Science From Jool's Atmosphere and Landing on Duna & Ike?

[The Flying Kerbal]

I'm gonna squeeze a few questions into this one, how's that for efficiency?

First Jool...  I've read and heard on numerous occasions that landing on Jool is impossible and any craft that tries it is going to be destroyed.  But what I'm not sure about is if there is science to be found in the upper layers of the atmosphere which could be transmitted back to Kerbin before a probe would be rendered inoperable?  There's no great rush on this one, a launch to the Jool system is still a long way off, but no harm in finding out these things in advance.

Much more pressing issues are over Duna and Ike.  I'm planning a jaunt in the very near future to fulfil a few contracts which include putting a satellite in a stationary orbit of Duna, and sending science back from the surface of the planet.  I'm also planning on putting together a second lander which could land on Ike, then packaging everything on top of one rocket and lighting the touchpaper.

Now questions:  The lander for Duna is going to be about one ton weight, the science package sits on top of a heat shield which should take the brunt of any heating during descent.  Would a probe as small as this be able to land only with parachutes, or does it need an engine to assist slowing down?  I've tested it pretty extensively around Kerbin, shooting it up to close to a 200K orbit, dropping the periapsis to just 15K and then leave it to gravity to see what would happen.  It came through the whole thing without a scratch, so I know it can certainly take a bit of heat.  However aero braking in the Dunaian atmosphere is a very different thing to Kerbin, so would a similar approach to landing there work too (without such a steep drop though)?

The last question is a simple one.  Is it possible to land a probe on Ike using only RCS?  I've done this successfully on Minmus, but I think Ike has more gravity, but not by much.  I'm trying to keep the weight of the whole package as low as possible, and if I didn't need engines - and the fuel to run them - on my landers, it would make them both super light.

Thanks everyone.

[bewing]

Jool:

IIRC, when you are in LJO, your surface velocity is around 4.5km/s. If you retroburn for a couple km/s of dV, then you can enter anything you want into the Joolian atmosphere. I entered a very standard SSTO of  mine that way. Jool only has 1 biome. The atmosphere is actually very gentle and forgiving -- it's just molecular hydrogen, really. The coldness of the atmosphere absorbs a lot of heat. The atmosphere has the consistency of honey. You decelerate to subsonic very quickly -- and continue to decelerate to below 200 m/s unless you light your engines and maintain a severe nose-down and very low drag attitude. Yes, you can get plenty of "in flight high" science experiment points. And then you can get plenty more "in flight low" science experiment points. What would be extremely difficult to do would be to get back to orbit again, out of the honey. The "surface" is 200km down. The pressure rises very gradually to a bit below Kerbin standard pressure at that point.

Spoiler

It is clear to me that Felipe intended that you should be able to land on Jool, because there is a full set of special experiment results defined for "landed on Jool". However, no surface collider was ever created, so you can't actually do it. I personally think it would be hilarious if you could. OTOH, the current devs have fits if you suggest that players should be able to land, so it's probably not going to happen. What actually happens is that there is a graphics glitch that begins at an altitude of about 2km, so there is a big black area on your screen. You sink (slowly) through the honey down to 0m altitude, and continue to sink through it. At -250m altitude, the kraken eats you.

 

Duna:

Heatshields have very low drag. Duna already has very low drag. If you use a heatshield on Duna, I think you will lose maybe 2 m/s of your speed before you hit the ground. However, it's not that hard to build something that will slow down to below 40 m/s on parachutes -- which is a survivable speed for lithobraking, using standard lithobrake techniques. But you would probably save a bit of mass by having a tiny engine and a tiny bit of fuel, instead of a clever lithobrake design.

Ike:

Ike has gravity very similar to the Mun -- a lot higher than Minmus gravity. To land on non-vernor RCS, I think your lander would have to be impractically small. A spark is probably a better choice.

 

 

 

Edited June 1, 2017 by bewing

[Spricigo]

Landing on Duna only with parachutes is possible,  but the weight of all the extra parachutes may not be worth it.  Personally I prefer to use parachutes to slow down and complete the landing with engines,  requires a trivial amount of fuel. 

