totm nov 2023 SpaceX Discussion Thread

[tater]

 

 

[tater]

 

 

[Exoscientist]

 Article in Nature does not find Mars Starship missions feasible:

About feasibility of SpaceX's human exploration Mars mission scenario with Starship.
Scientific Reports
volume 14, Article number: 11804 (2024) 
https://www.nature.com/articles/s41598-024-54012-0

  Bob Clark

[darthgently]

1 hour ago, Exoscientist said:

 Article in Nature does not find Mars Starship missions feasible:

About feasibility of SpaceX's human exploration Mars mission scenario with Starship.
Scientific Reports
volume 14, Article number: 11804 (2024) 
https://www.nature.com/articles/s41598-024-54012-0

  Bob Clark

Meh.  The breadth and scope that Nature weighs in on has become increasingly political and indistinguishable from other ideologically driven mass media.  It might as well be Rolling Stone or Mother Jones magazine at this point, imo

[AckSed]

If this comment is correct, they got the delta-V required to reach 250km LMO mixed up with a 500km LMO and misquoted the delta-V to reach 250km LMO orbit, for rendezvous while in that orbit with a separate Earth Return Vehicle orbiting in two different highly-elliptical Mars orbits.

[.50calBMG]

So someone who repeatedly uses incorrect data is pushing an article that uses incorrect data... Hm...

Edited August 2 by .50calBMG

[tater]

19 minutes ago, darthgently said:

Meh.  The breadth and scope that Nature weighs in on has become increasingly political and indistinguishable from other ideologically driven mass media.  It might as well be Rolling Stone or Mother Jones magazine at this point, imo

I realize English is not the first language of the authors, but man, that paper is terribly written.

[Nuke]

6 hours ago, darthgently said:

Meh.  The breadth and scope that Nature weighs in on has become increasingly political and indistinguishable from other ideologically driven mass media.  It might as well be Rolling Stone or Mother Jones magazine at this point, imo

this is what happens when there are no longer any standards in media. especially when a certain kind of company buys most of the advertising and then suddenly finds themselves with a lot of leverage over what can be reported.

[Ultimate Steve]

I spent four semesters and a summer working on this little guy:

And he's going up on the NG-21 mission tomorrow morning!

[darthgently]

16 minutes ago, Ultimate Steve said:

I spent four semesters and a summer working on this little guy:

And he's going up on the NG-21 mission tomorrow morning!

A 4.5 year gestation period then sending it to space right after it is born.  The struggles, sorrows, and joys of being a space-nerd-parent are deep.

Edited August 2 by darthgently

[Ultimate Steve]

59 minutes ago, darthgently said:

A 4.5 year gestation period then sending it to space right after it is born.  The struggles, sorrows, and joys of being a space-nerd-parent are deep.

2 years or so for me (4 semesters), project has been around for far, far longer than that. I'm not sure, but I want to say the current iteration of the plan was started somewhere around 2015 or 2016 with a targeted launch date of 2018, which, uh... Well, we got there eventually. Knock on wood. And that's just the modern incarnation of the project, I think there was an earlier 1U design that was worked on for several years before not being selected (NASA didn't want to pay to send something up without a science payload). And the team goes back even further than that, apparently they did experiments in a Zero G plane at one point back in the late 90's or early 2000's.

It has been a LONG road indeed.

And yeah, sorrows, struggles, and joys is an apt way to describe it. I could almost write a book about it.

Edited August 2 by Ultimate Steve

[AckSed]

So what is your science son supposed to do up there?

[Ultimate Steve]

28 minutes ago, AckSed said:

So what is your science son supposed to do up there?

The satellite is equipped with a software defined radiometer. At the risk of overexplaining, software defined radio technology replaces what would be physical components with code. It samples the incoming radio signal a bajillion times per second, and computers are so good these days that stuff like filters, modulators, demodulators, attenuators, and a bunch of other stuff, can be emulated via software. You don't need to go out and buy (and have space for) those components, you just drag them into the flowchart. You can also do this at the same time as stuff which would typically already be done in code, in the same interface. Doing math on the data, bit stuffing, printing it to a live spectrum plot, etc.

This is traditionally used for amateur radio (and indeed our ground station setup does use software defined radio for some of it) but our mission wants to see if this same technology can be used to make a low cost radiometer. How exactly it works is beyond me, the instrument is the product of the thesis of the professor running the satellite team. 

