Shakedown Cruise to Dres for a Modular Spaceship

[Syvwlch]

The Mission

Take a new modular SWERV-based design on a shakedown cruise to a new-to-me destination: Dres and plant a flag at the bottom of the planet's famous canyon.

We're bringing about twice the dV we need in the ship because we test-launched the configuration with the biggest hydrogen tank but ideally we want to stay on budget.

The Spaceship

After a couple interplanetary missions built around the SWERV engine, I wanted to stop throwing it away each time. It's not hard to build something that, from LKO, can go orbit anything else in the system and come back without aerobraking... so why not refuel it and go again?

I designed a modular ship with a core including a large cargo-bay, the engine, and a crew pod, to which various sizes of hydrogen tanks can be added either in the bay or in front via medium docking ports. The idea being to launch with minimal fuel & no crew, and then meet with both in LKO at a preexisting station. In the cargo-bay we're carrying a standard chemical-rocket 2-seat lander with 2km/s of dV.

The Station

We are using an LKO space-station with plenty of crew space.

Crew Launch

Crew goes up in a 6-seat SSTO.

Fuel Launch

Fuel goes up in one XL hydrogen tank with medium docking ports on either end along with a remote-piloted orbital tug to dock it to the station. This is excess to mission requirements but serves to prove we can launch this much fuel if necessary.

Ship Launch

Ship goes up crew-less with the lander in the cargo bay and the smallest hydrogen tank docked to the nose which is plenty to allow remote pilot RDV with the station. With the current levels of drags using cargo bays, this was the hardest of the three launches requiring comically large fins to control in the lower atmosphere.

Assembly and Crew Transfer

Ditched the small hydrogen tank and docked with the XL tank at the LKO station. Transfer crew, perform final checks, and we are ready to go!

Departure config: 13.5km/s dV for the ship and 2km/s for the lander.

Next Up:

Dres!

[Syvwlch]

Arrival at Dres

Used a direct-to-Dres ejection near the transfer window, with a fairly large plane change at the node and a tiny mid-course correction to fine tune intercept.

Captured in a 400x400km with significant inclination relative to the rings just to admire the view. 

dV spent to get to this point: 3.8km/s.

Bugs encountered:

The dV estimator seemed to struggle with this design and would sometimes report no fuel left. The engine still worked fine, but this would prevent maneuver planning because the projected trajectory would show no burn occurring. 

Workaround/fix was to disable crossfeed between lander and ship (which do not use the same fuel type). The estimator would still freak out sometimes but it never refused to project a maneuver after that.

[Syvwlch]

Landing

The landing was pretty straightforward.

Undock, adjust plane to place canyon's latitude under orbit on day side, lower periapsis, phase until canyon is where you want it, deorbit, and kill horizontal velocity right over canyon for a landing at the bottom where it's mostly flat.

EVA

The EVA was a little complicated as when Valentina popped out of the hatch the lander would jump up about twice its height. Letting go before the lander settled down resulted in Valentina being on the ground but not landed, so she skated around with her jetpack but could not plant a flag.

After a couple attempts managed to get her to ride the lander's ladder all the way back down, and dismount into a landed state. Sadly, the lander ended up clipped into a rock... tho she remained unphased. (sorry not sorry)

Ascent

Again, nothing too special to report on the ascent. 

Obviously, you need to burn straight up to clear the cliff face, but after that it's the usual dance to align your ascent with the target's inclination followed by some phasing to get a RDV and finally docking back inside the cargo bay.

At this point, if we ditch the lander our ship has 13km/s dV... almost as much as it had in LKO, but the point here is to reuse the hardware so we're bringing the lander (with 600m/s dV of methalox still onboard) back with us.

[Syvwlch]

Return to Kerbin

Did not wait for return transfer window, instead made direct burn to get periapsis down to touch Kerbin's orbit, another fairly large inclination burn, and then phased orbits to get my encounter on the next orbit. I find that easier to do than finding the transfer window experimenting in the tracking station.

With a couple mid-course correction burns, got my capture burn coplanar and coaltitude with the target LKO station, so was able to burn right into my final phasing orbit. Note that burn lasted 82 seconds... we're still very heavy with fuel!

And we're home with 6.4km/s of dV left in the ship, having spent 3.3km/s on the return. That's 47% of our starting LKO dV excess to requirements.

We could easily have done this with the next size down in hydrogen tanks, or we could have brought a lot more methalox along, to refuel the lander between visits to the surface.

[GalileOh-No]

I really like your assembly scheme, especially the lander/main engine combo + reusable modular assembly. For whatever reason, I want to build more hydrogen-based craft but struggle to keep them from turning into giant spacenoodles.

[Syvwlch]

Thank you!

I went thru the following evolution:

1. Duna Mission

Engine/Tank/Crew-Compartment with Lander on the nose:

2. Eeloo Mission

Moved the lander into a cargo bay, used a larger tank:

3. Dres Mission

Switched to modular reusable design, per rationale above.

I haven't tried launching that last configuration from the KSC. I struggled with the ship launch even with the smallest tank, but with enough fins and strap-on boosters I think it would be doable. This is more about trying something different and more interesting.

[Dunas Only Moon]

Ok.. I dare you to make a single launch eeloo mission.

This should be easy too.

[Syvwlch]

Already done, albeit with an earlier version that wasn’t modular. I can dig out the screenshots if you’re interested?