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46

Take a look at the SABRE engine. The goal is to achieve single stage runway liftoff/land to/from orbit with a hybrid engine capable of breathing air at low altitude but switching to stored oxidizer and operating like a rocket when it is not practical to use ambient air. The limitations of an air-breathing engine for space launch are that You can't go very ...


43

Systems that do this exist and more are being introduced. It's just that they hide their appearance and look somewhat different to what would be expected from what you describe. Orbital Sciences Corporation (now owned by Northrop Grumman) have been air launching the Pegasus satellite launcher since 1990 (almost 30 years). Virgin Galactic's 'White Knight' ...


22

According to Mark Hempsell, formerly Future Programmes Director at Reaction Engines Ltd., now CEO of Hempsell Astronautics Ltd., explaining the reason for SABRE's curved nacelle over at NasaSpaceFlight.com forum: Why a Curved nacelle? – the most frequently asked technical question. The answer is: the air intake on the front of the nacelle needs to ...


19

There are two major barriers: one is that thrust-to-weight ratio of jet engines is pretty poor (2 J58s massing more than 15 times what 9 Rutherfords do), the other is that it's hard to make an engine that performs efficiently over the wide range of speeds and altitudes that a first stage wants to cover. That said, Boeing at one point toyed with a concept ...


18

What is the use of a second stage using ramjet in a height where the remaining air is very, very thin? The Falcon 1 first stage is used up to a height of 90 km, the second stage reaches a height of 200 km where the satellite is put into the orbit. You would need three stages, the first with a rocket engine to get a speed where a ramjet may be used, the ...


12

Effectively it has been done, but not in the way you're thinking (or probably intending). The USAF launched its ASAT missile into space from an F-15 fighter aircraft. While not an orbital rocket, it's close. And for orbital rockets, there's Pegasus, launched from a converted L1011 Tristar mother aircraft. It's not a concept that ever really took off, ...


7

Thanks to many people answering and commenting, I think it could be summed up as follows: 1) For suborbital flight, height is important. Ramjets could be used for that. NASA even researched ramjet as a propulsion option. 2) BUT, if your goal is to reach orbit, the height does not matter that much. You can lift your space vehicle to an altitude, and it will ...


5

For straight vertical, it just doesn't make sense. Jet engines have a low TWR, you are adding a lot of complexity, and it won't gain you much at all. The only way it make some sense is from an airplane type delivery, which will give you a more ideal launch location, and some speed and altitude when you drop the rocket. But keep in mind, it requires a huge ...


4

Your base assumption is wrong: scramjets needs oxidiser However, they are designed to use atmospheric O2 as their oxidiser supply. Since the rocket needs to go to space, where there is no significant amount of oxygen, they cannot work up there. Indeed, they could be used for the narrow part between insufficient speed and too high altitude. This is ...


3

The key part to answer this question can be found at dangermouse.net. Specifically, this formula must be satisfied: $V_t > \frac{dm}{dt} / ( π\cdot r2 \cdot\ ρ)$ Where $V_t$= Velocity, $\frac{dm}{dt}$ is the minimum fusion rate of hydrogen, $ π\cdot r2 $ is the area of the funnel, and $ρ$ is the density of hydrogen in the interstellar medium. Right ...


3

There are three different devices being described here. The second two are closely related, while the first is different. The picture you have included is a device that functions first as a rocket until its solid rocket propellant is exhausted, and then reconfigures to use the rocket chamber as a ramjet chamber. It cannot operate as a ramjet before the ...


2

Though TWR of jet engines are low, you can still do it , if not 1 use 4 jet engines, if not 4 use 30 jet engines. You are going to reuse all jet engines anyway and fly them only just for few minutes. So you aren't going to lose a lot of money. But max speed they can provide is around mach 3 , which is less than half the speed of first stage of electron ...


2

The potential of a horizontal launch within the earth's atmosphere is very much limited by the atmosphere itself. At a low height the maximum speed is limited by the high atmospheric pressure and at medium height there is not enough oxygen left for the scramjet. But to get into a low orbit, much more speed and height is necessary, about 8 km/s speed instead ...


2

There is an entire Wikipedia article on the subject. One could call the Apollo lunar module a SSTO vehicle, as it made it to lunar orbit with one stage. Probably not what you're after, but still. Currently, there appears to be only one country other than Britain looking into the idea - the Romanians with their Haas 2C. On June 1, 2012, Romanian ...


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