Yet another Mars architecture

RobS · 2014-03-22 16:34:23

Yes, Moon Express. I forgot the name. There's an article about their smallest lander, designed to win the Google Prize, at http://www.gizmag.com/moon-express-mx-1 … der/30050/ . I also saw information about a medium sized lander that masses 2.5 tonnes and can be thrown to the moon by a Falcon 9, but now I can't find it. A sample return vehicle landed on the moon with the medium lander could bring 8 kg back to the Earth if it goes to the moon via the "weak boundary [or stability?] layer" over a 3-6 month period.

As for subsidy to Mars, it will be decades before someone can get there for $250,000. I doubt Musk could get people there for less than $100 million each!

SpaceNut · 2014-03-22 16:35:23

I do remember the Saturn fuel tank building block for a station with the program to which used them last just over a decade but the concept did go into the next launcher with shuttle fuel tanks wanted for the same purpose with the chances of doing the same during a 30 year use ending the same with none being used.

RobertDyck · 2014-03-22 17:25:09

Quaoar wrote:

RobertDyck wrote:
The upper stage would be filled with cryogenic propellant during launch, but equipment bolted to the inside of the tank. Once in space, the module would be vented of propellant, warmed, and filled with air. ?
This is very interesting even for an ERV in a Mars Direct like mission: the LH2 tank for ISRU has a big volume that can be used for habitat douring the trip.
How can be avoided equipment damage by liquid hydrogen?

A couple cut-away illistrations of Skylab:

The liquid hydrogen tank was living space, while the liquid oxygen tank was combination garbage dumpster and septic tank. That is, the toilet emptied into it, and the kitchen had a small airlock for kitchen scraps. This meant no door between tanks. Living space was the lowest part of the tank, with open mesh grid floor and ceiling. Astronauts were issued shoes with a triangular metal "heel" under the ball of the foot. Not the heel, the ball. They could insert this into a space in the open mesh grid of the floor, and twist to lock their shoes in place. Just twist the other way to release. But the primary reason for the open mesh grid, was this acted as the anti-vortex and anti-slosh baffles during launch. Also notice all consoles were mounted on outer walls. Living space had some walls and furniture, but the middle and upper part of the tank was open space. This was also to let liquid hydrogen flow during launch. A ring of storage compartments around the top could be used as a running track. Skylab had no centrifuge, but an astronaut could simply run. Didn't appear to provide centrifugal force, but they could run.

NASA film - Skylab #4 http://www.youtube.com/watch?v=S_p7LiyOUx0

There was a proposal in 1972 for an International Space Station. It would be a the same altitude ISS is now, and 50° inclination. Today it's 51.6°, so effectively the same orbit. One Skylab workshop would be launched on a Saturn 1B, but without the telescope mount, without the multiple docking adapter, and without the airlock. The first manned mission would be an Apollo CSM on Saturn 1B, and instead of the Lunar Module, it would carry the airlock. The CSM would dock, and attach the airlock to the Skylab workshop. The second manned mission would carry the multiple docking adapter. Then one more launch: another Skylab workshop, again on a Saturn 1B. So 4 launches of Saturn 1B, each of which cost less than a single Shuttle launch. And 6 months from start to US core complete. Canadian, European, and Japanese modules could be attached to the multiple docking adapter. It was expected those other modules would be the same size as the multiple docking adapter, so could be delivered by a manned mission. This proposed ISS would have been built in the 1970s, and more interior volume than ISS has today. It would not have the "windmill" solar panels of the telescope mount, but would have large solar panel "wings" on both workshops. But President Nixon said no.

To do that today? Skylab was based on the S-IVB stage, so 6.6 metre diameter. Falcon 9 v1.1 is only 3.7 metres diameter. Delta IV has a 5 metre diameter core module, but the upper stage is pitiful. You could build a custom upper stage for a Delta IV Medium. Make it 5 metres diameter. S-IVB was 17.68 metres long including thrust structure and J-2 engine. Make the new one something similar, but with a single RL10B-2 engine of the Delta IV upper stage. Or do it with a Falcon 9. Remember, Falcon 9 has an option for a 5.2 metre diameter payload fairing. So just make the entire upper stage that wide. Use the same Merlin 1D (Vacuum) engine it has now. Again, this "self launching" space module would be longer than a standard upper stage, but the upper stage is payload. So an upper stage as long as the current upper stage plus payload?

