32 votes
Accepted

Why will Starlink satellites use krypton instead of xenon for electric propulsion?

It's the same reason SpaceX often does things differently: Krypton is a lot cheaper. The satellites are designed to control costs. For example, each will maneuver with Hall-effect thrusters—ion ...
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  • 121k
19 votes

Have light gases like hydrogen or helium been explored for ion propulsion?

(Top edit: The Question asserts "Xenon and krypton are popular despite their heavy mass" and asks about exploring H or He ion propellants for improved Isp. This answer shows that lighter is not ...
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  • 12.3k
13 votes
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Is the propulsion for the Scorpion nuclear-thermal-electric ship concept viable and credible?

As with any hypothetical design, one is limited to consider if it's making some "unreasonable" assumptions. First, one may compare the claimed performance to existing technology. Nuclear ...
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11 votes

Cosmic rays can be new energy source

The problem is with the low energy density of cosmic rays in the universe. Individual cosmic rays are indeed very energetic, but there just aren't enough of them to be a significant power source for ...
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  • 17.9k
11 votes

Has ion propulsion ever been used in a deep space trajectory correction maneuver proper?

The latter: not really in a separate TCM, but integrated into long propulsive burns ... which may be updated after anomalies occur. TCMs are small maneuvers (possibly as small as 5-10 m/s) and used to ...
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  • 5,775
10 votes
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Ratio of low-thrust slow spiral to Hohmann transfer $\Delta V$?

This answer has the two-impulse Hohmann transfer $\Delta V$. It is: $$\sqrt{2x\over x+1}+\sqrt{1\over x}-\sqrt{2\over x\left(x+1\right)}-1$$ where $x$ is the ratio of the higher orbit radius to the ...
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10 votes
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Super Capacitor Stages

No Even if overall design makes a helicopter lifted first stage sensible you still need good energy density (power per KG of energy storage). Super capacitors have a special properties that make them ...
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10 votes
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How much of the world's xenon has been used in spaceflight altogether? Is it a lot? Did it cost a lot?

According to Wikipedia's article about xenon, the gas occurs at 87 ppb (parts per billion) by volume in Earth's atmosphere. Earth's atmosphere weighs 5.15×1018 kg. Dividing this by the density of air (...
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  • 116
9 votes

What is total impulse?

I'll expand on @OrganicMarble's answer, it seems to me that the link there to the page on Richard Nakka's Experimental Rocketry Web Site titled Determining Total Impulse and Specific Impulse from ...
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  • 148k
9 votes
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Why does the NASA NEXT engine use xenon?

This video explains it. In short, it all boils down to golden middle between energy requirements, thrust and specific impulse. Ionizing lighter noble gases requires much higher potential - much more ...
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  • 52.4k
8 votes

Can we thrust a rocket from earth using electric power?

The one thing which could conceivably fit your question and have a positive reply is an electromagnetic catapult. This would be an evacuated tube, typically hundreds of kilometers long, in which ...
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  • 18.9k
8 votes

Electrical Propulsion Thrust

Thrust isn't the bottle neck. Rather thrust to mass. In other words, acceleration. A 10 kilowatt Hall thruster exerts about half a newton. Half a newton is about a tenth of a pound or a little more ...
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  • 15.1k
8 votes

Where to send invention ideas?

There is a federal program for funding of small business research concepts. It is called the Small Business Innovation Research Program (SBIR). Each agency puts out a procurement document each year ...
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  • 1,989
8 votes

Why was SERT-1 put in a suborbital trajectory (4000 km apogee) while SERT-2 (1970-009A) was put in a 1000 km circular polar orbit?

