sevenperforce

Aye. Blue Origin's achievements are definitely impressive and I give them all kinds of props for that, but honestly every various attempt at reusability is the "first" for its own reasons. DC-X, Grasshopper, and F9dev (along with a few others) beat BO to VTVL rocketry. Earlier Falcon 9 launches beat BO to in-air restarts of launch vehicles during atmospheric re-entry. The X-15 and the Shuttle beat BO to intact recovery of a powered exoatmospheric vehicle. Blue Origin can lay claim to being the first company to launch a rocket vertically beyond the Karman line and return it to a vertical propulsive landing. Good for them. But we all stand on the shoulders of giants.

More thoughts......... If you're merely dropping people and you don't care a great deal about their safety, then a VTVL ship similar to the ITS Spaceship is a fine solution. However, if you need to drop cargo without a ground infrastructure, then you need a way to get your cargo down to the ground, and putting a crane system inside your spaceship does not seem like a nice solution at all. That's why I'd suggest going with rotating nacelles a la Firefly or V22 Osprey. This allows you to take off and land vertically on virtually any terrain, but land in a horizontal attitude and simply open up your TPS'd cargo doors and drop your cargo (or your troops) out that way. Using a turboramrocket is especially nice for this because you can do your final landing in pure-turbine mode so you don't land in a fiery conflagration. You'll still light the ground on fire when you launch, but that's beside the point. Yeah, this is just about my favorite kind of thread.

If there are no propellant depots on the surface then everything will have to be pure onboard ISRU. Can we posit that the colony ship could have dead-dropped self-contained robotic ISRU plants to a series of locations to enable surface refueling? What needs to be brought down to the surface and back up? Is it a cargo transport? A troopship? Does it need to carry crew and cargo at the same time, or would they be able to just do two separate drops? Air augmentation works just fine at zero airspeed. You'll get anywhere from 15-25% thrust augmentation at a standstill, due to induced airflow, but once you get up to around Mach 0.3 things really start cooking. Do your dropships need to do any sort of sorties while on the ground? That is, would they ever land at point A, then fly to point B, then return to orbit? If so, going ahead with a turbine is probably a good idea. If not, you can probably get away with a pure ramrocket. I don't think we'd need to posit a gas-core NTR; a solid-core NTR will be fine. A probative question is whether the planet was originally terraformed. If it was, then the likelihood that its orbital velocity is lower than Earth's is much higher. Earth is kind of an oddball. Our core is much denser than most terrestrial planets due to the collision with Theia that produced our moon.

Not gonna happen with this booster. But comparing the two is kind of pointless at this stage.

If you look closely at this photo, you can just make out what appears to be red-hot glowing grid fins.

Won't allow much in the way of ISRU, but as a "reverse shuttle" goes it's not a bad approach. Unfortunately there isn't really a good way to get much of a ramrocket effect going with the SERV/K-m vehicle bodyplan. Dense propellants for an SSTO is very important. Beamed power is great if you can come up with a way to beam power without atmospheric attenuation losses, but that's hard to do, even in a near-future setting. It also seems very handwavy even if it isn't trying to be. We can assume the fuel cores will be offloaded to the mothership for fuel reprocessing. Reprocessing will recover 55-95% of the uranium/plutonium. Not sure if wings will be needed. On the one hand, NTRs already have really poor TWRs; on the other hand, adding air augmentation via full turboramrocket will moderately increase TWR and significantly increase ISP at low altitudes. Water injection or LOX-afterburning is even better. If your concept of near-future developments permits lightweight but powerful actuation systems, then going with a body plan like a mini Firefly makes a lot of sense: turborocket LANTRs in rotating nacelles on the wingtips and an NEP ion engine in the tail, with takeoff and landing in horizontal attitude for safety and stability. From your description, I thought you were suggesting turnaround time of a few minutes. Half a day or so should be plenty of time for near-future ISRU.

Yeah, I believe so. Looks like the stage really got toasted.

I mean, technically the F9 RUD had to do with staging because, uh, the failure happened in one of the stages. Of course. But one could make the same connection about rockets that have engines. As a matter of fact, every single rocket that failed during the launch had at least one engine. I suppose they would say "well the failure happened in the stage that wasn't in use" which frankly doesn't make a lick of difference. While we're at it, how about the failure of the COPV that took out AMOS-6? That was a failure of a helium pressurant tank inside a composite tank during fueling. Which, you know, is what ARCA is proposing we use.

