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19

For the Space Shuttle: Using the same approximate curves (with all their assumptions and limitations) used in the answer to How does the Space Shuttle's SSME engine's thrust vary after ignition?, we can integrate the SSME flowrates to get a startup propellant consumption of: 416 lbm LH2, 2246 lbm LO2 per engine, and ~ 1248 lbm LH2, 6738 lbm LO2 ...

15

From what I've been able to find, the "fluff" is that the Epstein Drive electromagnetically accelerates the exhaust, improving propellant consumption over a "standard" inertially-confined fusion drive. Electromagnetically accelerating plasma is certainly physically plausible...real world ion and plasma thruster designs do just that. The problem is that ...

13

The properties of the fictional Epstein Drive are: Very high ISP with an exhaust velocity at least several percent of the speed of light Very high thrust while achieving that ISP or near to it, enough for 5+ g burns. Fusion powered. Based on the first two parameters, the thrust power is insanely high - this is not a fission sail, NTR, or low-power fusion ...

7

SRBs tend to be used for one of two types of purposes: The rocket core is the same, but sometimes needs a bit of extra performance (Atlas, Vulcan) The rocket core is hydrogen, and doesn't have enough thrust to get off the ground. For the first one, a solid rocket is preferable as the rockets need to be cheap and small, and solid rockets are much easier, ...

7

Fuel and time probably give different answers and it also depends on whether you want proved current hardware, engineering studies or wild speculation. Let's maybe consider some options: Chemical rockets a small rocket with a large fuel tank, using a high $I_{sp}$ fuel mix such as liquid hydrogen and liquid oxygen is an option. Freed of the need for enough ...

7

In the list of current operational launch vehicles, this is how GSLV stacks up. This is a comparable list, to compare it to N-1, Proton, R-7 would be an apples-to-orange comparison. Vehicle Deliverable Payload to GTO (kg) 1. Long March 4B/4C 1500 2. Long March 3A 2600 3. Soyuz STA-A/B w/ Fregat ...

6

What are the parameters of determining the launch capabilities of a rocket? The main parameter is "payload to orbit", but you have to specify which orbit you're using. In the answer by ASRI_306, 'payload to GTO' is used (i.e. geostationary transfer orbit). Strictly speaking, that's incomplete because there is more than one transfer orbit. 'GTO 1500' means ...

6

Liquid hydrogen makes a poor first stage fuel. First stages operate with the vehicle full of propellant and lifting itself directly against gravity, and need thrust more than specific impulse. That means a high mass flow rate, and liquid hydrogen's lower density makes it more difficult to pump enough of it through the engine. Solid rockets are from the high ...

5

Several political and practical factors are in play. The first is that the ISS is a multinational construction, so whole of craft risks from a high speed docking need to be signed off on by all parties, including those who are using other types of craft to deliver supplies (and therefore have no benefit from the risks being taken). It is perfectly possible ...

5

Retrograde thrust at periapsis doesn't lower the periapsis, it lowers the apoapsis. If you're trying to lower the periapsis, you need to apply thrust at apoapsis. If you're trying to lower your periapsis to a point absurdly close to the Sun, the most efficient option that avoids gravity assists is a bi-elliptic transfer: raise your apoapsis as high as ...

5

The difference between launching from the equator versus launching from Florida works out to about 55 m/s. Total velocity budget required to reach LEO is around 9400 m/s, so the difference is about half a percent. To launch Pegasus from the equator, the L-1011 would have to take off from Florida, fly 3000 km south, launch, then fly 3000 km home -- pretty ...

4

@GremlinWrangler talked about the approach aspect, but I'm going to mention the docking aspect. Docking is fundamentally a controlled, low-speed collision between two large pieces of hardware (ISS comes in at around 1M pounds, or around 450,000 kg). The soft capture system of the docking mechanism has to serve as alignment, capture, and shock absorber for ...

4

Having the exhaust moving horizontally over water will not do anything useful for the rocket, the exhaust has pretty much done all the 'work' it is going to do for the rocket by the point it leaves the nozzle. There would probably be some fascinating shock diamond like effects in the air water interface but rocket is gone by that point so the physics details ...

4

What is thrust ? Thrust is a force applied to an object that change its kinetic energy. In other words, it's the propulsive force. Usually measured in Newtons. With a rocket engine, thrust goes up when pressure goes down because the differential pressure at the mouth of the nozzle is higher. So no, thrust would in fact be lower than if the rocket gained ...

3

Possible but unlikely. If you want to join satellites securely than you need to add some kind of docking mechanism to the satellites and that adds a lot of complexity at which point you can just have thrusters to dodge debris or counteract the drag. Additionally I think having more satellites bunched up in one area means that if a collision happens there ...

3

The existing answer is good, but I'd like to touch on part of the thermodynamics: the nozzle. A rocket creates thrust essentially by converting pressure (coming from combustion) into velocity of a stream of gas. Most any rocket worth its salt does this with a converging-diverging nozzle that constricts the high pressure flow until it becomes supersonic, ...

3

First of all: Thermodynamics! A rocket is transforming potential chemical energy into kinetic energy -> You need more kinetic energy (= more mass and/or moving faster)? So you need more chemical energy at first. So yes, you are right, there is this factor "efficiency" which means: The more efficient you are, the more is the part of the chemical energy you ...

2

As Mark already pointed out: Retrograde thrust at periapsis doesn't lower the periapsis, it lowers the apoapsis. If you're trying to lower the periapsis, you need to apply thrust at apoapsis. This will be very important: every maneuver you plan effects basically the opposite site of your orbit.. want to lower Pericenter? -> retrograd thrust at Apocenter....

2

If you launch horizontally, you'll build up speed while you are in the thickest part of the atmosphere. Pretty soon (around Mach 1, ~300 m/s), you have to start gaining altitude to prevent overheating due to atmospheric drag. You'll also experience severe buffeting; aircraft that fly fast at low altitude need design features to reduce the vibration to ...

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