I have just recovered from this dreaded message: "Wait! Some of your past questions have not been well-received, and you're in danger of being blocked from asking any more." And now it is back.

I can't speak for the details of the question because its not an area I know much about

Maybe it just needs more words to describe your ideas? I had to read it a couple times.

@Criggie - she was a final blow :) And she is a smart person. It hurts :)

@TheMatrixEquation-balance So its about a launching platform in orbit, which uses the 120mm mortar to launch a small probe such that it starts faster than escape velocity, and the platform uses gravity assists to maintain its.. orbit ?

I'm probably using words wrong, appologies

and that the probes can do a straight-line transit to the outer planets with no further propulsion required ?

Is the launch platorm in orbit around earth, or is it doing repeated gravity assists around the inner planets ?

@Criggie - You are correct. It is a bit far fetched. But this subject was well discussed in the question.

I'll try editing the question in a bit. If you don't like the edit, then revert.

I was thinking about Earth's gravity assist as both - boost to compensate for recoil force and extra delta-v for probes.

I mod on Bicycles, and sometimes we get a good question but the author has left a lot of details out because they're "obvious" but in text, we can't see them

okay here's one point where my knowledge gaps show.

A gravity assist is when a craft passes near to a large body like a planet

but does not stay in orbit,

Is that right ?

Looking at Voyager and JUNO's gravity assists, they spend a long time floating around in space but no orbiting a planet, so that they can have a near-encounter with somthing big

that's what gives them extra speed

So if your launcher is in a stable orbit around a planet, that's not posible to get a gravity assist ?

Good question. In this case, the force of recoil might push it back into the Earth's orbit.

OR

if you're in orbit and you launch the probe straight down it will go faster but likely won't exceed escape velocity

like throwing a ball forward while standing on a train travelling forward, the train imparts more speed to the ball ?

There is an acceleration when pass the closest to the planet.

yes, but in orbit that is balanced when you're at apogee.

2 km/s is enough delta-v even if you are in a stable orbit. In this case, Moon orbit would be better. But then you will need to burn fuel to compensate for recoil.

Gravity assist only works when you don't fall into an orbit, and instead take a parabolic path.

conic path ? I forget

So - is the launch platform in your question in a stable orbit around a planet, or something else ?

Imagine what would happen if you did a burn from a stable orbit to get really close to the planet?

You will get a delta-v boost from gravity assist, but you will not be thrown out into space because the recoil force will push you back into orbit.

But you have to drag that fuel up to orbit in the first place.

May as well use that fuel to push the probe anyway.

Yes, but I thought it would be less fuel, than just compensating for recoil. Plus, you will get a significant delta-v boost from gravity assist.

hence why the "solar sail" idea has its followers. But they only push outbound from the star so not useful in orbit.

This is discussed in the question. Liquid fuel - cannot give you enough delta-v because it has to push all the fuel together with a probe. Stage 4 or Stage 5 does not help. And electrical-plasma propulsion is too slow.

For now, gravity assist is the only way to get around between planets. But it takes years to complete.

okay - standing back now, can you see how the question needs a lot more words to set the stage?

Right here, it has devolved into a series of clarifications and explanations

all that should be in the question already.

that's the info to be edited into the question

Does that make sense ?

Yes, but did you notice that none of the people voted to close - leave any notes? This is gang-busting. It is not a science.

You and I have done some development here - take the scroll back and edit it into your post.

I gotta work sorry. Out of time

Thanks anyway.

for the love of...no, I was not "the final blow." I was one of the first people to vote to close

why? Because the title question "What should be the mass of spacecraft going through Earth gravity assist maneuver to compensate for the 30 tons recoil force?" doesn't make any sense, and the body doesn't actually expand on the title question

Why don't I leave notes anymore? Because when you get feedback on your questions, you argue with the people who leave feedback

Thanks, somehow I feel better.

