Soviet manned Lunar program

[sevenperforce]

1 hour ago, fredinno said:

No, the reason seperate stages work for landers is the same reason staging is useful for orbital rockets; you drop the extra dry mass.

...what extra dry mass?

The ascent stage has a SLIGHTLY heavier engine, sure, but that's more than compensated for by the fact that you didn't have to carry a whole extra stinking engine down with you. 

Step 1: You launch an engine, a lunar module, a re-entry capsule stocked with consumables, landing legs, and four sets of fuel tanks to lunar transfer orbit.

Step 2: The engine uses 1 set of tanks to enter LLO, then drops them. 

Step 3: The engine, 2 sets of tanks, the lunar module, and the landing legs break off from the capsule and last fuel tank set. 

Step 4: Engine uses one set of tanks to land propulsively. Conduct lunar excursion. 

Step 5: Engine, lunar module, and full tank break away from empty tank, landing legs; ascend to LLO and dock with waiting capsule/tankage.

Step 6: Drop empty tank; head home on remaining tank. 

[KSK]

Some figures for reference. This is for the LM ascent engine. Note the last figure in particular.

Country of origin	United States
Date	1964-1972
Manufacturer	Bell Aircraft / Rocketdyne
Application	Lunar Ascent Stage/Spacecraft propulsion
Predecessor	Bell 8247
Successor	RS-18
Status	Retired
Liquid-fuel engine
Propellant	N2O4 / Aerozine 50
Cycle	Pressure-fed
Configuration
Chamber	1
Performance
Thrust (vac.)	3,500 pounds-force (16 kN)
Thrust-to-weight ratio	19.44
Isp (vac.)	311 seconds (3.05 km/s)
Dimensions
Length	47 inches (120 cm)
Diameter	34 inches (86 cm)
Dry weight	180 pounds (82 kg)

 

Now I don't know for certain that your design would need over 82kg of extra dry mass to support all the bits and pieces needed for your drop tanks but I'm thinking any difference is going to be pretty negligible. This isn't KSP. Engine weight really isn't much of a consideration.

[DECQ]

UR500 "Proton" will never carry people, look at what kind of fuel it work, and now Imagine UR 700 is a bunch attached to each other rocket with toxic fuel on the KSP sample, it did not take seriously, Chelomey received funds in competition with Korolev only due to the fact that his office was working son of the then Secretary General of the USSR. Imagine an accident at the start of the toxic giant UR700? What consequences

[Nibb31]

6 hours ago, sevenperforce said:

That was my point; it's not a Direct Ascent. Still a LOR.

But why would the LM be heavier? It should be substantially lighter. It doesn't have to carry a second engine.

Because an SSTO is always heavier than an MSTO design. A single stage that is going to perform a landing and a launch is always going to be heavier than two stages that do the same job. The engine isn't a huge extra weight, but you still have to carry that whole mostly empty stage back to orbit.

The advantage is that you can optimise each engine for the thrust requirement of that part of the mission. Multiple engines also provide the abort capability. Apollo could abort at any time during descent (Apollo 10). 

The penalty of a single-stage lander makes sense if you are going to leave it at EML1 or 2 to refuel and reuse it in a semi-permanent infrastructure. But in an Apollo/Constellation architecture, it's not worth it.

 

Quote

In fact, it would be virtually identical to the LM of Apollo, minus the weight of the ascent engine. Meanwhile, the orbiting command module is much smaller, containing only return-trip fuel, return-trip consumables, and the re-entry capsule. So the overall launch mass is considerably lower. Compared to Apollo, you save on the weight of an entire pressurized command module, an entire engine, and part of the descent fuel. 

No because the descent engine is larger and more powerful and consumes more propellant than the ascent engine, so you would have to carry more propellant to launch the entire LM than if you just launch the ascent stage.

The dV requirements for lunar surface to LLO and from LLO to lunar surface are actually similar ( ~1900m/s), so the amount of propellant you would need to launch the entire LM (ascent stage+descent stage) off the moon is basically the same as the amount carried by the fully fueled LM in the first place.

• The ascent stage only carried 2300 kg of propellant and a 85 kg engine to produce that dV.
• The descent stage carried 8200 kg of propellant and a 180 kg engine to produce the same amount of dV.

