24 votes
Accepted

Conceptually, the lower the propellant mass fraction the better, right?

Let's take, for example, the Saturn V rocket. Payload can be 140 tonnes to LEO. The third stage has a dry weight of about 10 tonnes, 119 tonnes fuelled. The second stage has a dry weight of about ...
J...'s user avatar
  • 807
15 votes

Is this a correct understanding of Tsiolkovsky's rocket equation?

Your question is about the behavior of the Tsiolkovsky rocket equation itself, in the limit of very small final mass (dry mass). Roughly: "is there any limit to delta-v in theory?" Using MathJax: $$ ...
uhoh's user avatar
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15 votes

Is this a correct understanding of Tsiolkovsky's rocket equation?

The implication of the rocket equation is that linear increases in ∆v require exponential increases in mass ratio for a single stage. There's not strictly a maximum delta-v -- if you redo your plot ...
Russell Borogove's user avatar
14 votes
Accepted

Flying fuel tanks! Which deep-space spacecraft had the largest fuel mass fraction?

I'm not up to a complete exhaustive survey of every possible contestant, so I've focused on relatively recent orbiters. I found a few that beat Cassini. The figures I've found so far are occasionally ...
Russell Borogove's user avatar
12 votes

Why will SLS Block I bring less mass to LEO than the STS shuttle system did?

It's always difficult to make apples-to-apples comparisons between the space shuttle and other launchers, because the orbiter is ambiguously part launcher and part payload. This is compounded by the ...
Russell Borogove's user avatar
11 votes
Accepted

How does tankage mass really scale?

NASA TM-78661 TECHNIOUES FOR THE DETERMINATION OF MASS PROPERTIES OF EARTH-TO-ORBIT TRANSPORTATION SYSTEMS agrees with the "proportional" method Main propulsion system tank mass, if non ...
Organic Marble's user avatar
11 votes

Conceptually, the lower the propellant mass fraction the better, right?

There are three components to a rocket (in some sense). Payload, vehicle and fuel (where vehicle includes fuel tanks, engines, etc. and fuel includes oxidiser). What you want, of course, is payload to ...
Steve Linton's user avatar
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10 votes
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How does the mass of launchers change over time between ground and orbit?

In almost all cases, the overall mass versus time curve for a multistage launcher will approximate an exponential decay curve; this is the nature of the rocket equation. Within each stage, if all ...
Russell Borogove's user avatar
9 votes

How much mass could the Saturn V rockets have landed on the Moon if nothing was coming back?

And here is the answer from the Apollo era perspective: "Popular Science" text from 1966: "What We'll Do on the Moon", written by dr. Wernher von Braun himself! - Google Books link Unmanned cargo ...
szulat's user avatar
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9 votes
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Are there active (as of 2020) developments in liquid-fuel tank technology?

The in-development Prime launcher from Orbex has an uncommon arrangement: One key aspect of propane is that it remains liquid at cryogenic temperatures. That enabled a “coaxial tank” design for ...
Bob Jacobsen's user avatar
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8 votes

Does a fully fuelled Starship in LEO have 0kg payload to Jupiter?

This is only a partial answer, but there are two major factors that make the performance of the three vehicles not comparable at all. There are two reasons why Starship is so much worse for missions ...
asdfex's user avatar
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8 votes

Conceptually, the lower the propellant mass fraction the better, right?

Paul's comment is correct. As always, when you try to figure out what is "better", you have to define what you are talking about. In this case, the author means better as in Higher delta V The ...
Antzi's user avatar
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8 votes

Could fuel be "hosed" (pumped) from the ground to a launcher?

There exist one way for this to work As pointed out by others before, a hose is heavy to carry along. However, if the propellant station had the same altitude and velocity as the rocket, it may be ...
SE - stop firing the good guys's user avatar
7 votes

Could fuel be "hosed" (pumped) from the ground to a launcher?

You'll lose more energy hauling that hose up than you could possibly save by pumping fuel in. A hose full of fuel is going to be heavy, not to mention you'll have quite a time keeping it out of the ...
Loren Pechtel's user avatar
7 votes
Accepted

If money weren't an issue, what's the best way to get maximum mass to LEO in 1 year? 5 years? 10?

