Russia announces a plan for Mars and Moon missions

[sevenperforce]

7 minutes ago, wumpus said:

Considering the cost of each lunar flight, the cost of the lander is in the noise.  There is no reason to make it reusable and little reason to bring it back (do you really want a heat shield on it?  You pretty much at least need to aerobrake, even if you are going to dock it on the ISS between flights).  Also how reusable will that engine be after using nitric acid (probably less bad than LOX, unless you are talking about the stuff similar to "red fuming nitric acid" from Ignition!, then all bets are off).

Oh, it certainly wouldn't come back. That's why I suggested orbital propellant transfer. You'd leave the lander in lunar orbit and simply refuel it between sorties.

So reuse is not suggested by the cost of the lander, but by the mass of the lander. Every kg you send to lunar orbit is costly; the more infrastructure you can leave in place, the better. 

7 minutes ago, wumpus said:

The rutherford engine is still extremely complex and untested, building reliable pressure-fed hypergolics aren't.  I'd  even expect it to be trivial to build one with Kerbal-style drop tanks, at least assuming that you dropped the tanks between burns (close one valve, eject, open another).  This should go a long way to fixing the efficiencies of pressure fed engines (or just use two like Apollo did.

Pressure-fed hypergolic drop tanks are probably the nearest-term solution, yes. You don't even have to drop the tanks between burns, necessarily; you just need some check valves. When one tank (or set of tanks) is at 5%, you open the valve on the next tank. Let them both run until the first runs dry, close that valve, drop it, and continue. 

An electronic turbopump would end up increasing efficiency and cutting down on tank mass, since the tanks only have to hold ullage pressure, not chamber pressure. But that really comes into play when you're talking about using propellant transfer instead of drop tanks.

7 minutes ago, wumpus said:

Everything I heard implied that the ascent engine was the most likely component to fail in Apollo.  The forces acting on it from launch (and pogo) to landing weren't completely known, and it had to be so extremely light...  Lots of nightmares at NASA about astronauts banging away on the ascent motor while air ran out).

Well, we have two solutions: first, we can test it, because the lander solution would ideally be used first for cargo. Second, we can use multiple engines for redundancy.

If the same lander design is used for crew and cargo (reusably or otherwise) then you need extra thrust anyway, to deal with a range of payload masses. So you'd end up with enough engines that you could lose one on crew ascent and still make orbit, albeit perhaps a lower one.

28 minutes ago, PB666 said:

For landings LH2/LOX is still plausible with a gateway of some sort, dark side landings and LH2 would be completely stable. Though I think for convenience methane would be a better choice. It is the moon, its not like is on the other side of the universe or Mars or something.

 

If you have a reusable lander vehicle, then you want indefinite loiter time.

28 minutes ago, PB666 said:

I agree, the cart here as about 3 light years ahead of the horse. Where are the resources for this moon mission going to come from, an agreement of an oil/gas oligarch?

https://www.nasaspaceflight.com/2018/03/nasa-courts-commercial-options-lunar-landers/

[PB666]

4 minutes ago, sevenperforce said:

https://www.nasaspaceflight.com/2018/03/nasa-courts-commercial-options-lunar-landers/

This doesn't belong in this thread and its an RFI. the lander demostrated is more or less a testbed, no PL.
 

[DDE]

4 hours ago, wumpus said:

Also how reusable will that engine be after using nitric acid (probably less bad than LOX, unless you are talking about the stuff similar to "red fuming nitric acid" from Ignition!, then all bets are off).

Nitric acid, red, fuming, inhibited with hydrofluoric acid. Actually, reportedly it would have quite a long operating life.

5 hours ago, sevenperforce said:

A resistance heater which produces kerosene vapors could also be used for autogenous fuel tank pressurization, and the warm vapor would act to prevent propellant freezing.

Or you could just inject some hypergolic fuel into your oxidizer tank, like R-36M does.

They call it Satan.

3 hours ago, PB666 said:

This does bring an issue however, we need a new SpaceX like designer to come up with a cheap way of keeping liquid lbp-volatiles in space.

Bit of a problem there; 1970s deep-space stages considered methalox or lighter hydrocarbons to be storeable.

Edited March 19, 2018 by DDE

[PB666]

13 minutes ago, DDE said:

Nitric acid, red, fuming, inhibited with hydrofluoric acid. Actually, reportedly it would have quite a long operating life.

Or you could just inject some hypergolic fuel into your oxidizer tank, like R-36M does.

The call it Satan.

Bit of a problem there; 1970s deep-space stages considered methalox or lighter hydrocarbons to be storeable.

