Xeldrak

What did you do in KSP today?

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Besides watching the Falcon Heavy launch (which was amazingly well done), I made a sort of testbed for a landing system for a replica. Hopefully this will be a pretty nice replica. Worried though cause its already at 300 something parts....

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Obligatory explosions

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And something from yesterday. Not too particularly happy with it, but it does look quite nice. Have to give credit to XB-70A for at the very least inspiring the design.

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I began work on a side friction roller coaster today.

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The track works well going straight, but I'm still working on turns

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The first turn I built was too flat, and the car slowed to a crawl. The second version, shown above, was too fast, and the car fell out. I'm thinking of trying to bank the turn.

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1 hour ago, qzgy said:

Besides watching the Falcon Heavy launch (which was amazingly well done), I made a sort of testbed for a landing system for a replica.

Uh.. Glad I'm not the only one..

Finally sent some semi-permanent crew up to the space station, since assembly has progressed far enough for habitation and life support.  But instead of keeping a shuttle up there all the time, I went with a Kerbin return pod.  SSTO Rocket with the lifter brought down with landing legs...although no effort was made to get it back to the KSC.

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Landing the lifter needs some practice.  Once I get it down without 'sploding an engine or two, I might try to get it to the KSC.

Edited by Geonovast

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So, what I've done today:

I gave up on removing "superfluous" Baby Sergeant stages from my NK-9 based sounding rocket. Sure, I don't need the delta-V... but I do need the mass up there to keep the thing aerodynamically stable.

 

On the unmanned end of things: this is now my second failure to get a radar mapping satellite to the Moon. The contract deadline is generous, but the financial people are getting upset. The first time was a bog-standard rocket failure on a Soyuz-Agena 1.

The second launch used the new Soyuz-Agena 1.1, the sole difference being that I'm using the 8D75K versions of the RD-107 and RD-108 engines, which have better performance and reliability... though I'd shell out the extra 100f/engine gladly just for the reliability improvements.

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The issue this time was an antenna malfunction that left the probe out of contact when it reached the Moon. An attempt was made to set up a kOS script to handle everything, but it failed for an utterly inexplicable reason. The nature of the antenna malfunction? This, we do not speak of.

I forgot to add a long-range antenna in the first place.

 

Mariners IV and V conducted flybys of their targets: Mars and Venus. An interesting peculiarity: Mariner IV left its magnetometer offline during much of the approach to conserve electricity, whereas Mariner V, closer to the Sun, did not.

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Mariner V's night-side transit of Venus happened to leave it in such an orbit that, by expending about half the remaining hydrazine propellant, it could arrange a second flyby of Venus, which will occur in about a year.

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On the crewed end of things, I am happy to report that there is a crewed end of things. Mercury 7* orbited Earth three times with Natalya Tseydlerina onboard, and Mercury 8, with Yana Gagarina** onboard, launched from Vandenburg into a polar orbit that lasted almost 18 hours. Both are in absolutely perfect conditions from perfectly safe 13G MECO of the Agena E booster and 9G reentries, and are not in the hospital.

*After the failed pad abort test, the successful pad abort test, the in-flight abort test, the totally-planned in-flight full-stack abort test, the unmanned test, and the test with Cheese the Space Monkey onboard.

**The resemblance to Yuri Gagarin has not escaped me, but Yana was a scientist and I wanted a pilot on the first flight just in case.

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Yana Gagarina even conducted a short EVA: data from this EVA will be used to scream at design bureaus until they make a better space suit enable more ambitious EVAs in the future that consist of more than clinging to the hatch.

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At least one more Block 1 Mercury spacecraft is on order, with the goal of rendezvous with an Agena target vehicle. This Agena vehicle will be a modified Agena-A upper stage, with solar panels, more antennae, and helium cold-gas thrusters instead of nitrous oxide thrusters so that RCS exhaust does not damage the Mercury vehicle. After this, however, the Mercury design may either be extended for more ambitious goals, or replaced by a "Gemini" proposal for a 2-seat, more advanced vehicle.

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Jade Station and all its infrastructure are finally, officially done. There was cake at mission control.

The station itself is complete, the mining base works like a charm, the science lander has proven capable, and now the final piece, the fuel lifter, has proven itself as well. It got to Minmus, landed, picked up a full load of fuel, took off, and docked with the station. Most critically, it did this and still transferred a good amount of fuel into the station's orange tank. I now have my first working, replenishable, orbital fuel station. There's an extra kerbal on board now (piloted the lifter over) who needs a ride back home, but after that...