But Quaoar asked about equipment damage. This requires building equipment sufficiently robust that will not be shaken loose by vibration of launch. Reduce vibration by starting with a launch vehicle that does not have solid rocket boosters. Internal equipment will have to be well secured. Use Teflon electrical insulation. Do not use cheap plastic like PE, PP, PET, etc., instead use fluoropolymers and polyimide. Electronics from the early 1970s used discrete components: transistors soldered to circuit boards with copper traces on just top and bottom. No microelectronics, and no multi-layer boards. Modern microelectronics could not withstand thermal shock of liquid hydrogen. So keep all electronics out. Either electronics in a module outside the tank, or just install electronics after crew arrives. Glass couldn't handle thermal shock either. Notice the Skylab workshop had windows in the multiple docking adapter and airlock, but not the workshop. However, Falcon 9 uses RP-1 and LOX, not liquid hydrogen. RP-1 is highly refined kerosene, storable at room temperature. It's chilled by the liquid oxygen tank, but not nearly as cold as LH2. Doing this with Falcon 9 would be a lot easier.

Last edited by RobertDyck (2014-03-22 17:28:44)

RobS · 2014-03-22 19:06:51

Of course, nowadays, rather than developing a new booster for the Falcon, they'd just launch a Bigelow inflatable. It'd also provide much better micrometeoroid protection. Skylab and Salyut didn't worry about that, but ISS does, and it has to because of the increased quantity of debris in LEO. I don't know what the mass of the shell of a Bigelow inflatable is. The cost of launching the added mass is less than the cost of the development of the self-launching station.

RobertDyck · 2014-03-22 19:39:38

Actually, Skylab did have a micrometeor shield. It was a metal screen pulled tight against the hull during launch, which popped out in space. In fact it's labelled on the image. It had a problem, ripped off during launch. The micrometeor shield was supposed to double as sun shade. They had to deploy a tarp as sun shade, make do without the micrometeor shield.

Is a Bigelow inflatable any less mass than a metal hull? A self-launching module has the mass of the upper stage plus payload. An inflatable is payload only, so less launch mass. And how durable is it? For a reusable spacecraft that travels from LEO to Mars orbit and back, say 10 missions with one every 26 months, so 260 months. That's 22 years. Can an inflatable last 22 years in space?

Falcon 9 can deliver 13,150 kg to LEO, but how much to ISS? Shuttle could deliver 28,800 kg to LEO, or 16,050 kg to ISS. Using that ratio, Falcon 9 without Dragon should deliver 7,328 kg. But that doesn't include dry mass of the upper stage. I can't find that, it appears SpaceX hasn't published that statistic. A self-launching module would have much more than a Dragon plus a Begelow BEAM.

RobS · 2014-03-22 20:01:14

Falcon 9 version 1.1 second stage has an empty mass of about 4.7 tonnes: http://www.spacelaunchreport.com/falcon9.html .

RobertDyck · 2014-03-22 21:53:21

Ok, so 12,000kg total to ISS. Rounding off to the nearest 100kg because that's what we have for stage 2. A little less than I was hoping for. And thrusters for rendezvous have to be included. Enough for ITV?

louis · 2014-03-23 05:22:37

RobS wrote:

Yes, Moon Express. I forgot the name. There's an article about their smallest lander, designed to win the Google Prize, at http://www.gizmag.com/moon-express-mx-1 … der/30050/ . I also saw information about a medium sized lander that masses 2.5 tonnes and can be thrown to the moon by a Falcon 9, but now I can't find it. A sample return vehicle landed on the moon with the medium lander could bring 8 kg back to the Earth if it goes to the moon via the "weak boundary [or stability?] layer" over a 3-6 month period.
As for subsidy to Mars, it will be decades before someone can get there for $250,000. I doubt Musk could get people there for less than $100 million each!

I was quoting a figure he's used before now. You've really got to disregard all the development costs before you can arrive at something like a true cost - Musk sadly can't ignore the development costs at present of course! However, if he can produce reusable rockets - rockets that can be used ten times over say and maybe develop an LMO-LEO "shuttle" with just short hop low mass landers at either end - then you might be getting towards that figure over time. All the rocket fuel could come from Mars - cutting down the costs of the LEO-LMO passage. Similarly, there's no reason why Mars can't supply the food and water for the LEO-LMO passage. Essentially the launch from Earth would just be of humans. I don't know how long an LEO-LMO could remain in service without needing to be replaced. The ISO seems to be holding up pretty well.

