Hacker News Board Hacker News, browsed like a classic message board
Live data from Hacker News

Akin’s Laws of Spacecraft Design

spacecraft.ssl.umd.edu

Post reply on HN
Print view View original

51–60 of 159 posts

Re: Akin’s Laws of Spacecraft Design

#51

Post by singleshot_ »

avmich wrote: post #16
Zandikar wrote: post #8

Earlier quoted context omitted.

Err, what? Keyword there: "New". SpaceX still faces large costs and delays in developing new launch vehicles, including starship, which is delayed and unfinished btw, so no matter how you try to spin it, Starship is not (currently) a good example of SpaceX being an exception to the adage. Artermis 3 isn't exactly cheap afterall, and if you don't know what that is but know what Starship is, that proves the adage this…

> The whole point of these two adages is that reusing an existing design is better than a new one. Yes, and that's put in doubt. Starship aims to improve on previous designs - in terms of affordability, that is, making human flights cheaper. This cheapness can't be realized with existing designs, so a new design becomes better in that regard. > SpaceX's REUSABLE rockets are great for a number of reasons yes, but by d…

> In software it's rather clear

In software, I perceive there to be almost no separation whatsoever between design and use. I’m using windows 11 right now, and sometime in the next few days it will silently download software patches that were designed over the last few days to address situations not considered in the original design of windows 11. Software goes back and forth from the design process to active use pretty much continuously these days.

Just an alternate perspective to think about.

Re: Akin’s Laws of Spacecraft Design

#52

Post by firewolf34 »

JoeAltmaier wrote: post #37

Number 13. Design is based on requirements. There's no justification for designing something one bit "better" than the requirements dictate. Isn't that the margin for error? I want to go up in a ship that's a little better than the absolute minimum.

Requirements set constraints which guide the development process. Without them set early on, you risk not understanding completely what you're setting out to do, you risk differing expectations/assumptions between members of your team, and you risk creep as the project goes on which means you will diverge from your intended outcome.

In any project, resources (time, money, etc) are limited so the most successful project will be one that uses resources most efficiently. So good explicit requirements allow you to determine the most efficient manner to achieve them as they codeify the problem and give you goalposts to optimize within.

This all relies on you being able to set good requirements from the outset, which can be done by understanding what you're setting out to achieve (the problem you're trying to solve).

I have a comment in this thread which discusses the consequences of this rule specifically. https://news.ycombinator.com/item?id=37069168

Re: Akin’s Laws of Spacecraft Design

#53

Post by Alupis »

avmich wrote: post #16
Zandikar wrote: post #8

Earlier quoted context omitted.

Err, what? Keyword there: "New". SpaceX still faces large costs and delays in developing new launch vehicles, including starship, which is delayed and unfinished btw, so no matter how you try to spin it, Starship is not (currently) a good example of SpaceX being an exception to the adage. Artermis 3 isn't exactly cheap afterall, and if you don't know what that is but know what Starship is, that proves the adage this…

> The whole point of these two adages is that reusing an existing design is better than a new one. Yes, and that's put in doubt. Starship aims to improve on previous designs - in terms of affordability, that is, making human flights cheaper. This cheapness can't be realized with existing designs, so a new design becomes better in that regard. > SpaceX's REUSABLE rockets are great for a number of reasons yes, but by d…

None of this is put in doubt though. Your points about SpaceX's potential for future cost savings and efficiencies are hardly realized today - particularly when considering the length of time that has been spent without a capable manned vehicle. If, fast forward a decade or two and SpaceX is still using today's designs (albeit, upgraded) and actually realized massive savings - then we can talk. However, I'd bet they're going to re-design and build brand new models along the way...

There's a reason military aircraft tend to have extreme service lives. It's far cheaper and effective to upgrade and refit/improve existing airframes with modern technology than it is to start from scratch - every single time.

Look at the F-35 program. It's not exactly fair because the design goals are vastly different - but upgrading aging F-15's has kept them on the battlefield for 47 years[1], and today they're still a seriously potent air superiority fighter. The F-15's of today are only similar in shape to the originals, however.

[1] https://en.wikipedia.org/wiki/McDonnell_Douglas_F-15_Eagle

Re: Akin’s Laws of Spacecraft Design

#54

Post by pdonis »

Razengan wrote: post #13

By the way, since you need to apply thrust from any direction to maneuver flexibly in 3D space (without wind or gravity), wouldn't spherical/disc(saucer) shaped spacecraft be the most efficient?

No. Such a craft would either need to have full thrust engines pointing in every possible direction (way too costly and overbuilt) or would have to have some way of rotating its full thrust engines to be at any arbitrary angle relative to the ship (which then means you have to transfer all the thrust through gimbal mounts or whatever you're using to be able to rotate the engines, and those things won't be able to withstand that kind of stress). It's much easier and simpler to point your full thrust engines in one direction (out the back of the ship), so the thrust gets transferred through the entire ship's fixed structure, and then have smaller thrusters to rotate the ship to point in the direction you want to go.