For your Ike lander my suggestion Is to drop the RCS and go with an ant engine. The vessel It will be actually lighter and more efficient. Even if your idea is to dock back a light craft can do it with not much extra effort. 

[Gordon Fecyk]

1 hour ago, The Flying Kerbal said:

I'm planning a jaunt in the very near future to fulfil a few contracts which include putting a satellite in a stationary orbit of Duna, and sending science back from the surface of the planet.

If you're not careful with positioning, Ike will eat this satellite sooner or later. The sat will drift closer to Ike over time until it falls in Ike's SOI.

While you can't get precisely Duna-stationary sats because of Ike, you can mirror Ike's orbit and then get a Duna-synchronous orbit that's close enough to stationary.

 

[Spricigo]

1 hour ago, bewing said:

 

Ike:

Ike has gravity very similar to the Mun -- a lot higher than Minmus gravity. To land on non-vernor RCS, I think your lander would have to be impractically small. A spark is probably a better choice.

still very doable. e.g.:

lander can:600kg; scientific instruments: 275kg; antenna 50kg; batterry+solar panels; 55kg; landing legs 60kg; probecore 100kg, reaction wheels 50kg; docking port 50kg; RCS thruster 240kg; monoropellant tank 150kg; monopropellant 1t.

total mass: 2,39t; max thrust 4kN;  ISP 240, deltaV 1270m/s. A bit more monopropellant for safety would be good of course but that is enough to show the feasibility.

 

But not the most efficient, given there is an alternative: no docking port,  RCS thurster and monopropellant -1,44t, ant engines 40kg, fuel tanks 1255kg, LFO 1t.

2,315t, 4kN, ISP 315, 1750m/s.

While the Spark have ISP 320, it also weight 100kg resulting in slight lower deltaV with a much better TWR (arguable excessive but convenient). Personally I go with an unnamed automated rover for science collection, later the rescuees take care of the kerbaled science so the ant is enough for me.

[Loren Pechtel]

When it comes to Jool you can get some of the science without losing your rocket.  Landing is lethal, atmospheric entry is not.  "Flying high" goes all the way to the top of the atmosphere, put your periapsis at the very edge of the atmosphere and collect your science, even the manned stuff.  Stay high enough and a Kerbal in a command seat is fine.  I've never tried an actual EVA.

Beware that the last time I was there the dewarp for hitting the atmosphere was bugged--it was triggering a couple of km into the atmosphere rather than at the very edge where it should.

[The Flying Kerbal]

Thanks for all the answers guys.  It looks like the majority decision is to use engines in both landers.  Well there's no point in me asking for the opinions of experts and then doing my own thing anyway, so I guess it's back to the drawing office to start adding ants to them.

As for the satellite, well the contract is for a PERFECTLY circular orbit of Duna with the Ap and Pe both at 2,880,000 meters with 0 degrees inclination.  It says this is a geostationary orbit, with the vessel over a specific area (which I can't remember right now).  So I'll just give it a wee go and will try to position it as close to the required specs as possible.  If I can hold it for ten seconds I'll get my money, and hopefully Ike will leave it alone long enough for it to help transmit any science back to Kerbin.

This will be the furthest the KSA has sent a mission in my Kerbal Universe to date, and I'm planning on fitting both landers with Communotron 16's while the satellite will be equipped with the RA-2 Relay Antenna.  Would this be enough for transmitting all science gathered from all sources back to the KSC?

 

[TopGull]

There's lots of good advice in here already, but I'll add my 2 cents about the Duna lander.  It's absolutely possible to safely land a small probe on just a parachute, and in my opinion it's an elegantly simple solution. I flew a mission where I stacked up a bunch of drop pod-style landers, and once I got into low orbit around Duna I popped them off one by one for pretty much automatic landings.

Each lander was built with the 1.25m payload bay (containing probe core and instruments), a 1.25m main chute on top, a couple of solar panels on the sides, and 4 cubic octagonal struts for landing legs. A couple of angled sepratrons gave ~200 m/s to deorbit, and since I was already in low orbit I was only dealing with 600-700 m/s in atmosphere. Heating was no issue even without a heat shield.

I think those landers were about 1 ton,  maybe a little less, but they landed slowly enough that the struts survived.