Soyuz Lunar Mission

[Urwumpe]

For the thinnest tanks, the stability comes from the internal pressure. But even if we calculate with a pressure loss during landing, that would void stability, just stiffening the tank structure or putting a light framework around the landing gear base, this should be still lighter than anything that is not self-carrying.

 

[N_Molson]

The docking window has been reduced to a bullseye, as suggested. The front window is smaller, it could become circular.

The spherical tanks have been replaced by a torus (that could be a little bigger).

The legs have been re-positionned to adapt the new chassis.

And the light is much better

With this concept, the torus tank could be "crushed" during a hard landing, if equipped with safety valves to avoid explosion (its supposed to be almost empty).

 

[Urwumpe]

With this concept, the torus tank could be "crushed" during a hard landing, if equipped with safety valves to avoid explosion (its supposed to be almost empty).

Almost empty is not the same as really inert, so we should better leave this be... but we could use the pressurized tanks as damper, pretty much like the tire of a car. Instead of really crushing them, we simply leave enough tolerance on inside and outside that they could compress a bit.

Remember: Oxidizer + Fuel... we need two such. if we use storable propellants, both tanks would be of equal size in volume.

But the shape starts to look pretty. any mass estimate of this already?

 

[N_Molson]

Remember: Oxidizer + Fuel... we need two such. if we use storable propellants, both tanks would be of equal size in volume.

I know, but the BreezeM tank is made that way... so there must be a torus inside the torus

Edit : or there can be 2 walls in the torus, that define 2 volumes.

Edit2 : for the first trials (I couldn't help), it set 2500 kilograms of dead mass and 4000 kilograms of fuel (total 6500 kg). Should be a little more I think. Without the crew, of course !

 

[T.Neo]

Remember: Oxidizer + Fuel... we need two such. if we use storable propellants, both tanks would be of equal size in volume.

Despite mixture ratio?

Or is the fuel density significantly lower?

 

[N_Molson]

From Astronautix :

Oxidizer: N2O4. Fuel: UDMH. Propellant Formulation: N2O4/UDMH. Optimum Oxidizer to Fuel Ratio: 2.61. Temperature of Combustion: 3,415 deg K. Ratio of Specific Heats: 1.25. Density: 1.18 g/cc. Characteristic velocity c: 1,720 m/s (5,640 ft/sec). Isp Shifting: 285 sec. Isp Frozen: 273 sec. Oxidizer Density: 1.450 g/cc. Oxidizer Freezing Point: -11 deg C. Oxidizer Boiling Point: 21 deg C. Fuel Density: 0.793 g/cc. Fuel Freezing Point: -57 deg C. Fuel Boiling Point: 63 deg C.

 

[N_Molson]

The more I'm thinking to it, the more I believe we'll need a descent booster for the LM in LLO... A Fregat stage could probably fit that role ; that Fregat would need a docking port. We'll have to plan very carefully the LLO rendez-vous manoeuvers.

My Dv calculations show that, with the limited ISP of the N2O4 fuel (about 3100 m/s), we would have an empty mass of 1750 kgs and a fuel mass of 5750 kgs (total : 7500 kgs).

The LK (1 seat) had an empty mass of 3160 kg, Apollo LEM was over 5000 kgs...

I think that, taking into account the advances in materials and computers provided by the current technology, we need, for two cosmonauts, a minimal empty mass of 4000 kgs.

Seeing the things that way, it seems difficult for the LM to have a lower mass than 8500 or 9000 kgs. For an empty mass of 4000 kgs, this leaves us just enough Dv for the final landing phase (after the Fregat jettison) and the ascent.

 

[Thorton]

So we have problem here Total LM mass was about 15000 kg, so if we reduce m0 of our lander to 4000, total mass would be at least 10000-11000 kg. I hope that KVTK+Fregat will be able to provide TLI, but not sure that it will be enough fuel left for LOI.

BTW, sorry for delay with KVTK, i've been busy last week.

 

[N_Molson]

Btw, what are the characteristics of the KVTK ?

With the figures, we can define the mass budget.

