Rocket Sizes for extra-planetary exploration

[Chads]

Hello!

I've gotten to where I can get to Minmus and the Mun easily, and have labs around both.  I even got my rover to the Mun finally (now I understand why my previous rover questions were met with a collective, 'meh' from the group. )

I haven't done much with space planes yet, and I'm thinking my next step is to start visiting the other planets.  I need roughly 10000 science points to finish unlocking the whole tree.  I do have many biomes to exploit yet on both the Mun and Minmus, but I've gotten the low-hanging fruit.

So, for my first probes to other planets, I'm trying to decide if less is more, or if I need to power of the really big guns that are out there.  I've only got about 1 million in cash (I forget what it's called), and still have some key upgrades to make (Kerbonaut center needs one more upgrade, as does Admin and the plane hangar).  I've been concerned about running out of funding.  Perhaps I shouldn't sweat it.

[Foxster]

Umm, is there a question there?

[Spricigo]

3 hours ago, Chads said:

So, for my first probes to other planets, I'm trying to decide if less is more, or if I need to power of the really big guns that are out there. 

Depends, less can be more and more can be more. Take the Tsiolkovsky Rocket Equation:

 

more I_sp  is more deltaV

more m_total  is more deltaV

more m_dry  is less deltaV

That said,  1.000,000,00 seems enough to a lot of exploration. If you can do kerbaled missions to surface of  Mun/Minmus and back, you also have Duna, Ike and Gily just a small step further, and Eve if you don't mind one way missions. Flyby missions may require more precision but not  more deltaV or thrust than a regular Moon landing and return.

 

[Reactordrone]

You can shoot probes to Duna fairly cheaply and if you send a few at a time they can act as mutual relay satellites.

 

 

Edited July 14, 2017 by Reactordrone

[Wanderfound]

You can get a crewed return mission with a full science load to pretty much anywhere for under √200,000.

 

 

A one-way probe mission to just about anywhere can be done for pocket change; √20,000 or less. For an easy target like Duna, a very small and low-tech rocket can manage it; just a few thousand credits.

[WanderingKid]

12 hours ago, Chads said:

I've gotten to where I can get to Minmus and the Mun easily, and have labs around both.  I even got my rover to the Mun finally (now I understand why my previous rover questions were met with a collective, 'meh' from the group. )

I personally find spending 20 minutes wandering around Mun playing avoid the crater to complete a crappy little contract relaxing on occasion, but I'm weird.

12 hours ago, Chads said:

So, for my first probes to other planets, I'm trying to decide if less is more, or if I need to power of the really big guns that are out there.  I've only got about 1 million in cash (I forget what it's called), and still have some key upgrades to make (Kerbonaut center needs one more upgrade, as does Admin and the plane hangar).  I've been concerned about running out of funding.  Perhaps I shouldn't sweat it.

Nope.  If you're sitting at 1 mill in funds you're in a good position for any launch.  It comes down to "What do I want to do".  For reference: Getting to Duna, without a landing and with a decent aerobrake is about as expensive as Minmus with landings.  It just requires higher precision and correct timing for the transfer.  It costs 950 to transfer out to Minmus, and about 1150 to get out to Duna.  Capture with Aerobrake (it takes a few revolutions) and you don't even worry too much about the cost of braking in system.  Returning, however, will cost you a good clip, unlike Minmus.  I forget how much offhand.

So, no, you really don't need the big guns.  If you're just bringing a series of satellites and probes, 1.25m parts are all you should need, though you'll want the RA-2 antennas, and the RA-10 is better for a mothership.  It's only when you start needing to transport landing craft and the like that you'll be looking at really wanting to invest in a modular 2.5m build out.  The 3.5 meter stuff I find to be overkill, usually, unless you're launching huge stations.  For my usual games they only come out when I've just reached 'Ah, heck with it' levels of "Let's visit MOHO!.. and land in the hole!... TWICE!.... WHEEEEE!"... or I'm launching some insane rig for the joy of it.

[qzgy]

I've got this neat little vector based SSTO that can probably do a grand tour lite (grand tour minus eve landing and return). That might be useful, except a bit high in the tech tree.

But for larger, more interplanetary missions, high ISP and delta-v numbers are very nice, actually almost essential. Depending on where you need to go and when, that kinda dictates the size. Almost always, for high efficiency missions, you have to sacrifice TWR. Doesn't necessarily mean bigger, but bigger is always more impressive. A couple of 2.5m parts will probably do for most places.

Maybe a neat idea would to be a couple Jool fly-bys and return. You can capture into joolian orbit using Tylo very easily, and set-up some maneuvers to hop in and out of SOIs before falling back to kerbin. Not sure of the delta-v budget though. 4000 to 5000 m/s of dV might work to go there and back, and hit up some nice science. You could also, as others mentioned, carry a couple of piggy-back probes/impactors to crash land and send some science back.

Edited July 14, 2017 by qzgy

[Chads]

I appreciate the feedback.  My Duna window is coming up in about 70 days, so I'll probably give that a try with a probe first.  I think I have a contract to put a satellite in orbit around Duna, too, so I'll give that a try.

I appreciate the pictures.  It helps confirm that I've got the right idea on some of these.