Re: Akin’s Laws of Spacecraft Design

#55

Post by Swizec »

avmich wrote: post #16
Zandikar wrote: post #8

Earlier quoted context omitted.

Err, what? Keyword there: "New". SpaceX still faces large costs and delays in developing new launch vehicles, including starship, which is delayed and unfinished btw, so no matter how you try to spin it, Starship is not (currently) a good example of SpaceX being an exception to the adage. Artermis 3 isn't exactly cheap afterall, and if you don't know what that is but know what Starship is, that proves the adage this…

> The whole point of these two adages is that reusing an existing design is better than a new one. Yes, and that's put in doubt. Starship aims to improve on previous designs - in terms of affordability, that is, making human flights cheaper. This cheapness can't be realized with existing designs, so a new design becomes better in that regard. > SpaceX's REUSABLE rockets are great for a number of reasons yes, but by d…

The “No new launch vehicles” adage reads to me as “Don’t develop a new browser when you make a website”

That doesn’t mean we never need or want a new browser. It just means that developing a browser is a separate project and if your fancy websites requires a new browser, it is in fact a browser development project, not a website project.

Re: Akin’s Laws of Spacecraft Design

#56

Post by dakr »

Eduard wrote: post #44
filiph wrote: post #2

I knew #36 and have used it in the context of software engineering. But much of the rest is similarly applicable. > #36 Any run-of-the-mill engineer can design something which is elegant. A good engineer designs systems to be efficient. A great engineer designs them to be effective.

how is this rule meaningful beyond platitude? "boss, I have finished the task. But this time, I activated great engineer mode , hence the result is not only elegant, but efficient and effective."

I take this progression to mean that the novice will design a part or subsystem that is good by itself. The more experienced engineer is thinking bigger by taking into account the effect of the larger design on the portion they are working on. The great engineer is thinking holistically and so also considers how the part affects the whole design.

The same thing applies, I think, to anyone who works on a team. The beginner thinks of the problem by itself. The more experienced member thinks of how the system will influence what they are building or doing. The senior member will think about how the thing they are doing/building will in turn affect the whole (and weigh the consequences).

Re: Akin’s Laws of Spacecraft Design

#57

Post by firewolf34 »

whats_a_quasar wrote: post #50
JoeAltmaier wrote: post #37

Number 13. Design is based on requirements. There's no justification for designing something one bit "better" than the requirements dictate. Isn't that the margin for error? I want to go up in a ship that's a little better than the absolute minimum.

This is the only one I have reservations about. It is also part of the engineer's job to understand the customer, understand what they need, and negotiate the requirements (within reason). It's hard (impossible?) for the customer to fully design exactly what they need, and it works much better to the engineers to build something with continuous customer input than to build rigidly to a spec sheet

You're describing the (albeit quite common) situation where requirements were not conclusive enough and need to be revised throughout lifetime of development, which can be natural as you begin to understand the problem space as you work within it. But the key is that the requirements should be as conclusive and accurate to resolving your problem as they possibly can be, at any given point in time.

In the "frictionless environment, ideal world" scenario - requirements should always be completed as close to the letter as possible and no further.

In the practical scenario, requirements should be written as close to perfect as can be achieved where perfect is defined as what is necessary to resolve your problem space, limited by your understanding of the problem space.

Re: Akin’s Laws of Spacecraft Design

#58

Post by karaterobot »

I have a subset of these printed out and tacked to a cork board in my office, and I refer to this website a few times a year. Very, very good stuff.

This one in particular was a big influence on me when I moved from engineering to design. It expressed what I'd felt but hadn't put into words. Not just the look, but nearly every aspect of a project is de facto path dependent, so you want to be as far upstream as possible. It's also why I volunteer to write a lot of documents I'm not strictly responsible for:

> 30. (von Tiesenhausen's Law of Engineering Design) If you want to have a maximum effect on the design of a new engineering system, learn to draw. Engineers always wind up designing the vehicle to look like the initial artist's concept.

Re: Akin’s Laws of Spacecraft Design

#59

Post by firewolf34 »

innrautha wrote: post #45
xNeil wrote: post #27

Earlier quoted context omitted.

What's a line of blame?

I took it to mean clearly delineated responsibilities (i.e. who gets blamed when a part / aspect doesn't work). If there are unclear boundaries between responsibilities, things will fall through the gaps when one group assumes another will take care of something.

Furthermore, when people are held responsible for quality completion of a task, they are often more driven to achieve the task at-quality. This must be balanced with not over-taxing them, but that's a given.
Post reply on HN