity boost from the driver without burning up in the lower atmosphere you should be able to keep the size of the craft within reason for conventional propellants.

I would argue for that, since electricity is the one quantity that should be reasonably cheap in space, at least compared to rocket fuels and/or expensive replacement parts.

 

[Hlynkacg]

You mentioned suborbital, right? Although it would restrict flexibility a fair bit, why not try some sort of mass driver to punch it up to speed at takeoff instead of all rocket propulsion? If you can get a decent velocity boost from the driver without burning up in the lower atmosphere you should be able to keep the size of the craft within reason for conventional propellants.

I would argue for that, since electricity is the one quantity that should be reasonably cheap in space, at least compared to rocket fuels and/or expensive replacement parts.

The problem with that plan is that being round-trip capable is one of the craft's basic mission requirements. If your landing site does not have a functioning mass-driver you're SOL.

Likewise I am leery of subjecting human cargo to 18+ G accelerations.

 

[BruceJohnJennerLawso]

The problem with that plan is that being round-trip capable is one of the craft's basic mission requirements. If your landing site does not have a functioning mass-driver you're SOL.

Likewise I am leery of subjecting human cargo to 18+ G accelerations.

That's what I thought too, perhaps unmanned gliders could be used to deliver components to establish a network. The acceleration doesn't necessarily have to be high, but it all depends on the design I guess.

It's not a perfect idea, but it might be worth considering. Mars is a really daunting environment to design for.

 

[Hlynkacg]

The acceleration doesn't necessarily have to be high

It does if you want the catapult track to be of a manageable length. I.E. a couple of miles long vice a couple hundred.

 

[BruceJohnJennerLawso]

It does if you want the catapult track to be of a manageable length. I.E. a couple of miles long vice a couple hundred.

Yes, but how manageable might it be if the track is mostly flat, & laid on a sloping grade (ie big long flat track going up a hill to a cliff)?

But if we are avoiding complications like that, it probably still can be done with conventional propellants. Methane LOX sounds ideal to me.

 

[Hlynkacg]

Yes, but how manageable might it be if the track is mostly flat, & laid on a sloping grade (ie big long flat track going up a hill to a cliff)?

I think you're underestimating the scale of this catapult. Restricting acceleration to 3 Gs (to avoid squishing the passengers) gives us a minimum track length of 425 Km to reach orbital velocity. Building it would be a major undertaking. You'd probably need some sort of re-usable martian shuttle to move men and equipment around the job site.

Speaking of which...

---------- Post added at 19:04 ---------- Previous post was at 17:44 ----------

I'm working on a few sketches based on Boeing's Blended Wing concept aircraft and NASA's proposed Ares probe.

Using a craft comparable in size mass to a C-130, with an all-up weight of 80 tonnes, exhaust velocity of 3600 m/s, and a mass ratio of 4. I a get Dv budget of 5 km/s while carrying 5 tonnes of cargo. More work needs to be done but I think this represents a good baseline to start from.

---------- Post added at 19:13 ---------- Previous post was at 19:04 ----------

Found some cool images in a Boeing patent application for a Super-Sonic blended wing airliner.

I'm already imagining those engine nacelles as vectorable aerospikes.