Red Dragon confirmed!!

[sevenperforce]

1 hour ago, fredinno said:

 

SpaceX doesn't seem to consider it too seriously though, NASA (literally the only potential customer for such a lunar lander) hasn't gotten any proposal from them for a Dragon V2 lander. The 'journey to Mars' hasn't stopped Boeing from props in a lander for example.

Not to mention Dragon V2 is probably too small- NASA wants a 4 person, 15 day lunar lander. Altair back in the constellation days had about 1.5x as much pressurised volume, just for that purpose.

Also, v2 landed has no regenerative power supply and unpressurised cargo bay to host experiments.

 

It's probably possible to use it as a lunar lander.

But it's doubtful that would ever happen. It's not like SpaceX wants to go to the moon.

I don't have the link in front of me but I am 90% sure I remember Elon saying, "We will be able to go to the moon, so why not? It's on the way to Mars, after all, so it wouldn't make sense not to go there too." Obviously the Word of Elon is not always directly representative of legitimate plans, but it means they are at least talking about it. 

And like I said, the uprated Falcon Heavy has enough dV to drop an unmodified Dragon V2 on the lunar surface. No big deal.

[CatastrophicFailure]

2 hours ago, sevenperforce said:

I 

And like I said, the uprated Falcon Heavy has enough dV to drop an unmodified Dragon V2 on the lunar surface. No big deal.

Are there any stats on the D2s delta v?

[Rakaydos]

1 hour ago, CatastrophicFailure said:

Are there any stats on the D2s delta v?

Looks ike 400 M/s is a good estimate

 

https://www.reddit.com/r/spacex/comments/33f75a/just_how_much_deltav_will_the_dragon_2_capsule/

[sevenperforce]

2 hours ago, CatastrophicFailure said:

Are there any stats on the D2s delta v?

Anywhere from 380 m/s fully loaded up to 540 m/s empty. That's at SL, though; vacuum thrust and specific impulse will be a bit higher.

[CatastrophicFailure]

Hmm. Y'know, I think landing on the moon is gonna take a teensy bit more than that...

[Rakaydos]

2 minutes ago, CatastrophicFailure said:

Hmm. Y'know, I think landing on the moon is gonna take a teensy bit more than that...

964 M/s from low orbit. Could be managed with a crasher stage, or with payload fuel tanks.

[CatastrophicFailure]

8 minutes ago, Rakaydos said:

964 M/s from low orbit. Could be managed with a crasher stage, or with payload fuel tanks.

Naw, it's gotta be something closer to 2km/s at least, there's an awful lot of moon up there. 

 

[tater]

A crewed lander needs to leave as well.

[fredinno]

6 hours ago, PB666 said:

The problem is that SpaceX is now traveling in uncharted territory, lets see what their cost structure is. If by recycling they attract future business, then potentially they could secure the whole recycling chain. On some parts it may only be necessary to reforge and anneal any deformations. Sure dumping your rocket on a barge in the Atlantic or gulf of Mexico is going to induce some rust, but you could go with a rust resistant metal which is similarly strong as steel (stainless steel, both common grades is not).

Some parts I could see persisting are the fuel tanks, their maximum stress only last for a few seconds, the second stage tank takes the brunt.

The tansk are filled for minutes on end before launch.

Also, rust-resistant material adds mass, cost, andcomplexity.

[Kryten]

The rocket's made of aluminium-lithium alloy, it's already rust-resistant.

[sevenperforce]

7 hours ago, CatastrophicFailure said:

Hmm. Y'know, I think landing on the moon is gonna take a teensy bit more than that...

Crasher stage. Falcon Heavy boosts across EML-1 or EML-2 onto a collision course with the moon, then restarts and burns retrograde to kill 98% of velocity. The Dragon separates, loses the trunk, and finishes the retrograde burn with a hover landing.

[CatastrophicFailure]

1 hour ago, sevenperforce said:

Crasher stage. Falcon Heavy boosts across EML-1 or EML-2 onto a collision course with the moon, then restarts and burns retrograde to kill 98% of velocity. The Dragon separates, loses the trunk, and finishes the retrograde burn with a hover landing.

Fair enough, but now it's back to the previous discussion arc... can a Falcon upper stage maintain it's LOX supply all the way to Lunar space?

 

[KSK]

32 minutes ago, CatastrophicFailure said:

Fair enough, but now it's back to the previous discussion arc... can a Falcon upper stage maintain it's LOX supply all the way to Lunar space?

It's certainly possible in principle - the Soviet Blok D used LOX and was intended for lunar flights, including MOI and PDI burns plus a final restart and use as a crasher stage. Whether or not the Falcon upper stage is similarly capable, I'm not sure.