In other words, to launch an entire LM from the surface of the Moon, you would need a fully fueled descent module. In your solution, you would save the 2500 kg of the ascent stage propulsion system, but by the same ratio, you would need something in the order of 30000 kg of propellant to actually land that 8200 kg of descent stage propellant on the lunar surface, which would also require a larger engine, which would also consume more propellant, etc...

The rocket equation is a harsh mistress, and that's why we use staging.

Quote

Now, if that crasher stage could carry enough fuel to boost itself back into orbit....

Actually, if you gave a Dragon V2 external tanks, I'm fairly sure that such a configuration could manage a manned moon landing and return with a Falcon Heavy and a Dragon V2 alone. 

The Dragon V2 only has a few hundred m/s of dV. You'd need more tanks, then more thrust, then more tanks, etc... You might be able to land a Dragon on the Moon or launch from the Moon to LLO if you filled it with with extra tanks, but you can't do both. 

Edited March 4, 2016 by Nibb31

[sgt_flyer]

1 hour ago, DECQ said:

UR500 "Proton" will never carry people, look at what kind of fuel it work, and now Imagine UR 700 is a bunch attached to each other rocket with toxic fuel on the KSP sample, it did not take seriously, Chelomey received funds in competition with Korolev only due to the fact that his office was working son of the then Secretary General of the USSR. Imagine an accident at the start of the toxic giant UR700? What consequences

toxic fuel has not a lot to do with manned or not. heck, NASA launched 10 manned gemini capsules atop a titan II rocket (with aerozine and n2o4)

https://en.wikipedia.org/wiki/Titan_II_GLV

[fredinno]

2 minutes ago, sgt_flyer said:

toxic fuel has not a lot to do with manned or not. heck, NASA launched 10 manned gemini capsules atop a titan II rocket (with aerozine and n2o4)

https://en.wikipedia.org/wiki/Titan_II_GLV

 

2 hours ago, sevenperforce said:

...what extra dry mass?

The ascent stage has a SLIGHTLY heavier engine, sure, but that's more than compensated for by the fact that you didn't have to carry a whole extra stinking engine down with you. 

Step 1: You launch an engine, a lunar module, a re-entry capsule stocked with consumables, landing legs, and four sets of fuel tanks to lunar transfer orbit.

Step 2: The engine uses 1 set of tanks to enter LLO, then drops them. 

Step 3: The engine, 2 sets of tanks, the lunar module, and the landing legs break off from the capsule and last fuel tank set. 

Step 4: Engine uses one set of tanks to land propulsively. Conduct lunar excursion. 

Step 5: Engine, lunar module, and full tank break away from empty tank, landing legs; ascend to LLO and dock with waiting capsule/tankage.

Step 6: Drop empty tank; head home on remaining tank. 

The dry mass are the tanks. You proposal is great-until you consider that crossfeed (required for drop tanks) is something that has never been done with anything larger than a Bris-M, let alone 4 levels of crossfeed (an engineering nightmare to connect that many tanks to one engine).

[DECQ]

3 hours ago, sgt_flyer said:

toxic fuel has not a lot to do with manned or not. heck, NASA launched 10 manned gemini capsules atop a titan II rocket (with aerozine and n2o4)

https://en.wikipedia.org/wiki/Titan_II_GLV

Apparently the Soviet Union was more worried for crew life, primarily used as a proton is not manned due to fuel and even the EAS system could not save the crew at the start of the accident. Because in fact developing a new ship "Federaziya" could run it at a cheaper proton instead Angara .It was not even considered as an option.

[cicatrix]

Reading about the space race I wonder why it was necessary to create super-rockets like Saturn V or N-1 at all?

Of course there had to to be reasons but why the idea of using ordinary surface to LEO rockets and subsequent orbital assembly of the transfer vehicle and the lander never prevailed? In the long run it would have been cheaper compared to the development and making of those rocket-monsters.

Edited March 4, 2016 by cicatrix

[DECQ]

14 minutes ago, cicatrix said:

Reading about the space race I wonder why it was necessary to create super-rockets like Saturn V or N-1 at all?

Of course there had to to be reasons but why the idea of using ordinary surface to LEO rockets and subsequent orbital assembly of the transfer vehicle and the lander never prevailed? In the long run it would have been cheaper compared to the development and making of those rocket-monsters.

