Author Topic: About reusable LM  (Read 2287 times)

Offline carmelo

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About reusable LM
« on: 02/13/2017 02:17 AM »
In case of reusable lunar module,how is possible do maintenance of this vehicle in space?
Reusables vehicles must be reviewed between a a flight and the other; you not can simply putting fuel and starting.
Generally maintenance of reusable space vehicles is very complex,and requires a specialized staff...
How you can make this in lunar orbit in a little orbital outpost,with the LM supposedly docked outside in  the vacuum of the space?

Offline Space Core

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Re: About reusable LM
« Reply #1 on: 02/13/2017 02:46 AM »
If ITS, New Armstrong or some equivalent happens, you might not need to service it in space.  If the lander could be made to fit in a reusable vehicle's cargo area, you could cycle it back to Earth for maintenance.

Online MATTBLAK

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Re: About reusable LM
« Reply #2 on: 02/13/2017 03:18 AM »
Maintenance of a reusable LM is going to be very difficult in zero g in spacesuits; unless it were designed from scratch to be serviceable and upgradable, as the Hubble telescope was - but that is not an apples-to-apples comparison. But when we are dealing with a 'reusable' LM in the near-ish future; it will be a first generation 'Version 1.0' reusable LM, with all those inherent challenges and difficulties. It's likely one of three scenarios will occur:

1: Reusable LM's will be kicked down the road for a long time - put in the too-hard basket - in favor of a lightweight, cheap as possible expendable vehicle that can get small crews or modest cargo down to the Moon. It would likely use storable, hypergolic propulsion.

2: If the new LM is single-stage reusable craft (my preference), it will likely have ton-toxic RCS systems and propulsion. Propellants will (likely) be LOX/CH4, LOX/Kerosene, or LOX/Propane. The Main Descent/Ascent Engine set could be a removable module that can be replaced with another engine module brought occasionally from Earth when the engine develops flaws or wears out. Spacewalking Astronauts could install the module and hook it up to the propellant tank plumbing. I should think that the propellant tanks could be unbolted and replaced in a similar manner. The pressure cabin could have modular, replaceable life support systems and the main flight avionics can be designed to be replaced as complete electronic 'boxes'. Modularity; always...

3: Two-stage, partially reusable. In some ways, this would be the easiest design. How? Well, the Descent stage could be an expendable, hypergolically fueled module designed for one-way descent use. But we could get a bit cunning with it: It's doesn't have to be a 'deadweight' bit of hardware after descent. If the stage could have one or two retractable solar array sets mounted on it, once the Ascent Stage leaves, the solar arrays could be deployed to provide power for a small Outpost - just plug in a heavy-duty extension cable and enjoy a couple kilowatts of power. During an Outpost buildup, if the Outpost was surrounded by a few descent stages, instead of a solar array set, perhaps a couple of those Descent Stages could have a metric ton or so of RTG power units mounted aboard to give long Lunar night power supplies.

The Ascent Stage: A reusable craft that is designed for 5 or 10 (whatever) reuses. It is mated with a fresh Descent Stage brought from Earth with each new arriving crew. The Ascent Stage could also have a modular, replaceable Ascent engine module - or at least a replaceable nozzle extension for each time that nozzle erodes past usefulness. I would recommend that the RCS and main propulsion be LOX/CH4, LOX/Propane or LOX/Kerosene. Propellant supplies to fill the Ascent stage could be brought from Earth by Commercial suppliers or as a 'Tanker Module' brought with Orion Astronauts for each landing mission.

For the second and third options, we can assume that the reusable lander is operating out of a Lunar Orbital station or Depot staging point. For the expendable option, a Lunar space station is not strictly needed. Such a vehicle depending on the exact configuration and propulsion design, could mass anywhere between 25 and more than 30 metric tons.
« Last Edit: 07/13/2017 11:16 PM by MATTBLAK »
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Offline A_M_Swallow

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Re: About reusable LM
« Reply #3 on: 02/13/2017 03:40 AM »
{snip}
For the second and third options, we can assume that the reusable lander is operating out of a Lunar Orbital station or Depot staging point. For the expendable option, a Lunar space station is not strictly needed. Such a vehicle depending on the exact configuration and propulsion design, could mass anywhere between 25 and more than 30 metric tons.


Anything that stays in orbit for more than 6 months and is visited at least twice is a space station. Propellant depot, staging post, repair hanger or full function are just the type of spacestation.