Quaoar · 2014-03-23 07:46:53

RobertDyck wrote:

The liquid hydrogen tank was living space, while the liquid oxygen tank was combination garbage dumpster and septic tank. That is, the toilet emptied into it, and the kitchen had a small airlock for kitchen scraps. This meant no door between tanks.

Thanks!
When the LOX tank become full, was the garbage flushed away in the space?

RobertDyck wrote:

To do that today? Skylab was based on the S-IVB stage, so 6.6 metre diameter. Falcon 9 v1.1 is only 3.7 metres diameter. Delta IV has a 5 metre diameter core module, but the upper stage is pitiful. You could build a custom upper stage for a Delta IV Medium. Make it 5 metres diameter.

Can it be done 7-8 meters of diameter? I read that a payload can be 1.6 times larger than the lower stage.

RobertDyck wrote:

Notice the Skylab workshop had windows in the multiple docking adapter and airlock, but not the workshop. However, Falcon 9 uses RP-1 and LOX, not liquid hydrogen. RP-1 is highly refined kerosene, storable at room temperature. It's chilled by the liquid oxygen tank, but not nearly as cold as LH2. Doing this with Falcon 9 would be a lot easier.

I fear RP1 may be difficoult to vent away: if it is almost like gasoline, will its smell remain in the rooms?
Probably LOX or LCH4 may be vented better.

Last edited by Quaoar (2014-03-23 07:49:14)

GW Johnson · 2014-03-23 13:37:04

Skylab was not launched with any propellants inside it, nor did it have any engines at all (which is in fact why it fell on western Australia). The Saturn 5 that launched it was two stages: first and second. Skylab was just dead-head payload made out of third stage hardware. The lost shield tangled tore off one solar wing and tangled the other into non-deployment. The first crew had to fix that. The freed the remaining wing and poked the sunshade "parasol" out through an airlock passage (don't remember which). Between the one wing and the Apollo telescope mount panels, there was barely enough electric power.

When the astronauts ran around the inside of those tanks, there was "artificial gravity", but only for so long as they continued to run. Use the astronaut's forward speed and the radius to those tanks, and you have the angular rate = forward speed divided by radius. The effective gravity is then radius x angular rate squared. You'll have to use consistent units, of course.

Skylab still had several tons of septic tank waste on board at entry. Best estimates of mass at entry were around 90 US (short) tons. I heard they picked up 75 tons of debris off the desert and some roofs in Australia. One big chunk was a 2-ton lead-lined film vault. Eyewitnesses said the main entering chunk didn't break up finally until it was down near Mach 1 at about 20,000 feet. That's about the conditions where Columbia's crew cabin finally crushed, by the way.

Agencies around the world lied about these things "burning up harmlessly", for years before, and years after, Skylab fell. The most egregious lie was told by the Russians about Cosmos 954, just before it fell on Canada. They said that a graphite nuclear reactor core "was designed to burn up on reentry". Total BS, that was.

GW

Quaoar · 2014-03-23 15:43:15

GW Johnson wrote:

When the astronauts ran around the inside of those tanks, there was "artificial gravity", but only for so long as they continued to run. Use the astronaut's forward speed and the radius to those tanks, and you have the angular rate = forward speed divided by radius. The effective gravity is then radius x angular rate squared. You'll have to use consistent units, of course.
GW

With 3 m of radius astronauts can have almost one gee running at 20 km/h.

RobS · 2014-03-23 15:45:25

And how many rpms is that? A lot more than 4! And no dizziness? Things like that make me wonder whether 4 rpm is a hard and fast limit. Of course, maybe they did it for only seconds, not minutes.

Excelsior · 2014-03-23 15:52:06

Wet/Dry workshops are a fantastic way to provide additional pressurized volume, which we can never really get enough of. Its a shame we never got do something with all the Shuttle tanks we burned up.

The idea is not dead. Unless of course they insist on using the SLS. Even with the advance of inflatables, there will still be a need for wide body second stages and decent stages, and there is no reason to not design them with re-utilization in mind, and to invest in executing that potential.

Even the first stages have potential. The 3.6m diameter Falcon cores would be pretty limited in an on-orbit application, but the Mars Colonial Transport is sure to have a useful diameter for this purpose. While the goal is to reuse the first stage and boosters to get things off the ground, if they have enough leftover fuel to do a cross range controlled landing, could they get to orbit by themselves post separation?