As far as I know Tips initially wanted to raise the ship in orbit of a few blocks, and NASA Rocket to establish a direct flight to the moon, "How UR700 / Vulkan". But in the end come to an almost equal options, it is the dawn of space exploration and the first docking took place relatively recently, today it looks more attractive after the huge experience in the construction of space stations.

As today's Russia that can not afford to build a Super Rocket only considers this option.

[radonek]

3 hours ago, sgt_flyer said:

toxic fuel has not a lot to do with manned or not. heck, NASA launched 10 manned gemini capsules atop a titan II rocket (with aerozine and n2o4)

Possible, yes. Easy, certainly not. And both Korolev and von Braun were known to oppose them. Its one of main reasons why Korolev wont cooperate with Chelomey.  AFAIK Titan was used in desperation to catch up with more powerful russian boosters. Same could be said about Long March which also uses toxic propelants.

17 minutes ago, cicatrix said:

Reading about the space race I wonder why it was necessary to create super-rockets like Saturn V or N-1 at all?

Of course there had to to be reasons but why the idea of using ordinary surface to LEO rockets and subsequent orbital assembly of the transfer vehicle and the lander never prevailed? In the long run it would have been cheaper compared to the development and making of those rocket-monsters.

Orbital assembly is way more complicated then what KSP makes it look like. Lifting whole thing in a single stack not only makes assembly much easier, but allows you to extensively test whole thing before launch. Especially at times when orbital rendezvous and docking was complicated adventure on its own.

[Nibb31]

Orbital rendezvous and docking was only proven during Gemini VII in december 1965. Apollo was already in full swing by then. NASA wasn't even keen on LOR at first because they didn't know if orbital rendezvous was actually possible.

Edited March 4, 2016 by Nibb31

[tater]

31 minutes ago, Nibb31 said:

Orbital rendezvous and docking was only proven during Gemini VII in december 1965. Apollo was already in full swing by then. NASA wasn't even keen on LOR at first because they didn't know if orbital rendezvous was actually possible.

Exactly, it took some selling.

I seem to recall that the Soviets came up with automated docking (Progress) as a possible lunar mission profile using smaller rockets (Soyuz stuff, so R7 I guess), and Earth Orbit Rendezvous. Not sure if it included the lander, or if it was an orbital flight concept. I'd look it up, but I have to make my kid a lunch to take to school, then leave, lol.

[DerekL1963]

2 hours ago, cicatrix said:

Reading about the space race I wonder why it was necessary to create super-rockets like Saturn V or N-1 at all?

Of course there had to to be reasons but why the idea of using ordinary surface to LEO rockets and subsequent orbital assembly of the transfer vehicle and the lander never prevailed? In the long run it would have been cheaper compared to the development and making of those rocket-monsters.

The overall architecture was being laid out at a time when they considered themselves to be doing well if one launch fired off on schedule - and on orbit assembly would require as many as (IIRC) four launches (depending on the architecture) in very short order (within a week).   Another issue is programmatic risk - you accept a helping of risk every time you push the "go to space today" button.   More launches equates for more chances for something to go wrong during launch which means more total risk.

[tater]

^^^ Exactly. On top of that, there is the problem of stuff sitting in orbit. Even if there is not a catastrophic failure on any of the launches, there could be weather delays that force a 24+ hour wait with the spacecraft parts (assembled or not) sitting there in orbit. They were worried about engine restarts enough as it was, without having to also worry about them possibly sitting around for many days first.

That's not to mention coming up with refueling in flight. The Soviets were sort of headed that way, and the Russian are still talking about a cislunar use of Soyuz, aren't they (all this time, and those kinks are not all ironed out)?

[sevenperforce]

9 hours ago, KSK said:

I don't know for certain that your design would need over 82kg of extra dry mass to support all the bits and pieces needed for your drop tanks but I'm thinking any difference is going to be pretty negligible. This isn't KSP. Engine weight really isn't much of a consideration.

You're forgetting all the bits and pieces needed to attach the actual LM's descent tanks to the descent engine.

8 hours ago, Nibb31 said:

The descent engine is larger and more powerful and consumes more propellant than the ascent engine, so you would have to carry more propellant to launch the entire LM than if you just launch the ascent stage.

The dV requirements for lunar surface to LLO and from LLO to lunar surface are actually similar ( ~1900m/s), so the amount of propellant you would need to launch the entire LM (ascent stage+descent stage) off the moon is basically the same as the amount carried by the fully fueled LM in the first place.