Ethane and Methane should be storable for long period.

You could dissolve ethane or propane in the kerosene under pressure, when the pressure is reduced it will outgas, otherwise it will be burnt in the stream.
Methane TP = 90.67K CP = 190.6K (-82.6, 46 bar)
Ethane - TP = 91K,  CP =  305.3 K (48 bar) Thus as long as you keep it below 305.3 but keep it constantly pressurized it will degass to an equilibrium pressure dependent on the temperature.
Propane - TP = 85.7K, CP = 369.522 K (43 bar)  This gives a wider range of values)
 

Wiki has the data sheets on all gases, just type [alk]ane (data page) where [alk] is the prefix Meth, Eth, Prop, But . . . . . .

These gases can be blended into the fuel to adjust the pressure of the tank at any given temperature.

Pure kerosene will not degas easily to pressurized easily, it has a reasonably low vapor pressure curve.
 

[wumpus]

3 hours ago, PB666 said:

I agree, the cart here as about 3 light years ahead of the horse. Where are the resources for this moon mission going to come from, an agreement of an oil/gas oligarch?

I'd assume that any design using a rutherford cycle would happen after much improvement over a currently 1-1 rocket.  The idea of taking a brand new engine (designed for single use with kerolox) and assuming it can be used for crew rated use with arbitrary fuels seems extreme.  Maybe working on "Elon time" you would have enough time to build such a thing (although I think it works the other way, if you pencil in something that makes the schedule laughably impossible (like Rocket Labs provides a crew-rated engine tomorrow) you will be expected to pretend harder that the schedule is real).  If you want redundant systems (in the *last* stage, have you played KSP at all?), I'm almost positive pressure fed systems scale down easier.

Quote

The spacecraft mass of 15103 kg was the total mass of the LM ascent and descent stages including propellants (fuel and oxidizer). The dry mass of the ascent stage was 2445 kg and it held 2376 kg of propellant. The descent stage dry mass (including stowed surface equipment) was 2034 kg and 8248 kg of propellant were onboard initially.

First, we should break our design into three parts.  First is the crew module.  Second is the ascent engine and fuel/oxidizer tanks.  Third is the descent engine and tanks.

Obviously, if we can dock the engine stack to the crew module and if it can survive arbitrary amounts of time in radiation and vacuum we reuse is obvious.  Unfortunately, that (the non-engine bits of the LM) was only 12% of the mass of the Apollo LM.

It may be tempting to combine the descent and ascent modules.  Unfortunately, had the Apollo program tried that, they would have certainly had to carry more mass (of fuel) to the LM than the entire mass of the disposable LM.  It may be possible to combine the ascent and descent engines and simply stage the descent fuel tank, but I suspect that the cost and mass is largely contained in the tanks.

A Rutherford engine might have wildly lighter fuel tanks, but don't be at all surprised if you leave at least one "decent battery" on the Moon.  Reducing dry weight does wonders to increasing delta-v, and it is quite likely that bringing new batteries means bringing less total weight.  Nevermind the whole issue that Rutherford engines should be considered experimental for even cargo vessels.  I don't think they have demonstrated (or even announced) any throttling capability.

The overall problem is a lot like going to Earth orbit.  There is a strong desire for SSTO (or in this case "single stage to the surface and back to orbit", and it "only" needs 3460m/s).  But the huge difference is that every gram of mass has an enormous cost, unlike launching from sea level with a zero "tax" on mass.  This makes staging and ignoring reuse much more likely than than without the "lunar orbit tax" (and it isn't clear that you can make a LM crew cabin reusable for less than a 12% mass budget).  There are great reasons to recover your first stage booster.  From then on, recovery gets harder and the returns smaller.  Going into another gravity well changes the numbers again, and may make reuse not worth it at all.

[Reactordrone]

On 3/19/2018 at 4:26 AM, sevenperforce said:

On the topic of moon landings -- is there any acceptable lunar ascent engine on the market today?

If you want an off the shelf solution the engine used on the Briz upper stage will do it for you. Similar thrust, propellants and Isp as the Apollo Ascent propulsion system.

 

 https://en.wikipedia.org/wiki/S5.98M

[Nibb31]

If we are going back to the Moon for more than flag and footprints, we are going to need a reusable lander, which is either:

• Refuelable
• Uses expendable replaceable tanks
• Or uses expendable replaceable descent-ascent stage

If you are not building some sort of reusable infrastructure, then there really isn't much point in going back to the Moon.

In all cases, for simplicity's sake, you need a single ascent-descent stage, which means a throttlable engine capable in the 50kN range with 4500 dV.