Unfortunately, water doesn't play too well with NTRs. Vacuum specific impulse is only 412 seconds. The reason LH2 gets such good specific impulse is that it partially disassociates into monatomic hydrogen due to the intense heat, but water does no such thing. What kind of turnaround time were you thinking for the dropship? How much time does it have to refuel? If your ship has access to water and atmospheric air, it can make ammonia, which boasts 520 seconds. It could add water injection (or LOX injection, as LOX will be a byproduct of the ammonia process) to boost thrust on takeoff. For an enter-land-and-relaunch profile, I'd think very hard about using an air turborocket or ramrocket, something to boost up your specific impulse and your thrust. Fuel will be a concern as well. NTRs don't have a great power cycle option to begin with. 24 hours of runtime will fission enough fuel that it needs reprocessing. So if there is a mothership or a home base for your rebels, they'll probably need to switch out their cores regularly.

On the launch pad, the crew enters the orbital module through the small port adjacent to the descent module.

Wouldn't it depend on distance, to some degree? A very large accretion disk could provide fairly constant insolation for a large range of distances.

AFAIK only one of the fairings was brought in. It's a bit banged up from what we've seen. I, for one, am waiting eagerly for the full landing video to be released.

Yeah, any black holes with anything close by will have an accretion disk. Because an accretion disk is nonspherical, it can produce really interesting habitable zones. A planet closely orbiting a brown dwarf that is itself orbiting a black hole would have a lengthy period of habitability.

Because they had a little extra CGI budget and decided to add something nonsensical? The website touted the benefits of having the "whole vehicle in orbit" and claimed that on-orbit refueling could allow it to do all kinds of BLEO stuff, but that's stupid. First, a vacuum specific impulse of 314 seconds isn't going to get you very far beyond LEO. Second, no one is going to launch a fuel tank just to refuel an unrelated booster. Third, any hypergolic second or third or fourth stage has as much capacity to be refueled on orbit as this "whole vehicle". Finally, the whole question is moot because the liquid helium pressurant tank would need to be filled on orbit, which ain't happening. I mean, technically the F9 RUD had to do with staging because, uh, the failure happened in one of the stages. But yeah, it seems slightly dishonest and very pop-speculative. At the same time, a pricetag of $1 million for a smallsat launch does beat out the current competition, even if it's not competitive with larger payloads. And a single-stage vehicle definitely can be launched from anywhere, which is one advantage. Small launchers like these could really benefit from being trucked up to a high-altitude point and launched from there. Wait, what? That was just goofy. Fairly certain that any problems this concept might have with meeting its performance specs would be more than solved by going GNOM-style. And the parallel (pun intended) option of going with strap-on COTS SRBs would make it quite competitive if they'd relax their "SSTO is the awesomest" obsession. Is the smallest LV to ever reach orbit the Lambda 4S?

If they were speaking through a mask rather than a helmet (e.g., something like a respirator) and their ears were open to the surrounding air, then they'd hear everyone's voices with a pitch phase-shifted really, really low. The ordinary vibrations in ordinary-density air would be frequency-multiplied when they hit lower-density air.

In all seriousness, a potentially more interesting poll/topic would have been topical, rather than based around just the names of a few companies. Like, what's the future of spaceflight: higher-efficiency lower-cost expendable multistage rockets? Partially-reusable multistage rockets? Expendable SSTOs? Reusable airbreathing spaceplanes? Fully-reusable multistage rockets? And is the answer different for manned vs unmanned flight? That's a topic worth discussing.

No! Don't touch my precious pineapple! That sounded awkward... Clearly the solution is a gmo modified wine that pairs with pineapple.

Of note: the claimed dry mass ratio is just 12% more than that of the ITS Tanker, which is pushing every envelope, has higher TWR engines and a lower vehicle TWR, and benefits hugely from the square-cube law. Then again, HTP is denser than LOX, which should help ARCA somewhat, and the ARCA vehicle wouldn't need TPS or RCS systems like the ITS Tanker. Hitting that dry mass would be tough.