Edited May 4, 2016 by KSK

[sevenperforce]

22 minutes ago, CatastrophicFailure said:

Fair enough, but now it's back to the previous discussion arc... can a Falcon upper stage maintain it's LOX supply all the way to Lunar space?

 

The longest (read: most fuel-efficient) route to low lunar orbit is a lunar swingby through EML-2, which takes 6 days. LOX boil-off is 0.2% per day, so you lose 1.2% of your LOX on that six-day transfer. Shouldn't have any trouble reserving enough dV for the crasher-stage landing. However, different trajectories do require a different number of restarts, so depending on the fuel cost of each restart it might be more fuel-conservative to use a faster, more expensive trajectory that requires only one restart for correction/injection.

I'm working on a pet project to find a viable route for a manned lunar landing using two FHE, a single unmodified DV2, and a moderately modified White Dragon for the lunar landing and ascent vehicle. I think I can get a crew of 3...maybe 4 if the math ends up being agreeable enough.

[KSK]

On 30/04/2016 at 6:27 PM, Kryten said:

NASA is buying crew launches as a service, they're not likely to decree no reuse. They're already allowing Dragon pressure vessel reuse for CRS.

Hmmm, I can't actually find a source for that lack of reuse. The CRS flights all used a new Dragon if I recall rightly, so I assumed that the CCrew flights would too. Well - you know what they say about the word 'assume'.

 

Edited May 4, 2016 by KSK

[CatastrophicFailure]

10 minutes ago, KSK said:

It's certainly possible in principle - the Soviet Blok D used LOX and was intended for lunar flights, including MOI and PDI burns plus a final restart and use as a crasher stage. Whether or not the Falcon upper stage is similarly capable, I'm not sure.

 

10 minutes ago, sevenperforce said:

The longest (read: most fuel-efficient) route to low lunar orbit is a lunar swingby through EML-2, which takes 6 days. LOX boil-off is 0.2% per day, so you lose 1.2% of your LOX on that six-day transfer. Shouldn't have any trouble reserving enough dV for the crasher-stage landing. However, different trajectories do require a different number of restarts, so depending on the fuel cost of each restart it might be more fuel-conservative to use a faster, more expensive trajectory that requires only one restart for correction/injection.

I'm working on a pet project to find a viable route for a manned lunar landing using two FHE, a single unmodified DV2, and a moderately modified White Dragon for the lunar landing and ascent vehicle. I think I can get a crew of 3...maybe 4 if the math ends up being agreeable enough.

Now, how does the recent adoption of supercooled propellants figure into all that?

Wait, there's a white dragon now?

[A Fuzzy Velociraptor]

9 hours ago, CatastrophicFailure said:

Naw, it's gotta be something closer to 2km/s at least, there's an awful lot of moon up there. 

 

I'm fairly sure it requires a little more than 4km/s to get to the moon.

9 minutes ago, CatastrophicFailure said:

Wait, there's a white dragon now?

White Dragon: Yes though its not what you expect.

[Kerbart]

7 minutes ago, A Fuzzy Velociraptor said:

I'm fairly sure it requires a little more than 4km/s to get to the moon.

From LEO that's what it takes to get to low lunar orbit. To the surface of the moon takes over 7 (it's cheaper to go to martian orbit!). Of course, when measuring from earth surface things will cost a whole lot more. Keep Heinlein's quote in mind!

[sevenperforce]

1 hour ago, CatastrophicFailure said:

Now, how does the recent adoption of supercooled propellants figure into all that?

Wait, there's a white dragon now?

By the time you get to cislunar space the difference between starting with supercooled propellants and non-supercooled propellants is negligible.

A modified Dragon V2 I call the White Dragon. White for the moon (even though I know full well the moon is basically the color of asphalt). Radiatively-cooled nozzle extensions for the SuperDracos, no heat shield, larger propellant load, larger internal batteries, stripped-down trunk, and compressed air tank for repeated repressurization to allow multiple EVAs. Might need to launch inside a fairing.

Edited May 4, 2016 by sevenperforce

[PB666]

1 hour ago, A Fuzzy Velociraptor said:

I'm fairly sure it requires a little more than 4km/s to get to the moon.

White Dragon: Yes though its not what you expect.

lol, you can say that again, not steering us into nerdy offtopiclandia.

[fredinno]

10 hours ago, Kryten said:

The rocket's made of aluminium-lithium alloy, it's already rust-resistant.

Not rust- proof. If my understanding is correct, the sea-water would still corrode it,beginning with the lithium.

After all, if that wasn't the case, and boosters were impervious to seawater, SpaceX would just recover boosters by chute and sea landing (and probably a final slowdown burn before hitting water.

