Dynetics vehicles and discussion

[EchoLima]

Does anyone know if the entire lander can launch on one Vulcan?

[tater]

9 hours ago, EchoLima said:

Does anyone know if the entire lander can launch on one Vulcan?

https://www.spacelaunchreport.com/vulcan.html

Vulcan could launch the ascent part, but a second launch would be required for the drop tanks since the whole thing has to mass what, 30 tons?

[mikegarrison]

Does this lander come with a free personality test?

[Nightside]

16 hours ago, mikegarrison said:

Does this lander come with a free personality test?

I can’t stop laughing about this name, but was it an intentional reference?
I googled around a bit to see if it was deliberate, but found nothing. It seems like a bland shell corporation more than anything.

Last year I read a excellent bio of golden age sci-fi, editor John W Campbell and his 3 protégés Isaac Asimov, Robert Heinlein, and L Aron Hubbard Called Astounding!

really interesting to learn about the development of Hubbard’s personality cult in the context of other authors who started out speculating about the future then went on to start making history themselves.

 

[mikegarrison]

2 minutes ago, Nightside said:

I can’t stop laughing about this name, but was it an intentional reference?
I googled around a bit to see if it was deliberate, but found nothing. It seems like a bland shell corporation more than anything.

Last year I read a excellent bio of golden age sci-fi, editor John W Campbell and his 3 protégés Isaac Asimov, Robert Heinlein, and L Aron Hubbard Called Astounding!

really interesting to learn about the development of Hubbard’s personality cult in the context of other authors who started out speculating about the future then went on to start making history themselves.

It's been widely claimed (whether true or not) that Hubbard told his SF-author colleagues that if someone really wanted to become rich, that person should found a religion.

[tater]

9 minutes ago, mikegarrison said:

It's been widely claimed (whether true or not) that Hubbard told his SF-author colleagues that if someone really wanted to become rich, that person should found a religion.

I want to say they played poker together, and one was Robert Heinlein... who wrote a book about a guy doing just that to shake the rubes down.

Edited May 9, 2020 by tater

[Nightside]

39 minutes ago, tater said:

I want to say they played poker together, and one was Robert Heinlein... who wrote a book about a guy doing just that to shake the rubes down.

Oh, it went WAAAAAAAAAAAAAAAAAAAAAAAAAAAY beyond playing poker, the details are probably too salacious for this forum, but if you have any interest in that era the book I linked above is great.

[kerbiloid]

Spoiler

The lander NavBall extension

Spoiler

The second crewmember is Auditor.

 

Edited May 10, 2020 by kerbiloid

[wumpus]

15 hours ago, tater said:

I want to say they played poker together, and one was Robert Heinlein... who wrote a book about a guy doing just that to shake the rubes down.

Heinlein wrote at least one to shake the rubes down, and another to become dictator of America.  He said they were depressingly easy to write.

[RCgothic]

How does any of this relate to the Dynetics Lander? I'm sorry, but I came adrift at the personality test.

[tater]

29 minutes ago, RCgothic said:

How does any of this relate to the Dynetics Lander? I'm sorry, but I came adrift at the personality test.

It's space related, and we are science fiction geeks as well (likely as a group)... pretty easy to go sideways.

Wish I had some dynetics content to add...

 

 

[StrandedonEarth]

53 minutes ago, RCgothic said:

How does any of this relate to the Dynetics Lander? I'm sorry, but I came adrift at the personality test.

Because...

Then a moderator comes along:

Followed by rejoining the main line:

I must say I like this design.It would be nice if the drop tanks could be replaced and the the craft be at least partially re-used. Bonus points if they could make the crew compartment into a detachable or at least modular pod, so that the propulsion segment could function as a reusable cargo lander dropping cargo pods.

 

[kerbiloid]

37 minutes ago, tater said:

we are science fiction geeks as well (likely as a group)...

and can easily miss the simplest explanation like "dynamic" + "kinetic".

[sevenperforce]

On 5/10/2020 at 11:00 AM, StrandedonEarth said:

I must say I like this design.It would be nice if the drop tanks could be replaced and the the craft be at least partially re-used. Bonus points if they could make the crew compartment into a detachable or at least modular pod, so that the propulsion segment could function as a reusable cargo lander dropping cargo pods.

Yeah, I had suggested something along these lines a few months ago.

NASA's initial studies had proposed a notional three-stage lander with an ascent module at 9-12 metric tonnes, taking crew from the lunar surface to NRHO (2.6 km/s). If we assume Dynetics represents a bare-bones, minimum-mass "space taxi" design, then let's baseline that at 9 tonnes. I think Dynetics will use cryos, but let's suppose they used pressure-fed hypergolics, because that's what NASA was originally planning.

The Apollo descent stage had a dry-mass-to-props ratio (legs and tanks) of 5.3:1; the Delta-K upper stage has a dry-mass-to-props ratio of 7.0:1. If we suppose the Apollo ascent module had ratios similar to a Delta-K upper stage, then that suggests the tankage and thrust structure of the Apollo ascent module massed around 336 kg with the engine and capsule massing 2011 kg.

At 312 s isp, a notional 9-tonne vehicle would burn 5.15 tonnes of props to get from the lunar surface to NRHO. Borrowing the ratios from the Delta-K puts tankage and thrust structure at 736 kg, leaving engines and capsule massing 3114 kg. The engine of the Apollo ascent module massed 1.7% of its GLOW; if we use the same value (assuming TWR will be similar), then that puts the notional 9-tonne lander's engine at 157 kg and the capsule and payload at just 2957 kg, a mass growth of just 53% for having doubled the crew. Skinny.

So let's use this value and plug in the numbers for the Dynetics launcher.