Online brickmack

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Re: About reusable LM
« Reply #4 on: 02/13/2017 03:56 AM »
A lunar lander operates in a MUCH less stressful regime than a launch vehicle. Theres no reentry forces whatsoever. The engines produce orders of magnitude less thrust and usually burn for less time per mission. G forces are lower. Pressure differential is constant throughout the flight. Etc. If you can make a rocket that can reliably last 1 earth-launch mission before needing refurbishment (ie, the bare minimum for a reusable vehicle), and magically put that rocket on the moon, it should last several flights before receiving the same level of damage.

Offline A_M_Swallow

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Re: About reusable LM
« Reply #5 on: 02/13/2017 04:02 AM »
The Centennial Challenger 'Lunar Landers' required to be able to take off again within a hour. Masten's entry Xombie has had 227 flights. Their records may show the sort of servicing landers will need.
http://masten.aero/vehicles-2/xombie

NASA's Project Morpheus lander was also reusable. There may be some very interesting information in its repair logs.


I see 4 categories of repairs and replacements:

a. Consumables, like propellant, food and air. Replaced every trip.

b. Mechanical consumables, items that need replacing every 2 or 3 flights. If they cannot be made to last a long time require them to be easy to change. I suspect that the heat protection on the feet may fit this category along with spark plugs.

c. Normal, things like engines that last several flights. They may have to be specified to be reused 10 or 50 times. Space walks and robots may be needed to repair or replace them.

d. Unfixable, one or more of these break - possibly in a crash - and the lander is scrapped.

Offline Paul451

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Re: About reusable LM
« Reply #6 on: 02/20/2017 11:15 AM »
If ITS, New Armstrong or some equivalent happens, you might not need to service it in space.  If the lander could be made to fit in a reusable vehicle's cargo area, you could cycle it back to Earth for maintenance.

Errr, if ITS is possible, then why would you need a separate lunar lander? ITS would be the reusable, refuellable lunar lander.

Offline Space Core

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Re: About reusable LM
« Reply #7 on: 02/20/2017 01:53 PM »
If ITS, New Armstrong or some equivalent happens, you might not need to service it in space.  If the lander could be made to fit in a reusable vehicle's cargo area, you could cycle it back to Earth for maintenance.

Errr, if ITS is possible, then why would you need a separate lunar lander? ITS would be the reusable, refuellable lunar lander.

I thought about that too, since it has been demonstrated on this forum in multiple threads that ITS could do a landing and return from the Moon using tankers.  Ultimately, it comes down to effeciancy versus use; How many times will it be used, and how?

It would require R&D and useage of this vehicle to cost less than just using ITS and tankers.  I think areas where a small dedicated lander could shine are tip-of-the-spear sortie type missions, areas an ITS couldn't practically go, or even to setup a landing pad for an ITS.

But there is no guarantee the economics work out.  Using an entire ITS is less efficient, but might prove cheaper if launch costs get low enough.  It's still too early to tell, imho, so I like seeing multiple approaches being considered.

Offline Propylox

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Re: About reusable LM
« Reply #8 on: 07/13/2017 07:33 PM »
In case of reusable lunar module, how is possible do maintenance of this vehicle in space?
Reusables vehicles must be reviewed between one flight and the other; you can not simply keep putting fuel and starting.
Generally maintenance of reusable space vehicles is very complex, and requires a specialized staff...
How you can make this in lunar orbit in a little orbital outpost, with the LM supposedly docked outside in  the vacuum of the space?
Maintenance of a reusable LM is going to be very difficult in zero g in spacesuits; unless it were designed from scratch to be serviceable and upgradable ...

2: If the new LM is single-stage reusable craft (my preference), it will likely have ton-toxic RCS systems and propulsion. Propellants will (likely) be LOX/CH4, LOX/Kerosene, or LOX/Propane. The Main Descent/Ascent Engine set could be a removable module that can be replaced with another engine module brought occasionally from Earth when the engine develops flaws or wears out. Spacewalking Astronauts could install the module and hook it up to the propellant tank plumbing. I should think that the propellant tanks could be unbolted and replaced in a similar manner. The pressure cabin could have modular, replaceable life support systems and the main flight avionics can be designed to be replaced as complete electronic 'boxes'. Modularity; always... ...
"Modularity; always..." should be applied to all manned BLEO designs, from LV to LM. I'd suggest #2, a fully-reuseable propulsion module similar to Curiosity's Skycrane as the basis for a single-stage manned mission, downmass mission and eventually cargo transfer (a box which delivers supplies to the surface, then retrieves cultivated food, water, etc for the LLO station).