 

[Thorton]

Here is the KVTK specs:
m0 = 4400 kg (RCS system and fuel included)
m_fuel = 19600 kg
Thrust = 98 kN
isp = 463 s.

 

[N_Molson]

Good news, the KVTK should be powerful enough to put the Soyuz in lunar orbit.

That "cryogenic" ISP really helps !

Dv = 4542.03 * ln(31500/11650)
Dv = 4517.87

Now, if we add a Fregat atop the KVTK (heavy payload for the "poor little" ProtonM )

I assume a LM of 10 tons for now

Dv1 = 4542.03 * ln(24000+6400+10000/4400+6400+10000)
Dv1 = 4542.03 * ln(40400/20800)
Dv1 = 3015.34 m/s ; velocity gain at the end of the KVTK burn

Dv2 = 3256.92 * ln(6400+10000/11050)
Dv2 = 1285.99 m/s ; additional gain of velocity after the Fregat burn.

DvT = Dv1 + Dv2
DvT = 3015.34 + 1285.99
DvT = 4301.33 m/s ; total velocity gain of our 10-tons payload after the burns.

So, on the paper a 10-tons LM is go for the Lunar Orbit ! But we have to consider that the KVTK will need to perform a burn for LEO insertion (because the KVTK+Fregat stack is well over the ProtonM payload capacity).

If we are really too short on Dv, there's an alternative that need another launch :

Launch 1 : Send a LM in LLO that has just enough propellant for the final landing phase and the ascent phase.

Launch 2 : Send a Fregat in LLO.

Launch 3 : Send a "Fregat2" in LLO

Launch 4 : Send the Soyuz in LLO, then :

a) The Soyuz docks the LM and power it up (fuel cells plugged or switched on).
b) Crew transfer to man the LM.
c) The manned LM performs a rendez-vous & docking with the orbiting Fregat.
d) The Fregat brakes the LM until the final landing phase.
e) While in free fall, the LM undocks and perform an avoidance manoeuver.
f) The LM lits its engine. Final landing phase : the pilot has to show its skills !
g) Lunar Landing and EVA.
h) Liftoff ! The legs and the chassis that supports them stay on the Moon.
i) The LM achieves LLO (no more than 30-40 kms of altitude are needed).
j) The LM burns its last drops of fuel to perform a rendez-vous & docking with the Soyuz.
k) Undocking.
l) The Soyuz performs a rendez-vous with Fregat2.
m) TEI
n) MCC
o) Reentry
p) Landing & recovery (at least !)

Edit : it could be well advised to have another rocket (I guess that Baikonur pads will all be used in the operation so probably elsewhere) ready to launch another Fregat in LLO, just in case the Fregat2 fails and the TMA is stranded in LLO... The expedition could carry food & water for 1 month, just in case...

 

[jwcornish]

Forwarned is forearmed. Found a great explaination of ln and e at http://betterexplained.com/articles/demystifying-the-natural-logarithm-ln/

 

[N_Molson]

Reading this thread, I learned that an enhanced version of the Fregat (Fregat-SB) is going to be tested this month :

http://www.orbiter-forum.com/showthread.php?t=17135&page=6

Could serve our purpose.

 

[Thorton]

Do you have any info about it?

 

[N_Molson]

From Russianspaceweb :

NPO Lavochkin also proposed the Fregat-2 version of the upper stage, equipped with a jettisonable external tank. If lifted by the Zenit rocket, the Fregat-2 could deliver 2,300 kilograms of payload into the geostationary orbit, while in combination with the Proton M rocket, 4,000 kilograms could be inserted into the same orbit. (118) The vehicle was later renamed Fregat-SB, where SB stands for "sbrasyvaemye baki" or "jettisonable tanks," and its first mission was scheduled to be the launch of the Spektr-R scientific satellite onboard the Zenit-3M rocket. The routine preflight processing of the vehicle was planned at the assembly building at Site 31 in Baikonur.

I quickly searched about it, it seems very hard to find data. Maybe we'll know more after the Zenit-3M launch ?

