sevenperforce

Well, unlike in KSP, there's no "track object/find Pe/Ap" option, so they'd have to get an exact measurement of the apoapse velocity and then do the same thing again the next time around. Aerocapture would look like a small meteor skipping off the atmosphere, and then you'd be able to "go dark" all the way around to apoapsis. Another option would be to raise your apoapsis only slightly, so it was still in the upper atmosphere, but only barely. Then you'd just look like you were a meteor that had aerocaptured and was slowly decaying, when in reality you could be snapping pictures or whatever else you wanted to be doing. Eventually you'd re-enter altogether.

If you want to do a stealth orbital insertion (as opposed to a stealth entry), then you can make a very very small correction burn far away, placing you on an aerobraking trajectory just low enough to aerocapture into an unstable high orbit. Then, any sufficiently low-thrust engines permit any number of correction burns to adjust your orbit to wherever you want it.

Working on it. My current design doesn't quite have enough dV in the terminal stage.

Fixed that for you. To make it perfectly clear: regular sunglasses will do NOTHING to protect your eyes. Nothing whatsoever. In fact, they will make things worse, since your pupil will dilate wider and allow in more light. There are three ways to safely view the eclipse: With the naked eye, during totality, as long as the corona is perfectly round and there's no crescent peeking around the edge. With approved solar filter glasses that block 100% of high-energy light, 100% of infrared light, and 99.9% of visible light. If you have solar glasses, you can test whether they are "approved" by looking directly at an incandescent bulb from less than 6". If you see anything glowing other than the filament (this may include a slight reflection of the filament off the back of the inside of the bulb), they aren't real solar filter lenses. With your back to the sun, using a pinhole camera that projects the image of the eclipse behind you onto a surface in front of you. Unless you're doing one of the above three things, you WILL do permanent damage to your eyes. Worse than if you happened to glance at the sun on an ordinary day.

Err...unless I'm wildly off somewhere, this is still true whether you do a gravity turn or not. Of course, by the time you get close to staging, you've started to get a centrifugal (not centripetal) assist, but that really starts showing up after staging in most TSTOs.

Yeah. Losses due to gravity can be calculated very simply: t x g, where t is flight time and g is the acceleration due to gravity. For TSTOs this typically holds true up through staging. So if you take 100 seconds to get to staging, your gravity losses are 981 m/s. If you take 50 seconds to get to staging, your gravity losses are 491 m/s. Thus, gravity losses are (effectively) inversely proportional to TWR. It's really quite dramatic. Instantaneous drag is proportional to the density of the air times the square of the velocity. But air density decreases exponentially with altitude. At first, the square of velocity ramps up faster than decreasing air density, but most rockets hit MaxQ fairly early. As long as your ascent isn't almost completely flat, air density will be dropping faster than the square of velocity after MaxQ, and so you have only gravity losses to worry about.

In theory, an SSTO has fewer engines, less maintenance, and fewer failure points. In practice, it's just unattainable, and the theoretical advantages are miniscule.

Most rocket engines gimbal from 0 to 4 degrees in any direction, although early models (and NK's current models) use multiple control engines with only one axis of gimbal freedom each. The SSME engines had a ridiculous 10+ degree gimbal in every direction because of how much the CoM changed during ascent. All the engines on the Falcon 9 gimbal, but the center engine has more gimbal than the outer ones because it has slightly more clearance. Although all the engines on the Falcon 9 are reusable, only three are plumbed with ignition fluid for in-air restart. It uses one engine for most landings but it sometimes uses the other two for part or all of the landing burn when it needs extra thrust for low-margin suicide burns.

The 1:1 glide ratio is with the Block 5 grid fins. That video was hella cool, though. I was amazed to see the transonic shock forming around the tail just before the landing burn ignition. Also surprised by how long the landing burn was.

Indeed, but I made the challenge the way I did for a reason, haha. Otherwise people would just pile on the engines and forget. This requires people to be at least a little bit creative. Yes, it looks good in the movies. One of the things I was curious about is whether we'd end up with designs that look a lot like scifi, or designs that look more utilitarian. It may be that I should alter the requirements of this challenge to say that warp time is not counted, or counted differently...not sure of the best way to do it.

Jet-drop staging can be good for polar orbits of small satellites that don't need to stay aloft for very long.

You can do this, but it's a huge waste of dV.

