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SE - stop firing the good guys

 Discussion on answer by GremlinWrange…

Imported from a comment discussion on space.stackexchange.com/...
SE - stop firing the good guys
Apr 14, 2023 06:55
Sorry, I am not open to that.
 

 The Pod Bay

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SE - stop firing the good guys
Feb 5, 2023 22:05
Maybe a self-answer of how to find these before and after transfer ellipses would be useful?
SE - stop firing the good guys
Feb 5, 2023 22:05
user image
SE - stop firing the good guys
Feb 5, 2023 22:04
It does somewhat, 700 - 1200 m/s of delta-v saved, even if the turning angle of Mars is puny
SE - stop firing the good guys
Feb 5, 2023 22:04
Investigated "Does a Mars flyby help for returning from the asteroid belt?"
SE - stop firing the good guys
Oct 21, 2021 06:05
75 years ago, first image of Earth from space. V-2, 105km altitude, 1946.
SE - stop firing the good guys
Oct 21, 2021 06:04
user image
SE - stop firing the good guys
Jul 12, 2021 21:40
Looks like I'm in the cool kids club now though.
SE - stop firing the good guys
Jul 12, 2021 21:39
user image
SE - stop firing the good guys
Jul 12, 2021 21:39
Turns out Kepler eggs aren't egg shaped :(
SE - stop firing the good guys
Jul 12, 2021 19:28
@uhoh Do you like your Kepler eggs sunny side up?
SE - stop firing the good guys
Jul 9, 2021 10:50
5
Q: Orbital insertion with "inertial parachute"?

SE - stop firing the good guysInspired by Is there any way to land a rover on the Moon without using any thrusters?, but off-topic as a solution as that question asks specifically about crumbling zones. The idea: A spacecraft heading for the Moon will remain linked to the spent upper stage with a tether. With a small initi...

orbital-mechanics the-moon
SE - stop firing the good guys
Jul 9, 2021 10:50
Simulation looks promising
SE - stop firing the good guys
Jul 9, 2021 10:50
user image
SE - stop firing the good guys
Jan 5, 2021 16:53
@uhoh Yes.
SE - stop firing the good guys
Jan 4, 2021 13:42
Official confirmation of anthropomorphism of robotic spacecraft for public outreach being an actively used and effective strategy would be an interesting thing to have.
SE - stop firing the good guys
Jan 4, 2021 13:41
4
Q: Why does NASA now call its rovers "robotic scientists?"

Camille GoudeseuneNASA's 2020 July 13 press release about the Mars 2020 mission calls its rover Perseverance a "robotic scientist." Is this press release, or at least this mission, the first usage of this term? Why doesn't NASA just call Perseverance a robot or a rover like its predecessors? Sure, it has some au...

terminology perseverance robotic-missions robotics autonomy
SE - stop firing the good guys
Nov 16, 2020 10:31
Which combined with the intuition that bi-tangential transfers are efficient somewhat settles the planar case.
SE - stop firing the good guys
Nov 16, 2020 10:30
5
Q: Ellipse tangential to two arbitrary ellipses sharing a focus

SE - stop firing the good guysIn orbital mechanics, a bi-tangential transfer uses an elliptical orbit touching two other orbits. They are generally very efficient. Suppose you have two arbitrary planar ellipses, sharing a focus $O$. Their second foci are $A$ and $B$. A bi-tangential ellipse would be a third one, also sharing...

geometry conic-sections
SE - stop firing the good guys
Nov 16, 2020 10:30
The most valuable contribution so far actually came from the math people:
SE - stop firing the good guys
Nov 16, 2020 10:30
@uhoh As you might have guessed, I keep trying to get the "simple" two-body-with-zero-mass-satellite problem cracked before moving on to more complex transfer problems. It's putting up quite a lot of resistance so far!
 