This sort of launch vehicle would play very, very well with air augmentation, too. Just a simple aluminum panel stretched across the face of each aerospike would cost very little while boosting thrust and ISP nicely. EDIT: Here are some additional specs.... Length: 16 m Diameter: 1.5 m Dry mass: 550 kg Launch mass: 16,290 kg Payload mass: 100 kg Engine: Pressure-fed linear aerospike Nozzle: 80:1 expansion ratio, 80% cut Engine coolant & pressurant: Liquid helium Number of chambers: 16 Nozzle cooling: Ablative + RP-1 film Propellant: HTP + RP-1 Burn duration: 272 s Thrust (SL): 22,920 kgf Thrust (vac): 33,500 kgf Isp (SL): 230 s Isp (vac): 314 s Propellant flow rate: 100 kg/s Mixture ratio: 7.46:1 Tank pressure: 20 barg Chamber pressure: 16 barg

Whooooops! 16 meters. 53 feet. I meant to put it in metric but I put the Imperial number instead. Yeah, avoiding the hype train is a good idea; this company has produced a lot of odd concepts in the past without a lot of consistency. Like, they made a tiny $700 electric skateboard and a $19,000 ducted-fan hoverboard. So...I'm not really sure what they're up to. But you're right, the basics seem good. If you're going to go for a pure-rocket expendable SSTO then it needs to be simple, cheap, and reliable while simultaneously taking advantage of every last drop of TWR and ISP savings it can get. "Cutting-edge" and "simple/cheap" don't often play well together. But composite tanks, room-temperature propellants, and a regenerative pressure-fed linear aerospike are all readily achievable tech that cross-enable. Plus, HTP is hypergolic with RP-1 so that makes it even simpler. And I think the linear aerospike is definitely a better way to go than a toroidal aerospike. Not only does it permit regenerative cooling with cheaper, lighter-weight materials, but it natively enables thrust vectoring and roll control via differential thrust, which a single-chamber toroidal aerospike completely lacks.

Not necessarily. Dwarf planet has nothing to do with size. Based on the planetary discriminant equation, Mercury would be considered a "dwarf planet" if it was further from the sun. Officially, the current definition of "non-dwarf planet" is "gravitationally rounded body that dominates its orbit". But the planetary discriminant equation, which predicts whether a given body will eventually dominate its orbit, depends on the mass and the distance from the star. So even Earth could be considered a dwarf planet if it was far enough away, even if it did in fact dominate its orbit.

This had been discussed on the forums a few years ago, but now ARCA (a rather odd company that doesn't seem to know what its market is) has released a glitzy CGI video of its "Haas 2CAJ" smallsat SSTO launcher. While the company's track record isn't very good, the combination of technologies and solutions in their idea seems solid enough. Here's a bunch of specs on it. It's a 16-meter-high smallsat SSTO burning RP-1 and HTP with a projected payload of 100 kg to LEO, using a rather large linear aerospike engine and a composite frame/tank with common bulkheads. Claimed launch price is just $1 million. As these things go, it's not a bad idea. HTP/RP-1 is about the only non-exotic prop combo with a higher impulse density than kerolox, and it also permits higher thrust than kerolox, which helps make up for the lower TWR of linear aerospike engines. It's pressure-fed, which would typically be the death knell for an SSTO, but since the linear aerospike engine doesn't require a high chamber pressure it's not a bad idea. Pressure-fed engines also typically have very poor tankage ratios, but the composite tanks can handle higher pressures. The pressurant is liquid helium that is passed through an engine heat exchanger, simultaneously cooling the big aerospike engine and saving on the weight of a turbopump, which further mitigates the low TWR of the aerospike. The linear aerospike allows for roll, pitch, and yaw authority through differential throttling alone, which saves on the mass of a gimbal system. The use of HTP comes with its own set of handling challenges, but it is cheaper than LOX, requires no insulation, and requires less demanding materials specifications than LOX. All in all, not a bad concept. Whether they will pull it off or not, I don't know. They fuss and fret over the horrors of staging, but honestly this could be very competitive if it was offered with the option of COTS parallel SRBs. Base configuration for smallsats, a couple of SRBs for larger LEO comsats, or a quad of SRBs for big LEO comsats or GTO smallsats. Better than trying to fuss with a second stage.

Hah! Don't think the Dragon would fit in the fairing, though...and the fairing is required in order for FH to receive certification. Speaking of which, I don't know how they'd attempt to recover S2 if they expect it to be certified.

Oh, so they are speaking through their helmets, in normal Earth atmosphere, without electronic amplification? In that case you have sound traveling at one speed which is then attenuated by the glass, phase-shifted (with compression losses) by air of a different density, then attenuated again by glass, then phase-shifted again. So it would be REALLY muffled and slightly distorted, but not a different pitch. So yes, basically correct. Risk of edema is there, yes, but otherwise altitude sickness mostly has to do with lack of oxygen, not with the pressure itself. People can last for long periods of time at very low pressure as long as the partial pressure of oxygen is high enough.

I guess we'd need to know a little more about the setup. Are they talking in the Martian atmosphere? What sort of helmets are they using? Is there an electronic relay?