A cone with a sharp transition will have more parasitic drag than a cone with a smooth/rounded transition, due to boundary-layer separation at the interface.

Looking good! I did mean that it needed VTOL engines on a separate thrust axis, but I won't fuss about it.

It depends on your launch vehicle's thrust-to-weight ratio. As a good rule of thumb, I typically try to pitch over gradually enough that my heading always stays inside the prograde marker, but rapidly enough that I hit 45 degrees (halfway over) at around 500 m/s. That's for KSP, obviously; pitchover for real-world launch vehicles is going to be different. A vehicle with very high TWR can execute the pitchover much lower in the atmosphere than a vehicle with a lower TWR, but the curve of airspeed vs pitch angle is going to be pretty similar across the board.

You're right. I dug up the old Falcon 9v1.0 user guide: https://www.spaceflightnow.com/falcon9/001/f9guide.pdf

Of note -- the F-35B has the radar cross-section of a 2 cm steel marble, if I recall correctly.

I've seen it phrased this way: If you could drive the average sports car straight up through the air, without a roadway, then it would take just a little over two hours of driving to reach the altitude of the International Space Station. But you'd still only be moving at 0.7% the speed of the International Space Station.

From Wikipedia: "The F-117A's faceted shape (made from 2-dimensional flat surfaces) resulted from the limitations of the 1970s-era computer technology used to calculate its radar cross-section. Later supercomputers made it possible for subsequent aircraft like the B-2 bomber to use curved surfaces while maintaining stealth, through the use of far more computational resources to perform the additional calculations." The B-2 was far more radar-invisible and has completely smooth surfaces.

Common misconception, actually. Ugly angular shapes are no better at scattering radar signals than curved ones. The shape of the F-117 was due to the fact that computers of the era were not powerful enough to solve the equations for proper geometry of a smooth radar-scattering surface, and so they had to make do with a multiplanar solution.

I'd like to see a 2.5-m or 3.75-m LANTR. Two operating modes; can run on fuel alone or on fuel + oxidizer. Slightly higher specific impulse than the LV-N in fuel-only mode, with a lower TWR, but massively improved thrust in fuel+oxidizer mode. Enough to make pure-nuclear SSTOs at least vaguely feasible.

I see a lot of requests for pivots, motorized parts, and the like, which makes sense. A lot of players would like to be able to make stock rotating engine nacelles, folding wings, and similar structures in stock without resorting to hacks. Of course, this is on the List of Things Not To Request However, this could be realized very easily if updates were made to the AGU. First, make the AGU enable crossfeed automatically, so that the engines on the grabbed vehicle or structure automatically drained tanks on the primary vehicle. Second, make the AGU's attachment points show up in the KSC, so that you could launch a ship with the AGU already engaged. Third, add some of the fine tweakable functionality (gimbal lock on/off, etc.) to the available action groups for the AGU. That's all you need. You could connect engines or wings or entire ship segments to the rest of the ship using the AGU (or AGU pairs, for single-axis rotation) in the KSC, then use action groups lock or unlock the rotation of those AGUs. Might need to rig up some thrusters to actuate the rotation but that's secondary. It could be something as simple as "press 1, then 2 to rotate to the second position; press 3, then 2 to rotate back in the opposite direction".

I'd like to see an option for actuation toggles to be available as action groups, if only to be able to turn off or cripple RCS attitude control while translating on docking approaches. I often run into docking approaches where I'm dealing with small craft which have active stabilization, but using the RCS for this will prevent me from making a clean approach. It would be nice to have action groups preprogrammed to switch off the RCS+SAS link, so I could use RCS translation but leave SAS on so I could hold attitude using reaction wheels only.

Yeah, I'd love to see an air-augmented engine. Or, even better -- a setting or module that allows existing intakes to increase the thrust and specific impulse of rocket engines. Maybe an Exhaust and Airflow Diverter, a 1.25-m module you place between a 1.25-m intake and a 1.25-m engine to combine the airflow with the rocket exhaust. I'd love even more to see an aerodynamics update that allows you to build your own intake to combine with rocket exhaust but that's just wishful thinking.

And even in KSP, it's barely break-even unless you're using the RAPIER engine. Try using any jet engine other than the RAPIER for a first stage (vertical launch) and see whether you can get better overall mass ratios than an optimized equivalent-mass rocket stage.