- The propulsion module's maintenance would be complex.
Maintenance Schedule Summary: Drain tanks and remove remaining Propylox  ;) tank. Inspect/replace hypergolic helium baffles or just replace tanks. Inspect propellant lines and electric pumps. Inspect/replace the OME (depending on burn time/thrust) and main engine (replaced every other mission).

 -- My conclusion was hypergolic thrusters and OMS with common tankage and the ability for the OME to function as auxiliary/emergency thrust to the main engine. This, along with associated helium pressurization, would be refilled from the LLO station's similar system. The hypergolic tank's helium baffles can only be cycled so many times. Either the tanks (scaled at over 250kg total propellant = over 15sec of emergency thrust) would need to be drained and replaced or, if conjoined spheres similar to Fregat, only the baffles would need replacing.
I selected an RD-0214 as the OME with a revised O/F ratio and 39.4kN emergency thrust, but under orbital operations it would operate at partial throttle. Eventually the OME would need replacing (currently rated at 270s at 31kN), especially after an emergency burn analogous to a Mig-21's Tumansky R-25 running emergency boost.

 -- My conclusion for the main engine was C3H6, alternately called propene or propylene, with LOX. I refer to this propellant combination as Propylox  ;) It is only a few seconds isp shy of Methalox. Propylene has a density of 610kg/m^3 and a liquid phase of 88K (overlapping LOX) to 225K, operating as a thermal buffer for storability. The propulsion module would have three identical propellant tanks, two of which are jettisoned on the surface after landing (and designed for use as future habitable vessels). Additionally, six electric pumps could transfer propellant from one tank to the next to drain the ejected and fill the returning.
As the tanks are only used once, there's no maintenance. Three new, full tanks are installed in LLO prior to each mission. However, the pumps and plumbing would require regular in-space inspection and occasional replacement. I selected an RD-58 derivative as the main engine, operating at 53.3kN and high isp like the RD-58MF. It's modified for Propylox  ;) and utilizes four combustion chambers, similar to a Yuzhmash RD-8. These four chambers are mounted aside the RD-0214's four chambers, creating a LM Skycrane. The RD-58(P) would be replaced every other mission as each mission burns around 12mT of propellant over around 850s while existing RD-58Ms are rated to 1200s at 85kN.


- The habitat module maintenance is comparatively minor.
It would need outfitting prior to each mission, from consumables to specific equipment and suits. As outlined by Matt, components like ECLSS, tanks and electronics would need periodic replacement performed in LLO.
« Last Edit: 07/13/2017 10:44 PM by Propylox »

Offline Propylox

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Re: About reusable LM
« Reply #9 on: 07/13/2017 11:04 PM »
I see 4 categories of repairs and replacements:

a. Consumables, like propellant, food and air. Replaced every trip.
b. Mechanical consumables, items that need replacing every 2 or 3 flights. If they cannot be made to last a long time require them to be easy to change. I suspect that the heat protection on the feet may fit this category along with spark plugs.
c. Normal, things like engines that last several flights. They may have to be specified to be reused 10 or 50 times. Space walks and robots may be needed to repair or replace them.
d. Unfixable, one or more of these break - possibly in a crash - and the lander is scrapped.
The question of reusability comes down to time vs money. That's to say an astronaut's time is often more valuable than parts. The second issue is everything degrades at different rates, so at what point should the entire system be scrapped rather than bother replacing parts?

Considering my outline above: The main propellant tanks last one flight. Everything else is fine and the tanks can be easily replaced, so they are. The main engine lasts two flights. It's replacement is more complicated, so should the entire propulsion module be scrapped? I wouldn't.
The hypergolic baffles may last four or six flights while the OME lasts twelve - unless emergency thrust is required. Should we bother replacing the baffles, or just the two tanks entirely? Should the OME be replaceable like the main engine, or is this where everthing's scrapped? Considering the OME could run emergency thrust on its first mission, and it's similar arrangement to the main engine, I'd make it replaceable.

The remaining systems - structure, thrusters, pipes, electric pumps, communications, navigation, two RTGs and power control system will probably last forever, but would all require regular tests and inspections. Are inspections even worth it? Would X-ray scanning cubesats circling about help? If any of these highly-integral systems neared failure, or their tested lifetime, I'd remove the RTGs and scrap the rest.
« Last Edit: 07/13/2017 11:07 PM by Propylox »

Offline tea monster

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Re: About reusable LM
« Reply #10 on: 07/14/2017 04:53 PM »
You could build the vehicle with modular assemblies locked into a frame-like chassis, sort of like boards in a computer case. The assemblies would be designed as much as is possible to fit through a standard docking hatch.