Edited March 20, 2018 by Nibb31

[kerbiloid]

Or to wait until gas core reactor + microwave beam will be available.

Split the regolith, using gas core reactor, extracting oxygen. Use LOx as a monopropellant, heating it with microwave beam powered by gas core reactor.

Use the gas core reactor to melt and disperse aluminium landing stages, using simple non-throttable engines for ascent.
Cast aluminium things from the melted landing stages and fallen tanks.

P.S.
Waiting for thermonukes is even better. There is enough ³He in regolith to split the regolith burnt to extract this ³He into metals and oxygen.
Then you have enough metals to build, enough oxygen to use as monopropellant heating it with microwave beam.
The only question: what for?

Edited March 20, 2018 by kerbiloid

[Nibb31]

Waiting for new technologies means that you can wait forever. It takes decades for a new technology to go from TRL 1 to TRL8 or 9.

It's like never buying a new phone or a new car because next year's model will always be better.

Edited March 20, 2018 by Nibb31

[kerbiloid]

21 minutes ago, Nibb31 said:

Waiting for new technologies means that you can wait forever.

Let's hurry up, or the Moon will escape?

22 minutes ago, Nibb31 said:

It's like never buying a new phone or a new car because next year's model will always be better.

It's like never buying a horse, when cars will appear soon.

[sh1pman]

38 minutes ago, kerbiloid said:

It's like never buying a horse, when cars will appear soon.

It's like never buying a horse while having no clue when the cars appear, if ever. 

[kerbiloid]

4 minutes ago, sh1pman said:

It's like never buying a horse while having no clue when the cars appear, if ever. 

It's like never buying a horse while having only rough estimations when the cars appear, to ride it in a desert with no air, water, minerals, grass, camels, almost nothing except the dust.

[sh1pman]

Just now, kerbiloid said:

It's like never buying a horse while having only rough estimations when the cars appear, to ride it in a desert with no air, water, minerals, grass, camels, almost nothing except the dust.

Are there estimates for gas-core reactors?

There's scientific value for going to the Moon. It's a good place to study and develop the means for short term (and subsequently, long term) habitation on other planetary bodies.

[kerbiloid]

Just now, sh1pman said:

Are there estimates for gas-core reactors?

Are there estimates of kerosene amount to be delivered to the Moon, and financial/scientific returns?

2 minutes ago, sh1pman said:

There's scientific value for going to the Moon. It's a good place to study and develop the means for short term (and subsequently, long term) habitation on other planetary bodies.

Which is anyway useless until gas core/thermo nuke reactors appear.
Which will anyway be collected much faster once gas core/thermo nuke reactors appear.

[DDE]

20 hours ago, wumpus said:

I'm almost positive pressure fed systems scale down easier.

They absolutely do, and at low flows, positive displacement pumps outmatch turbines.

8 hours ago, sh1pman said:

Are there estimates for gas-core reactors?

Funny you should ask.

18 hours ago, Reactordrone said:

If you want an off the shelf solution the engine used on the Briz upper stage will do it for you. Similar thrust, propellants and Isp as the Apollo Ascent propulsion system.

Briz-M has that donut drop tank some people here were asking for.

[sh1pman]

1 hour ago, DDE said:

Funny you should ask.

I know about RD-600. As far as I know, the project is long dead, and nobody is working on it. So it doesn’t answer my question.

[kerbiloid]

8 hours ago, sh1pman said:

I know about RD-600. As far as I know, the project is long dead, and nobody is working on it. So it doesn’t answer my question.

Apollo project is dead. People can't go to the Moon.

[PB666]

The moon is dead, just a trivial random fact that i thought inwould interject. 

[kerbiloid]

56 minutes ago, PB666 said:

The moon is dead

Then we don't need to hurry with moononauts. It won't run away.
Though automatic probes and orbiters are welcomed.

P.S.
Both Moon and Mars are 4.6 bln years old.
Both of them are in habitable zone of Solar System.
If there are ET civilizations, there must be several old landing places.
So, if someone wants to force the Moon or Mars humanization, he/she would begin with total research of widely available NASA photos. Once any traces of alien presence were found, there will be no question: send people there or not.

This costs nothing except electricity.

Edited March 21, 2018 by kerbiloid

[sh1pman]

2 hours ago, kerbiloid said:

Apollo project is dead. People can't go to the Moon.

Where have I ever said GCNRs will never be built again? 

Someone here said there were rough estimations of when GCNRs and thermonuclear engines appear. Half a century-old soviet project is not a valid estimation, because no work is being done on it. 

Edited March 21, 2018 by sh1pman