RobertDyck · 2014-03-23 16:09:31

GW Johnson wrote:

Skylab was not launched with any propellants inside it, nor did it have any engines at all (which is in fact why it fell on western Australia). The Saturn 5 that launched it was two stages: first and second. Skylab was just dead-head payload made out of third stage hardware.

That is how it was finally launched, but not what it was designed for. It was designed to be launched on a Saturn 1B, in the manner described. But after Nixon cancelled Apollo, the Saturn V rockets for Apollo 18, 19, and 20 were left over. So they launched Skylab with the first and second stages that were for Apollo 18. It was less expensive to build the third stage for Apollo 20 as Skylab, because it wasn't finished so they didn't need to tear apart anything. Just because it didn't actually launch that way, doesn't change the fact it was designed to.

By the way, the big solar panel wings for the Skylab workshop were attached to the outside, covered in an aerodynamic shield during launch. Dragon uses the exact same system. So SpaceX has that technology down. You know, SpaceX really has integrated all the lessons learned. The Dragon side wall angle is the same as Mercury or Gemini, which is steeper than Apollo. The interior hull is shaped more like the Apollo command module. Solar panels like Skylab. Etc.

Quaoar · 2014-03-25 02:10:16

To GW:

Why not to redesign your modular spaceship, in a way that avery propellant module, after vented can be used as an habitat?

F15+fleet+concept.png

So every propellant module lived in low Mars orbit will became a space station, that will grow at every mission

F14+propellant+module.png

GW Johnson · 2014-03-25 09:42:05

Hi Quaoar:

Well, in the mission plan those illustrations came from, no empty tank was discarded, at the cost of bigger-than-minimum ships. Most would be left in orbit about Mars for future but unspecified use. Some would be in LEO upon the ship's return. Those could be either refueled or re-purposed. It's so expensive to launch stuff, I figured why throw stuff away?

I suppose that rearranging the internal structure of such a module might make it more appealing as habitat space, once vented. There would have to be included some sort of access door through which to load the interior equipment one might want. The propellant transfer piping would have to be designed for easy removal, as well.

And, to utilize the space inside both tanks, there would have to be some sort of connecting doorway designed-in. I'd guess that most of this could be designed-in with low (but non-zero) impact on the inert structure mass fraction of the module-as-a-propellant-tank in its initial mission.

GW

Last edited by GW Johnson (2014-03-25 09:43:46)

Quaoar · 2014-03-25 15:04:49

GW Johnson wrote:

Hi Quaoar:
Well, in the mission plan those illustrations came from, no empty tank was discarded, at the cost of bigger-than-minimum ships. Most would be left in orbit about Mars for future but unspecified use. Some would be in LEO upon the ship's return. Those could be either refueled or re-purposed. It's so expensive to launch stuff, I figured why throw stuff away?
I suppose that rearranging the internal structure of such a module might make it more appealing as habitat space, once vented. There would have to be included some sort of access door through which to load the interior equipment one might want. The propellant transfer piping would have to be designed for easy removal, as well.
And, to utilize the space inside both tanks, there would have to be some sort of connecting doorway designed-in. I'd guess that most of this could be designed-in with low (but non-zero) impact on the inert structure mass fraction of the module-as-a-propellant-tank in its initial mission.
GW

Thanks GW:

A space station in LMO may be very useful for for exploration and colonization.
A modular spaceship like your rigid baton can be done with thermal protection on the belly of every module to perform aerocapture or the thermal load will be to much for LH2? In this case, an umbrella like thermal shield like ADEPT on the head module can be used?

RobertDyck · 2014-03-26 06:58:29

Quaoar wrote:

When the LOX tank become full, was the garbage flushed away in the space?

No. Skylab was designed for finite life. There was no provisions to refill the oxygen tank. No way to empty the garbage tank.

Quaoar wrote:

RobertDyck wrote:
To do that today? Skylab was based on the S-IVB stage, so 6.6 metre diameter. Falcon 9 v1.1 is only 3.7 metres diameter. Delta IV has a 5 metre diameter core module, but the upper stage is pitiful. You could build a custom upper stage for a Delta IV Medium. Make it 5 metres diameter.
Can it be done 7-8 meters of diameter? I read that a payload can be 1.6 times larger than the lower stage.

Atlas V heavy and Delta IV heavy were sized to replace the Shuttle. So their payload fairing was sized for payloads of the same as Shuttle's cargo bay. Falcon 9 has the same size.