Suborbital flights are cheaper and good enough for a proof-of-concept. A one hour flight was considered sufficient to sequentially operate the two engines and obtain the desired test data. ...
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7 votes
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Will the ISS have electric propulsion to maintain altitude? Is there enough power for it?

the VASIMR test planned by Ad Astra has been cancelled: On December 8, 2008, Ad Astra signed an agreement with NASA to arrange the placement and testing of a flight version of the VASIMR, the VF-200, ...
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  • 121k
6 votes
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Can we thrust a rocket from earth using electric power?

tldr; No, our current technology is far too weak. Electrostatic Thrusters The term 'electric power' when it comes to engines can mean a few things, but the closest we currently have in spaceflight ...
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  • 9,834
6 votes
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What is Australia's Bartolomeo platform? When does it arrive at the ISS; when and where will it be attached?

Bartolomeo is not Australian but European. It's a platform designed by Airbus DS. It will be installed outside the Columbus laboratory on the COL-EPF (Columbus Laboratory Module Exposed Payload ...
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  • 121k
6 votes
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Mass ratio of solar-electric versus radioisotope thermo-electric power for propulsion; beyond how many AU do RTGs win?

With current technology: 4.3AU. From wikipedia, it appears that the most powerful flight-proven RTG had a power density of 5.4W/kg. From NASA, current (as of 2017) solar technology has a power ...
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6 votes

What's the final word; does the EmDrive drive work or not?

There is no theoretical reason to think it would work. Its inventor based it on his fundamental misunderstandings of relativity and basic Newtonian mechanics. (Amusingly, Shawyer's analysis assumes ...
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6 votes
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What's this small source of glowing blue plasma next to Psyche's Hall effect thruster for? What does it do and why does the plasma curve and connect?

It is the hollow electron emitting cathode used to produce the plasma. The electrons are moving within an electric and a magnetic field so they are moving on a circular path. The electrons are hitting ...
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5 votes

Will the Neumann drive start testing aboard the ISS some time in 2018?

This ion drive will be installed on the Airbus DS Bartolomeo platform as part of the FAST mission (Facility for Australian Space Testing) in mid-2019.
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  • 121k
5 votes

Can we thrust a rocket from earth using electric power?

Short answer : No. We do not have storage capacity of energy in either electric or chemical form that would allow to convert back the chemical energy into electric energy if required, and allow us to ...
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  • 51
5 votes

Electrical Propulsion Thrust

In principle, ion thrusters can be scaled to very large thrusts, but their thrust per watt of input power is inherently low. This means that the power supply for any electrical thruster is going to be ...
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5 votes
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Usages of electric propulsion versus chemical engines

Your question really contains most of the answer. As you note, electrical propulsion is unusable for liftoff from large bodies; the engines have far less than 1:1 thrust-to-weight ratios (in Earth ...
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5 votes

What is the most energy efficient & inexpensive propulsion system other than chemical fuel oxidizer that could be used in rockets?

For inexpensive, especially per ton of payload launched to high velocity you could consider the nuclear shotgun or project orion. There are a few environmental and regulatory issues, and the shotgun ...
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5 votes

Why is hydrazine used in arcjet thrusters?

Specific heat, also known as heat capacity, in J/kg K (Joules per kilogram per Kelvin). Water, of all liquids, has the highest specific heat; ammonia and hydrazine have much lower specific heats. Also,...
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5 votes

Is it possible to protect a Cubesat's electronics from 100g of acceleration?

It is certainly possible to mount electronic components to survive 100G, see HARP which had instrumented rounds firing at thousands of G. The fundamental step is to mount everything in epoxy with the ...
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5 votes

How to calculate the kilowatt hours (kW-h) needed for a solar-electric engine to produce a given delta-v?

Ion thrusters are usually specified with two numbers: thrust and electrical power. As an example, let's take the NSTAR engine of DS1. According to Wikipedia it produced 92 mN thrust at a power of 2.3 ...
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  • 12.7k
5 votes
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What's the lowest altitude that an ion engine has been used for a significant orbital maneuver?

JAXA's Tsubame satellite is planned to orbit to altitudes as low as 180 km, using an ion engine to reboost. It was launched in January 2018 into an initial orbit at ~480 km, its orbit will be ...
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