To get from the lunar surface to NRHO is still 2.6 km/s but now we need an extra 500 m/s or so for final descent, approach, hover, and landing. It's okay if that seems a little high; I'll deal with it in a second. We also need to borrow values from the Apollo descent module because we are dragging along landing legs. Total propellant fraction needs to be 63.72%; props come to 7768 kg, which means inboard tanks and thrust structure of 1466 kg and a staging mass of 12.19 tonnes. At liftoff it's going to be 10.35 tonnes, which means matching Apollo will call for around 176 kg of engines, give or take. This cuts our total dV at staging to 3.025 km/s, leaving 425 m/s for descent, approach, hover, and landing, which will still work well enough.

Now how do we get there? Well, we need to go from TLI to NRHO to LLO and then all but 425 m/s of the 1.87-km/s descent dV. It's 430 m/s from TLI to NRHO, 730 m/s from NRHO to LLO, and 1445 m/s from LLO to drop tank staging, for a total of 2.61 km/s. Propellant fraction will need to be 42.66%, but here we can use the better mass ratio of the Delta-K upper stage. We need 10.29 tonnes of props, 1942 kg of tankage, and a total TLI mass of 24.6 tonnes. The drop tanks themselves mass 12.236 tonnes. Note that this conveniently splits the total vehicle mass up into two almost exactly equal blocs, which is useful if you do a very very distributed launch.

Total TLI mass of 24.6 tonnes actually brings this very close to the direct performance capabilities of a single expendable Falcon Heavy. It's definitely within range if you use a longer, cheaper NRHO transit, or if you switch over to cryos. Alternately, you can launch the capsule and inboard tanks to LEO on a single-stick Falcon 9 with droneship recovery, then launch the drop tanks on a Falcon Heavy with the center core expended, leaving more than enough props to perform the TLI.

What's interesting is the cargo capabilities of this system. If we strip away the capsule, we get a drop-and-go potentially-reusable lander with a dry mass of 1.64 tonnes which can make some pretty interesting deliveries. It only needs 2.2 tonnes of props to return itself to NRHO after dropping off cargo on the lunar surface, which means it can deliver 6.1 tonnes if launched from TLI. If fueled up at NRHO, it can deliver a whopping 7.2 tonnes to the lunar surface. And of course if it needs to fly expendable it can send much more: 10 tonnes if launched from TLI; 11.2 tonnes if launched from NRHO. Imagine what NASA could do with an 11.2-tonne surface asset.

Of course this pales in comparison to Starship, but so does everything.

Edited May 11, 2020 by sevenperforce

[magnemoe]

On 5/2/2020 at 4:13 AM, sevenperforce said:

Not quite asparagus bc there are no engines on the drop stages.

If I had more time I would pixel-count and guess at the relative prop capacity of each tank. Did Dynetics give any indication of what props or engines it wanted to use?

Yes, this like drop tanks of fighter jets. are the tanks docked or do you need the gateway station to add new ones?
Drop tanks are much cheaper than stages as its just an tank, yes you need docking systems but most here will be on the lander with the transfer stage handle the control. 
Yes this require transfer stage to circulate around moon and meet the lander so it can dock to the tanks. 

 

[sevenperforce]

37 minutes ago, magnemoe said:

Yes, this like drop tanks of fighter jets. are the tanks docked or do you need the gateway station to add new ones?

My guess is that it's like a radial decoupler attached to a docking port. So you dock the tanks using a reusable docking mechanism capable of high-pressure prop transfer, but when it is time to drop them, they are dropped using a sacrificial element. Once safely at NRHO (or perhaps even on the surface) you can carefully drop the discarded portion of the docking mechanism.

37 minutes ago, magnemoe said:

Drop tanks are much cheaper than stages as its just an tank, yes you need docking systems but most here will be on the lander with the transfer stage handle the control. 
Yes this require transfer stage to circulate around moon and meet the lander so it can dock to the tanks. 

I broke down and did the pixel count.

Looks like the volume of the drop tanks is 238% the volume of the inboard tanks. My estimate had 7,768 kg of props on the inboard tanks and 10,290 kg of props on the outboard tanks, which is closer to 132%. Maybe the render is not very good.

[Barzon]

On 5/7/2020 at 2:37 PM, tater said:

Vulcan could launch the ascent part, but a second launch would be required for the drop tanks since the whole thing has to mass what, 30 tons?

From what I've heard from a HLS guy, I believe the drop tanks are launched individually, for a total of 3 launches.

[sevenperforce]

18 hours ago, Barzon said:

From what I've heard from a HLS guy, I believe the drop tanks are launched individually, for a total of 3 launches.

Hmmm.

Based on the above render, I would guess at the diameter of the inboard tanks at around 3.1 meters. 2.7 cm per pixel. Estimated internal volume of 41 cubic meters per tank. With methalox that would be 68 tonnes which is clearly nonsense.

[tater]

 

[StrandedonEarth]

 

[SuperFastJellyfish]

1 hour ago, StrandedonEarth said:

 

Spoiler

 

[kerbiloid]

They have only one way to disprove. By naming their first ship with the (forbidden name).

[tater]

 

Live in 18 minutes (showing their mockup).

[tater]

Pretty low res mockup.

They said about the size of the Apollo LM. Does that mean it's not much more than 16 tons (needs more dv, obviously, to make up for Orion)?

Large door is better, and seems spacious for the crew getting out of their suits in a bag (to catch the dust). A dedicated airlock seems like a better design to me (Altair). I like the cargo delivery aspect of this one, decent for placing a rover because it's low-slung.

 

[sevenperforce]

34 minutes ago, tater said:

They said about the size of the Apollo LM. Does that mean it's not much more than 16 tons (needs more dv, obviously, to make up for Orion)?

I assume they're talking about overall gross volume.