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# Testing RT-5 Contract - at very low speed!

## Question

Hey Kerbinians! (?)

Disclaimer: noob with positive attitude.

My problem: Test RT-5 "Flea" Solid Fuel Booster in flight over Kerbin

Conditions to be met before staging:

- flea booster (trivial)

- kerbin (early carrer, so I am there)

- flying (if I want to check the altitude marker it seems to be a requirement...check)

- altitude 42,000 to 46,000 m (check)

- speed 10 m/s to 110 m/s (???)

So I managed to check everything except the speed with the following rocket (in order top down in the rocket reflected as well in the staging):

- mk16 parachute

- mk1 pod

- tr-18a stack decoupler

- flea booster with 14.0 (10% capacity) of solid fuel

- tr-18a stack decoupler

- hammer booster with 337.5 of solid fuel

I manage to check everything (except speed) with an Orbital Speed between 10 and 110 m/s without going green, so I guess the contract wants me to achieve that range of velocity for the Superficial speed (could that be right?) I don't see another option the light simply never goes green!! Ever!... So I tried decreaseing surface velocity by conteracting the typical parabolic flight to as much vertical as possible (70-80º East) to be fully perpendicular to kerbin up and down. The lows I achieved was 111 m/s!!!! haaaa almost there... but it was just one time, normally it goes down to 150-170 m/s (with an orbital speed around 30 m/s).

Edited by vert flea
word added for clarity - "East"

## Recommended Posts

• 3

The speeds in the contracts are always Surface speeds. Never orbital speeds. So for very low speeds, you have to launch vertically -- you can't launch eastward.

It is difficult to get the speed to go to zero at exactly the right altitude, but you can do it by choosing the right SRB with the right amount of fuel. If you throttle the SRB a little bit, you will also lose some altitude and speed.  Additionally, you can turn your craft sideways to increase drag, if you think you are going to go too high.

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I wouldn't bother with a contract like this until I had a throttleable LFO engine.  That way, you could kill most of your speed at your AP.

Also keep in mind that you can test the booster without staging it.  If you right click on it, there should be a "Run Test" button.

It also doesn't need to burn for the test, so you can empty it all the way and essentially treat it like a science experiment.

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You can adjust the burn rate of solid engines in the VAB.

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Hey there @vert flea, and a very warm welcome to you!

The contract wants you to have the speed between 10 m/s and 110 m/s at the same time as you are higher than 42,000 but lower than 46,000 m. So all you really need to do is slow the rocket down (as you know). To do that, the easiest way is to launch straight up and possibly remove some more fuel from the booster so that the booster burns out and gently coasts up to around the maximum contract height before falling back. This helps reduce the speed because the speed on the meter is actually vertical speed AND horizontal speed measured together. You only need vertical speed to complete the contract. =)

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1 minute ago, Geonovast said:

I wouldn't bother with a contract like this until I had a throttleable LFO engine.

But it's really, really easy

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Just in case you don't know yet, you can click on the navball speed indicator to toggle between referentials.

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Thanks a lot for trying to help guys! Unfortunately no success so far...

4 hours ago, Deddly said:

Hey there @vert flea, and a very warm welcome to you!

The contract wants you to have the speed between 10 m/s and 110 m/s at the same time as you are higher than 42,000 but lower than 46,000 m. So all you really need to do is slow the rocket down (as you know). To do that, the easiest way is to launch straight up and possibly remove some more fuel from the booster so that the booster burns out and gently coasts up to around the maximum contract height before falling back. This helps reduce the speed because the speed on the meter is actually vertical speed AND horizontal speed measured together. You only need vertical speed to complete the contract. =)

Thank you for the very nice welcome and for coasting the post to the right place!

I have tried exactly what you have described before (and tried it again just to make sure) with the setup that I described. It this last attempt for example I reached the apoasis of 45km, having the altitude check box green since 42km I waited patiently (for not so many seconds... lol) for the speed check box to go green...but no game

In summary the rocket went up passed 42km, reached the highest altitude of ~45 km, started to fall back to kerbin, and passed through 42km, taking little (high stupidity level) Iruna back home unharmed

I am starting to suspect a bug, given that it is not the first buggish behaviour I encounter...maybe I should have stated before, I am running this in a ps4.

Thank you Geonovast for the info, I didn't know about the run test option, might come in handy. I put some fuel on the flea booster just to provide some weight, I made several testing in sandbox before going for the real deal, and to achieve the most precise apoasis I found that a take-off aiming 80º East is best with the fuel amount combination I described originally.

Thanks Corona (nice beer, but great bottle geometry for the perfect sip!), I made sure to first follow all tutorials with discipline, Prof. von Kerman gave me the same useful hint

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1 hour ago, bewing said:

The speeds in the contracts are always Surface speeds. Never orbital speeds. So for very low speeds, you have to launch vertically -- you can't launch eastward.

It is difficult to get the speed to go to zero at exactly the right altitude, but you can do it by choosing the right SRB with the right amount of fuel. If you throttle the SRB a little bit, you will also lose some altitude and speed.  Additionally, you can turn your craft sideways to increase drag, if you think you are going to go too high.

I launch (slightly) eastward to try to make the trip as vertical as possible, meaning that the utopic goal would be to land almost back on the launch pad. But going vertical as you say (keeping prograde at 0º position during the entire flight) was my first bet, but although orbital speed is minimal at apoasis the surface velocity is too high at 42-46km, ~200-300 m/s.

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OMG I am such a wally

It is indeed as easy as just going up, what a waste of precious Kerbin space funds!!

Sorry guys, I achieved the mission, I just needed to go UP like everyone said! lol what a Newbie indeed

Like in science, sometimes a person just has to come back to the initial first strategy and try it again..and follow the KISS strategy!

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I'm glad you worked it out. Well done! It would be great if you could click the little tick box to the top-left of one of the replies that you feel answers your question most concisely, to mark the issue as solved and others will find it easier to locate the answer when they search for the same problem. Thanks!

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