Dynetics vehicles and discussion

[tater]

8 minutes ago, Barzon said:

It's not that big without the drop tanks, if the JSC design is accurate - which I presume it would be.

There was a video with a shot where the tanks were bigger and horizontally arranged, can't find it though.

[Ziggy Kerman]

On 5/2/2020 at 12:51 PM, Barzon said:

From what I've heard, I believe this is Dynetics's plan, and I'm 80% sure the lander is Methalox.

I think it's Hydrolox so they can refill completely on the Lunar Surface

5 minutes ago, tater said:

There was a video with a shot where the tanks were bigger and horizontally arranged, can't find it though.

Like the mockup?

[tater]

8 minutes ago, Ziggy Kerman said:

Like the mockup?

Yeah, but not the one we have seen with the gold foil over the vertical tanks.

[Barzon]

21 minutes ago, tater said:

There was a video with a shot where the tanks were bigger and horizontally arranged, can't find it though.

That's the JSC mockup.

(I can't figure out how to embed images from twitter, so I've just posted the tweet)

[tater]

3 minutes ago, Barzon said:

(I can't figure out how to embed images from twitter, so I've just posted the tweet)

[sevenperforce]

On 1/7/2021 at 6:01 PM, Silavite said:

Dynetics completes their continuation review. There's also a strong implication they're using methalox.

https://www.dynetics.com/newsroom/news/2021/dynetics-achieves-critical-nasa-milestone-and-delivers-key-data-on-lunar-lander-program

Is it possible to do an autogenous pressure-fed methalox expander cycle?

E.g., you use part of the LOX to cool the chamber, allow it to expand, and then pipe it back to the LOX tank to maintain pressure. Same with CH4 but you use it to cool the bell instead.

I don’t think that would work. But maybe? It seems like you wouldn’t be able to get a continuous pressure drop.

If not, then maybe you split the autogen gas from the expander outlet...half is pushed through a low-temperature turbine and dumped downstream in the engine bell and half is pressed by the turbine and passed back to the tanks.

It would not work for huge engines due to the inherent square-cube issues of the expander cycle but it could be good for small engines, like a lunar lander. The simplicity of pressure-fed engines and a low-temperature turbopump would be pretty reliable. Maybe they could even mix some TEA-TEB into the methane to bypass having an ignition system altogether.

Then you could just have solar-powered resistance heaters to make sure your tanks are fully pressed, since they are autogenous and pressure-fed. You could refill the tanks as many times as needed. 

[tater]

Presumably later in the dev work they start drilling holes in various structures to remove mass?

[kerbiloid]

Spoiler

  

1 hour ago, tater said:

Presumably later in the dev work they start drilling holes in various structures to remove mass?

It worked in ISS, why shouldn't here?

 

[RCgothic]

Basically, Dynetics' design was overweight and had to find mass to lose. But the report also states there were significant risks of mass *increases* still to come which would also need to be countered, and the report did not expect that was feasible.

Sounds like Dynetics bit off more than they could chew with their concept, even though it would have been a great capability if they'd been able to get it to work.

This is the sort of thing armchair speculators can't predict. It was a surprise Dynetics was rated this low, but there was no way we could evaluate things like mass budgets or lack of progress on development of the critical MULE refueler.

[StrandedonEarth]

Something like the Dynetics system will eventually be needed for the low ladder height, although it may take a few more iterations. Completely modular would be the way to go. Swappable and refillable tanks, along with a detachable central cargo/crew module. Land, detach, refuel, lift back to orbit for the next run skyctane style 

[RCgothic]

From an outsider view, Dynetics seemed to have a better design than Blue and more achievable than SpaceX. If I were NASA I'd have had a preference for Dynetics all other things being equal.

But the report rated their technical plan as marginal, and having read the decision summary I agree with it. It's a surprise Dynetics came in third, but on the basis of progress so far, I think NASA were right to rate Blue 2nd and Dynetics 3rd.

[tater]

Yeah, I actually assumed Dynetics would win. Clearly their entry was not ready for prime time.

 

[kerbiloid]

On Elon Time scale...

[RCgothic]

I think the Elon Time joke is well past time it was retired. Just doesn't ring true anymore.

[tater]

Just now, RCgothic said:

I think the Elon Time joke is well past time it was retired. Just doesn't ring true anymore.

Elon time vs Boeing time, for example.

[kerbiloid]

35 minutes ago, RCgothic said:

I think the Elon Time joke is well past time it was retired. Just doesn't ring true anymore.

Will be when we see actual starships and lunar landings, rather than a reusable middle-to-heavy class rocket and a capsule of highly doubtful scheme.

Maybe Dynetics is not perfect, but it definitely looks more perfecter than dancing pipes on every landing, going to become habitats.

Edited April 17, 2021 by kerbiloid

[RCgothic]

Dynetics was deservedly rated third, in part because NASA didn't believe they were capable of delivering on the proposed timescale due to low TRLs and negative mass budget, and that's all moot because  NASA couldn't afford it anyway.

NASA believe SpaceX are most capable of delivering on the required timescale and at a price NASA can afford. That's all there is to it.

[YNM]

4 hours ago, StrandedonEarth said:

Something like the Dynetics system will eventually be needed for the low ladder height, although it may take a few more iterations. Completely modular would be the way to go.

Still think that to support surface ops you need one lander like they proposed. Swap the pressurized module for a platform, you can tie whatever on it and deliver it to the surface and back.

3 hours ago, RCgothic said:

I think the Elon Time joke is well past time it was retired. Just doesn't ring true anymore.

Well everyone else is now the one having it on them. Now that he has proven to be able to do what everyone was able to do in the past, while the rest is having more and more problems to justify their pace, makes the rest is the one that's running on Elon Time...

[wumpus]

On 4/17/2021 at 2:56 PM, RCgothic said:

I think the Elon Time joke is well past time it was retired. Just doesn't ring true anymore.

Still works with Tesla, and Elon time doesn't match calendar time.  But there's no point in criticizing Spacex for Elon time when it is vastly more accurate than Boeing, NASA or Roscosmos time.

Does Rocket Lab meet its published schedules?

I'm not sure Elon makes any predictions about self-driving cars anymore.  He might be slightly more careful about PR now.