Idea "Man on the Earth" project.

[agentgonzo]

Just a question... assuming those lunar people can survive 1G, then what is their maximum? If it's 1.5G, then your launch vehicle has to be very inefficient.

I would imagine that the descent would be more of the problem for this. I think that apollo astronauts experienced about 4-5g when reentering and shuttle astronauts experience 2-4g on reentry. Also an interesting point (but best to ignore it) would be that without an atmosphere to play with, the Lunatics may not have reseached thermodynamics as much as we had and may not know of the bernouille principle and aerodynamic lift from winged craft.

IMO by far the hardest part would be to drop an Atlas-sized launch vehicle down from orbit in a ready-to-launch or ready-to-assemble-to-launch state without damaging it. It'd need to land point-up or have a construction facility to get it ready to launch. Descent-to-and-launch-from-Earth requires the vast majority of Delta-V of the entire trip.

 

[T.Neo]

Descent-to-and-launch-from-Earth requires the vast majority of Delta-V of the entire trip.

Braking the LRV and Earth lander into LEO is done through aerobraking. Basically, no Dv is needed, except to raise the periapsis above the atmosphere. The Earth lander then needs enough Dv to deorbit, and further fuel for the last minutes of the descent.

EDIT:
Here is the ELC preliminary:

 

[Linguofreak]

I have an idea for the Earth lander. I think it should completely conceal the ascent stage, and on liftoff the ascent stage should use it as a sort of "launch silo".

Basically what I was thinking.


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IMO by far the hardest part would be to drop an Atlas-sized launch vehicle down from orbit in a ready-to-launch or ready-to-assemble-to-launch state without damaging it. It'd need to land point-up or have a construction facility to get it ready to launch. Descent-to-and-launch-from-Earth requires the vast majority of Delta-V of the entire trip.

Yes, and it's fairly likely that in real life it would be impossible. The whole thing that even gave me the idea was when someone on a mailing list I'm on mentioned the idea of dropping and recovering a 15 man special ops team on a hostile Earth-sized planet with chemical rockets alone. I explained that by the time you drop the rocket, launch facility, and the defenses neccessary to ward off hostile locals from your very visible launch complex (without hostile locals why would you need a special ops force in the first place?), you've dropped enough mass that you may as well drop an entire army and take the planet by brute force.

Then, of course, I came here and started the Man on the Earth project, which is at least somewhat more plausible considering that you don't have to drop a tank battalion, a fighter squadron, and an anti-aircraft regiment to defend the rocket while your special ops guys are doing their thing.


-----Post Added-----

Braking the LRV and Earth lander into LEO is done through aerobraking. Basically, no Dv is needed, except to raise the periapsis above the atmosphere. The Earth lander then needs enough Dv to deorbit, and further fuel for the last minutes of the descent.

EDIT:
Here is the ELC preliminary:

Hrmm. Yeah. We'll need some kind of "garage" in the Earth lander for the LRV so the LRV can survive aerobraking. If the LRV is to be used as an escape vehicle during launch, it has to enter this garage when it does the T&D maneuver.

 

[T.Neo]

Hrmm. Yeah. We'll need some kind of "garage" in the Earth lander for the LRV so the LRV can survive aerobraking. If the LRV is to be used as an escape vehicle during launch, it has to enter this garage when it does the T&D maneuver.

Yeah, I was thinking that. Maybe not In the lander, but attached to it. I also think that the LRV's landing legs should be kept in a stowed position for most of the journey.

EDIT:
Also, why have the ELC have a viable docking tunnel, why not instead dock the two together like Gemini and do an EVA transfer?

 

[T.Neo]

What booster, Linguofreak? The booster that lifts the entire vehicle from the Moon, or the booster from Earth?

NOTE: Could a mod please move this thread to "developments"? It has become an active project.

 

[Linguofreak]

What booster, Linguofreak? The booster that lifts the entire vehicle from the Moon, or the booster from Earth?

Earth booster. We need to know how much that weighs to know how much the lander will weigh, which we need to know to figure out how much the moon launcher will weigh. (Oh, by the way, if you're responding to a PM in a thread, it's good to note that you're responding to a PM, otherwise people not party to the PM get confused).

It's got a payload of about 2500 kg, so we're going to have to design a booster that can lift that, not weigh too much, and be technologically reasonable for something that gets dropped, all at the same time.

NOTE: Could a mod please move this thread to "developments"? It has become an active project.

 

[T.Neo]

It's got a payload of about 2500 kg, so we're going to have to design a booster that can lift that, not weigh too much, and be technologically reasonable for something that gets dropped, all at the same time

2500kg is more then Mercury, but less then Gemini. So one could assume a launcher halfway between the two.
The tank structure will have to be sturdy yet light, possibly gaining strength from the pressure of the fuel inside.
We'll have to have some sort of staging to get to orbit. Either 1.5 like Atlas, or drop tanks. A full-blown two stage system seems way too complicated to me, with two engine systems, etc.

 

[Linguofreak]

I don't know. Can we do stage-and-a-half? We'd need a fairly stable fuel that didn't require alot of complexities to store, and I'm a bit afraid that we might not be able to get the ISP needed out of such a fuel.

 

[T.Neo]

I don't know. Can we do stage-and-a-half? We'd need a fairly stable fuel that didn't require alot of complexities to store, and I'm a bit afraid that we might not be able to get the ISP needed out of such a fuel.

