Lowest cost per ton to LKO

[Temstar]

After being away from KSP for ages (since 0.21) I decided to come back to try it again. Love 1.05 so far, career is really cool with contracts and now having to worry about budgets and cost of your launch vehicles.

Which brings us to the point of this thread - in my days the only stat for a launch vehicle that really mattered was the payload fraction, we never really paid attention to the cost of parts back then. Now that we have to pay for launches the "cost per ton to LKO" is becoming very important. In your experience what method of putting payload in orbit nets you the lowest cost per ton?

I've tried a fully recoverable, aerospike powered SSTO rocket that can put a 10 ton payload into 75km x 75km orbit, payload fraction just under 10% . If I'm very accurate with landing and get it near KSC it costs me about √7000 to recover, refurbish and refuel the launch vehicle, so that's √700 per ton. Is this a good number? It seems in 1.04 version of the stock payload fraction challenge people are getting upwards of 40% payload fraction with SSTO spaceplanes. Is SSTO spaceplane now the king of low cost to orbit?

[Venusgate]

[quote name='Temstar'] Is SSTO spaceplane now the king of low cost to orbit?[/QUOTE]

It's totally a playstyle thing.

SSTO rockets are likely to have a lower payload to cost rate, even with airbreathing engines, but they are also significantly easier to design, and fly, and take much less time and skill to re-enter.

Re-entry is no[B]w [/B][SIZE=1](thanks, Starhawk)[/SIZE] significantly more challenging than in previous versions, so designing for it can be a struggle if you're not just going to slap a handfull of heatshields on your vessel. Edited November 17, 2015 by Venusgate

[Starhawk]

The thing with spaceplanes is that, once you get the hang of it, you can put your vehicle right back down on the runway for 100% recovery and thus you pay only the fuel costs. In my experience this is the lowest cost method.

It does take significantly longer to design and tweak a spaceplane than a rocket, though. So, as Venusgate indicated, it depends on your playstyle.

It may be that Venusgate intended to say that reentry is [B]now[/B] significantly more challenging than in previous versions... If so, I would agree.

Happy landings!

[GoSlash27]

Absolutely, SSTO spaceplanes are the king of low cost to orbit.

The downside is that you have to actively recover it in order to reap the savings and the penalty for failure is high.

If you want to orbit payloads for cheap and not spend most of your time recovering the launch vehicle, a 2- stager with a SRB lower is the way to go. It does demand better design skillz to go that way, but for one- off launches it's hard to beat.

Best,
-Slashy

[Temstar]

I suppose a SSTO spaceplane does place some restrictions on payload because of cargo hold dimensions. Payload with very offset CoM might also upset the balance of the plane. For oddball payload one might still need rockets.

But fuel and crew (the two things that need the most trip between surface and LKO) don't actually need a cargo bay so can benefit the most from a workhorse SSTO spaceplane.

[Starhawk]

[quote name='Temstar']I suppose a SSTO spaceplane does place some restrictions on payload because of cargo hold dimensions. Payload with very offset CoM might also upset the balance of the plane. For oddball payload one might still need rockets.

But fuel and crew (the two things that need the most trip between surface and LKO) don't actually need a cargo bay so can benefit the most from a workhorse SSTO spaceplane.[/QUOTE]

My thoughts exactly.

I still use cargo spaceplanes for certain things, but the dimensions of the cargo bays restrict what they can be used for.

Happy landings!

[KerikBalm]

Not really, that's what fairings are for:
[img]http://i.imgur.com/wrNkvOF.png[/img]

[img]http://i.imgur.com/FOfPjuO.png[/img]

That's my design updated for 1.05, just as capable as before (more or less).

After 2 launches in 1.04, I had this:
[img]http://i.imgur.com/sakQadZ.png[/img]
Pretty much if you can launch it with a rocket, you can launch it with a spaceplane.

The cost of the fairing adds to the cost per ton to orbit, but its still under 300 funds per ton to orbit for such oversize payloads

[Starhawk]

[quote name='KerikBalm']Not really, that's what fairings are for:
[URL]http://i.imgur.com/wrNkvOF.png[/URL]

[URL]http://i.imgur.com/FOfPjuO.png[/URL]

That's my design updated for 1.05, just as capable as before (more or less).

After 2 launches in 1.04, I had this:
[URL]http://i.imgur.com/sakQadZ.png[/URL]
Pretty much if you can launch it with a rocket, you can launch it with a spaceplane.

The cost of the fairing adds to the cost per ton to orbit, but its still under 300 funds per ton to orbit for such oversize payloads[/QUOTE]

I thought of your stuff briefly while I was typing my previous post.

I should have said that the dimensions of cargo bays restrict what [I]my[/I] spaceplanes can be used for.

Happy landings!

[Pecan]

Landing anywhere close to KSC will get you 90% or more of your costs back. The main drawback to planes such as KerikBalm's is, obviously, the huge initial investment and the single-point of failure (as Slashy said). A SSTO rocket for any payload will cost considerably less than a comparable spaceplane, so you have to ask yourself how many times you're likely to use a particular model. I've found that a typical spaceplane (if there is such a thing) pays for itself after 3 - 5 flights. For that reasons most of us only use spaceplanes, if at all, for fuel and crew to orbit, as you suggest if interested in economics. Note, however, that with ISRU (ore mining) in particular it is quite possible to make a Single Stage vehicle to anywhere and there are a number of people who specialise in such things. Edited November 17, 2015 by Pecan

[KerikBalm]

Well, a *single point of failure* can be mitigated by in orbit construction. Even with my huge SSTO, I'm putting together some payloads that are 3 or even 4 pieces.

My main laythe mission is composed/going to be composed of the following:
*ship/station core that will serve as a fuel depot, orbital hab and research lab in laythe orbit (detachable 4x LV-N propulsion unit to also serve as a tug and leave the ship as a station)
*Additional habitation module mounted so it could plausibly spin to generate gravity for the long journey)
*Ejection stage (will be reused, but stays in Kerbin SOI) to send it on a Jool intercept
*Laythe lander - launches itself, a 6 kerbal amphibious SSTO seaplane, with a full complement of science instruments

A scanning probe is already on the way, I don't know if I'll find a good ore spot or not, if I do... I may make a mining ship to take fuel up to the orbital depot, or I may mine on Val.
I'll probably also want to send a surface Hab down to laythe, I may want to use the station-ship to remain a station.. in which case I'll launch another ship that can rotate a hab section (unless I re-use the one currently in Duna orbit), or I'll take the kerbals back with it... and I may want to send a non-rotating station to be in permenant laythe orbit.

That's already the "3-5 flights" for the laythe mission I've set up.
I already flew multiple flights for my Eve mission (station, Gilly ISRU, a single use eve lander)
I also sent a ship (rotating hab, 2 launches), a station, 2x ISRU (1 for duna, 1 for Ike), a rover, a LV-N tug, 2x surface habs to Duna.

Then there was my 2 flight launch of the moho mission, and single flight launch of a Dres mission...
So yea... its getting plenty of use in career.