Quote from: Comga on 04/02/2017 06:09 amWhy else would you assume direct injection?Does it make it easier or harder, more or fewer, longer or shorter windows?I honestly don't see an advantage. I think it's just all these old thoughts sitting on hold in my head while SpaceX slowly improves their capabilities making them irrelevant.
Why else would you assume direct injection?Does it make it easier or harder, more or fewer, longer or shorter windows?
I still don't see how this mission can be accomplished. AFAIK there are no planned launches for FH with a Dragon capsule before 2020 other than this, and only two FH flights total. It seems almost impossible to imagine that the third FH flight and very first FH Dragon flight will be a manned tourist flight.Unless SpaceX has several other FH flights up their sleeves, this mission sounds very improbable.
It was stated be Elon Musk that center core of FH9 had to be redesigned so it probably is not to be considered 'pretty much the same' as F9 core.
Quote from: QuantumG on 04/02/2017 06:35 amQuote from: Comga on 04/02/2017 06:09 amWhy else would you assume direct injection?Does it make it easier or harder, more or fewer, longer or shorter windows?I honestly don't see an advantage. I think it's just all these old thoughts sitting on hold in my head while SpaceX slowly improves their capabilities making them irrelevant.Direct ascent would mean a narrow window. You could do it from all four pads instead of just three.There are certain performance advantages that a free return could get from it. In one scenario, you might even get the side benefit of easier core recovery, possibly even RTLS. And, from a standpoint of operations, you get a much simpler mission profile, while losing the potential safety advantage of ECLSS / human / SC checkout before TLI.Been thinking about this too. One interesting aspect is to align the trajectory along a certain lunar gravimetric gradient of mascons, which nicely fits with a Vandenberg inclination direct ascent on the asymmetrical free return.
Quote from: Space Ghost 1962 on 04/02/2017 06:42 pmDirect ascent would mean a narrow window. You could do it from all four pads instead of just three.There are certain performance advantages that a free return could get from it. In one scenario, you might even get the side benefit of easier core recovery, possibly even RTLS. And, from a standpoint of operations, you get a much simpler mission profile, while losing the potential safety advantage of ECLSS / human / SC checkout before TLI.Been thinking about this too. One interesting aspect is to align the trajectory along a certain lunar gravimetric gradient of mascons, which nicely fits with a Vandenberg inclination direct ascent on the asymmetrical free return.What do you mean by "all four pads"?
Direct ascent would mean a narrow window. You could do it from all four pads instead of just three.There are certain performance advantages that a free return could get from it. In one scenario, you might even get the side benefit of easier core recovery, possibly even RTLS. And, from a standpoint of operations, you get a much simpler mission profile, while losing the potential safety advantage of ECLSS / human / SC checkout before TLI.Been thinking about this too. One interesting aspect is to align the trajectory along a certain lunar gravimetric gradient of mascons, which nicely fits with a Vandenberg inclination direct ascent on the asymmetrical free return.
By "narrow window" do you mean the timing constraints are tighter for direct launch than for a launch into a parking orbit? Can you explain?
Briefly - using the barycenter of the Earth Moon system you can use it for a dV advantage, but it is highly dependent on a specific time, and on how/when you deplete US. Specifics gets quite wordy here so won't take this further.
QuoteBriefly - using the barycenter of the Earth Moon system you can use it for a dV advantage, but it is highly dependent on a specific time, and on how/when you deplete US. Specifics gets quite wordy here so won't take this further.can't this advantage be taken with planning the couple of times around LEO so the position is the same as if you did a direct?
Just a thought that occurred to me: What is the maximum velocity that that FH central core can achieve and still have sufficient propellent for braking, re-entry and landing burns? I ask because I'm thinking that they may be planning to run the central core longer to reserve more upper stage propellent for the TLI.[EDIT]Just to clarify: I think that the optimum launch flight plan would involve RTLS for the outboard cores but a drone landing for the central core. I'm wondering just how far out they can push the central core's return point before the EDL propellent reserve drops below safe minimums.
Nice bit of work, OS. One question: That hypothesised lunar apogee burn: Would that require the Dragon to carry extra propellent to maintain sufficient reserves for Earth approach manoeuvres and would it need a modification to the Superdracos (expansion cones)?
The problem is for an accurate insertion you have to be at the right place at the right time in your orbit for TLI.
If trying to continue the TLI burn from your orbit insertion burn, you are unlikely to be in the right place due to various random effects like variations in thrust, Isp, wind direction and air pressure with altitude.
Unless by then they already have plenty of experience in fully powered landing I expect them to do parachute landing with propulsive assist. Which will have limited precision so they need something like Edwards Airforce base?
Quote from: guckyfan on 04/10/2017 07:55 amUnless by then they already have plenty of experience in fully powered landing I expect them to do parachute landing with propulsive assist. Which will have limited precision so they need something like Edwards Airforce base?Parachutes with propulsive assist, Soyuz style but much softer, makes sense, but is even Edwards big enough given the dispersion from the lunar return trajectory? Do they even need the main chutes? Could this be done with just the drogue chutes?