While I didn't have to make it, I did have to fix it and modify it and get it to talk nicely with the satellite's main computer, and calibrate it, and figure out how to power the 9 Watt instrument from a power supply that was not designed to power something that power hungry and...

If all goes well we should be able to point it at Earth and see how much moisture is in the soil in any given (large) area. The satellite is capable of taking a 10 minute measurement at 1 sample per second every 2 ground station passes, assuming the battery is filled up in that time, although we will start slower. I'm not sure how precise the data will be. I will be ecstatic if we get back data at all, moreso if we can tell apart an ocean from a desert.

I'll be ecstatic if the thing even beeps at us. I forget the exact statistic, but half of all university cubesats either don't succeed or don't even get to the point where they can beep (which puts full successes much lower). And I think that number includes graduate teams, our team has been entirely undergraduate except for the professor writing the program for the experiment and doing a lot of administrative stuff. Given the seemingly endless troubles we've had, the issues that were cropping up until the last minute, and many other things, I'm not expecting much. My personal victory threshold is a single occurrence of 2 way communication.

[tater]

 

[Nuke]

its so clean, hardly any tubes.

[tater]

 

[darthgently]

Evolution of Raptor, this is the way

 

[Flavio hc16]

27 minutes ago, darthgently said:

Evolution of Raptor, this is the way

 

" Raptor 3 is going to be so simple and streamlined, that people will think that we forgot some parts".

 

Elon during one of the tour with Everyday astronaut 

[CBase]

2 hours ago, Flavio hc16 said:

Elon during one of the tour with Everyday astronaut 

In the same interview he explained that they integrated a lot of pipes inside the walls of main parts, so complexitiy is there, just tightly integrated. This looks ready for mass production.

I was once part of embedded device development and it looked much like this: First version has lots of standard parts even with wires around some connections and each iteration got much cleaner look until the final device had only few ICs (some custom) on a multilayer PCB. Creating these is a lot of effort, but drives manufactoring costs down by magnitudes.

[darthgently]

34 minutes ago, CBase said:

In the same interview he explained that they integrated a lot of pipes inside the walls of main parts, so complexitiy is there, just tightly integrated. This looks ready for mass production.

I was once part of embedded device development and it looked much like this: First version has lots of standard parts even with wires around some connections and each iteration got much cleaner look until the final device had only few ICs (some custom) on a multilayer PCB. Creating these is a lot of effort, but drives manufactoring costs down by magnitudes.

Not having all those pipes exposed should make the engines much more durable if a neighboring raptor RUDs.  I'd guess it would help keep various internal temperature fluctuations more predictable too as the fluids share more heat sink/source mass with less outside surface influence.

Definitely mass production oriented.  So great looking

[AckSed]

Daaang, that's clean.

[StrandedonEarth]

Pipes in part walls is really leveraging the capabilities of 3D-printed parts, which I know they use.

[Exoscientist]

23 hours ago, AckSed said:

If this comment is correct, they got the delta-V required to reach 250km LMO mixed up with a 500km LMO and misquoted the delta-V to reach 250km LMO orbit, for rendezvous while in that orbit with a separate Earth Return Vehicle orbiting in two different highly-elliptical Mars orbits.

 

 However, the comment is from an anonymous user posting from a social media account. So we can’t know if the commenter has any knowledge in the field.

  Bob Clark

[tater]

 

 

[RCgothic]

1 hour ago, Exoscientist said:

 

 However, the comment is from an anonymous user posting from a social media account. So we can’t know if the commenter has any knowledge in the field.

  Bob Clark

I've double-checked the table maths and the referenced Sopegno Et Al article.

Table 4 does indeed use only a 250km orbit, but Sopegno uses 500km. The correct DV of target altitude should be 3315m/s not 3430m/s in Lines 3 and 4. So the DV losses for lines 3 and 4 should be 1069m/s and 1060m/s respectively, not 954m/s and 945m/s.

The commenter is accurate. Maybe do a minimum of legwork yourself before casting aspersions next time.

Also, intuitively, all other things being equal on a nearly airless body, the higher the TWR the less the gravity losses. Line 2 having higher losses than Line 1 despite higher TWR warrants further explanation IMO.

 

Edited August 3 by RCgothic