If a thruster malfunctioned, then you'd remove the thruster assembly and swap in a spare. The faulty assembly could then be returned to Earth for repair.  As most of the parts would be designed to fit through hatches used on spacecraft, it might be eventually possible to set up a repair module on either the ISS or a lunar base so that the more simple repairs could be done on site without cycling parts through Earth's gravity well.

If you designed it with expansion in mind, it might even be possible to link different assemblies together or even vehicles to provide more processing power or thrust for bigger jobs without having to design and test a new vehicle.

Offline Jim

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Re: About reusable LM
« Reply #11 on: 07/14/2017 05:20 PM »

If a thruster malfunctioned, then you'd remove the thruster assembly and swap in a spare. T

so what is a "thruster assembly"?  A nozzle with a thrust chamber?  Does it include the cat bed (assuming it is mono prop).  Does include the valve?  Valve driver electronics?  How much of the tubing?  How many plumbing connections does it have?  Or does it include the propellant tank itself and what about the pressurant?  Is it safe to bring inside or are there flammability, high pressures or toxicity issues?

Offline Jim

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Re: About reusable LM
« Reply #12 on: 07/14/2017 05:22 PM »
Would X-ray scanning cubesats circling about help?

No, because we can't even do that type of diagnostic test on earth with complex metallic systems.

Offline Propylox

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Re: About reusable LM
« Reply #13 on: 07/14/2017 07:49 PM »
Would X-ray scanning cubesats circling about help?
No, because we can't even do that type of diagnostic test on earth with complex metallic systems.
What about "non-complex"? My specific concerns are the propellant lines from powerhead to combustion chambers on the OME and main engine, as well as fatigue in the metal and/or composite structural beams (there's vibration and torsional stress). Is inspecting worth the hassle, of just estimate lifecycle and scrap when approaching it.

Offline Jim

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Re: About reusable LM
« Reply #14 on: 07/14/2017 08:00 PM »
Would X-ray scanning cubesats circling about help?
No, because we can't even do that type of diagnostic test on earth with complex metallic systems.
What about "non-complex"? My specific concerns are the propellant lines from powerhead to combustion chambers on the OME and main engine, as well as fatigue in the metal and/or composite structural beams (there's vibration and torsional stress). Is inspecting worth the hassle, of just estimate lifecycle and scrap when approaching it.

Still not doable from the exterior

Offline A_M_Swallow

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Re: About reusable LM
« Reply #15 on: 07/16/2017 10:01 AM »
You could build the vehicle with modular assemblies locked into a frame-like chassis, sort of like boards in a computer case. The assemblies would be designed as much as is possible to fit through a standard docking hatch.

If a thruster malfunctioned, then you'd remove the thruster assembly and swap in a spare. The faulty assembly could then be returned to Earth for repair.  As most of the parts would be designed to fit through hatches used on spacecraft, it might be eventually possible to set up a repair module on either the ISS or a lunar base so that the more simple repairs could be done on site without cycling parts through Earth's gravity well.

If you designed it with expansion in mind, it might even be possible to link different assemblies together or even vehicles to provide more processing power or thrust for bigger jobs without having to design and test a new vehicle.

Items like fuel tanks will probably be too big to go through a standard docking hatch. The spacestation's arm would have to extract the new tank from the side of the cargo vehicle and insert it into the lander. The electrical, mechanical and liquid (pipes) connections would need attaching. A tank could be full or empty.

What goes into an assembly is a decision that involves many trade-offs. Mass, size, cost, reusability and astronaut time. The optimal answer is likely to change with time.

Offline DougSpace

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Re: About reusable LM
« Reply #16 on: 07/16/2017 04:18 PM »
The architecture should be lunar-based meaning that there should be a base on the Moon with a garage that the lander can be brought into and so the lander could be fixed there in a short-sleeved environment.  If, however, there was to be a breakdown of a lander in orbit, another, refueled, Moon-based lander would then ascend to the stranded vehicle, attach to it, and bring it back to the lunar surface where it could be repaired within the garage.  However, this assumes the presence of a base and crew.  Prior to this achievement, reusable landers (i.e. ferries) would be left stranded wherever they are at.  Then, after the crew arrives, then the landers could be brought to the garage as I have explained and so the value of the stranded lander would be redeemed as it is repaired.

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