 Discussion between SE - stop firing t…

Imported from a comment discussion on space.stackexchange.com/...
SE - stop firing the good guys
Jan 22, 2023 21:09
It really is just one burn, in a very concrete sense. Where you end up depends only on when the burn stops.
SE - stop firing the good guys
Jan 22, 2023 21:08
Yes!
SE - stop firing the good guys
Jan 22, 2023 21:08
LEO -> LTI is just lifting the apoapsis, and when lifting the apoapsis the orbit temporaryly becomes a GEO transfer for a brief moment.
SE - stop firing the good guys
Jan 22, 2023 21:07
Map case in point from the github issue: LEO -> GEO transfer -> LTI is the same as LEO -> LTI
SE - stop firing the good guys
Jan 22, 2023 21:05
When the intermediate node does not introduce an extra burn, but merely happens partway through a burn, it doesn't add any extra overhead.
SE - stop firing the good guys
Jan 22, 2023 21:04
General rule of going through an intermediate node is optimal:
SE - stop firing the good guys
Jan 22, 2023 21:02
But looking closer at that issue, it claims 2590 m/s from LEO to LTI. That is not correct. The real value is 3120 m/s, so something may be fishy there
SE - stop firing the good guys
Jan 22, 2023 21:00
Not always. The github issue was that the map was using a suboptimal chain. But an optimal chain can still be represented as a map
SE - stop firing the good guys
Jan 22, 2023 20:56
Delta-v maps are made so that you can always just sum up the values along the path.
SE - stop firing the good guys
Jan 22, 2023 20:56
Reason. To go from A to B, and then to B to C is not always the most efficient route. Some times a cheaper route A to C exists.
SE - stop firing the good guys
Jan 22, 2023 20:55
To calculate an iternary consisting of multiple burns is not always that simple.
SE - stop firing the good guys
Jan 22, 2023 20:54
First point: To calculate a single burn is always just simple vector math. Subtract the target velocity from the original velocity.
SE - stop firing the good guys
Jan 22, 2023 20:52
@Vlad The problem pointed out in that issue is correct, but the proposed solution of summing squares is not a general solution to all maneuvres. For the limited problem talked about in the github issue (single body, two burn transfers), it appears valid.
SE - stop firing the good guys
Jan 22, 2023 20:52
That is not the case.
SE - stop firing the good guys
Jan 22, 2023 20:52
@Vlad You're probably referring to v^2 = v_infty^ + v_e^2. The "tricky" thing about that scenario is that the velocity vectors aren't in the same place, one is deep inside a gravity well and one is outside of it.
 

 Discussion on answer by SE - stop fir…

Imported from a comment discussion on space.stackexchange.com/...
SE - stop firing the good guys
Jul 19, 2021 14:48
This is starting to get lengthy. Feel free to edit in a summary.
SE - stop firing the good guys
Jul 19, 2021 14:48
@Cadence That would no longer be radar though, just plain radio astronomy.
 

 Discussion between Nathan Merrill and…

Imported from a comment discussion on puzzling.stackexchange.c...
SE - stop firing the good guys
Nov 13, 2020 15:21
Added. I agree with you that it's not possible to develop this further unless one more clearly defines what a "puzzle" is.
SE - stop firing the good guys
Nov 13, 2020 15:10
I think it would be useful if I could edit this discussion down to something that can fit as an extra section to the answer.
SE - stop firing the good guys
Nov 13, 2020 15:09
That would be the difference between the 1) and 2) strategies in your original question. 1) says that "yes, this is solvable", while 2) says that "no, this is not solvable". Which is what this whole thing is about.
SE - stop firing the good guys
Nov 13, 2020 15:06
There are thus two (incompatible) interpretations, both of which say the answer is "yes".
SE - stop firing the good guys
Nov 13, 2020 15:05
Which still solves the initial constraints of your original question.
SE - stop firing the good guys
Nov 13, 2020 15:04
If there are multiple valid solutions to a problem, an assumption of there being only one can end up with picking different ones.
SE - stop firing the good guys
Nov 13, 2020 15:04
Which is not invalid.
SE - stop firing the good guys
Nov 13, 2020 15:04
So an uniqueness argument will find different ones, depending on the order.
SE - stop firing the good guys
Nov 13, 2020 15:03
There CAN be different solutions.
SE - stop firing the good guys
Nov 13, 2020 15:03
In the subtly different restated problem,
SE - stop firing the good guys
Nov 13, 2020 15:03
In my original intention, the secret pieces of information are treated differently, and thus have only one solution. But there your argument does not work.
SE - stop firing the good guys
Nov 13, 2020 15:03
Backtracking a bit to your re-statement of the puzzle as "[SUM] = [A] + [B]", there are obviously multiple solutions. As such, different uniqueness arguments finding different ending up at a different solution is not actually a problem.