Would drop tanks still be feasible then?
I dread the complexities of a two stage craft.

 

[AstroCam]

Remember, the lunanites probably had no knowledge of atmospheric re-entry (until recently).... so that means Airlaunched return vehicles, and possibly aerobraking are out of the picture. Bummer.

Maybe a cluster of solid fuel stages are droppped into the atmosphere, and any that survive are turned into a stage-and-a-half launcher?

 

[Linguofreak]

Would drop tanks still be feasible then?
I dread the complexities of a two stage craft.

We already have the lander. The thing is effectively already a two-stager. And I don't think drop tanks or boosters would reduce the complexity much. If you want to get rid of staging complications, I'd think you'd have to go completely SSTO.

 

[T.Neo]

Bear in mind, that a Titan II (I think, may have the exact mark wrong) first stage was SSTO capable, using 60's/70's tech, including hypergolic fuels, albeit with a small payload.

SSTO isn't as impossible as one would imagine. It is only when one tries to add a heavy heatshield for reuse that SSTO runs into problems.
SSTO launchers have never been built because they have low tolerances and mission requirements often grow.

Since we are limiting ourselves to a 2500 kg payload, (and also making provision for return samples), we might be able to get away with an SSTO launcher.

Maybe...

 

[AstroCam]

I still think dropping liquid fuel rockets through the atmosphere is a bad idea - too many parts to break. Scattering dozens of solid fuel boosters over the area, and only needing 1 to work would provide quite a sfety margin, hell, you might even lob extra experimental samples into orbit for later pickup if you have a spare booster or two....

 

[Andy44]

Remember, the lunanites probably had no knowledge of atmospheric re-entry (until recently).... so that means Airlaunched return vehicles, and possibly aerobraking are out of the picture. Bummer.

Obviously they would send lots of unmanned missions to probe the nature of Earth's environment, including the atmosphere, before committing to a manned mission, so this isn't true.

In addition, these people have lots of knowledge of fluid dynamics, since they can build rocket engines, so they would not be strangers to supersonic air flow problems.

 

[Linguofreak]

Andy, what do you think about 2 stage vs. 1.5 stage?

T.Neo, I just tried out the ELC (took me long enough), and it also is rotated by 90 degrees. Looks good otherwise.

I did have a thought about the LRV: Do we want the crew cabin to be a cone? It looks good, but it serves no aerodynamic purpose (since this isn't an atmospheric vehicle), and probably makes the cabin a bit more cramped for the crew than might be necessary. You're the mesh designer, though, so I'll leave it up to you.

 

[T.Neo]

I did have a thought about the LRV: Do we want the crew cabin to be a cone? It looks good, but it serves no aerodynamic purpose (since this isn't an atmospheric vehicle), and probably makes the cabin a bit more cramped for the crew than might be necessary. You're the mesh designer, though, so I'll leave it up to you.

Yeah, if it serves no real purpose, I'll make the LRV more like the modules on the ISS, cylindrical with endcones.

 

[Andy44]

Andy, what do you think about 2 stage vs. 1.5 stage?

I'm not sure. I guess whichever scheme is simplest in terms of preparing for launch.

If by 1.5 stages you mean something like Atlas, that may work, since an Atlas-type booster could be delivered un-fueled and pre-assembled. Just erect it, fuel and pressurize it, and go. But the Space Shuttle is also a stage-and-a-half vehicle, and is obviously much more complex.

Once you have gone through all the other pros and cons of preparing for launch, the job of actually stacking a 2-stage vehicle for launch may not be that bad.

Ease and simplicity, as well as idiot-proofing, is the key, since you're going to have to prep for launch with only 2 or 3 people, which is absolutely unheard of for an Earth launch. And we Earthlings have been doing it for half a century, now. Even ballistic missile subs with pre-canned rockets require more than 3 people to operate the "launch base".

 

[T.Neo]

Maybe:
-The main lander, carries the crew to the surface, and contains the launcher to bring them back to LEO.

-The logistics lander, contains all mission hardware and living quarters for the crew during their stay.

Just erect it, QUOTE]
If the rocket is delivered in one piece, my current design floating in my head is a vertical landing, which would mean no need to erect the launcher.

fuel and pressurize it,[/

Where would this fuel come from? We're likely landing in the middle of the desert, so no water, and we don't have months to make propellant. Add to that, 60's tech, which means it'll have less efficiency. A seperate lander for fuel perhaps?

 

[Andy44]

Well, if you're going to land it fueled, that's alot of mass and a delicate machine to land on a heavy-gravity body like Earth, you'd need a large parachute or landing rockets or both, and if it lands on uneven terrain, then what? If it is loaded with liquid rocket fuel, this gets even scarier. Maybe landing the propellant seperately is a good idea. You could pressurize the booster's tanks for transport using an inert gas like nitrogen, in order to stiffen the structure and make it better able to take the abuse of the journey. (In fact the old Atlas required pressurization just to keep from crompling like a beer can under it's own mass.)

 

[T.Neo]

You could pressurize the booster's tanks for transport using an inert gas like nitrogen, in order to stiffen the structure and make it better able to take the abuse of the journey. (In fact the old Atlas required pressurization just to keep from crompling like a beer can under it's own mass.)

Stiffening with nitrogen? I like that idea.

Maybe It'd be a good idea to ship more then one fuel lander, or have a contingency reserve in the fuel lander, to compensate for losses.