US Explorer 1, Van Allen Radiation Belts

Explorer 1 was first US satellite designed and built by the Jet Propulsion Laboratory (JPL), The mission followed the the first 2 Soviet satellites, Sputnik 1 and Sputnik 2. Explorer 1 was launched on January 31, 1958 atop the Juno I booster from Cape Canaveral in Florida. It was the first spacecraft to detect Van Allen radiation belts. 
Redstone, Jupiter-C and Mercury Redstone to compare 

 The original lifetime of the satellite before the orbital decay was estimated 3 years. The high power transmitter was powered for 31 days and the low power transmitter for 105 days. The Explorer 1 stopped data transmission on May 23, 1958, but against the assumptions it remained in orbit for another 12 years and reentered the atmosphere on March 31, 1970. 

The total mass of satellite was 13.37 kg,  including 8.3kg of instrumentation, compared to 83.6 kg of Sputnik 1. Explorer 1 had 2 antennas to transmit data from scientific instruments. A 60 mW transmitter fed a dipole antenna operating on 108.03 MHz and a 10 mW transmitter fed turnstile antenna operating on 108.00 MHz. For the electronics was used mostly germanium and silicon transistors, mainly due to weight. Electric power was provided by mercury chemical batteries making up to 40 per cent of the payload weight. 



Explorer 1 in full scale during the conference confirming the satellite was in the orbit: William H. Pickering, James Van Allen, and Wernher von Braun

Explorer 1 contained scientific instruments such as Geiger Müller tube to detect cosmic rays, however most of the time instrument was saturated; few temperature sensors; acoustic detector and wire grid detector to detect micrometeorite.

The most important result, came from what in the beginning looked like a mistake. Sometimes instrumentation showed expected cosmic ray counts and sometimes it showed strange zero counts. Later after Explorer 3 it was found that the original Geiger counter was saturated by the radiation coming from a belt of charged particles trapped by the Earth's magnetic field, known as Van Allen radiation belts. 

Note: Second belt was discovered by Pioneer 3 (launched by Juno II on December 6, 1958) 

Van Allen radiation belts: Outer and inner





Comments

Post a Comment

Popular posts from this blog

Space Shuttle orbiter

Image
The Space Shuttle orbiter is the spaceplane component of the Space Shuttle, a partially reusable orbital spacecraft system that was part of the discontinued Space Shuttle program. Operated from 1977 to 2011 by NASA. Orbiter is the part of the Space Shuttle system that looks like an airplane. The size is very similar to that of standard medium size commercial passenger jet such as Boeing 747.   Figure 1: Discovery approaches the International Space Station (ISS) on STS-121; source: wiki Six orbiters were built for flight: Enterprise, Columbia, Challenger, Discovery, Atlantis, and Endeavour. Space Shuttle Enterprise (Orbiter Vehicle Designation: OV-101) was the first orbiter of the Space Shuttle system. Rolled out on September 17, 1976, it was built for NASA as part of the Space Shuttle program to perform atmospheric test flights after being launched from a modified Boeing 747. It was constructed without engines or a functional heat shield. As a result, it was not capable of spaceflight
Read more

Rocket engine propellants

Image
A rocket engine uses stored rocket propellants as the reaction mass. Reaction mass forms a high speed propulsive jet of fluid, usually high temperature gas. Rocket engines are type of engines using reaction, producing thrust by ejecting mass rearward, according to the Newton's third law of action and reaction. Most rocket engines use the combustion of reactive chemicals to supply the necessary energy, but non-combusting forms such as cold gas thrusters and nuclear thermal rockets also exist. RD-180 test firing at Marshall Space Flight Center, source wiki Rocket engines produce thrust by the ejection of an exhaust fluid that has been accelerated to high speed through a propelling nozzle. The fluid is usually a gas created by high pressure combustion of solid or liquid propellants, consisting of fuel and oxidizer, inside a combustion chamber. As the gases expand through the nozzle, they are accelerated to very high speed, and the reaction to this pushes the engine in the opposite dir
Read more

Exercise on single stage vs. two-stage rocket

Image
Exercise: 1. Single stage rocket:  Before a rocket begins to burn fuel, the rocket has a mass of  m r,i =2.81×10 7 kg, of which the mass of the fuel is  m f,i =2.46×10 7 kg. The fuel is burned at a constant rate with total burn time is 510 s and ejected at a speed v e = 3000 m/s relative to the rocket. If the rocket starts from rest in empty space, what is the final speed of the rocket after all the fuel has been burned? What we know: initial rocket mass m r,i =2.81×10 7 kg initial mass of the fuel m f,i =2.46×10 7 kg t = 510 s v e  = 3000 m/s So, we can calculate the dry mass of the rocket m r,d =m r,i -m f,i =0.35×10 7 kg. The mass ratio is then R = m r,i  /m r,d =8.03. So, the final speed of the rocket is then: V r,f =Δv r =v e lnR=6250m/s. 2. Two-stage rocket:  Now, we have similar example, the same rocket as in the previous example, but the fuel will be burnt in two stages ejecting the fuel in each of the stages at the same relative speed (v e  = 3000 m/s).  In first stage, the a
Read more