Duna, here we come!

 

 

Oh, also I launched a sentinel satellite into orbit around the sun just slightly farther out than Kerbin itself. But nobody cares about that.

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Sent Valgas on a training mission to Minmus.

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He does have a way of getting into unusual scrapes. Resilient though, survived this one too.

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Got really really annoyed with Ion Engines!  (or rather by my sloppy design of Ion powered craft)

 

I launched 4 Ion powered ScanSat satellites for Eve, Gilly, Duna and Ike a while back and had them parked in orbit waiting for the window.  What I'd failed to take in to account though was that a large part of the burn would need to take place in Kerbins shadow, and they each only had enough battery for probably 100m/s burn.  I ended up pushing the Ap out near the limit of Kerbin SoI over 5 or 6 separate orbits before the final ejection burn of around 200-300 m/s, and still had to make adjustments once they cleared the shadow in order to get an intercept.  For 4 bloody satellites!  Won't be doing that again in a hurry.

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I've never managed to do anything interesting with ion engines. Things are just so slow.

Closest to interesting that I got was making a sun-diving probe, but I must've gotten some numbers wrong because the antenna I put on it was too weak and I couldn't reach it just when it was time to do some science. Might do that again one of these days...

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I don't really find the speed much of an issue, you can run the burns at 4x speed easily, and I thought a light weight satellite with over 4km/s dv would make life simpler.  I was wrong :D

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So... I want to ask some question. Does placing high-gimbal engines on top of rocket (like on nosecone or around upper stage) works better for stability compared to having engines placed on the bottom like regular rocket?

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3 hours ago, ARS said:

So... I want to ask some question. Does placing high-gimbal engines on top of rocket (like on nosecone or around upper stage) works better for stability compared to having engines placed on the bottom like regular rocket?

Generally speaking, the closer to the nose the engines are (gimballed or not), the more stable the craft. If you manage to put the centre of thrust in front of the centre of mass, it's passively stable: the mass is being pulled by the engines rather than pushed by them.

In practice it's not an issue most of the time though; instability is usually caused by balance or aerodynamic problems. For example, having a light, draggy payload at the nose and heavy, slippery engines and tanks toward the rear will make the rocket want to flip backwards while in the atmosphere. Or if the CoM and CoT don't line up, it will want to turn in some direction when firing the thrusters in space.

(This means that sometimes a gimballed engine at the tail can help stability -- for example, I put one on the tail of my big, asymmetrical spaceplanes, where it cancels out the thrust torque caused by having the CoT below the CoM.)

Edit: Crossed out a bit of incorrect information. See the posts below -- I was mistaken about this. Engine position along the axis of CoT does not matter with regards to stability.

Edited by Brikoleur

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I've been doing dress rehearsals for Operation Beach Head simultaneously using the old 2x Aquila system and the new Gizmo device.

I realized today, that in addition to:

Gizmo is a:

  • heavy lifter [LKO]
  • it's a super tanker
  • it's an orbital fuel dump/habitat
  • it's an interplanetary transit vehicle
  • and it's an expeditionary force

It can also be:

  • a lunar hotel (occupancy 30)
  • a Telemagic control tower

I tried Twin Boars and reverted to Mammoth.  Especially with a load on the payload deck, it is going to need them.  I also went to the same 6-way symmetric configuration Aquila uses, as it gives more combinations for balancing payload symmetrically.

And I added 7x HitchHiker cabins on the ground floor to serve the lunar hotel role.

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Spoiler
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The nukes are ugly[*].    They give the "hotel" the ability to relocate, I guess.  Otherwise they can be jettisoned and scrapped (via the Tracking Station).

 

* yeah, I know.  "everything I do is ugly..."

  but functional! :)

Edited by Hotel26

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6 hours ago, Ace in Space said:

Jade Station and all its infrastructure are finally, officially done.

I'm a craft file now? :confused:

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3 hours ago, Brikoleur said:

I've never managed to do anything interesting with ion engines. Things are just so slow.

Closest to interesting that I got was making a sun-diving probe, but I must've gotten some numbers wrong because the antenna I put on it was too weak and I couldn't reach it just when it was time to do some science. Might do that again one of these days...

One of the thing I use the ION engine for is to put those with a tiny tank on communication relay satellite. I am not delivering the sat with that engine, yes way too long, but I have those in place if adjustment to the altitude/trajectory is necessary. They can get the job done :)

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Bervey Kerman made it up to the peak and planted the flag at the Crater Rim Tracking Station.   Hurrah!  Next challenge:  the crashed flying saucer!