6 hours ago, CatastrophicFailure said:

Fair enough, but now it's back to the previous discussion arc... can a Falcon upper stage maintain it's LOX supply all the way to Lunar space?

 

Why not? H2 is a serious contender for Lunar landing vehicles, and CH4 was used on Altair, which boils off faster than Lox.

5 hours ago, sevenperforce said:

The longest (read: most fuel-efficient) route to low lunar orbit is a lunar swingby through EML-2, which takes 6 days. LOX boil-off is 0.2% per day, so you lose 1.2% of your LOX on that six-day transfer. Shouldn't have any trouble reserving enough dV for the crasher-stage landing. However, different trajectories do require a different number of restarts, so depending on the fuel cost of each restart it might be more fuel-conservative to use a faster, more expensive trajectory that requires only one restart for correction/injection.

I'm working on a pet project to find a viable route for a manned lunar landing using two FHE, a single unmodified DV2, and a moderately modified White Dragon for the lunar landing and ascent vehicle. I think I can get a crew of 3...maybe 4 if the math ends up being agreeable enough.

Why is the most efficient route to the moon to go through EML-2?

4 hours ago, sevenperforce said:

By the time you get to cislunar space the difference between starting with supercooled propellants and non-supercooled propellants is negligible.

A modified Dragon V2 I call the White Dragon. White for the moon (even though I know full well the moon is basically the color of asphalt). Radiatively-cooled nozzle extensions for the SuperDracos, no heat shield, larger propellant load, larger internal batteries, stripped-down trunk, and compressed air tank for repeated repressurization to allow multiple EVAs. Might need to launch inside a fairing.

But why? SpaceX doesn't have lunar plans (landing on the moon has litttle relavence to Mars, and Elon has been shown to prefer a direct-to-mars pathway, not a lunar first option) and it's too small for NASA Orion/SLS Manned Lunar missions.

[Kryten]

Just now, fredinno said:

Not rust- proof. If my understanding is correct, the sea-water would still corrode it,beginning with the lithium.

Al-Li gets passivating coating, same as straight aluminium. 

 

1 minute ago, fredinno said:

After all, if that wasn't the case, and boosters were impervious to seawater, SpaceX would just recover boosters by chute and sea landing (and probably a final slowdown burn before hitting water.

Aside from the fact that that would expose engine elements which clearly aren't Al-Li, that would be very difficult to deal with on a purely structural level. Shuttle SRB's only managed it because they were thick steel.

[sevenperforce]

13 minutes ago, fredinno said:

Why is the most efficient route to the moon to go through EML-2?

But why? SpaceX doesn't have lunar plans (landing on the moon has litttle relavence to Mars, and Elon has been shown to prefer a direct-to-mars pathway, not a lunar first option) and it's too small for NASA Orion/SLS Manned Lunar missions.

Funky orbital mechanics and the Oberth effect. If you take a Hohmann transfer straight to the moon, you end up having to add the moon's orbital speed to whatever speed you enter the lunar SOI with, which means you need a lot of dV. Getting to EML-1 or EML-2, on the other hand, preloads almost all your energy during your translunar injection burn in LEO, so you only need a few m/s to slide over into an elliptical lunar orbit and then a small burn to circularize. EML-2 is better for this because it is closer to the moon than EML-1, but it costs more to reach. However, if you use the moon's own gravity for an assist, you can reach EML-2 even cheaper than EML-1, which makes it the best option.

Longer transfer time though.

Elon definitely wants to go direct to Mars when he goes to Mars, but he has talked about going to the moon as practice.

[fredinno]

1 hour ago, Kryten said:

Al-Li gets passivating coating, same as straight aluminium. 

 

Aside from the fact that that would expose engine elements which clearly aren't Al-Li, that would be very difficult to deal with on a purely structural level. Shuttle SRB's only managed it because they were thick steel.

"Al-Li gets passivating coating, same as straight aluminium."

I don't understand.

 

BTW,Shuttle SRB'S were planned to use graphite epoxy and filament wound casing numerous times in the past, and still be reused.

In any case, that's why I added the engine burn at the end. Such a burn would slow a booster stage down to 0 velocity before hitting the water.

 

[StrandedonEarth]

5 hours ago, fredinno said:

"Al-Li gets passivating coating, same as straight aluminium."

I don't understand.

Pure aluminum and it's alloys (I imagine there are probably exceptions) quickly forms a protective layer of aluminum oxide when exposed to air, Scratch it, and the exposed aluminum oxidizes and the layer is restored. That's why aluminum is so corrosion resistant. The same principle applies to the chromium used in stainless steel. Mercury, however, will mess up that process.

Edited May 5, 2016 by StrandedonEarth