13 hours ago, Reactordrone said:

 

Reactordrone, what's the engine on this guy?  I can't quite tell.  Looks like you put the whole thing in a fairing?  I've just started playing with those in earnest.

[Rocket In My Pocket]

25 minutes ago, Chads said:

Reactordrone, what's the engine on this guy?  I can't quite tell.  Looks like you put the whole thing in a fairing?  I've just started playing with those in earnest.

I can't say for sure but I'd wager it's the Spark.

http://wiki.kerbalspaceprogram.com/wiki/48-7S_"Spark"_Liquid_Fuel_Engine

Also, as a roundabout way of answering your original question here's a quick pic of my most recent career save's manned Duna orbit and return mission, as you can see it's not terribly large and only uses a Terrier engine. It was sent up empty by a launcher and then fueled up at a station in LKO.

Edited July 14, 2017 by Rocket In My Pocket

[Cpt Kerbalkrunch]

@Chads Not to be glib, but your interplanetary ships can be as large or small as you want. It simply depends on what you intend to do when you get there. Are you going unmanned, or sending Kerbals? That will dictate what size ship you need, for the most part. For my first forays beyond Kerbin, I sent four ships at roughly the same time (which I thought was a lot back then). Two ships went to Duna/Ike and the others went to Eve/Gilly. The first ship of each pair was a probe with a survey scanner (and all the other science equipment I had), and the second was a manned ship with 2 Kerbals (a pilot and an engineer) and drills/converter. Each probe went to its planet and scanned for ore, then went to its moon and did the same.

Since I was completely inexperienced, and had no idea what to expect, I felt that this approach would give me maximum flexibility and a good safety net. Each ship would land on its planet, mine for ore and refuel, then head to its moon and do the same before going home. Your already on the forum, so you probably know more than I did at that point. In which case, you can probably guess that I went 3 for 4. The Eve mission was a spectacular failure. Or perhaps a "successful failure". I learned a lot, and since I just reloaded and went to Gilly instead, I probably saved myself a huge hassle because, knowing what I know now, the ship never would've left the surface anyway.

Anyway, after launching the 4 vessels, I was so broke I couldn't afford to launch another. I had to timewarp ahead and complete the missions. I had taken about half a dozen contracts, and all of them cashed in (except plant flag on Eve; took another decade before I tried again). The money I got from those contracts (not to mention the ton of science) propelled my entire space program, and I've never looked back. So, I wouldn't sweat the cash. Just accept the contracts and bring what you need to fulfill them. And if you can grab more doable contracts on the way, grab 'em. Afterward you'll see, interplanetary contracts are so lucrative that they pay for themselves with some cash left over. And if you stack contracts, you'll have a lot left over. Soon you'll be swimming in cash and won't need to worry about it at all.

So, my recommendation? Send some Kerbals. It's always more fun, I think. And the experience (for you and your Kerbals) is invaluable. Hope all goes well.

[Spricigo]

36 minutes ago, Rocket In My Pocket said:

I can't say for sure but I'd wager it's the Spark.

http://wiki.kerbalspaceprogram.com/wiki/48-7S_"Spark"_Liquid_Fuel_Engine

Also, as a roundabout way of answering your original question here's a quick pic of my most recent career save's manned Duna orbit and return mission, as you can see it's not terribly large and only uses a Terrier engine. It was sent up empty by a launcher and then fueled up at a station in LKO.

Yes, its a spark. But keeping in the tradition of roundabout way of answering I offer this lander. (Delivery vessel sold separately)

1 hour ago, Chads said:

I appreciate the feedback.  My Duna window is coming up in about 70 days, so I'll probably give that a try with a probe first.  I think I have a contract to put a satellite in orbit around Duna, too, so I'll give that a try.

My suggestion: send a bunch of satellites. One to fulfil the mission objective and a few to start to setup the relay network.

I setup my network around each planet with:

• A pair of Long Range Relay in polar elliptical orbit, one with apoapsis over the north pole and the other over the south pole. The apoapsis is vary high but still  low enough to reach a vessel with a single communotron 16 at the equator.
• Four Short Range Relays in a square formation, equatorial orbit a distance from the surface equal to the radius of the celestial body (320km for Duna).

Details:

Spoiler

 

My typical short range relay satellite is an probecore OKTO, oscarB fuel tank, ant engine, 3xOX-4L solar panel around the octo, Z100 battery,  thermometer and HG-5 antenna. (it cost 4750, weight 467,5kg, have 1700m/s and 0,5 TWR).  Four of those (plus 3x TR-2C separators an decoupler) weight about 2t.

A FL-T400 and a spark, carrying the short range satellites, provides 1900m/s with 0.5 TWR, plenty to go from Low Kerbin Orbit to Duna Orbit*.  Put everything inside a 1,25 fairing and design a launch vehicle to put it in Kerbin's orbit (The CoM will probably be very low, to avoid it flipping during ascent don't use fins...use wings).

The long range satellite antenna will depend on the required range, otherwise pretty similar to the short range relay. For Eeloo, Jool and Dres RA-100, for Duna, Eve and Moho, RA-15, HG-5 for others.

*Actually enough to reach any celestial body (with use of gravity assists) but that is besides the point. One can always add more fuel and change to a more efficient engine to increase deltaV.