sevenperforce

That's the sort of question I like! They haven't published one, to my knowledge, but if it can take 8.3 tonnes to nominal GTO (2.5 km/s out of LEO) then it can take at least 3.4 tonnes to TLI (4.1 km/s out of LEO). And they're claiming 4 tonnes to trans-Martian injection.

Everything you said, except that not even Musk's koolaid is THIS spiked.

After it was pointed out that KerbAir's first medium-range regional jet had twice the passenger capacity required, we scrambled to find a replacement submission. Now we are proud to announce our Econoclass medium-range passenger jet, the Flopping Dolphin! This is definitely the jet for airlines on a budget. At a little over $19 million, it is priced far below any other medium-range jets and below most short-range jets. Seating is admittedly cramped, with the central economy cabin lacking direct window access, but the single engine in the tail means very little cabin noise. Detractors argue that having two cockpits is unnecessary, but our engineering department assures us that the redundancy of two separate cockpits is an added safety bonus. Our acquisitions department also indicates that having two separate flight decks is actually less expensive than one larger two-seat cockpit. The taildragger orientation keeps the nose pointed up for shorter takeoffs, and the V-tail further reduces costs. Takeoff with flaps (AG1) is achieved below 80 m/s. With a cruising altitude of a little over 4 km, cruising speed of 247 m/s, and a range of 1,600 km, this jet is just within the requirements of a medium-range regional jet. But its low part count and low fuel consumption means it is very affordable to operate, at $0.50 per passenger-km for fuel costs. Craft file here.

As others have said, a jet engine doesn't give you meaningful dV...and honestly a jet engine is probably more complex to build/operate than a hybrid-fueled rocket. Exhaust vanes will work well enough if they're tungsten, but that's expensive and the servos would definitely be heavy and very very expensive. Aerodynamic fins are cheaper, simpler, and easier to work with. The advantages of parallel staging seem dramatic, if you can pull it off. Stage separation is a very dicey maneuver, and doing an air-start of the upper stage engine is an added complication. Parallel staging allows you to use common cores (meaning less testing) and ground ignitions. Here's a thought. What about a hybrid/vapor pressure-fed rocket using catalyzed HTP as the oxidizer and autogenous pressurant (perhaps with liquid nitrogen as an auxiliary coolant) and jellied petrol as the fuel? The biggest problem with hybrid rockets is getting an even burn surface (combining liquids and solids is hard), but napalm would flow and vaporize rapidly enough that this wouldn't be an issue, and the HTP would decompose and vaporize so you wouldn't have liquid-on-solid at any point. If the napalm used aluminum salts as a gelling agent, you could easily get upwards of 260 seconds of isp. While both napalm and HTP are extraordinarily dangerous, they are well-studied and present no particularly exotic handling requirements. HTP can be manufactured with a fairly inexpensive lab setup and petrol is, of course, widely available. If the rocket was equipped with chutes and peroxide-charged (or nitrogen-charged) airbags, it could be easily recovered and refueled much more simply than typical hybrid rockets, since napalm pours readily. An alternate option would be to add a powdered oxidizer to the fuel in very low quantities, so the solid/gel fuel would burn on its own. This would ensure a consistent burn but still allow for partial throttling like a typical hybrid.

I can perform the Cobra if I throttle down the Panthers so that TWR is < 1 without afterburners. Throttle low enough that you have level sustained subsonic flight, then increase the throttle to max and immediately nose up to a stall before the Panthers have time to spin up. As soon as you stall, but before the Panthers have throttled up, hit the afterburner to immediately push your TWR over 1. Then you can use thrust vectoring to dance on your tail for a bit. Once you start to accelerate, kick the afterburners off and nose forward again.

It's only impossible for a passively stable vehicle. All real jet fighters have the center of pressure well behind the center of mass, and there is no way to invert this. But in KSP, with airbrakes and other drag-altering mechanisms, it's not necessarily impossible to get the center of pressure to change. Then all you need is off-axis yaw to do a 180-degree spin. That's why I also added the "fly backwards" challenge. With some action groups, it should be possible to get a plane that can fly backwards or forwards, and if you can do that, you can definitely pull a Crazy Ivan. The side engines on the Serenity are some sort of nuclear air-turborocket. Wow, gorgeous! Kudos to you.

Yeah, that's what I was guessing.

Will it only be visible from a single point at a time?

Everyone asks this once, haha. The niobium-alloy engine bell is so thin at the base that it can easily be bent during transport, ascent, and staging. Only once the MVac is at full throttle is the exhaust pressure high enough to keep the engine bell perfectly round. So SpaceX attaches a circular stiffener ring to the edge of the engine bell to ensure it maintains its shape until the MVac throttles up, at which point the heat and expansion breaks it off and sends it flying. Every gorram time. The metal pusher extends straight up the center of the engine bell and presses against the throat, which is by far the strongest part of the engine bell. Honestly, it's one of the strongest components on the entire second stage, probably second only to the payload adapter. If the edge of the bell clipped the interstage during separation and was just slightly bent, then the exhaust pressure would straighten it back out. If its structural integrity was breached, even slightly, then it would rip itself apart on ignition. I wonder if the nozzle extension is frangible enough to separate completely if that happened, essentially leaving behind an underexpanded SL Merlin. Reduced thrust and isp but perhaps enough to reach a lower orbit. Holy crap! That's impressive. I wonder if it would've had enough margin for S1 recovery...or at least a recovery attempt.

If the soot from carbon in kerosene is what makes the kerolox exhaust trail glow, why didn't the Black Arrow have a visible exhaust plume?