2 hours ago, Brikoleur said:

Generally speaking, the closer to the nose the engines are (gimballed or not), the more stable the craft. If you manage to put the centre of thrust in front of the centre of mass, it's passively stable: the mass is being pulled by the engines rather than pushed by them.

That was the idea behind the design of Goddard's first liquid-fuelled rocket, wasn't it?   Nozzle out front?

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After hours editing the config files, I finally started my new carrer save, with an (almost) realistic progression.

dxtmH97.pngThis is the Low-Atmosphere Data Collector, the first rocket launched in this save.

5rZJ5ah.pngThe rocket breaking the sound barrier...

5rjT50k.png...And falling.

Eq5OmMp.pngParachutes opened!

wdtA6so.pngAnd the rocked landed near to the Launchpad.

And this is just the beginning of an long journey...

 

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2 hours ago, Brikoleur said:

Generally speaking, the closer to the nose the engines are (gimballed or not), the more stable the craft. If you manage to put the centre of thrust in front of the centre of mass, it's passively stable: the mass is being pulled by the engines rather than pushed by them.

 

7 minutes ago, MaxwellsDemon said:

Bervey Kerman made it up to the peak and planted the flag at the Crater Rim Tracking Station.   Hurrah!  Next challenge:  the crashed flying saucer!

That was the idea behind the design of Goddard's first liquid-fuelled rocket, wasn't it?   Nozzle out front?

Yes: Goddard fell prey to the pendulum fallacy. Aerodynamics do not actually work that way, unfortunately, or it would've been an elegant design. The key issue is that the engines are falling at the same rate as the rest of the rocket.

Scott Manley on the subject: https://www.youtube.com/watch?v=Tx4cjP-GRAY

Anyways, on my end, just unlocked early hydrolox engines, and I'm playing with various Centaur-like upper stage designs. I toyed with Vulcan-style reusability, but that drives up cost of a 2-engine Centaur by 45%, mass by 5%, and reduces dV by 7%. Fuel lines are expensive in RP-0, and that's the only way to bypass the heat shield. Given that a lot of these Centaur uppers will be used to eject well past LEO, I decided to just go with an expendable design.

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3 hours ago, ARS said:

So... I want to ask some question. Does placing high-gimbal engines on top of rocket (like on nosecone or around upper stage) works better for stability compared to having engines placed on the bottom like regular rocket?

Short answer? No. If the rocket is extremely long and thin than having the engines on top does make it more structurally sound which could increase stability. But there is a difference between structural stability, and flight stability. The idea that having the engines in top keeps the rocket stable comes from the idea that it will act as a pendulum, however in a pendulum the arm is suspended on some kind of joint allowing it to rotate freely, and most importantly, it is attached to something which is being held up vertically, counteracting the force of gravity. If you glued up the joint of a pendulum such that it couldn't rotate, it wouldn't work, and if a pendulum was in a free fall in the air, it wouldn't work, and if a pendulum was being accelerated on a rocket which was traveling at 45° from the horizontal, the pendulum wouldn't point straight down, it would point in the opposite direction of it's acceleration, which in this case would be 45° from the horizontal. The Pendulum fallacy, as some call it, comes from the earliest days of rocketry and is an example of a concept formed not out of calculations and testing, but rather common sense logic, which isn't always reliable.

Edited by Kronus_Aerospace
Correction

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19 minutes ago, Starman4308 said:

Aerodynamics do not actually work that way, unfortunately

... thinking about it ...

Hey, you're right, it doesn't. I always thought of my craft in terms of CoM and CoL so I never gave this much thought. In air the only thing that matters is that the tail is draggier and lighter than the nose, and in space that the CoT lines up with the CoM longitudinally. 

This is what I love about KSP (and talking about it) -- you learn something every day!

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4 minutes ago, Brikoleur said:

... thinking about it ...

Hey, you're right, it doesn't. I always thought of my craft in terms of CoM and CoL so I never gave this much thought. In air the only thing that matters is that the tail is draggier and lighter than the nose, and in space that the CoT lines up with the CoM longitudinally. 

This is what I love about KSP (and talking about it) -- you learn something every day!