---------- Post added at 08:34 PM ---------- Previous post was at 08:31 PM ----------

From what I can understand, its more or less the concept of a Fregat with an external jettisonable tank, formerly named "Fregat-2".

The "Fregat-2" was (or is) supposed to look like that :

 

[N_Molson]

Tranquillity here. The Eagle has la.... huh Houston we have a problem ! There are already people over there ! :lol:

Seriously, I think that our LM should be much lighter than the original LEM. Given that the LK empty mass was 3,160 kg, our LM should be in the 3,300-3,500 kg (empty mass) range, no more. And less than 10 tons fully fueled.

So I think we're going to be fine with the KVTK.

 

[Urwumpe]

The chosen propellant has a density of 1.18 g/cc (all together), so the tanks would need to be about 8.474 m³ + Ullage volume large. I would say the dimensions are close, maybe just a tiny bit too small.

 

[N_Molson]

According to Anim&tor, my torus dimensions are :

Torus diameter : 0.4 m
Hole diameter : 0.775 m

(the "hole diameter" is defined for a circle, not a torus, so that's in reality the diameter of the torus at it's thickest points).

From there, to calculate the volume of a torus, we have to intellectually "unfold" it to get a cylinder :

Check if I make mistakes, but in theory :

base area = 0.2*Pi² ~= 1.9739
length = 2*Pi*0.775/2 = Pi*0.775 = 2.4347

Volume = base * height
Volume = 1.9739*2.4347
Volume = 4.8058 m3

I may be mistaken, but that's far away from the number you give.

Detailed info on the torus here : http://whistleralley.com/torus/torus.htm

 

[N_Molson]

OK, empty mass is still the n°1 problem if we want to avoid the "LOR rendez-vous with Fregat" solution, which seems a little complex.

What do we really need aboard (excepted the propellant) ? A lot of things, please report what I forgot, we'll search the mass later :

Structural
- Hull & Window... | Soyuz TMA BO =1,370 kg (including the docking system) | Mass => 1,100 kgs ?
- Chassis (stays on the Moon)
- Landing legs & ladder (stays on the Moon)

Propulsion & Propellants
- External torus tank (stays on the Moon)
- Internal cylindrical tank (wraps the engine)
- RCS tank
- 1x S5.92 engine (1.03*0.84 meters, 2 thrust modes) | Mass => 75 kgs
- RCS engines...
- Backup engine(s)... (I'd say something like 4x 3-4kN engines)

Interfaces
- Docking port & tunnel
- EVA Hatch

Navigation
- Radar Altimeter (the electronics is just a card)
- Radar Antenna (for the altimeter)
- Instrument panel, commands & MFDs
- Backup tools : sextan, hand-held LASER telemeter...
- INS & associated gyroscopes/accelerometers | Mass => 1 kg

Communications
- S-Band antenna (long range, Moon->Earth)
- HF antenna (short range, lunar surface->lunar orbit)
- VHF antenna (lunar EVA, space communications at close range).

Electrical
- 2x? Fuel Cells (1 Main, 1 Backup ?)... Space Shuttle cells weight 122.5 kgs each, but are too powerful for our purpose (12kW each) !
- Wires, relays and "connectics"...
- Cabin lights (DEL ?)
- Coolant fluid & plumbing
- Radiator

Life Support
- Water (partly produced by fuel cells ?) tank.
- LOX tanks (for breathing)
- N2 tanks (pressurization)
- Thermal controller (ice sublimator ?) + fan...
- CO2 scrubbers (LiOH canisters)
- H2O absorber/recycler (humidity control)

Consumables
- Food (2-3 days)...
- Drinking water (2-3 days)...

Lunar EVA
- Tools, flags & misc...
- Scientific payload/experiment ? ...
- 2x LEVA suits (Krechet-94) | Mass = 106*2 => 212 kgs

 

[Wishbone]

If you have O2 for a week, no need to carry extra food for 10 days. What level of exploration are you going to achieve - how many samples will go back to Earth? Need a drill, a hammer, lots of grey tape and quite a few trash bags...