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pdx_m3s
Active Member
Can anyone else confirm this is what it means? If so, wow. Technically it wouldn't ascend "back to orbit" because it would be travelling slower, and thus not have orbital speed. But it could ascend to a certain height.
pdx_m3s
Active Member
Think of it as if it is approaching from a highly elliptical orbit. It will dip into the atmosphere to scrub speed as it approaches and through perigee and then move back out towards apogee (as it will be carrying enough speed to do so). It will then dip back in after coming back from apogee towards perigee, scrub more speed, and depending on speed/altitude continue to de-orbit in atmosphere or head back out into space to apogee and repeat.
if mapped, it would look like an elliptical orbit with a fixed perigee and an apogee that keeps moving closer to earth becoming more circular.
So, roughly like what Neil Armstrong was doing in that X-15? Skipping off the atmosphere?
pdx_m3s
Active Member
Skipping is a slightly different maneuver, but similar concept. Skipping involves aerodynamic lift. Not sure if Starship will have enough to actually pull up and increase altitude via lift.
That makes a lot more sense. So each pass is roughly one orbit around the planet. Can't wait until Elon's talk!
Watts_Up
Well-Known Member
Does any parts of the Raptor Spacex Starhopper will be reused in the next fly?
I cannot see what happen to it since the successful launch and landing.
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I cannot see what happen to it since the successful launch and landing.
I recall Elon saying that the Starhopper will not fly again, it will be converted to a stationary Raptor test stand.
pdx_m3s
Active Member
Each pass would involve a small dip into the upper atmosphere close to earth (perigee) and then swing way into space at apogee.
The Mars MRO performed this maneuver hundreds of times over a 6 month period to slow down and reach its final orbit, using very little fuel:
That thread has lots more pics, including some new wings, the mobile platform, etc.
And end of the day pic: Mary on Twitter
Seeing those two pieces on cranes is exciting!
Back on the orbital mechanics stuff, an interesting side effect of multiple passes is that it allows the vehicle to enter orbit in the new system in a more conservative manner. A no-propellant single aerobraking pass has to make a pretty deep atmospheric cut to scrub enough energy to remain in that system's orbit, and that deep cut requires high precision with high consequences. Multiple shallower cuts can scrub the same amount of energy, but:
--Without as much thermal loading, so the thermal system can be lighter and less complex
--With less front end precision and more end-state precision, since the spacecraft can 'east in' to the system and then has multiple opportunities for corrections
--Without as much propellant assist, if the capture's energy dissipation is a hybrid between propulsion and aerodynamics
--Can be time-tailored by trading the number of passes with the effectiveness of each pass.
From a SpaceX perspective, what's [probably] even more interesting is flipping the above (and no doubt other elements) into opportunities. For instance, while this is a bit of Captain Obvious, consider that for a given thermal performance a spacecraft can dissipate more energy over multiple passes than it can over one pass.
That has huge upside to it, because the spacecraft could gangbusters out of the helio orbit into the Martian system, potentially with significantly more energy than the traditional Hohmann-ish transfer orbit. The Hohmann is often used because it is the most energy efficient way to get from point A to point B, but the downside is a very limited on launch window and the mission is pretty much stuck on duration. A straighter trajectory to the Martian system would get there faster and/or open a launch window from what is currently ~days or ~weeks to easily many weeks if not months. Result!
--Without as much thermal loading, so the thermal system can be lighter and less complex
--With less front end precision and more end-state precision, since the spacecraft can 'east in' to the system and then has multiple opportunities for corrections
--Without as much propellant assist, if the capture's energy dissipation is a hybrid between propulsion and aerodynamics
--Can be time-tailored by trading the number of passes with the effectiveness of each pass.
From a SpaceX perspective, what's [probably] even more interesting is flipping the above (and no doubt other elements) into opportunities. For instance, while this is a bit of Captain Obvious, consider that for a given thermal performance a spacecraft can dissipate more energy over multiple passes than it can over one pass.
That has huge upside to it, because the spacecraft could gangbusters out of the helio orbit into the Martian system, potentially with significantly more energy than the traditional Hohmann-ish transfer orbit. The Hohmann is often used because it is the most energy efficient way to get from point A to point B, but the downside is a very limited on launch window and the mission is pretty much stuck on duration. A straighter trajectory to the Martian system would get there faster and/or open a launch window from what is currently ~days or ~weeks to easily many weeks if not months. Result!
If you are scrubbing a lot of speed on arrival via multiple passes, that means a large Martian orbit which means a long period between braking passes.
I'm picturing this, but with Mars
Of course. On MRO, for instance, "long period" was ~hours, maybe a day or two for the first couple orbits.
Of course, the goal of MRO capture was to achieve low orbit, not to land, and of course MRO was using delicate solar arrays to provide a lot of the drag, not dedicated thermal surfaces like a lander would have on it anyway. And of course, minimizing total time was not part of the the MRO mars capture objective.
Rattle those variables around in the Boggle cup of mission optimization and one could imagine an efficient capture on the order of a week or two. If such an optimization could reduce transit time by a month or more on a human mission, that's a solid deal. Or, if such an optimization could increase the landed load on a cargo mission by 10-20%, that's also a solid deal.
Wow.
Do all those engines gimbal?
Someone on reddit noted with awe just how much empty space there is around these three large engines...
Do all those engines gimbal?
Someone on reddit noted with awe just how much empty space there is around these three large engines...
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