Another thing people often times do not take into account is drag, an aircraft can be perfectly balanced in terms of it's trust and CoL and CoM placement, as in they are right on top of each other. But drag forces could cause the craft to pitch down or up if left to it's own devices. Another thing is when flying SSTO space planes it is best to take flight profiles that require minimal user input, because of the drag generated by the control surfaces. I have had many craft in which drag was actually the cause of my stability problems. Having more drag in front of the CoM than behind it has a very similar affect to having the CoL in front of the CoM, as it will cause the craft to flip over backwards, we all know this from aero braking with a rocket and having it flip around 180 degrees, but we rarely think about the force of drag the same we do with lift and thrust, even though we should.

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8 minutes ago, Kronus_Aerospace said:

Another thing people often times do not take into account is drag, an aircraft can be perfectly balanced in terms of it's trust and CoL and CoM placement, as in they are right on top of each other. But drag forces could cause the craft to pitch down or up if left to it's own devices. Another thing is when flying SSTO space planes it is best to take flight profiles that require minimal user input, because of the drag generated by the control surfaces. I have had many craft in which drag was actually the cause of my stability problems. Having more drag in front of the CoM than behind it has a very similar affect to having the CoL in front of the CoM, as it will cause the craft to flip over backwards, we all know this from aero braking with a rocket and having it flip around 180 degrees, but we rarely think about the force of drag the same we do with lift and thrust, even though we should.

This is all true.

I would add another thing: CoL shift when changing pitch. This happens especially easily if you have lifting surfaces near the nose... in particular, canards or Mk2 spaceplane parts. Even if the CoM and CoL look perfectly fine in the hangar and your plane behaves perfectly decently when handled gently, it might suddenly flip to unstable when you pull a harder manoeuvre.

Last time this bit me was with the Abaddon, my second attempt at visiting Eve by plane. Orpheus with a redesigned nose made it.

I also share your experience with launch profiles: in particular I've found the often-recommended straight-and-level (or nearly) high-altitude acceleration run is self-defeating because any speed you gain with it is lost manoeuvring out of it. Planes that have enough thrust that you can just fly them to ca 5k and then point them up at somewhere around 17 degrees, give or take a degree or two, tend to ultimately burn less fuel getting the job done (as well as being less fussy to fly). 

Edited by Brikoleur

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I had a pretty slow day over all yesterday. The day started with the Duna atmospheric entry of the Waste of Time 7 parts testing probe, which was sent to conduct a test of Kerbaloons parachutes in the Dunan atmosphere. The craft reached the target parameters and conducted the test successfully, but the intended return to orbit did not take place owing to a lack of delta-V. The craft sat down along the equatorial midlands around 12 m/s, fast enough to smash the engine though the module itself survived; it has been re-classed as a relay and will remain on the surface of Duna. The replacement contract was to rescue engineer Edfield Kerman from the orbit of Ike. The Ikeport space station's Spamcan 7a lander was dispatched to retreive Edfield from his shipwreck, affecting a successful rendezvous and pickup.
 

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Edfield clutching to the side of the Spamcan over Ike with his debris tumbling off in the background. Makes you wonder how he got into this mess in the first place, you know?

Edfield will return to Ikeport later today if all goes according to plan. Since Laggin' Dragon currently docked at the Dunaport space station has an extra seat available, I'll probably send him to join the ongoing Second Duna Expedition upon his return to the station. 

Not much else happened. The Boop-Boop 7a probe Kerbin Omicron (yes, I'm up to Omicron - fifteen unnecessarily probes over Kerbin and only enough Greek letters for another nine) was put into equatorial Kerbin orbit for contract. Pilot Helming and engineer Suus Kerman finally got to Minmus directly from Mün in their Gusmobile 7 craft after a 28-day transit, and a new Exxon Valdez 7a heavy fuel module was docked up to the Kerbinport space station. I have plans to go pick up engineer Dilnard Kerman from the Hojo Alpha outpost on Mün with the rover Indecision at the Piper Alpha refinery to bring him to the refinery in order to perform a recharge job while Leedorf is visiting Duna, but I plan to wait for local daylight before that happens. I also need to start the excursions of the second Duna expedition to the Dunan surface.

One last thing I have in the pipe is the replacement of Necessary Evil's heat shield, which is snugged in tightly on the bottom of the craft's CM and itself covered with the craft's SM, and due to time spent in close proximity to Kerbol is completely depleted at this point. Planning for this repair mission began yesterday with the design of I Like Hubcaps 7, which will take six Kerbals up to perform a KAS repair job. Definitely going to be one of the largest and probably convoluted repair jobs I've ever done, but I'm hopeful when everything's said and done that the craft's emergency ejection system will still work if it's ever needed. Screenies on that one for sure.

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