several people very kindly point out that your assertion that mortar propellant is better than liquid rocket fuel is wrong, and point to search terms to help you with that, and yet here you are keeping up with the "liquid fuel cannot give you enough delta-V" nonsense

but I wouldn't have even known you'd said anything if Crigglie hadn't brought it up, because I've had you on ignore ever since you said that people getting shot near me was the matrix trying to tell us stuff or some rot

but just to expound on their general theme: start writing questions that don't deserve to be closed, and I won't vote to close them

"liquid fuel cannot give you enough delta-V" nonsense - It was not me who said that a hard limit on liquid fuel theoretical possibilities - is around a 'direct Jupiter' delta-v

start with taking a physics 101 course so you know that mass doesn't offset acceleration

I don't know what course you need to listen to the people you interact with instead of deciding your idea is awesome and people just don't get what you're saying

ignore's back on though. Hope that answered your question.

@ErinAnne - "so you know that mass doesn't offset acceleration" - during your flyby Earth within 15 ml, more mass (of spacecraft) translates into more energy added (gravity assist delta-v). At some point, recoil from mortar will be equal to this added energy (delta-v).

SpinLaunch space gun earthsky.org/space/spinlaunch-slingshot-to-space

@TheMatrixEquation-balance when you make posts that don't take into account basic maths/physics, nobody is going to bother reiterating that message to you. They are just going to vote to close, as it's not a real question

@TheMatrixEquation-balance no. That's not how this works

GremlinWranger and others voted to leave the question open.

@TheMatrixEquation-balance and your point is? The system allows for a sufficient number of users to vote to close low quality questions. It's not because they are your questions. It's because you tend to post questions which do not meet requirements. As Erin said, if you start writing posts that don't deserve to be closed, people won't close them

If this is a low quality question, why GremlinWranger would bother to answer it? Maybe you just don't understand my question?

According to SE rules, if you try to close the question that was answered and up-voted, you have to (expected) explain yourself (give a reason).

@TheMatrixEquation-balance That is incorrect. Anybody can vote to close any question, without comment if they so choose

Please don't make up nonsense to try to justify your argument

Also, many people try to answer terrible questions - it does not make the question good, and while sometimes a really good answer can sort of save a marginal question, it generally doesn't

You keep objecting to loads of people giving you advice on how to post better questions, and you argue with almost everyone about it. The people who really know the physics of space best have mostly given up responding to you - for reasons such as the explanation Erin gave you

The onus is on you to make your questions worth voting up and keeping, because the ones that aren't just cost everyone else time and effort - folks do not get paid to put up with nonsense, so you need to make it worthwhile

@TheMatrixEquation-balance For many of your questions there is no understanding because what you wrote is not based on reality. Many folks have suggested fully reading and learning a space-101 course before writing some of your posts, as you would realise that they should never have been posted

It is just your black & white opinion. The real answer is always somewhere in the middle.

@TheMatrixEquation-balance not really. There are quite a few folks who vote your posts down because while there is variation in quality for everyone, many of yours are just blatantly outside our quality requirements. And as before, you are refusing to take this on board.

Listen: you get the downvotes and votes to close on your posts that deserve them. If you don't want those votes to close, improve your posts. You have had guidance from so many people. Take it, and your problem goes away

If you keep refusing that guidance, and trying to say it's someone else's opinion, will just not help you

And you are likely to get back to being suspended or question banned

It's up to you

Now, I'm done for the evening, as this is all stuff you have already been told. I'm out

Out of respect for GremlinWranger's research on my question, I did add clarification updates. space.stackexchange.com/questions/63793/…

@RoryAlsop this bit is the key to me. It isn't just that there's a knowledge gap, it's that the question isn't even real. What mass should I make this space vehicle I've dreamed up with a hyperspecific mission so that when it does something its speed changes by the right amount?

engaging with that credulously is dozens of "well, momentum is conserved so..." laying out all the basic physics involved

and whatever the actual answer to the question would end up being doesn't even matter. The question wasn't real, it was an excuse to bring up the idea

and judging by the pattern, it's an excuse to fight about the idea with people. It's trolling.

and the answer to trolls is downvote, vote to close, don't engage