Adventure tourism is a huge business because it is accessible. Raise the cost of entry, and you lower the access and the demand. There are a lot of people with a significant amount of money, but there are not as many people who can throw six or seven figures at a single brief experience. A ride on the Vomit Comet will run you $5,000. A guided trek up K2 is four times as much, at $20K. The South Pole, which exceeds LEO in terms of amenities, will run between $30K and $60K, and it attracts only a few hundred people a year. Only a small fraction of those people would be able to afford a trip ten times more expensive, which is nowhere near enough volume to make tourist LEO trips profitable. Because it is cheaper to do it with trick photography on Earth. You can't switch gears from talking about a tourist industry (adventure tourism) to a for-profit industry (film). No film production company is going to foot a massive bill for something they can achieve less expensively.

Which is precisely why you can't "hitch a ride on a comet".

I'm not sure at an amateur level you could build two stages large enough to get you to orbit. The smallest orbital rocket that's has ever been attempted [1] has three stages. Yeah, with solids you definitely need more than two stages. What if you used parallel hybrids on the lower stage and then a solid-fueled kick stage for the orbital insertion? Aerodynamic guidance on the core and peroxide monoprop RCS on the payload for upper-stage guidance.

Since my first medium-range entry had twice as much passenger capacity as it needed, I'll submit a new design first thing tomorrow. I've gotten it made; I just have to actually upload the craft file and take pics.

Okay, here's your base image. Just add a star for each mission you complete in sequence, rather than having a separate badge for each mission. That way signatures don't get cluttered. For example, my current badge would have three stars, but once I complete EM-2, I'd delete it and replace it with a four-star badge.

**sigh** Can you post EM-2 just so I can get started? I'm a bit overeager. Want me to design more...eh...aesthetic badges?

No, no, sorry for the confusion. It's a 7-year recycle period for the overall transit cycle set. So there are varying cycle lengths, but the placement of Mars and Earth relative to the cycler repeats every seven years.

You could try doing diminishing returns. +5 points per kerbal up to 5 total, then +2 points per kerbal up to 10 total, then +1 points per kerbal up to 20 total. So the most you could get by spamming kerbals would be +45.

The Aldrin Cycler is one particular solution to the overall Mars Cycler problem. Here are a few different possible cycler periods. One thing you can do is have a cycler with a long transit time (e.g., five months) on one leg and a short transit time (e.g., 18 months) on the other leg. This allows you to send cargo on the long transit leg and crew on the short transit leg. With two or three cyclers running in parallel, you can have reasonably regular transits for crew or for cargo. An Aldrin cycler repeats transit periods every seven years without requiring mid-course corrections, but in KSP, you'd need a mid-course correction at least every other cycle.

Thought I'd broach the discussion of what, exactly, it would take to get an amateur rocket to orbit. Obviously I'm not suggesting that anyone attempt to build an orbital rocket in their backyard. This is more a design question -- what would be the simplest, cheapest, most dependable option for getting a rocket into orbit at an amateur level? Things to consider include: Staging: Serial or parallel? Fuel: Liquid, hybrid, or solid? Guidance: Gimbal, differential thrust, or aerodynamic? Parallel staging would allow you to light all your engines on the ground, which is nice if you use liquid or hybrid. But it may not be as efficient since crossfeed is not really feasible. Gimbaling is probably well beyond the capacity of amateurs, but differential thrust is a possible guidance mechanism if you use parallel staging with hybrids or liquids. Aerodynamic guidance will work for lower serial stages but you'd probably need spin-stabilization for the upper stage. If you did go with a liquid or hybrid rocket, what propellants would be used? The kerosene-and-peroxide combination of Black Arrow is promising; both are pretty readily available and there is already a lot of literature on amateur use of peroxide monopropellant for jetpacks. The primary difficulty with a liquid-fueled design is cycle use; pressure-feeding is tricky to get right for an amateur operation, but anything with a turbopump is probably also too complicated. A pressure-fed hybrid rocket with something like jellied gasoline and self-pressurizing peroxide is a high-thrust option with respectable specific impulse.

Multistage rockets for suborbital international travel are a bit messy, though. You'd almost definitely want a single-stage vehicle. Of course then you have to deal with very, very limited launch and landing sites.

The challenge: Build an aircraft that can pull a Crazy Ivan. If you don't know what a Crazy Ivan is, watch this awesome scene from Firefly: Simply, a Crazy Ivan is a mid-air 180. It works best with aircraft which have two engines mounted rather far apart and best if those engines are reversible. At full throttle, one engine is reversed, producing a dramatic torque that results in a 180-degree yaw. Then the engine is switched back to normal and the engines fire together, stopping the aircraft in midair and then taking off in the opposite direction. Rules: Aircraft engines only (no rockets) Aircraft control surfaces only (no RCS or reaction wheels) Must be capable of normal rolling takeoff and landing Goals: Pull a Crazy Ivan Using reversible thrust on both engines, fly your plane backward Take off and land backward or forward Good luck!

What makes you say that? Have they ever shown the capability to ignite a liquid-fueled second stage?

There are a varying range of estimates on just how far the current incarnation can reach. With its lofted trajectory yesterday it reached a 2,802 km apogee and landed 933 km downrange. Worst-case scenario, how far do we think it could reach? The single-stage Hwasong-12 is 3,700-6,000 km. Probably someone misreported km as miles, then converted back to km.

Very nice! I see based on the wiki that it's UDMH and either NTO or nitric. GG is impressive, though. Any word on whether the US was liquid or solid?