Opinion-based, but I'll give it a shot. In the timeframe of one year, it's not possible to develop any new launch technology of consequence; we have to rely on existing launchers, with a couple of ...
Russell Borogove's user avatar
6 votes
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Is this a plot of Isp vs propellant mass fraction for a SSTO vehicle?

More precisely, this is a plot of the mass fraction required to achieve some target delta-v. As David Hammen points out, the curve seems to be a closer match to ~7.6 km/s, which would would be in the ...
Christopher James Huff's user avatar
6 votes
Accepted

What are Mass Rate(∆v)/∆v, Mass Rate(Isp)/Isp and time of burn(MR)/MR graphs?

These graphs show different visualizations of the Tsiolkovsky rocket equation: (source: wikipedia article) The equation relates change in velocity to engine efficiency and the propellant mass ...
Organic Marble's user avatar
6 votes
Accepted

How much fuel can Falcon 9's upper stage bring to orbit, without any other payload?

Should be pretty close to the payload to LEO: 22.8 tons. Maybe a bit more if you design a new second stage with larger tanks and a nose cone.
Hobbes's user avatar
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6 votes

Conceptually, the lower the propellant mass fraction the better, right?

All good answers and comments so far. The question summary, "Conceptually, the lower the propellant mass fraction the better, right?" is correct if you abandon the assumption of a specified propellant ...
Tom Spilker's user avatar
  • 18.3k
6 votes

Is this a correct understanding of Tsiolkovsky's rocket equation?

No, that is not quite right. Let's first state and describe the Tsiolkovsky Rocket Equation: $\displaystyle \Delta v = V_e \times \ln(\frac{m_i}{m_f})$ $\Delta v$ is delta v, the change in velocity ...
DrZ214's user avatar
  • 4,566
6 votes

Could fuel be "hosed" (pumped) from the ground to a launcher?

The simple solution is to launch from much higher up. Either an air launched rocket or launch from a raised platform. (Both have been described, and one has been used.) Or just begin the launch ...
Andy's user avatar
  • 5,178
5 votes

Could fuel be "hosed" (pumped) from the ground to a launcher?

Additional problems I see are having a pump that can move the required amount of fuel at the rate required to the height required while overcoming shock losses as the hose unrolls and travels upwards. ...
Fred's user avatar
  • 13.1k
4 votes

mass of propellant required + rocket equation

Here is what I did. The Centaur second stage of an atlas V401 will perform 4 maneuvers such that $\Delta v_{\rm tot} = \Delta v_1 + \Delta v_2 + \Delta v_3 + \Delta v_4 =$ 6.3 km/s. For the Centaur ...
Jorafb's user avatar
  • 111
4 votes
Accepted

Would the Space Shuttle External Tank have made orbit as a VT SSTO with 6 SSMEs?

What the equations I used completely ignore is initial thrust to gross launch mass which'd surely affect gravity drag? ... What is the assumption behind the 9.7 km/s delta-v on the Wikipedia page as ...
Russell Borogove's user avatar
3 votes

Fuel needed for rocket lift-off as a function of the altitude

We need a fair number of approximations here... Let's ignore atmospheric losses, since according to Russell Borogov's comment these are dwarfed by gravity losses. Let's also assume that the rocket ...
Florian Castellane's user avatar
3 votes

If money weren't an issue, what's the best way to get maximum mass to LEO in 1 year? 5 years? 10?

In 1 year all aerospace companies resources could be requisitioned / maxed out (I'm assuming it's a free for all war like situation here). For example there would probably be scope to launch more ...
Slarty's user avatar
  • 9,303
2 votes

Propellant Density Calculation for LOX/Kero

I'm a bit confused about what you are actually asking about. The things you mention, oxidizer and fuel density, are inputs into the equation. So you should use the densities for whatever system you ...
Organic Marble's user avatar
2 votes

Conceptually, the lower the propellant mass fraction the better, right?

How far a rocket can go is measured in $\Delta v$ (delta-v). In orbital mechanics, you reach places by changing your velocity and thus your orbit. $\Delta v$ is given by the Tsiolkovsky rocket ...
Polygnome's user avatar
  • 6,926
1 vote

How much fuel, (in tons) will a dedicated tanker be able to deliver to a starship in LEO?

This is equivalent to asking "how much payload mass can Starship + Superheavy put into LEO per launch". It's just that in the case of a tanker the "payload" is fuel rather than ...
Ajedi32's user avatar
  • 914

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