Quaoar wrote:

I fear RP1 may be difficoult to vent away: if it is almost like gasoline, will its smell remain in the rooms?
Probably LOX or LCH4 may be vented better.

That is an issue. RP-1 would probably smell like diesel fuel. If you have any upholstery, then it would smell like diesel. Besides, if the goal is to maximize size of the ITV, then a large propellant tank is a good thing. So light-weight low-density propellant is desirable. That brings us back to LH2 for the upper stage.

My mission plan includes an ITV of the same size as an ISS module. That could be launched by any vehicle that launched station modules, so Proton or Shuttle. Since Atlas V Heavy and Delta IV Heavy replaced Shuttle, they should do it. Would require a rendezvous system like the Russians use. Dragon and Cygnus already have that. So does the European ATV and Japanese HTV. This just requires larger thrusters for the module to do it. Using a self-launching system just increases the size.

GW Johnson · 2014-03-26 09:28:42

RP-1, Jet-A, JP-5, and K-1 are all just about the same petroleum product. The real differences are just filtering cleanliness and additive packages. They stink, but not quite as bad as diesel. The residues persist, and continue to stink. I doubt a kerosene tank could ever be vacuum-cleaned well enough to use as a habitat. The heavier fractions cling to things, in spite of vapor pressure-driven cleaning into vacuum. I don't know for sure, but pure single substances like liquid hydrogen, oxygen, and methane might clean-up far better. But the caution is porosity: propellant soaked into small pores won't vacuum clean very well. Even metal tank walls have this porosity. That's why you never weld on an empty gasoline tank, no matter how many years it has been dry.

GW

RobS · 2014-03-26 09:38:22

Perhaps the emptied tank could be sprayed with a plastic sealant before use, or maybe some solvent (liquid methane?) could be cycled through it before refurbishment.

Quaoar · 2014-03-26 10:06:30

Another solution may be to use an enflatable tank inside an empty space: when the propellant is burned, astronauts throw away the tank and mount the forniture.

RobertDyck · 2014-03-26 12:53:36

Launch vehicles:
Delta IV Heavy: 28,790kg to 200km @ 28.7°
Atlas V Heavy: 29,400kg to 200km @ 28.5°
Falcon 9: 13,150kg to 185km @ 28.0°
Falcon 9 Heavy: 53,000kg to 185km @ 28.0°

Using the ratio of Shuttle's payload to LEO vs ISS, that would give Delta IV Heavy 16,000kg to ISS. Shuttle's payload to LEO is 185kg, so that's not quite accurate. Falcon 9 Heavy could lift 29,500kg to ISS. Again, that payload mass includes rendezvous system. But we said Falcon 9 with a self-launching upper stage could lift 12,000kg to ISS. Would that be worth it? Or just launch as payload with Falcon Heavy?

::Edit:: Mass for the Falcon 9 with a self-launching upper stage is based on the propellant it currenty uses. Changing to LH2 would give higher Isp, so more mass to orbit. But only a marginal increase; perhaps as high as 16,000kg. Again, compared to Falcon 9 Heavy, is it worth it?

Last edited by RobertDyck (2014-03-27 07:40:31)

GW Johnson · 2014-03-28 09:49:50

Quaoar's "enflatable" in post 346 just above is a fuel bladder. That is an old technology long used in aircraft fuel tanks and some missiles. It works with room-temperature-storable-type propellants.

There are always possibilities, of course, but I know of no elastomerics suitable for bladder service with cryogenics. That means there are no such technologies available "off-the-shelf" and ready-to-use.

If you burden a new vehicle development program with new technology development, it never actually flies. That's been the history of such things. For a vehicle you really want to fly, pick only off-the-shelf technologies. Leave the new technology development for programs specifically so intended.

Just advice from an old development engineer.

GW

RobS · 2014-03-28 10:24:24

I think Quaoar's idea was to store the RP1 in the tank itself, but to inflate a plastic "liner" of some sort before you build in the tank, to keep the RP1 residue and its smell out of the habitable area. That might work.

GW Johnson · 2014-03-28 17:34:14

RobS:

I suppose putting the bladder inside after using the tank for propellants would work. But, there is a risk. An accidental tear in the bladder lets propellant residues contaminate your atmosphere.

For any tank space that once contained fuels, that's a fire/explosion hazard in air, or especially oxygen. For any former oxidizer tank except a LOX tank, that's a poisonous contaminant problem.

GW

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