• The ascent stage only carried 2300 kg of propellant and a 85 kg engine to produce that dV.
• The descent stage carried 8200 kg of propellant and a 180 kg engine to produce the same amount of dV.

In other words, to launch an entire LM from the surface of the Moon, you would need a fully fueled descent module. In your solution, you would save the 2500 kg of the ascent stage propulsion system, but by the same ratio, you would need something in the order of 30000 kg of propellant to actually land that 8200 kg of descent stage propellant on the lunar surface, which would also require a larger engine, which would also consume more propellant, etc...

Here, I'll actually run the numbers so you can see what I'm talking about. My hypothesis is that with a throttleable engine and break-away drop tanks (neither of which were possible from an engineering perspective during Apollo), a single engine would result in a lower initial LM mass.

The initial LM massed 15.2 tonnes on separation from the CM, for an effective dry mass of 7 tonnes. Since we know the specific impulse of the descent engine was 311 seconds, this allows us to estimate the onboard dV: 2,363 m/s. However, this included two minutes of hover time, or 194.6 seconds, reducing the actual descent dV to 2,169 m/s.

The 7 tonnes of dry mass comprised the descent engine (180 kg), the descent tanks (m_TD), the landing legs (m_LL), and the ascent launch mass (m_AL). We don't know those three values; that's why I used symbols. However, if the ascent dV was comparable to the descent dV, then based on the ascent engine's specific impulse we can estimate the mass fraction at 51%, with m_AL = 4.517 tonnes and an ascent dry mass of 2.217 tonnes. T/W ratio at launch was 2.18. The descent tanks and landing legs together (m_TD + m_LL) mass 2,663 kg.

Let's suppose I use the stock descent engine for both burns (even though a smaller engine would be able to do the trick, if my hypothesis is correct). Ascent launch dry mass goes from 2,317 kg to 2,412 kg...bad, I know.

But I also know that the ascent engine was fixed-thrust; it couldn't be throttled. Using its thrust, exhaust velocity, and mass flow, I can determine that its burn period was 438.6 seconds, representing 711.4 m/s of gravity drag losses. Since the thrust of the stock descent engine is 2.8 times greater, that shaves off 458.46 m/s of gravity drag, reducing our required ascent dV to 1,711 m/s. Our fuel requirement? 1,817 kg, for an ascent launch mass of 4,229 kg.

So...what does our dry mass look like on the descent stage?

The descent stage dry mass is now the ascent launch mass (4,229 kg) and the descent tanks and landing legs (2,663 kg) for a total dry mass of 6,892 kg. This means we only need 8,072 kg of fuel to match the descent dV of 2,363 m/s. A net total LM mass savings of 237 kg.

Of course, a smaller engine could therefore be used, further reducing fuel and weight.

10 hours ago, Nibb31 said:

The Dragon V2 only has a few hundred m/s of dV. You'd need more tanks, then more thrust, then more tanks, etc... You might be able to land a Dragon on the Moon or launch from the Moon to LLO if you filled it with with extra tanks, but you can't do both. 

Right, it was the "or" that I was talking about. Thrust won't be a problem; the Dragon V2 has plenty of that for a moon landing. I was talking about a crasher stage configuration, where a separate stage "drops" the Dragon at a negligible velocity. It would then return to orbit on its own for LOR.

[KerBlammo]

18 hours ago, Panel said:

I liked the crasher stage on the LK. It seemed like a very kerbal way of doing things.

 

My Direct Ascent Munar Lander has a crasher stage like that! (Its also the launcher's second stage, LKO circularizer & Munar transfer stage).

[Hannu2]

On 4.3.2016 at 3:03 PM, cicatrix said:

Reading about the space race I wonder why it was necessary to create super-rockets like Saturn V or N-1 at all?

Of course there had to to be reasons but why the idea of using ordinary surface to LEO rockets and subsequent orbital assembly of the transfer vehicle and the lander never prevailed? In the long run it would have been cheaper compared to the development and making of those rocket-monsters.

Other writers told about difficulties of orbital assembly. Other thing is time. It was literally a space race and both participants feared that competitor win the race. They could not think what would be the most economic solution in long run. It is why there was so abrupt collapse of US space programs after Apollo. These solutions was far too expensive to be suitable for any commercial utilization of space and it took decades to build almost everything from scratch.